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MMA9559L Intelligent, Motion-Sensing Platform Software Reference

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1. MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 61 4 3 4 Functions 4 3 4 1 mma9559 vars t mma9559 vars addr get void The Freescale firmware uses an instance of the mma9559 vars t structure to store the variables used for its configuration and control The operation of the firmware can be modified and or observed through this control structure Since the address of the structure instance may change in future releases of the firmware this function is provided to enable the user code to find the address of the structure and use it NOTE This function calls the ROM trap function to get device information from the ROM code This causes both this function call and the ROM trap being on the supervisor stack at the same time consuming a large part of the supervisor stack This function should not be called from within a user exception handler or a user trap call because that would exceed the supervisor stack space Return Address of the Freescale firmware data structure MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 62 Freescale Semiconductor Inc 4 3 4 2 events t mma9559 events set clear events t set events events t clear events This function updates the mma9559 vars t events and events missed fields with the supplied set events and clear events parameters The mma9559 vars t events missed field is updated
2. FCSR_SF 1 Clear interrupt source Add Start of Frame event to the events to be signaled asserted events EVENT BITFIELD EVENT START OF FRAME break default code to handle the other exception sources break return events signal events to be signaled activated Events can also be managed by FIFOs See FIFOs on page 24 In this case events that are associated with FIFOs are signaled when the FIFO contains data and the FIFO events are cleared when the FIFO is empty Events are normally handled in a simple execution loop within the user main function The user firmware selects an active event bit and performs the required processing When the processing has completed the event bit can be cleared using the mma9559 events set clear function Alternatively if the event is associated with a FIFO it is cleared when the last data is read from the FIFO Two functions are provided to assist with the selection of the event to process mma9559 events find first selects the highest priority event that is active and returns the event number from 0 to 31 for the chosen event mma9559 events find next selects the next active task in a round robin manner working from the least significant bit to the most significant bit and then wrapping around again The mma9559 idle function is used to put the MMA9559L into the lowest permissible power state when no computational work is required The function
3. clear event mma9559 events set clear 0 EVENT_BITFIELD event else if there are no outstanding events then go to sleep mma9559_idle hi Event signaling can also be used creatively by tasks in the main execution loop When one task completes it can wake up the next task by signaling the appropriate event Internal state variables can be used to process more time consuming tasks Some tasks may reguire longer execution times to complete their processing The event scheduling is cooperative rather than preemptive reguiring long tasks to break up their processing into multiple shorter executions Internal state variables may be used to keep track of the processing state of the task Such tasks may deliberately not clear the event that causes them to run but instead leave it set for the task to execute repeatedly to perform the rest of the processing steps Only when all of the required executions have been performed is the event bit cleared Using FIFOs for inter process communication may be easier when some longer tasks are difficult to break up The mma9559 vars t structure also contains an events missed field The bits in this field are set whenever an event is signaled and the event bit is already active in the event field This situation indicates that the scheduler may be losing events because a new occurrence of the event has been signaled before the processing for the previous event has been c
4. csr mma9559 afe csr get Read the current AFE CSR value See also void mma9559 afe offsets set int16 data ptr e enum afe csr options t Return The current setting of the AFE CSR options MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 53 4 2 4 9 void mma9559 afe offsets set int16 data ptr This function gets the current AFE accelerometer user offset values The mma9559 afe trimmed sensor data get and mma9559 afe raw sensor data trim functions add user programmable offset values to the trimmed accelerometer readings These values may be set or read by the user The offset values are treated as values in the 8g range where the hex value 0x4000 equates to 1g and are adjusted automatically to the appropriate g range when the g range is changed with the mma9559 afe csr set function The values can be determined by putting the device into the 8g mode reading the accelerometer values without the effects of gravity and negating these values Example 4 9 int16 offsets 3 0 0 0x4000 X Y and Z offsets in 8g mode mma9559 afe offsets set offsets The user offset values are reset whenever the device is reset See also void mma9559 afe trimmed sensor data get int16 trim ptr Parameter data ptr Address containing the three accelerometer user offset values MMA9559L Intelligent Motion Sensing Platform Software Ref
5. Enumerator Description BOOT TO ROM On the next non power on reset execute the ROM command line interpreter BOOT TO FLASH On the next non power on reset execute the firmware loaded in the flash memory MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 82 Freescale Semiconductor Inc 4 5 1 2 enum rmf func t This value specifies the ROM command to execute For more information on the operation and data formats for the commands see the User Callable ROM Functions section of the ROM chapter in the MMA955xL Intelligent Motion Sensing Hardware Reference Manual MMA955xLHWRM See also void mma9559 rom command rmf func t func id void addr Enumerators Table 4 20 enum rmf func t enumerators Enumerator Description RMF DEV INFO Retrieves device information data structure RMF FLASH PROGRAM Programs flash memory through the flash controller RMF FLASH ERASE Erases flash memory through the flash controller RMF EXTENSION Executes extended flash functions RMF CRC Calculates the CRC over a range in memory RMF CI Transfers command to the ROM based command interpreter RMF CHANGE CONFIG Updates the device capabilities configuration RMF FLASH PROTECT Protects the flash against accidental erasure and programming RMF FLASH UNPROTECT Unprotects access to the flash program and erase functions RMF FLASH UNSECURE Modifies the current security status of th
6. MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 71 4 3 4 11 int mma9559 user trap2 int dO int d1 int d2 void a0 void a1 This function issues a trap instruction that calls the function registered in the firmware variables structure entry user trap handler 2 The parameter variables are passed to the trap function and their usage is determined by the user trap handler function Return The integer value returned by the user trap handler function NOTE The user trap handler can be called directly using the asm trap TRAP USER 2 instruction This function makes it easier to set the parameter values Parameters Table 4 13 int mma9559 user trap2 parameters Parameter Description d0 First integer parameter user defined meaning d1 Second integer parameter user defined meaning d2 Third integer parameter user defined meaning a0 First pointer parameter user defined meaning al Second pointer parameter user defined meaning MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 72 Freescale Semiconductor Inc 4 3 4 12 int mma9559 user trap3 int dO int d1 int d2 void a0 void a1 This function issues a trap instruction that calls the function registered in the firmware variables structure entry user trap handler 3 The parameter variables are passed to the trap function and their usage
7. This macro creates an events t bit field from the event number The MMA9559 firmware supports up to 32 events numbered from 0 to 31 The events t data type can represent multiple events by using a single bit for each event This macro provides an easy way to create the events t bit field from an event number MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 56 Freescale Semiconductor Inc 4 3 2 Enumerations 4 3 2 1 enum idle config t This value is used by the mma9559 idle use stop config to set how the idle bits bit field is used to modify the idle mode operation See also void mma9559 idle use stop config idle config t config idle bits t bits Enumerators Table 4 4 enum idle config t enumerators Enumerators Description IDLE USE STOP FC CLEAR Clear remove a bit in the use stop fc field ofthemma9559 idle t structure IDLE USE STOP FC SET Set a bit inthe use stop fcfield ofthemma9559 idle t structure This forces the idle function to stop using the Stop FC mode so that the system clock still runs at full speed IDLE USE STOP SC CLEAR Clear remove a bit in the use stop sc field of the mma9559 idle t structure IDLE USE STOP SC SET Seta bitin the use stop sc field of the mma9559 idle t structure This prevents the idle function from using the Stop NC mode allowing the system clock to still run MMA9559L Intelligent Moti
8. 0 1 Freescale Semiconductor Inc 4 4 3 2 void mma9559 fifo reset volatile mma9559 fifo t fifo ptr This function resets the FIFO variables to empty the FIFO and clears any currently signaled event bits for the FIFO When the FIFO is reset all data in the FIFO is discarded and the FIFO data structure is re initialized Example 4 18 mma9559 fifo reset mma9559 fifo t amp fifol pointer to the FIFO structure to be reset See also Reset the FIFO on page 27 Parameter fifo ptr Address of the FIFO data structure to be reset MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 78 Freescale Semiconductor Inc 4 4 3 3 int mma9559 fifo pop volatile mma9559 fifo t fifo ptr uint8 data ptr unsigned int entries This function copies the requested number of entries from the FIFO to memory starting at the supplied data pointer If the FIFO contains less entries than the number of entries requested only the number of entries in the FIFO are copied After the data has been copied from the FIFO the data is discarded from the FIFO buffer freeing space for new data If the FIFO is empty after the data has been read the events associated with the FIFO are cleared It does not corrupt the FIFO to attempt to pop data off an empty FIFO or to read more data entries from a FIFO than it contains Either action however results in all of the available entries being read and the FI
9. 2G Use 2 g range AFE CSR CAMODE TEMP Measure X Y Z and Temperature AFE CSR CMODE 10BIT Use 10 bit conversion See also void mma9559 afe csr set afe csr options t options void mma9559 afe csr set afe csr options t options Table 4 2 enum afe csr options t enumerators Enumerator Description AFE CSR GRANGE 8G Set the AFE to the 8g range so each LSB is 0 244 mg AFE CSR GRANGE 4G Set the AFE to the 4g range so each LSB is 0 122 mg AFE CSR GRANGE 2G Set the AFE to the 2g range so each LSB is 0 061 mg AFE CSR CAMODE NONE Do not measure anything with the ADC s fourth channel AFE CSR CAMODE TEMP Use the ADC s fourth channel to measure the temperature sensor AFE CSR CAMODE EXT Use the ADC s fourth channel to measure the external inputs AFE CSR CMODE 10BIT Perform a 10 bit ADC conversion so the six LSBs are 0 AFE CSR CMODE 12BIT Perform a 12 bit ADC conversion so the four LSBs are 0 AFE CSR CMODE 14BIT Perform a 14 bit ADC conversion so the two LSBs are 0 AFE CSR CMODE 16BIT Perform a 16 bit ADC conversion using all 16 data bits MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 43 4 2 2 2 enum framerate t This enumeration configures the FIC Frame Interval Counter frequency through the CK OSCTRL register The frame interval counter is the primary mechanism for waking the device up perio
10. Frame interval counter The MMA955xL hardware is designed on a frame structure Each frame starts when the FIC Frame Interval Counter reaches the configurable frame rate timer interval and creates a Start of Frame exception This exception can be used in the user exception handler to start a sequence of activities to be executed in each frame The frame rate interval is set by calling the function mma9559 framerate set with one of the following parameter values e FRAMERATE NONE Disables the FIC preventing the device from waking up periodically e FRAMERATE 3906HZ Configures the FIC to run at 3906 Hz e FRAMERATE 1953HZ Configures the FIC to run at 1953 Hz e FRAMERATE 977HZ Configures the FIC to run at 977 Hz e FRAMERATE 488HZ Configures the FIC to run at 488 Hz e FRAMERATE 244HZ Configures the FIC to run at 244 Hz e FRAMERATE 122HZ Configures the FIC to run at 122 Hz e FRAMERATE 61HZ Configures the FIC to run at 61 Hz e FRAMERATE 30HZ Configures the FIC to run at 30 5 Hz e FRAMERATE 15HZ Configures the FIC to run at 15 3 Hz e FRAMERATE HZ Configures the FIC to run at 7 6 Hz e FRAMERATE 4HZ Configures the FIC to run at 3 8 Hz e FRAMERATE 2HZ Configures the FIC to run at 1 9 Hz e FRAMERATE 1HZ Configures the FIC to run at 0 95 Hz e FRAMERATE POINTSHZ Configures the FIC to run at 0 48 Hz e FRAMERATE POINT2HZ Configures the FIC to run at 0 24 Hz Setting the frame rate to FRAMERATE NONE reduces the power consumption of the devic
11. amp buffer y MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 91 For more information about using this function see the related IIR Filter applications note AN4464 Digital Filtering with MMA955xL Parameters Table 4 26 int16 mma9559 iir filter parameters Parameter Description input Filter input data value coef Pointer to the IIR filter coefficient data structure buffer Pointer to the working data buffer used by the filter 4 6 3 Typedefs 4 6 3 1 typedef struct mma9559 coef t mma9559 coef t This structure is used to hold the coefficients for an IIR filter The methods for calculating the coefficients for the filter is beyond this reference manual but a sample low pass filter is given in the following example Example 4 29 6th order Chebyshev type 2 lowpass filter cutoff at fs 4 static const mma9559 coef t lp cheby6 6 filter order 6 14 coefficient shift 1 16384 16384 441 a0 bO 1 000000 0 000244 a0 value not used 16546 1637 al bl 1 009888 0 099915 20052 3191 a2 b2 1 223877 0 194763 8837 3925 a3 b3 0 539368 0 239563 3957 3191 a4 b4 0 241516 0 194763 624 1637 a5 b5 0 038086 0 099915 78 441 a6 b6 0 004761 0 000244 See also e intl6 mma9559 iir filter int16 input const mma9559 coef t coef void buffer MMA
12. as shown in the following code Example 4 27 int32 buffer ORDER each int32 holds a pair of 16 bit yn xn values A three channel low pass filter could be implemented as shown in the following example Example 4 28 6th order Chebyshev type 2 lowpass filter cutoff at fs 4 static const mma9559 coef t lp cheby6 6 filter order 6 14 coefficient shift 1 16384 16384 441 a0 bO 1 000000 0 000244 a0 value not used 16546 1637 al bl 1 009888 0 099915 20052 3191 f a2 b2 15223877 0 194763 8837 3925 a3 b3 0 539368 0 239563 3957 3191 a4 b4 0 241516 0 194763 624 1637 ab b5 0 038086 0 099915 78 441 a6 b6 0 004761 0 000244 hi buffers are global to maintain their contents across function calls int32 buffer x 6 buffer to hold X intermediate values for 6th order filter int32 buffer yv 6 buffer to hold Y intermediate values for 6th order filter int32 buffer z 6 buffer to hold Z intermediate values for 6th order filter Function to low pass filter X Y and Z channels void filter intl16 output intl6 input output mma9559 iir filter inputtt amp lp_cheby6 amp buffer x Filter X data output t Filter Y data outputtt mma9559 iir filter inputtt amp lp_cheby6 amp buffer z Filter Z data mma9559 iir filter inputttw amp lp cheby6
13. data onto the FIFO as it becomes available 4 Pop data off the FIFO in the tasks that process the data 5 Reset the FIFO to discard the current contents of the FIFO and restore it to its empty state FIFOs are normally created as global variables so that they are always permanently allocated and are never de allocated They may also be created as local variables within functions in which case they are allocated on the user stack If they are on the user stack the user must ensure that they are not referenced after they have gone out of scope and been removed from the stack 2 5 1 Instantiate FIFO The data buffer and control variables for each FIFO are held in a single data structure The data structure can either be created on a per instance basis or by creating a data type that enables multiple instances of the same FIFO to be created A FIFO instance can be created with the FIFO STRUCT macro as in the following code that creates the FIFO test fifo That FIFO can hold up to FIFO MAX ENTRIES entries where each entry is the size of the mma9559 afe data t data type FIFO STRUCT FIFO MAX ENTRIES sizeof mma9559 afe data t test fifo An alternate method of creating a FIFO is to create a data type for the required FIFO configuration and instantiate one or more FIFO variables from the data type with the same configuration In the following example the fifo 20 t data type is created and used to create fifo 1 and fifo 2 variab
14. enable system and software implementers to use Freescale Semiconductor products There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document Freescale Semiconductor reserves the right to make changes without further notice to any products herein Freescale Semiconductor makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does Freescale Semiconductor assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability including without limitation consequential or incidental damages Typical parameters that may be provided in Freescale Semiconductor data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts Freescale Semiconductor does not convey any license under its patent rights nor the rights of others Freescale Semiconductor products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the Freescale Semiconductor product
15. exception sources that become active are handled once the interrupt priority mask is returned to 0 by the call to the mma9559_interrupts_restore function A critical section can be created as shown in the following example Example 4 13 int status mma9559 interrupts disable start critical section mma9559_interrupts_restore status restores previous interrupt level mask If the critical section is never nested this solution can be simplified by removing the status variable and making the parameter to the mma9559 interrupts restore function zero See the following example Example 4 14 mma9559 interrupts disable start critical section mma9559 interrupts restore 0 enables interrupts Return The value of the status register including the interrupt priority mask before the interrupts were disabled See also void mma9559 interrupts restore int status e Interrupts and critical sections on page 22 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 68 Freescale Semiconductor Inc 4 3 4 8 void mma9559 interrupts restore int status This function is used in conjunction with the mma9559 interrupts disable function to enable user code to create critical sections that cannot be interrupted by exceptions See int mma9559 interrupts disable void for more information e fusercode supports nested critical sections then the status parameter should be the val
16. filter int16 input const mma9559 coef t coef void buffer Fields Table 4 25 mma9559 coef t fields Field Description uint16 order Defines the order of the filter and determines the size of the coef ary array uint16 shift Specifies the number of fractional bits in the coefficients to determine how many bits to right shift the output of the filter int16 coef ary Holds the coefficient values for the filter The number of coefficients is determined by the order of the filter and is calculated as 2 order 1 for example for a sixth order filter there are 14 coefficients MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 90 Freescale Semiconductor Inc 4 6 2 Functions 4 6 2 1 int16 mma9559 iir filter int16 input const mma9559 coef t coef void buffer This function applies the supplied input data to the specified IIR filter The coefficient structure is predefined for each particular transform The same coefficient structure may be reused such as for each channel of the X Y and Z accelerometer data The buffer is used to hold the previous X n and Y n values In order to keep the previous values the buffer must be persistent therefore it is either global or static It is updated by the filter function on each execution as new data enters into the filter The size of the buffer depends on the order of the filter and is 2 order words long This is declared
17. how to associate fifol with the EVENT_FIFO event value Example 2 10 ret mma9559_fifo_init mma9559 fifo t amp fifol pointer to the FIFO structure EVENT BITFIELD EVENT FIFO bitfield of associated events 25 maximum number of data entries sizeof mma9559 afe data t number of bytes in each data entry The return value from mma9559 fifo init is 0 if the initialization is successful If the initialization fails the value is 1 If the values for the maximum number of entries or the bytes per entry are invalid 0 or greater than 255 the initialization fails The buffer size the product of the maximum number of entries and the bytes per entry is not checked to see if it exceeds the space reserved during the FIFO instantiation 2 5 3 Push data onto the FIFO Data can be stored in a FIFO after it has been successfully initialized Data is always stored as an integer number of data entries and is copied byte by byte into the FIFO from the supplied data pointer Since the data entry size was already set when the FIFO was configured all that must be provided is the number of data entries to be stored Usually data is pushed onto the FIFO one at a time but the writing of multiple entries also is supported If the FIFO does not have enough empty data entries to store the data the push operation is limited to the amount of free space in the FIFO The mma9559 fifo push function returns th
18. int16 data 5 Raw or trimmed value for each axis sensor MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 45 4 2 4 Functions 4 2 4 1 framerate t mma9559 framerate set framerate t rate This function configures the FIC Frame Interval Counter with the supplied frequency If the frame rate is invalid it is ignored and the frame rate is not adjusted Example 4 2 framerate t framerate framerate mma9559 framerate set FRAMERATE 488H2 If the rate value is FRAMERATE NONE the IDLE BITS CKOSC bit is cleared in the mma9559 idle t use stop sc field enabling the mma9559_idle function to use the StopNC stop mode unless some other setting of the idle_config_t structure prevents it If the rate value is any other valid rate the IDLE_BITS_CKOSC bit is set in the mma9559 idle t use stop sc field preventing the mma9559 idle function from using the StopNC mode and stopping the FIC from running NOTE Atthe highest supported frame rate of 3 906 kHz the 16 bit and 14 bit AFE conversion cannot be completed within the frame interval as a result only an AFE conversion length of 12 bits or less should be used See also enum framerate t Frame interval counter on page 14 User main on page 37 Return The resulting frame rate value is the frame interval counter This should be the same as the requested value unless the requested va
19. is determined by the user trap handler function Return This is the integer value returned by the user trap handler function NOTE The user trap handler can be called directly using the asm trap TRAP USER 3 instruction This function makes it easier to set the parameter values Parameters Table 4 14 int mma9559 user trap3 parameters Parameter Description d0 First integer parameter user defined meaning d1 Second integer parameter user defined meaning d2 Third integer parameter user defined meaning a0 First pointer parameter user defined meaning al Second pointer parameter user defined meaning MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 73 4 4 FIFOs The MMA9559L Freescale firmware supports the use of FIFOs for inter process communication with a configurable FIFO structure definition and a set of functions to manage them For overview information see FIFOs on page 24 4 4 1 Macros 4 4 1 1 define FIFO STRUCT max entries bytes per entry struct uint32 rsvd 2 uint8 data max entries bytes per entry The MMA9559L firmware provides functions to store and retrieve data in FIFOs The FIFO data structure contains a common set of internal variables that are the same in every FIFO and a data buffer whose length is determined by the number of data entries in the FIFO and the size of each entry The entry si
20. of the values in the volatile registers in the calling function A trap handler normally appears similar to the following example The parameters are the values in the dO dl d2 a0 and al registers when the trap call is issued The use of the parameters is up to the user code MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 35 Example 3 3 User Trap Handler function declaration int user trap handler declspec register abi int do int dl int d2 void a0 void X31 User trap Handler function definition example int user trap handler declspec register abi int do int dl int d2 void al void al switch d0 case 0 return 0 first integer parameter second integer parameter third integer parameter first pointer parameter second pointer parameter MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 36 Freescale Semiconductor Inc 3 4 User main The user main function is called from the startup code It should initialize all key variables and enter an infinite loop waiting for events and processing them when they occur Events are signaled in the User Exception Handler The exception wakes up from the mma9559 idle function and keeps processing until all of the signaled events have been cleared At that point the function again calls the m
21. ptr uint8 data ptr unsigned ma eni e Sox d ex ed prd CERO ARE BUM RE REO e d ERE ux 79 4 4 3 4 int mma9559 fifo push volatile mma9559 fifo t fifo ptr uint8 data ptr unsigned int entries cscs oh dau eka Kes nos Rx daa d d dua 80 4 4 3 5 int mma9559 fifo entries used volatile mma9559 fifo t fifo ptr 81 4 4 3 6 int mma9559 fifo entries free volatile mma9559 fifo t fifo ptr 81 as Oer EIGNE kek eae eae KOREA de deae Ros deed rA S dale odo bbe eka od 82 451 Enumeralions scia KC RO do SE AC ORARE Qe EG RI ede ERED 82 225 131 omm DOOL BOE is eh cee wewead a eie texucaxcw wo dd a wens 82 4 5 1 2 enum rit TUNG Ka mo oo naa aom eed EUR EORR e 83 nor Bb SO DEDE inaceueWqdusazenign ad da dad dd d ad dx olus a idea RE d dd 84 45 2 1 mma9559 device M O Teo en an Ra OON ERR e EORR PRE ED 84 4 5 2 2 union rmf _return t chads aos kao NB eee FUP nase TR RC RC UN e RR 85 Lor PONENS Lean dO HEC e edo acd dedic d dE dod ee eee Y p deor 86 4 5 3 1 void mma9559 boot options set boot options toption 86 4 5 3 2 int mma9559 device info get int length mma9559 device info t addr 87 4 5 3 3 void mma9559 rom command rmf func t func id void addr 88 En NLIS ausa pd Ew dare dd e pO CX UC ED RE EO ROO E CHE Deiode do ewes 89 4 6 1 Data structures 0 0 0 0 eee 90 21 mtis COG deste aa saban AS Ra Rek OB ZA Ea ESSE 90 SEDE FUNCIONS 422 2249 43 5 eh os oh se Ta ee eee Redes os sis S Wd D eens 91 4 6 2 1 int16 mma9559 iir fil
22. status parameter If any of the interrupt priority mask bits are set the interrupt priority mask is set to 7 to mask all interrupts Otherwise the interrupt priority mask is set to 0 to enable unmask the interrupts MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 23 2 5 FIFOs Most applications needs can be met using the Events and Scheduling capabilities where an event can be signaled in the user exception handler and handled in the main execution loop This works when the tasks in the execution loop are short and can be completed before the next interrupt or AFE sample Occasionally longer processing is required processing that takes more time than the interval between interrupts AFE samples In such cases the AFE samples would be lost if the regular event method was used This can be handled in a couple of ways Break the longer tasks into a number of smaller sections which can each be executed separately See Events and scheduling on page 18 Use FIFOs for inter process communications as described in more detail in this section FIFOs provide a configurable amount of buffering between tasks in order to store data before being processed This can be used in situations where the tasks with longer execution times execute infrequently and the total average processing time per AFE sample is less than the AFE sample period The FIFO provides a means for
23. the lowest possible power The Freescale firmware reserves the lower 16 idle bits and already uses the two least significant idle bits DLE BITS CKOSC Used by the frame interval counter to prevent the use of StopNoClock when the frame interval counter is being used DLE BITS AFE Used by the AFE to force the use of StopFastClock when the ADC is performing a conversion User code may use any of the upper 16 bits that have the prefix IDLE BITS USER See also void mma9559 idle void e Power on page 28 Parameters Table 4 10 void mma9559 idle use stop config parameters Parameter Description config Selects which field and type of modification to make bits Designates the bits to be modified in the selected field MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 66 Freescale Semiconductor Inc 4 3 4 6 void mma9559 idle void This function executes the idle processing function to sleep until the next exception The mma9559 idle function manages the CPU Stop modes to use the lowest possible power This is done using the Stop mode based on the configuration set in the mma9559 idle t fields and the mma9559 vars t events field If the mma9559 vars t events field is non zero then return This occurs if there are unhandled events that should be processed before entering Stop mode If the mma9559 idle t stop cfg field is negative then return This enables t
24. to mark any events that were signaled in the set events parameter were not set in the clear events parameter and are still active in the events field The mma9559 vars t events field is updated setting the events signaled in the set events parameter and marking the events in the clear events parameter If an event is set in both the set events and the clear events fields the event is signaled Any events that have been associated with FIFOs using mma9559 fifo init are masked indicating that they can only be signaled and cleared by the FIFO functions and cannot be modified by user code including this function The function performs the operations shown in the following example Example 4 11 set events amp mma9559_vars events_fifos Clear events amp mma9559 vars events fifos mma9559 vars events missed set events amp clear events amp mma9559 vars events mma9559 vars events set events clear events amp mma9559 vars events The mma9559 vars t events field may be modified in an exception handler which means it must not be modified in User mode This is because User mode cannot ensure an atomic transaction is not interrupted by an exception unless it is modified within a critical section that cannot be interrupted The mma9559 events set clear function runs with interrupts masked providing a safe way for user code to modify the events field without the risk of being interrupted by an exce
25. user offsets can be set using the mma9559 afe offsets set function Example 4 6 mma9559 afe data t trimmed afe data mma9559 afe trimmed sensor data get trimmed afe data data The trimmed sensor values are stored in the array of 16 bit signed integers in the order e Accelerometer X axis e Accelerometer Y axis e Accelerometer Z axis Temperature e External input The temperature and external input values remain unchanged if the AFE_CSR is not configured to measure them using the fourth ADC channel NOTE The user must ensure that the supplied data structure is large enough to hold the values from all of the axis sensors The number of axis sensors is set in the NUM SENSOR AXIS definition See also void mma9559 afe offsets set int16 data ptr e mma9559 afe data t e Analog Front End AFE on page 15 Parameter trim ptr Address to store the trimmed AFE sensor data values MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 51 4 2 4 7 void mma9559 afe csr set afe csr options t options This function configures the AFE Analog Front End by setting the AFE CSR Control and Status Register contents The AFE CSR is not directly accessible in User mode so this function enables it to be set by the user The function also preserves some fixed configuration settings The AFE CSR controls three parameters of the AFE operation Grange selec
26. 2 bytes giving a total of 112 bytes supervisor stack usage Waking up from idle sleep mode to handle an exception and then getting an IRQ INT exception The mma9559_idle function uses 8 bytes of stack space the Freescale portion of the exception handler uses 36 bytes and the INT IRQ handler uses 12 bytes for a total of 56 bytes Additional stack space will be used by functions called in the user exception handler There are 128 bytes available and 56 bytes already have been used with 72 bytes of supervisor stack space remaining Since the user exception handler runs on the user stack it is only necessary to count Freescale firmware functions This enables any Freescale function exceptmma9559 device info get to be safely called from within the exception handler Being in a user trap function and then getting an IRQ INT exception A user trap function consumes 20 bytes of supervisor stack space and the INT IRQ exception handler takes 12 bytes for a total of 32 bytes that leaves 96 bytes available for calling Freescale firmware functions or other user trap calls This enables any Freescale function except mma9559 device info get to be safely called from within the user trap handler If the user trap handler calls other user trap handler functions or is recursive an additional 20 bytes of stack space is used for each instance MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Fr
27. 4 int mma9559 events find next events t events int current event 65 4 3 4 5 void mma9559 idle use stop config idle config t config idle bits t bits 66 4 3 4 6 void mma9559_idle void on eR Rm Ban bana dde Ra 67 4 3 4 7 int mma9559 interrupts disable void ii 68 4 3 4 8 void mma9559 interrupts restore int status aan 69 4 3 4 9 int mma9559 user trapO int dO int d1 int d2 void a0 void a1 70 4 3 4 10 int mma9559 user trap 1 int dO int d1 int d2 void a0 void a1 71 4 3 4 11 int mma9559 user trap2 int dO int d1 int d2 void a0 void a1 72 4 3 4 12 int mma9559 user trap3 int dO int d1 int d2 void a0 void a1 73 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc Section Number Title Page 4 4 1 1 define FIFO STRUCT max entries bytes per entry struct uint32 rs vd 2 uint8 data max entries bytes per entry 74 SE DS SN 11d vd SH ESTA hikkii PRU EU ed o en OOS 15 4 4 2 1 mma9559 MO Un ohn kas dw de ER OR REX OR donor WR KR RRR ERS EES T5 A3 FUNCIO iis she ded anna ana a a a nee dg dd d d 76 4 4 3 1 int mma9559 fifo init volatile mma9559_fifo_t fifo ptr events t events unsigned int max entries unsigned int bytes per entry 76 4 4 3 2 void mma9559 fifo reset volatile mma9559 fifo t fifo ptr 78 4 4 3 3 int mma9559 fifo pop volatile mma9559 fifo t fifo
28. 84 bytes of its 2 KB of RAM 2 2 1 Flash memory The MMA9559L has 16 KB of flash memory located at the address range 0x0000 0000 to 0x0000 3FFF The flash space is assigned as shown in the following table Table 2 1 Firmware flash usage Flash Region Size bytes Usage 0x0000 0000 to 0x0000_07FF 2048 Freescale primary firmware including the exception table 0x0000 0800 to 0x0000 0803 4 User firmware startup vector Contains the address of the user firmware startup code to execute 0x0000 0804 to 0x0000 3FFB 14328 User firmware image 0x0000 3FFC to 0x0000 3FFF 4 Optional Cyclic Redundancy Check CRC and default Flash Options Register FOPT value The startup vector stored at 0x800 is used to locate the startup function in the user firmware If this vector is not OXFFFF FFFF the Freescale firmware jumps to it after the firmware initialization is complete This vector is normally set in the vector table entry in the user project exceptions c 2 2 2 RAM The MMA9559L has 2 KB of RAM located at the address range 0x0080 0000 to 0x0080 07FF This space is assigned as shown in the following table Table 2 2 Firmware RAM usage RAM Region Size bytes Usage 0x0080 0000 to 0x0080 OOFF 256 Variables for ROM code trim and Freescale firmware 0x0080 0100 to 0x0080 077F 1664 Space for user firmware variables heap and user stack 0x0080 0780 to 0x0080 07FF 128 Supervisor stack
29. 9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 92 Freescale Semiconductor Inc Appendix A Revision History This appendix describes corrections to the MMA9559L Intelligent Motion Sensing Platform Software Reference Manual For convenience the corrections are grouped by revision A 1 Changes Between Revisions 0 and 0 1 Rev 0 of this document was published on Feb 1 2012 Table A 1 Changes Between Revisions 0 and 0 1 Chapter Description Chapter 2 Firmware In Table 2 1 Firmware flash usage for flash region 0x0000 0804 to 0x0000_3FFB Overview corrected the size to 14328 was 14332 which is wrong Mar 8 2012 Fixed a typo in Section 2 5 4 Pop data off the FIFO changed Since the FIFO push operation is performed to Since the FIFO pop operation is performed MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 93
30. A9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 84 Freescale Semiconductor Inc 4 5 2 2 union rmf return t This returns a value from the ROM command accessible as a value or a pointer ROM commands return a single value that can be either a pointer or a value depending on which function was called The mma9559 rom command function returns a pointer that can be assigned to the ptr field in the union and handled by user code as either a pointer or a value depending on which ROM command was executed See also e void mma9559 rom command rmf func t func id void addr Fields Table 4 22 union rmf return t fields Field Description void ptr Return value handled as a pointer unsigned long val Return value handled as an integer MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 85 4 5 3 Functions 4 5 3 1 void mma9559 boot options set boot options t option Sets the execution path for the next non POR reset This function enables the execution path on the next reset other than a power on reset to be configured to run either the ROM command interpreter or to execute the user firmware in flash When the device first powers up the boot mode is loaded with the FOPT settings from the flash location at Ox3FFE This is set in the flash code image On subsequent resets the FOPT settings are not reloaded from
31. CSR C4MODE EXT Uses the ADC s fourth channel to measure the external inputs e AFE conversion mode Sets the number of bits for the AFE conversion AFE CSR CMODE 10BIT Performs a 10 bit ADC conversion so the 6 LSBs is be 0 AFE CSR CMODE 12BIT Performs a 12 bit ADC conversion so the 4 LSBs is be 0 AFE CSR CMODE 14BIT Performs a 14 bit ADC conversion so the 2 LSBs is be 0 AFE CSR CMODE 16BIT Performs a 16 bit ADC conversion using all 16 data bits For example to configure the AFE to capture 10 bits of data in the 2g range ignoring the fourth ADC channel the code in the following example would be used Example 2 1 Configure the AFE Control and Status Register mma9559 afe csr set afe csr options t AFE CSR GRANGE 2G Use 2 g range AFE CSR CAMODE NONE Measure X Y Z channels only AFE CSR CMODE 10BIT Use 10 bit conversion The current AFE configuration can be read using the mma9559 afe csr get function The AFE conversion is started by calling the mma9559 afe conversion start function This is normally called within the user exception handler when a Start of Frame exception occurs but the function can be called from anywhere in user code When the AFE completes the AFE sample it creates a Conversion Complete exception The user exception handler canrespond to this exception by enabling a sequence of operations to use the AFE data Normally this se
32. E 0o ce he mina cede Ca boa E 3 Maa Gan BD Bok Ds MO A dr Ba We 10 Chapter 2 Firmware Overview 2 1 Firmware elements and functionality ii 11 22 Memory and CPU IUSSI sad sin ee io wiae bank ea ea Kena beban al Ad seus 12 ERI Peels ose id obe E d oed ha a daa a dd dau di ieee D acudir eA Gea 12 222 RAN Louie sit aea Aa rin ad araa B alaa a d d E doe dre ara i at aa d ae didi d it d 12 2 2 3 Supervis r Stak USAGE eiusd ado ead KKR KAN bo Kak Kh OEE e de 13 mg Maono SUDO 14 eli TR RO B EP d ede a EID LC Ke del dl d OR FUA 14 2 3 1 Frame interval counter ado ow ia ER Ba PEN ol E Qe A Je eei 14 ros ANIG RON ENG APE Luonazsez ausa na dA dad LEES eh iban naa Sh 15 2 0 DO MOS CONG acarieni a h dik an ai i iae laia di DL ERR dE d bis 17 24 Events and Senet ck eee dad ce Baws ee E RE QE uS Kenakan Un ERE EE 18 BRI BINE eid cde En Additis d d dide hh Le ee Tan RB Oa 18 24 2 DNE yay hace ack See boa dod ut ae ee RERO RII dict as he ERREUR dE 21 2 4 3 Interrupts and critical sections ke pawn ed REK BW DIO RE RR PO eee 22 ES PEEL Lacon bon sana ee bone rca see b hi qol A Rim e dicta aos di e od 24 Z5 In Pbi bento one koe ana ena me 942 UA naa d du dx dd 25 2985 INNES FIPS occdd sasa teen eh on eh ae AB Lea Cu sedan seaeda 25 2 5 3 Push data onto the FIFO 1514423 40 A REN ACRI IS iiaeie t RR AC ee 26 254 PUR CAA DD PIFO uua quick ha Rd bd HORE ee bh ER ed OR d o 27 2 5 59 Resetihe ae Reba epu ded de eade edem d a oed o RR RRO 27 EOD Oh
33. FO being emptied Example 4 19 ret mma9559 fifo pop mma9559 fifo t amp fifol pointer to the FIFO structure uint8 afe data data pointer to the start of the destination buffer 1 the number of data entries to retrieve If the FIFO has not been successfully initialized with the mma9559 fifo init function no data is read from the FIFO and the return value is 0 NOTE The buffer addressed by the data ptr parameter must be large enough to hold the number of bytes being popped This value must be greater than or equal to the entries parameter multiplied by the number of bytes per entry set when the FIFO was initialized This function does not check the size of the data buffer Return The actual number of entries that were popped off the FIFO and copied to the data pointer Parameters Table 4 17 int mma9559 fifo pop parameters Field Description fifo ptr Address of the FIFO data structure to obtain data data ptr Address of the structure to store the popped data entries Number of entries to pop off the FIFO MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 79 4 4 3 4 int mma9559 fifo push volatile mma9559 fifo t fifo ptr uint8 data ptr unsigned int entries This function copies the requested number of entries from the memory starting at the supplied data pointer into the FIFO If the FIFO does not hav
34. MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Devices Supported MMA9559L Document Number MMA9559LSWRM Rev 0 1 03 2012 e SRY o z 600 freescale e Xtrinsic Energy a Efficient Solutions by Freescale How to Reach Us Home Page www freescale com Web Support http www freescale com support USA Europe or Locations Not Listed Freescale Semiconductor Inc Technical Information Center EL516 2100 East Elliot Road Tempe Arizona 85284 1 800 521 6274 or 1 480 768 2130 www freescale com support Europe Middle East and Africa Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen Germany 44 1296 380 456 English 46 8 52200080 English 49 89 92103 559 German 33 1 69 35 48 48 French www freescale com support Japan Freescale Semiconductor Japan Ltd Headquarters ARCO Tower 15F 1 8 1 Shimo Meguro Meguro ku Tokyo 153 0064 Japan 0120 191014 or 81 3 5437 9125 support japan freescale com Asia Pacific Freescale Semiconductor China Ltd Exchange Building 23F No 118 Jianguo Road Chaoyang District Beijing 100022 China 86 10 5879 8000 support asia freescale com For Literature Requests Only Freescale Semiconductor Literature Distribution Center 1 800 441 2447 or 1 303 675 2140 Fax 1 303 675 2150 LDCForFreescaleSemiconductor hibbertgroup com Information in this document is provided solely to
35. Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 37 case EVENT SLAVE PORT Slave Port Maibox write if sp writes amp 0x01 ues add user code here break mma9559 events set clear 0 EVENT BITFIELD event clear event else mma9559_idle if there are no outstanding events then go to sleep yi MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 38 Freescale Semiconductor Inc Chapter 4 Functional Details This chapter provides the details for the following functional categories and special topics 4 1 Memory and CPU usage Hardware support Events and scheduling FIFOs Other functions TIR filter Memory and CPU usage This section documents the resources used by each of the MMA9559L Freescale firmware functions in terms of Supervisor Stack Space RAM and CPU cycles and time In examining the firmware s use of memory and the CPU there are three scenarios to consider When in a Freescale firmware function all interrupts are disabled except for the INT IRQ interrupt The supervisor stack usage for each of the Freescale functions is shown in the Supervisor stack usage on page 13 The total stack usage could also include an additional 12 bytes for the IRQ INT interrupt as the worst case usage in this scenario is mma9559 device get info 100 bytes plus the IRQ handler 1
36. Platform Software Reference Manual Rev 0 1 32 Freescale Semiconductor Inc The INT IRQ pin is a non maskable interrupt In order to prevent it from preempting already running exception processing that exceeds the supervisor stack space the pin is handled by a thin handler The handler disables the IRQ interrupt and signals a Level 5 software interrupt that is maskable The user trap handler has to acknowledge clear the software interrupt and re enable the INT IRQ pin interrupt Example 3 2 User Exception Handler function declaration declspec register abi int vector User Exception Handl events t user exception handler ler function definition example This function is called in User mode with interrupts disabled masked declspec register abi int vector events t events 0 switch vector case case case case case case case VectorNumber_VL5swi INTC_CFRC 0x3A IRQSC IRQACK 1 IROSC IROIE 1 break VectorNumber Vtpmlovf TPMSC TOF 0 break VectorNumber Vtpmlch0 TPMCOSC CHOF 0 break VectorNumber Vtpmichl TPMC1SC_CHIF 0 break VectorNumber_Vmtim MTIM16SC TOF 0 break VectorNumber_Vpdb_a PDB_SCR_SA 1 break VectorNumber_Vpdb_b PDB_SCR_SB 1 break events_t user_exception_handler e
37. a get 24 88 11 mma9559 afe raw sensor data trim 52 210 26 mma9559 afe trimmed sensor data get 52 218 27 mma9559 boot options set 24 79 10 mma9559 device info get 100 718 90 mma9559 events find first 0 8 1 mma9559 events find next 0 65 8 mma9559 events set clear 24 103 13 mma9559 fifo entries free 0 39 5 mma9559 fifo entries used 0 16 2 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 40 Freescale Semiconductor Inc Table 4 1 Firmware s use of RAM and CPU Continued Function Runs CFU cycles Time ps bytes approximately us mma9559 fifo init 24 106 13 mma9559 fifo pop 40 145 E 12 6 B mma9559 fifo push 3 40 134 E 22 6 B mma9559 fifo reset 24 103 13 mma9559 framerate set 28 105 13 mma9559 idle 8 34 4 mma9559 idle use stop config 24 87 11 mma9559 iir filter order Oo 40 143 9 O mma9559 interrupts disable 12 44 6 mma9559 interrupts restore 12 46 6 mma9559 rom command RMF DEV INFO 0 68 515 64 mma9559 user trapO 20 101 13 mma9559 vars addr get 24 76 10 1 Ez The number of entries that are being transferred B The size of each entry in bytes O The order of the filter The CPU time may be calculated for the blank cells by calculating the number of CPU cycles and dividing by 8 The CPU usage of the mma9559_fifo_pop andmma9559 fif
38. a single function call This function trims previously read semi trimmed sensor values that were read using the mma9559 afe raw sensor data get function and optionally pre processed The trim processing is identical to the mma9559 afe trimmed sensor data get function Example 4 5 mma9559 afe data t raw afe data mma9559 afe data t trimmed afe data mma9559 afe raw sensor data trim trimmed afe data data raw afe data data NOTE The user must ensure that the supplied data structure is large enough to hold the values from all of the axis sensors The number of axis sensors is set in the NUM SENSOR AXIS definition See also void mma9559 afe raw sensor data get int16 data ptr e mma9559 afe data t Analog Front End AFE on page 15 Parameters trim ptr Address to store the trimmed AFE sensor data values data ptr Address of the raw AFE sensor data to be trimmed MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 50 Freescale Semiconductor Inc 4 2 4 6 void mma9559 afe trimmed sensor data get int16 trim ptr This function reads the data from the AFE sensor hardware registers and applies the trim calculations to provide the accurate values The accelerometer sensor values are corrected for gain and offset using device specific trim values User specified offsets are also applied to account for offsets caused by board mounting during the assembly process The
39. assignable idle configuration bit IDLE BITS USER 9 User assignable idle configuration bit IDLE BITS USER 10 User assignable idle configuration bit IDLE BITS USER 11 User assignable idle configuration bit IDLE BITS USER 12 User assignable idle configuration bit IDLE BITS USER 13 User assignable idle configuration bit IDLE BITS USER 14 User assignable idle configuration bit IDLE BITS USER 15 User assignable idle configuration bit MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 59 4 3 3 Data structures This section describes the data structures used in the events and scheduling functional category 4 3 3 1 mma9559 idle t This structure holds the configuration variables that control the operation of the device when the mma9559 idle function is called The use of this structure is described in the mma9559 idle function The use stop fc and use stop sc fields can be modified inside the user exception handler function While these fields can be read anywhere any code that modifies them should only be executed when interrupts are disabled This can be achieved in three ways e Within the user exception handler Or user trap handler functions e When interrupts are disabled using the interrupts disable function Using the mma9559 idle use stop config function See also void mma9559 i
40. break default break return events signal events to run in the main execution loop MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 34 Freescale Semiconductor Inc 3 3 User trap handler Although most firmware developers do not need to use these capabilities the user firmware may optionally create up to four user trap handlers The trap handlers can be called by any of the supplied functions mma9559 user trapO mma9559 user trapl e mma9559 user trap2 mma9559 user trap3 Alternatively the trap call can be issued directly using the following assembly trap instructions asm trap TRAP_USER_O asm trap TRAP_USER_1 asm trap TRAP USER 2 asm trap TRAP_USER_3 When issuing a trap call directly with an assembly instruction the user code is responsible for setting the required values in the registers The MMA9559L firmware handles the trap exception masks the interrupts switches to User mode with interrupts still masked and calls the appropriate user trap handler When the user trap handler function completes control returns to the MMA9559L firmware The firmware leaves the return value in the DO register and restores the Program Counter and Status Register to their previous state before the trap call The firmware does not save and restore the volatile registers because the trap call is treated as a function call The compiler takes care
41. ception handler Or user trap handler functions e When interrupts are disabled using the interrupts disable function e Using the mma9559 idle use stop config function The user exception handler and user trap handler fields can be loaded with the addresses of the respective user functions if they are present If no handlers are present they are set to 0 See also e void mma9559 idle void e mma9559 vars t mma9559 vars addr get void e events t mma9559 events set clear events t set events events t clear events Fields Table 4 7 mma9559 idle t fields Field Description volatile events t events Currently signaled events See Events and scheduling on page 56 volatile events t Events that were signaled before they had been cleared from the previous time that they had events missed been signaled See Events and scheduling on page 56 events t events fifos Events that are associated with FIFOs should not be modified by user code See FIFOs on page 74 uint16 afe cm gain AFE trim configuration Do not modify uint8 afe fs shift AFE trim configuration Do not modify mma9559 idle t idle Idle stop mode configuration See mma9559 idle t on page 60 user exception handler t Address of the user exception handler user exception handler user trap handler t Addresses of the user trap handlers These are optional but should be set prior to issuing the user trap handler 4 associated trap call
42. configuration bit reserved for Freescale use IDLE BITS RSVD 7 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 8 Idle configuration bit reserved for Freescale use IDLE_BITS_RSVD_9 Idle configuration bit reserved for Freescale use IDLE_BITS_RSVD_10 Idle configuration bit reserved for Freescale use IDLE_BITS_RSVD_11 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 12 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 13 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 14 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 15 Idle configuration bit reserved for Freescale use IDLE BITS USER 0 User assignable idle configuration bit IDLE BITS USER 1 User assignable idle configuration bit MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 58 Freescale Semiconductor Inc Table 4 5 enum idle bits t enumerators Enumerator Description IDLE BITS USER 2 User assignable idle configuration bit IDLE BITS USER 3 User assignable idle configuration bit IDLE BITS USER 4 User assignable idle configuration bit IDLE BITS USER 5 User assignable idle configuration bit IDLE BITS USER 6 User assignable idle configuration bit IDLE BITS USER 7 User assignable idle configuration bit IDLE BITS USER 8 User
43. considers the events field and if any event bits are still signaled set when the mma9559 idle function is called it returns immediately to allow the events to be processed The function only enters a CPU Stop mode to save power when the mma9559 vars t events field is 0 When an exception occurs the MMA9559L wakes up from STOP mode and runs the exception handler The mma9559 idle function then returns back to the scheduling loop in the main function The mma9559 idle use stop config function can be used by user code to adjust the lowest permissible power state when required by hardware For more details see Power on page 28 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 19 The discussed commands can be combined in a simple execution loop within the main function as shown in the following example Example 2 5 events t events int event 0 Initialization to set up the Freescale firmware data structure Loop forever processing events while 1 retrieve the bitfield of active events events mma9559 vars ptr events if events if there are any active events select the next event to process with priority scheduling or use mma9559 events find next for round robin scheduling event mma9559 events find first events priority scheduling switch event insert code to respond to each of th vents her
44. could create a situation where personal injury or death may occur Should Buyer purchase or use Freescale Semiconductor products for any such unintended or unauthorized application Buyer shall indemnify and hold Freescale Semiconductor and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claim alleges that Freescale Semiconductor was negligent regarding the design or manufacture of the part Freescale the Freescale logo CodeWarrior ColdFire and the Energy Efficient Solutions logo are trademarks of Freescale Semiconductor Inc Reg U S Pat amp Tm Off Xtrinsic is a trademark of Freescale Semiconductor Inc All other product or service names are the property of their respective owners 2012 Freescale Semiconductor Inc All rights reserved Ww Z freescale Contents Chapter 1 About this Document 1 1 Overview Quos sumado doppi dm OM hawa aa d d ic eben ohm ana any dh ab dio d o di 7 Tc S Mur 7 LLS BUG fo ies oa ede Sob ADA 2 Rad RE Baud book be KAB bdo 7 ele Document SUCUT sd brik cass 65 pnd i EM KEKE EN e ed pde e ie 7 he TOMUS NI BODIES ekien ba dad do eC Od eda pol dn etd 8 Pu MAN EN ANE oy nd dcr dps aed dir DE ede EO CF ERR AULA Te doi E di ee APER bi 9 E
45. cs indicate variable command parameters Book titles also are italicized Prefix of 0x to denote a hexadecimal number Suffix of b to denote a binary number Abbreviations for registers are shown in uppercase Specific bits fields or ranges appear in brackets For example RAMBARIBA identifies the base address field in the RAM base address register A 4 bit data unit An 8 bit data unit A 16 bit data unit A 32 bit data unit In some contexts such as signal encodings x indicates a do not care Used to express an undefined numerical value NOT logical operator AND logical operator OR logical operator Field concatenation operator Indicates that a signal is active low MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 1 4 References 1 MMA955xL Intelligent Motion Sensing Hardware Reference Manual MMA955xLRM also see the MMA955xL documentation webpage 2 The P C Bus Specification Version 2 1 January 2000 Philips Semiconductors 3 PC Bus Specification and User Manual NXP Semiconductors Document UM10204 Rev 03 19 June 2007 4 ColdFire Family Programmer s Reference Manual CFPRM Rev 3 03 2005 Freescale Semiconductor Inc 5 IIR Filter application note AN4464 Digital Filtering with MMA955xL MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc Chapter 2 Firmware Overvie
46. de Example Provides sample code that can be used as a template for creating user code e Functional Details Gives the technical details of the firmware s macros enumerations data structures and functions MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 7 1 2 Terms and acronyms AFE Analog Front End API Application Programming Interface CC Command Complete CI Command Interpreter CMD Command COCO Conversion Complete CRC Cyclic Redundancy Check DFC Data Format Code EVM Evaluation Module FIFO First In First Out Data structure FOPT Flash Options Register GPIO General Purpose Input Output IIR Infinite Impulse Response MBOX Mailbox MCU Microcontroller MTIM Modulo Timer Module PDB Program Delay Block RCSR Reset Control and Status Register SFD Start Frame Digital TPM Timer Program Module MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 8 Freescale Semiconductor Inc 1 3 Conventions This document uses the following notational conventions cleared set MNEMONICS mnemonics italics 0x0 Ob REG FIELD nibble byte word longword X n I OVERLINE When a bit takes the value 0 it is said to be cleared when it takes a value of 1 it is said to be set In text instruction mnemonics are shown in uppercase In code and tables instruction mnemonics are shown in lowercase Itali
47. dically to take some action such as reading the AFE values The frame interval counter register is accessible in User mode but a function is provided to set the frame rate for two reasons The upper three bits of the CK OSCTRL register control other attributes of the oscillator and should be preserved when the frame rate is changed e In order for the frame interval counter to run the lowest power idle mode that can be used is Stop SC slow clock This is ensured by setting the IDLE BITS CKOSC bit in the idle mma9559 idle t use stop sc field While this field can be accessed by user code it should only be modified while interrupts are disabled either in the exception or trap handlers or when interrupts have been disabled If the frame rate is set to FRAMERATE NONE the IDLE BITS CKOSC bit in theidlemma9559 idle t use_stop_sc field is cleared to enable idle mode to drop to the lowest power Stop NC no clock mode If the frame rate is set to any other valid value the IDLE BITS CKOSC bit in the idle mma9559 idle t use stop sc field is set to prevent the idle mode from dropping below the Stop SC slow clock mode If the device enters the Stop NC state the frame interval counter does not run and cannot wake the device at the start of each frame See also e framerate t mma9559 framerate set framerate t rate Table 4 3 enum framerate t enumerators Enumerator Description FRAMERATE NONE The FIC
48. dle void void mma9559 idle use stop config idle config t config idle bits t bits Fields Table 4 6 mma9559 idle t fields Field Description int8 stop cfg Override the normal idle mode stop configuration based upon the value of this field stop cfg 0 do not use any Stop mode stop cfg 0 use the supplied value as the Stop mode stop cfg 0 use the use stop fc and use stop sc fields vuint32 use stop fc If this is non zero then STOP mode must use StopFC Fast Clock mode vuint32 use stop sc If this is non zero and use stop fc is zero then STOP mode must use StopSC Slow Clock mode MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 60 Freescale Semiconductor Inc 4 3 3 2 mma9559 vars t This structure holds all of the variables that are used by the Freescale firmware Most of these variables can be used by the user firmware to configure and control the operation of the Freescale firmware User code obtains the address of the data structure using the mma9559 vars addr get function The events and events missed fields can be read anywhere but since they can be updated by the Freescale exception handler function any code that modifies them should only be executed when interrupts are disabled These fields are described in Events on page 18 and FIFOs on page 74 Modifying the two fields can be achieved in three ways e Within the user ex
49. e 32 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 47 4 2 4 3 void mma9559 afe interrupt clear void This function resets the AFE conversion complete bit that is set on the completion of the ADC conversion It also clears the IDLE BITS AFE in the mma9559 idle t use stop fc As a result the mma9559 idle function is no longer forced to use StopFC fast clock during any idle time NOTE Since the Freescale exception handler already executes this functionality whenever an AFE conversion complete exception occurs users do not normally need to call this function unless they are operating with interrupts disabled MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 48 Freescale Semiconductor Inc 4 2 4 4 void mma9559 afe raw sensor data get int16 data ptr This function gets the raw semi trimmed data from the AFE sensors Normally the trimmed AFE sensor values are read using the mma9559 afe trimmed sensor data get function which reads the hardware registers and applies the trim calculations in a single function call This function copies the semi trimmed sensor values directly from the AFE hardware registers into the supplied data structure The raw sensor values can then be trimmed using the mma9559 afe raw sensor data trim function This can be useful in saving power when basic operations can be performed on the sens
50. e A7 registers to provide the stack pointer so that the MMA9559L firmware only permits a single level of interrupts to be processed eliminating the risk of reentrant code and a limit is placed on the amount of RAM required for the supervisor stack Interrupts are disabled when the device is in a critical section or executing an MMA9559L firmware function a user trap call or the exception handler However the INT pin is a non maskable interrupt that can always execute even when the interrupts are masked The INT pin uses a special lightweight interrupt handler that converts the non maskable INT interrupt to a maskable software interrupt But in doing so it consumes 12 bytes of stack space Usage of the supervisor stack space should be analyzed to ensure that it does not exceed the reserved space otherwise it starts to overwrite the user stack space and may corrupt the user program For details on the different operational scenarios and the amount of stack space used by each function see Memory and CPU usage on page 39 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 13 2 3 Hardware support User code can access the underlying functionality of the MMA955xL hardware but the MMA9559L also provides functions to fully enable some key hardware capabilities This section explains how these functions can be used For more details see Hardware support on page 42 2 3 1
51. e Reference Manual Rev 0 1 Freescale Semiconductor Inc 27 2 5 6 Other FIFO functions The following additional FIFO functions are provided by the firmware mma9559 fifo entries used Returns the number of data entries currently used in the FIFO mma9559 fifo entries free Returns the number of data entries currently unused in the FIFO 2 6 Power The MMA9559L device supports four major power modes listed below from highest to lowest e System clock running at full speed 8 MHz with the CPU running RunFastClock e System clock running at full speed 8 MHz with the CPU stopped StopFastClock System clock running at slow speed 62 5 kHz with the CPU stopped StopSlowClock e System clock and CPU stopped StopNoClock Ideally the device would always run in the lowest power mode StopNoClock but that is not feasible because of interactions with the hardware For instance e In order for the frame interval counter to run and wake the device up periodically the system clock must be running in either Fast or Slow Clock rates but cannot be stopped in the No Clock mode The AFE ADC requires the system clock to be running at full speed in order for the conversion to complete Once the ADC conversion is complete the clock rate may be reduced In order to accommodate dynamic changes of the stop mode clock rate the mma9559 idle t structure is used It contains two 32 bit fields use stop fc use stop sc Whene
52. e device MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 83 4 5 2 Data structures 4 5 2 1 mma9559 device info t This structure holds device information that is derived from a combination of the ROM device version information and firmware version information The device_id rom version and hw version values are retrieved from the ROM device information e The fw version build code part number reset cause and security state are reported by the MMA9559L firmware Fields Table 4 21 mma9559 device info t fields Field Description uint32 device id ROM Pseudo random part identification value uint16 rom version ROM ROM version code major minor uint16 fw version FW Firmware version code major minor uint16 hw version ROM Hardware version code major minor uint16 build code FW Firmware build number and date code The value is encoded in the following bit fields 15 12 Daily build number 0 to 15 11 8 Build month 1 to 12 7 3 Build day 1 to 31 2 0 Build year 2010 to 2017 uint16 part number FW BCD encoded part number For example 0x9559 uint8 reset cause FW Lower five bits from the RCSR reports reset source uint8 secure mode FW Lower two bits of FOPT report the security mode of the device Values 2 secure Otherwise not secure MM
53. e enough space empty FIFO entries to store the requested number of entries then only the number of entries fitting within that space are copied The events associated with the FIFO are signaled every time this function is called regardless of the number of entries that are pushed into the FIFO If the number of entries to be pushed into the FIFO exceeds the space in the FIFO the FIFO overflows The entries that do not fit are not stored in the FIFO and the events bit field associated with the FIFO are set in the mma9559 vars t events missed field The FIFO is not corrupted by attempting to push data into a full FIFO or to write data entries that exceed the available space However the excess data in both scenarios are not stored in the FIFO and are lost Example 4 20 ret mma9559 fifo push mma9559 fifo t amp fifol pointer to the FIFO structure uint8 afe data data pointer to the first byte of the first entry 1 the number of data entries to store If the FIFO has not been successfully initialized with the mma9559 fifo init function no data is read from the FIFO and the return value is 0 NOTE The buffer addressed by the data ptr parameter must contain the correct number of bytes to match the number of entries being pushed The parameter s value must be equal to the entries parameter multiplied by the number of bytes per entry set when the FIFO was initialized This function does not check the size o
54. e interrupt clear void 0 005 48 4 2 4 4 void mma9559 afe raw sensor data get int16 data ptr 49 4 2 4 5 void mma9559 afe raw sensor data trim int16 trim ptr int16 data ptr 50 4 2 4 6 void mma9559 afe trimmed sensor data get int16 trim ptr 51 4 2 4 7 void mma9559_afe_csr_set afe_csr_options_t options 52 4 2 4 8 afe csr options t mma9559_afe_csr_get void 53 4 2 4 9 void mma9559 afe offsets set int16 data ptr 54 4 2 4 10 void mma9559 afe offsets get int16 data ptr 55 4 3 Events and scheduling reese EI TT LT o LO TO LOT TT 56 SOT RENE vuole dade Sardis d asma d d ab kab dps qua meh ede cues 56 4 3 1 1 define EVENT BITFIELD b events_t 1 lt lt b 56 dk MMI ANN 1553449 22923 5 6455464 SEA da x dd NEEL eee eee 57 4 3 2 1 enum idle_config_t in ideo rhe ACC SER E D GR CU d RR RC n 57 4 3 2 2 enum idle_bits wim ane ccd nannaa naana annann 58 4 3 8 Data structures anana a ccc ee eens 60 2203 mma dE SNN NN NN ST ainkaan BAE kti 60 a Emo VAS T eriek d OU reaR E Aek e OE REC CROCO 61 ROT FUNCIONS rr 62 4 3 4 1 mma9559 vars t mma9559 vars addr get void 62 4 3 4 2 events t mma9559 events set clear events t set events events_t clear_events uiu ee ha mna aa acea RN DR Wek Den eee 63 4 3 4 3 int mma9559 events find first events t events 64 4 4 FIFOs 4 4 1 4 3 4
55. e interval counter is being used to wake the device periodically then the clock must remain running so either Stop Fast Clock or Stop Slow Clock modes must be used when stopping the CPU but not Stop No Clock in fast or slow mode To stop the CPU and determine which clock rate to use the mma9559 idle function can be called whenever there is no other software to run For more information on this usage see Events and scheduling on page 18 For a more detailed explanation of the clock s operation see Power on page 28 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 17 2 4 Events and scheduling While the MMA9559L firmware does not provide a task scheduler it does provide the main components that can be used to create a simple execution loop scheduler in the form of Events This section explains how these functions can be used For more details see Events and scheduling on page 56 2 4 1 Events The MMA9559L firmware supports up to 32 events each one represented by a single bit in the mma9559 vars tevents field Whenever an event is signaled activated the corresponding bit is set in the events field When the event is handled the bit is cleared The MMA9559L firmware does not use any of the event bits allowing the assignment of the 32 bits by the user firmware In this implementation the least significant bit of the events bit field corresponds to eve
56. e number of entries that were actually pushed onto the FIFO allowing user code to check that the requested data was stored correctly If the number of entries stored does not match the requested number of entries to push the FIFO overflows and the associated event bits are set in the mma9559 vars events missed field If the FIFO has not been successfully initialized the return value is always 0 No data is stored in the FIFO Example 2 11 ret mma9559 fifo push mma9559 fifo t amp fifol pointer to the FIFO structure uint8 raw data data pointer to the first byte of the first entry 1 the number of data entries to store MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 26 Freescale Semiconductor Inc Since the FIFO push operation is performed within the firmware with interrupts disabled it is an atomic transaction This ensures that multiple asynchronous processes can safely push data into the same FIFO without any risk of interruption or corruption 2 5 4 Pop data off the FIFO Data can be read from a FIFO after it has been successfully initialized Data is always read as an integer number of data entries and is copied byte by byte from the FIFO to the supplied data pointer Since the data entry size is already set when the FIFO was configured all that is needed is the number of data entries to be fetched Data can be read as single or multiple entries If the FIFO does not c
57. e to the lowest level because the clock to the FIC is disabled The power consumption will generally increase as the frame rate is increased When the frame interval is set to a frame rate of FRAMERATE NONE the Start of Frame exception does not occur to wake the device The device can be awakened by the mailbox or INT pin exceptions MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 14 Freescale Semiconductor Inc 2 3 2 Analog Front End AFE The hardware registers for the Analog Front End AFE cannot be directly accessed by user code They can be controlled and monitored through the functions provided in the Freescale firmware The AFE can be configured using the mma9559 afe csr set function that takes a single parameter which combines one of each of the three configurable aspects of the AFE by OR ing them together The three aspects and their configurable elements include e G mode range Selects the G range operating mode by selecting one of the following AFE CSR GRANGE 8G Sets the AFE to the 8g range AFE CSR GRANGE 4G Sets the AFE to the 4g range AFE CSR GRANGE 2G Sets the AFE to the 2g range e Fourth channel data source Selects the source of the data for the fourth channel of the AFE AFE CSR C4MODE NONE Does not measure anything with the ADC s fourth channel AFE CSR C4MODE TEMP Uses the ADC s fourth channel to measure the temperature sensor AFE
58. eescale Semiconductor Inc 39 4 1 1 Supervisor stack As described in Memory and CPU usage on page 12 the last section of RAM is reserved for the supervisor stack that is used whenever the firmware is running The user exception handler and the user trap handler functions are called from the Freescale firmware but are run in User mode using the user stack space rather than using the supervisor stack space Four other firmware functions do not use any supervisor stack space because they are in line functions that are expanded in the customer code and do not issue any trap call Those functions are e mma9559 events find first mma9559 events find next e mma9559 fifo entries free mma9559 fifo entries used Since the MMA9559L clocks at 8 MHz when the CPU is running the CPU time needed for the remaining functions can be estimated by dividing the CPU usage in cycles by eight The following table gives the memory space CPU cycles and time required for firmware functions Table 4 1 Firmware s use of RAM and CPU Supervisor CPU cycles 2 Function stack usage approximately Time ps bytes Exception Handler 36 115 14 mma9559 afe conversion start 24 77 10 mma9559 afe csr get 24 83 10 mma9559 afe csr set 40 217 27 mma9559 afe offsets get 24 78 10 mma9559 afe offsets set 24 78 10 mma9559 afe interrupt clear 24 80 10 mma9559 afe raw sensor dat
59. er RON ea Hem an Na aa d Rd e urna Eq anda IR Dua rbi Grid a 28 26 POW Aere 28 Chapter 3 User Code Example Bl PROUD edi ba T Re dee Re aa ae A ado anne La Mp ae eRe 31 3 2 Us rexceplion handlef ken ICD EC ROC RR a or d Rt o 32 3 3 LENS handiei a aor dro OR Jefe de en o eoe MR Oe eae Tek eet NAN EN PN eee d 35 a4 UE NOISE On alba IR dde drin diac d AR d d et Rd n dedo 6 a 06 UI o e Gd dn ax 37 Chapter 4 Functional Details 41 Memory and GPU Usage esros woo CROCO ode ol EEEREN dole Ge ead 39 4 1 1 Supervisor stack 0 ccc eee n 40 42 Hardware SOPO ain ice torancadecede ast 52 Rtas DEROER si eveebdeusaedeea 42 SUM PA bala cede eee ahhh bed oa Sk Sede Se Ades oo d dU dd Meee ing 42 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 3 Section Number Title Page 4 2 1 1 define NUM SENSOR AXIS 5 selle 42 222 EDU NEUE Li kanan erie Pol ba mann AN One Oo le EN DAS Ran hn ad ed 42 4 2 2 1 enum afe csi OPO E iud p kkn d en en WORK RR I i EGER RR CR EN 42 4 2 2 2 enum NAME Una Ce rad RO ee ewe dake ACRCRCCR UR Ie 44 ea CA 05 11 oo ph ee de Ka bd dd a SEEDED ORE OE de eR OES 45 4 2 3 1 mma9559_afe data Livcovisecteadeseddveddaticrinedevecthus 45 Aad FUNCIONS nuasuconwed vadit d ni web end AE a a d 46 4 2 4 1 framerate t mma9559_framerate_set framerate_t rate 46 4 2 4 2 void mma9559 afe conversion start void 22005 47 4 2 4 3 void mma9559 af
60. erence Manual Rev 0 1 54 Freescale Semiconductor Inc 4 2 4 10 void mma9559 afe offsets get int16 data ptr This function enables the user to read the current values of the three accelerometer user offset settings The offset values are in 8g mode with the hex value of 0x4000 corresponding to an offset of 1g Example 4 10 int16 offsets 3 X Y and Z offsets in 8 g mode mma9559 afe offsets get offsets NOTE The user must ensure that the supplied data structure is large enough to hold the values from all three of the accelerometer axes See also void mma9559 afe offsets set int16 data ptr Parameter data ptr Address containing the three accelerometer user offset values MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 55 4 3 Events and scheduling This functional category manages events and task scheduling The MMA9559L firmware creates events and provides a set of functions to manage them and use them to schedule tasks or activities These tasks or activities include 4 3 1 Signaling and clearing up to 32 events Selecting events using priority or round robin scheduling algorithms Providing configurable power saving idle control Disabling or restoring interrupts for critical sections Providing prototypes for user created exception and trap handler functions Macros 4 8 1 4 define EVENT BITFIELD b events t 1 b
61. es earlier e aN and bN are the filter coefficients that are fixed for a particular filter response In this implementation the input output and coefficient values are all 16 bit signed integers but the intermediate accumulation of the result uses a 32 bit accumulator that is right shifted at the end of the operation to normalize the result For more detailed information see the related IIR Filter applications note AN4464 Digital Filtering with MMAO955xL MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 89 4 6 1 Data structures 4 6 1 1 mma9559 coef t This structure is used to hold the coefficients for an IIR filter The methods of calculating the coefficients for the filter is beyond this reference manual but an sample low pass filter is shown in the following example to illustrate how the data structure is used Example 4 26 6th order Chebyshev type 2 lowpass filter cutoff at fs 4 static const mma9559 coef t lp cheby6 6 filter order 6 14 coefficient shift 1 16384 16384 441 a0 bO 1 000000 0 000244 a0 value not used 16546 1637 al bl 1 009888 0 099915 20052 3191 a2 b2 1 223877 0 194763 8837 3925 a3 b3 0 539368 0 239563 3957 3191 a4 b4 0 241516 0 194763 624 1637 a5 b5 0 038086 0 099915 78 441 a6 b6 0 004761 0 000244 hi See also e intl6 mma9559 iir
62. evice info t addr This function retrieves a combination of identification and version information from the ROM code and the MMA9559L device and copies it into the data structure at addr To avoid overflowing the supplied data buffer the caller must provide a length parameter that limits the number of bytes that are copied to the supplied data buffer as shown in the following example Example 4 24 mma9559 device info t device info storage to hold the returned device information device info length mma9559 device info get sizeof mma9559 device info t maximum number of bytes to read amp device info address of buffer to receive data NOTE This function uses a large amount of the supervisor stack space so it should never be called from within the user exception handler function or any user trap handler function Return Reports the number of bytes copied into the buffer which is the minimum of the length parameter and the length of the available device identification and version information Parameters Table 4 23 int mma9559 device info get parameters Field Description length Size of the receiving buffer in bytes addr Address of the buffer into which the device information is being copied MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 87 4 5 3 3 void mma9559 rom command rmf func t func id void add
63. f the data buffer Return The actual number of entries that were copied from the data pointer and pushed into the FIFO Parameters Table 4 18 int mma9559 fifo push parameters Field Description fifo ptr Address of the FIFO data structure data ptr Address of the structure from which the data is pushed entries Number of entries to push into the FIFO MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 80 Freescale Semiconductor Inc 4 4 3 5 int mma9559 fifo entries used volatile mma9559 fifo t fifo ptr This function returns the number of entries in the FIFO that currently contain valid data User code may pop this many entries off the FIFO without running out of data The FIFO may still contain data after this many reads because more data may be pushed onto the FIFO by interrupt handlers while the FIFO is being read The FIFO should not run out of data Example 4 21 used entries mma9559 fifo entries usedQ mma9559 fifo t amp fifol pointer to the FIFO structure Return The number of entries in the FIFO that currently contain data that can be popped off the FIFO Parameter fifo ptr Address of the FIFO data structure 4 4 3 6 int mma9559 fifo entries free volatile mma9559 fifo t fifo ptr This function returns the number of entries in the FIFO that currently are empty User code may push this many entries into the FIFO without running out of FIFO
64. he use of Stop modes to be disabled for debug purposes If the mma9559 idle t stop cfgfield is positive that value is loaded directly into the STOP CR register and a stop issued This enables testing of particular Stop configurations but should not generally be used If the mma9559 idle t stop cfg field is 0 and the mma9559 idle t use stop fc is non zero the device uses StopFC fast clock mode If the mma9559 idle t stop cfg and use stop fc fields are O and the mma9559 idle t use stop sc field is non zero the device uses StopSC slow clock mode If the mma9559 idle t stop cfg use stop fc anduse stop sc fields are all zero the device uses StopNC no clock mode the lowest power mode See also mma9559 idle t mma9559 vars t MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 67 4 3 4 7 int mma9559 interrupts disable void This function can be used to create critical sections in user firmware that is not interrupted by exceptions This implementation supports the use of nested critical sections accidentally or deliberately by enabling the user to record the interrupt level mask interrupts when they are disabled The interrupts are restored to their original value when the interrupts are restored The user exception handler anduser trap handler run with the interrupts disabled therefore these functions are not required for either of these handlers Any
65. ing Platform Software Reference Manual Rev 0 1 64 Freescale Semiconductor Inc 4 3 4 4 int mma9559 events find next events t events int current event The purpose of this function is to find the next active event for round robin scheduling This function may be used in conjunction with the Events and Scheduling functionality of the Freescale firmware to provide a basic scheduling capability for a user s execution loop This function returns the number of the next highest priority event bit that is set in the events field and a lower priority than the current event The priority is arranged such that the least significant bit LSB of the events parameter is the highest priority event which generates the return value 0 The most significant bit MSB of the events parameter is the lowest priority event which generates the return value 31 If there are no active priority bits lower than the current event the selection wraps around and the highest priority active event is returned Calling this function with a current event parameter of 32 or higher causes the function to return the highest priority active event Return The priority number of the next highest priority active task in the events bit field that is lower than the current event from 0 for the LSB to 31 for the MSB If there are no active priority bits the value 32 is returned Parameters Table 4 9 int mma9559 events find next parameters Parameter Descript
66. initializes the FIFO data structure The structure first must be defined using the FIFO STRUCT macro that creates a customized FIFO variable or data type At run time the FIFO structure must be initialized using this function Whenever data is pushed into the FIFO the events in the events field is signaled and the event is cleared when either the last data is popped off the FIFO leaving it empty or the FIFO is reset The events are also added to the mma9559_vars events fifos field which means they can be signaled or cleared by the user exception handler or the mma9559 events set clear function The max entries nd bytes per entry values both must be in the range of 1 to 255 If either value is out of this range the function returns a value of 1 and leaves the FIFO structure marked as unconfigured The following example Initializes fifol e Sets the FIFO size to the same values that were used in the FIFO data type maximum entries of 10 entry size of 2 bytes e Associates fifol with the EVENT FIFO event Example 4 17 Instantiate the FIFO to reserve the memory space FIFO STRUCT 2 sizeof mma9559 afe data t fifol At run time initialize the FIFO before using it ret mma9559 fifo init mma9559 fifo t amp fifol pointer to the FIFO structure EVENT BITFIELD EVENT FIFO bitfield of associated events 2 maximum number of data entries sizeof mma9559_afe_data_t number of by
67. ion events The events bit field to be searched for the next event current event The currently running priority level 0 to 31 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 65 4 3 4 5 void mma9559 idle use stop config idle config t config idle bits t bits This function enables the mma9559 idle t use stop fcanduse stop sc fields to be configured from user space The mma9559 idle t fields are modified directly by the Freescale exception handler and may also be modified by the user exception handler function To avoid modification of these fields from user space or corruption of the fields by an exception during processing the user code must use a critical section disabling then enabling interrupts or call this function Example 4 12 Set a use StopFastClock bit so that idle will use Stop Fast Clock mode mma9559 idle use stop config IDLE USE STOP FC SET Set bit s in the Use Stop Fast field IDLE BITS USER 0 Bits to be set When the hardware has finished running clear the bit to allow normal Stop mode operation mma9559 idle use stop config IDLE USE STOP FC CLEAR Clear bit s in the Use Stop Fast field IDLE BITS USER 0 Bits to be cleared These fields are used by the mma9559_idle function to determine which Stop mode to use when the device is idle to achieve
68. ion handler The user exception handler code is modified written by the user to perform the following functions e Clear the source or mask the interrupt that caused the exception e Optionally perform processing based on the interrupt This should be short to limit the interrupt latency e Do either of the following Ifthe user wants to use the scheduling capabilities described in Events and scheduling on page 18 Signal events by setting a return value that causes the execution of code in the main function loop If the user does not want to signal events Return 0 When the user exception handler function completes control returns to the MMA9559L firmware The firmware signals the events based on the return value from the user exception handler function restores the volatile registers and restores the Program Counter and Status Register to their previous states before the exception occurred NOTE Two of the interrupts sources operate differently from the other interrupt sources The vectorNumber Vconversion complete vector occurs on the completion of an AFE conversion and uniquely clears the interrupt source without requiring the user exception handler function to clear it The user exception handler function may still perform processing or signal events when this exception occurs but it does not need to clear the AFE conversion complete interrupt source MMA9559L Intelligent Motion Sensing
69. is disabled and does NOT wake up the MMA9559L periodically FRAMERATE 3906HZ Configures the FIC to run at 3906 Hz FRAMERATE 1953HZ Configures the FIC to run at 1953 Hz FRAMERATE 977HZ Configures the FIC to run at 977 Hz FRAMERATE 488HZ Configures the FIC to run at 488 Hz FRAMERATE 244HZ Configures the FIC to run at 244 Hz FRAMERATE 122HZ Configures the FIC to run at 122 Hz FRAMERATE 61HZ Configures the FIC to run at 61 Hz FRAMERATE 30HZ Configures the FIC to run at 30 5 Hz FRAMERATE 15HZ Configures the FIC to run at 15 3 Hz FRAMERATE 8HZ Configures the FIC to run at 7 6 Hz FRAMERATE 4HZ Configures the FIC to run at 3 8 Hz MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 44 Freescale Semiconductor Inc Table 4 3 enum framerate t enumerators Enumerator Description FRAMERATE 2HZ Configures the FIC to run at 1 9 Hz FRAMERATE 1HZ Configures the FIC to run at 0 95 Hz FRAMERATE_POINT5HZ Configures the FIC to run at 0 48 Hz FRAMERATE POINT2HZ Configures the FIC to run at 0 24 Hz 4 2 3 Data structure 4 2 3 1 mma9559 afe data t The mma9559 afe data t structure is used to contain a set of raw or trimmed AFE sensor data taken during a single AFE sample A 16 bit signed value is stored for each axis sensor where the number of axes sensors in each sample is defined in the NUM sENSOR AXIS macro See also e framerate t mma9559 framerate set framerate t rate Field
70. les Example 2 9 typedef FIFO STRUCT 10 2 fifo 20 t fifo 20 fifol fifo2 2 5 2 Initialize FIFO Once the FIFO data structure has been created through the definition of a FIFO variable the space for the FIFO structure has been reserved but the contents of the FIFO structure must be initialized before it is used Initialization of a FIFO occurs at runtime and performs the following steps Sets the events that are associated with the FIFO and reserves them in the mma9559_vars events fifos field It also clears the associated events in case any events were already signaled because the FIFO is now empty and contains no data Sets the maximum number of data entries that the FIFO can hold and the size of each data entry MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 25 Both values must be greater than 0 and less than 256 The product of the maximum number of entries and the size of each entry must be less than or equal to the size that was reserved when the FIFO variables was created Normally the values are the same as when the FIFO variable was created instantiated e Resets the internal variables so that the FIFO is empty From Example 2 9 on page 25 fifol may be initialized with the following code to set the FIFO size to the same values that were used in the FIFO data type maximum entries of 10 each entry is 2 bytes The following example shows
71. lue was invalid in which case the current frame rate setting in the frame interval counter is returned Parameter rate The frame rate setting for the frame interval counter frequency MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 46 Freescale Semiconductor Inc 4 2 4 2 void mma9559 afe conversion start void This function triggers the AFE to start an ADC conversion cycle The duration of the conversion depends on the AFE_CSR configuration When the conversion completes the VectorNumber Vconversion complete exception occurs and can be used by the user exception handler to start subsequent processing This function can be called from anywhere in user code but is usually called from within the user exception handler function when the Start of Frame interrupt is serviced to minimize the jitter on the AFE sampling Example 4 3 declspec register abi events t user exception handler int vector exception vector number case VectorNumber_Vstart_of_frame Start of Frame FCSR_SF 1 Clear interrupt source mma9559 afe conversion start Start a new AFE conversion break The function also sets the IDLE BITS AFE in the mma9559 idle t use stop fc field so that the mma9559 idle function uses StopFC fast clock during any idle time The ADC requires the system clock to run at full speed during the AFE conversion See also User exception handler on pag
72. ma9559_idle function to enter a low power sleep Example 3 4 void main void mma9559 afe data t afe data events t events i nt event nt frame ctr 0 PNG Get the address of the mma9559 variables structure mma9559 vars ptr mma9559 vars addr get Register th xception handler and any trap handlers mma9559 vars ptr user exception handler user exception handler mma9559 vars ptr user trap handler 0 user trap handler Setup the slave port mailboxes to generate an interrupt when written to SP SCR SP SCR amp SP SCR EN MASK SP SCR PS MASK SP SCR ACTIVE CSR MASK SP SCR STOP EN MASK SP SCR WIE MASK Configure the AFE and Frame Interval Counter mma9559 afe csr set afe csr options t AFE CSR GRANGE 8G Use AFE 8 g mode AFE CSR C4MODE NONE Do not use the 4th ADC channel AFE CSR CMODE 16BIT Use 16 bit ADC conversion mma9559 framerate set FRAMERATE POINT2HZ Set the frame rate to 1 5 Hz Loop forever processing events while 1 events mma9559 vars ptr events if events select the next event to process event mma9559 events find first events priority scheduling switch event case EVENT_AFE_DATA AFE Conversion Complete frame_ctrt t mma9559_afe_trimmed_sensor_data_get afe data data add user code here break MMA9559L Intelligent
73. never the FIFO contains data In order to easily identify which FIFO contains data it is best to use an event bit in only one FIFO That enables the appropriate FIFO to be uniquely identified by the event bit when the event is signaled If an event is associated with a FIFO by being set in the events field when the FIFO is initialized the event is added to themma9559 vars events fifos field That prevents the event from being signaled by the user exception handler code or modified by the ma9559 event set clear function The events missed field in the mma9559 vars t structure is used slightly differently for events that are associated with FIFOs In this case the events missed event bit is set whenever the FIFO overflows because it cannot store all of the data entries that are being pushed into it This situation indicates MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 24 Freescale Semiconductor Inc that the scheduler may be losing events because one or more FIFO samples were not stored on the FIFO although user code may make some accommodation for this The events missed field is never cleared by the Freescale firmware and may be used as a diagnostic to identify problems with the chosen FIFO size FIFOs are used with the following steps 1 Instantiate the FIFO variable to reserve the space for the FIFO structure 2 Initialize the FIFO at run time to configure it before it is used 3 Push
74. nt 0 which may be treated as the highest priority event The most significant bit of the event field corresponds to event 31 which may be treated as the lowest priority event The currently signaled active events can be read directly from the MMA9559L firmware mma9559 vars t data structure events field but it should not be modified except through the return value from the user exception handler or using the mma9559 events set clear function Events are normally signaled in the user exception handler which is created by the user and exists in the user firmware The easiest way to signal events is for the user exception handler to return an event bit field as the function return value where the corresponding bits have been set for the events that should be signaled With this the Freescale exception handler takes care of signaling the events MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 18 Freescale Semiconductor Inc This methodology enables the user exception handler to complete its work quickly keeping the interrupt duration short A simple user exception handler is shown in the following example Example 2 4 declspec register abi events t user exception handler int vector exception vector number events_t events 0 Events to be signaled defaults to none switch vector case VectorNumber_Vstart_of_frame Start of Frame
75. o push functions depends on the number of entries that are being transferred E and the size of each entry in bytes B Once the number of cycles has been calculated the CPU time can be determined by dividing by 8 The CPU usage of themma9559 iir filter function depends on the order O of the filter Once the number of cycles has been calculated the CPU time can be determined by dividing by 8 The CPU time for the mma9559 rom command function depends on which of its ROM functions are being executed The stack usage is fixed however because the ROM functions do not use stack space The ROM Device Info function was used for the measurement of the CPU cycles and time in Table 4 1 W N MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 4 2 Hardware support Enables user code to access key hardware functionality of the MMA955xL device The MMA9559L Freescale firmware provides a set of functions that enable access to key areas of functionality in the MMA955xL hardware These areas include e Frame Interval Counter FIC Creates a periodic interval timer e Analog Front End AFE Configures and reads the sensor hardware values 4 2 1 Macros 4 2 1 1 define NUM SENSOR AXIS 5 Specifies the total number of axes sensors in the AFE Analog Front End These include e Accelerometer X Y and Z Temperature e External input 4 2 2 Enumerations 4 2 2 1 enum afe_csr_o
76. ompleted and the event bit cleared MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 20 Freescale Semiconductor Inc The events missed field is never cleared by the Freescale firmware and may be used as a diagnostic to identify problems with the scheduling of event processing The events missed field has a slightly different operation when associated with FIFOs See FIFOs on page 24 2 4 2 Initialization The user firmware must perform some initialization steps to configure the MMA9559L firmware before the user exception handler can run or events can be used The initialization steps are 1 Retrieve the address of the MMA9559L Freescale firmware data structure This structure is needed in order to read the currently signaled events and to set the pointers to the user handler functions The address does not change at run time and it only needs to be read once 2 Set the pointer to the user exception handler function This must be done before any exceptions are enabled or the firmware may end up trapped in the exception handler because the exception cause is not being cleared 3 Optionally set the pointer to the user trap handler functions This is only required if user trap functions are being used and the pointer should be set before the user trap is called If a user trap is called before the pointer is initialized the trap call function just returns but the system does not lock u
77. on Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 57 4 3 2 2 This value may be used individually or combined by the mma9559 idle use stop config function to set how the bit field is used to modify the idle mode operation Bits can be individually set to separate tasks allowing tasks to modify the idle mode configuration without overwriting the configuration set by other tasks or activities enum idle bits t These bit fields also can be used to directly modify the idle config t fields within the user exception handler function The fields also can be used whenever interrupts are disabled e The first 16 idle bits are reserved for Freescale use and should not be used by user code e The second set of 16 bits are available for user code See also void mma9559 idle use stop config idle config t config idle bits t bits Enumerators Table 4 5 enum idle bits t enumerators Enumerator Description IDLE BITS CKOSC Sets the idle configuration for the FIC Frame Interval Counter IDLE BITS AFE Sets the idle configuration for the AFE Analog Front End IDLE BITS RSVD 2 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 3 Idle configuration bit reserved for Freescale use IDLE BITS RSVD 4 Idle configuration bit reserved for Freescale use IDLE_BITS_RSVD_5 Idle configuration bit reserved for Freescale use IDLE_BITS_RSVD_6 Idle
78. ontain enough valid data entries to store the data the pop operation is limited to the number of non empty entries in the FIFO The mma9559 fifo pop function returns the number of entries that were actually popped off the FIFO allowing user code to check that the requested data was retrieved correctly If the number of entries read does not match the requested number of entries to pop the FIFO underflows If the FIFO has not been successfully initialized the return value is always 0 and no data is read from the FIFO Example 2 12 ret mma9559 fifo pop mma9559 fifo t amp fifol pointer to the FIFO structure uint8 raw data data pointer to the start of the destination buffer 1 the number of data entries to retrieve Since the FIFO pop operation is performed within the firmware with interrupts disabled it is an atomic transaction This ensures that multiple asynchronous processes can safely pop data off the same FIFO without any risk of interruption or corruption 2 5 5 Reset the FIFO A FIFO can be returned to an empty state discarding its contents and resetting the associated events using the mma9559 fifo reset function This is useful for quickly discarding the contents of a FIFO without having to read all of the data entries Example 2 13 ret mma9559 fifo reset mma9559 fifo t amp fifol pointer to the FIFO structure to reset yi MMA9559L Intelligent Motion Sensing Platform Softwar
79. or data such as decimation prior to applying the trim calculations Example 4 4 mma9559 afe data t raw afe data mma9559 afe raw sensor data get raw afe data data The raw sensor values are stored in the array of 16 bit signed integers in the order e Accelerometer X axis e Accelerometer Y axis e Accelerometer Z axis Temperature e External input The Temperature and External input values do not change if the AFE CSR is not configured to measure them using the fourth ADC channel NOTE The user must ensure that the supplied data structure is large enough to hold the values from all of the axis sensors The number of axes sensors is set in the NUM SENSOR AXIS definition See also void mma9559 afe trimmed sensor data get int16 trim ptr void mma9559 afe raw sensor data trim int16 trim ptr int16 data ptr e mma9559 afe data t e Analog Front End AFE on page 15 Parameter data ptr Address to store the raw AFE sensor data values MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 49 4 2 4 5 void mma9559 afe raw sensor data trim int16 trim ptr int16 data ptr This function trims the supplied raw AFE sensor data to produce trimmed AFE sensor values Normally the trimmed AFE sensor values are read using the mma9559 afe trimmed sensor data get function which reads the hardware registers and applies the trim calculations in
80. p MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 21 This initialization normally occurs at the beginning of the user main function The pointer to Freescale firmware data structure can be a global variable to avoid retrieving it multiple times The following example gives initialization code Example 2 6 void main void Instantiate local variables Retrieve the address of the mma9559 variables structure mma9559 vars ptr mma9559 vars addr get Register the user exception handler must occur before interrupt sources are enabled mma9559 vars ptr user exception handler user exception handler Register any user trap handlers only needed if there are any user trap handlers mma9559 vars ptr user trap handler 0 user trap handler0 mma9559 vars ptr user trap handler 1 user trap handler1 mma9559 vars ptr user trap handler 2 user trap handler2 mma9559 vars ptr user trap handler 3 user trap handler3 Interrupt sources can now be enabled Loop forever processing events while 1 hi 2 4 3 Interrupts and critical sections Interrupts are treated in a simple manner Only one level of interrupt is permitted therefore interrupts can never be nested or reentrant The only exception is the INT pin IRO which is non maskable This pin is handled with its own special handler as e
81. ption and without needing to create a critical section Return The resulting value of the mma9559 vars t events field Parameters Table 4 8 events t mma9559 events set clear parameters Parameter Description Set events Bits that are set in this parameter are signaled in the mma9559 vars t events field clear events Bits that are set in this parameter are cleared from the mma9559 vars t events field MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 63 4 3 4 3 int mma9559 events find first events t events This function may be used in conjunction with the Events and Scheduling functionality of the Freescale firmware to provide a basic scheduling capability for a user s execution loop The function returns the number of the highest priority event bit that is set in the events field The priority is arranged so that the least significant bit LSB of the events parameter is the highest priority event which generates the return value 0 The most significant bit MSB of the events parameter is the lowest priority event which generates the return value 31 Return The priority number of the highest priority active task in the events bit field from 0 for the LSB to 31 for the MSB If there are no active priority bits the value 32 is returned Parameter events The events bit field to be searched for the first event MMA9559L Intelligent Motion Sens
82. ptions t This enumeration configures the AFE Analog Front End through the AFE CSR Control and Status Register Since the AFE_CSR is not directly accessible in User mode it can be accessed using the Freescale mma9559 afe csr set and mma9559 afe csr get functions The AFE CSR controls three parameters of the AFE operation Grange selection The AFE can operate in 2g 4g or 8g range e Fourth Conversion The X Y and Z accelerometer channels are measured using three out of four of the ADC channels The fourth channel can be disabled or used to measure the temperature or external ADC input e Conversion mode The ADC can perform a 10 12 14 or 16 bit conversion A higher bit conversion gives more resolution in the result but takes longer to complete such that more power is consumed The significance of the most significant bit remains the same in all conversion modes In other words if the conversion mode is less than 16 bits the least significant bits of the raw sensor value is 0 The AFE_CSR setting value is normally constructed by OR ing one entry from each of the three sections and casting it to the correct type as shown in the following example MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 42 Freescale Semiconductor Inc Example 4 1 Configure the AFE Control and Status Register mma9559 afe csr set afe csr options t AFE CSR GRANGE
83. quence is executed in the main execution level rather than in the user exception handler MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 15 The AFE registers contain semi trimmed data values that need to complete the rest of the trimming process before they can be used In most cases the user exception handler responds to the Conversion Complete exception by signaling an event and the code in the main execution loop reads the trimmed AFE data using code similar to the following example Example 2 2 mma9559 afe data t afe data Variable to hold the trimmed AFE data Read and trim the AFE data mma9559 afe trimmed sensor data get afe data data NOTE The signaling of an event is described in more detail in Events and scheduling on page 18 In a few circumstances it may be desirable to read the raw semi trimmed data values and then complete the trimming later Two situations where this might be useful are e AFIFO is being used to pass data from the user exception handler to the main execution loop The data samples are being filtered and decimated before use Since the trim process in this device is linear it is permissible to filter and decimate the semi trimmed data and then trim the result The FIFO case could be implemented with code like the following example Example 2 3 In the user exception handler mma9559 afe da
84. r This function provides access to the ROM functions documented in the MMA955xL Intelligent Motion Sensing Hardware Reference Manual MMA955xLHWRM For details on the operation of these functions see that document s ROM chapter Example 4 25 rmf return t rmf ret rmf ret ptr mma9559 rom command RMF DEV INFO ROM function to be called Get Device Info 0 this command does not take any arguments Return Either provides the address of a parameter block containing the result of the command or returns a value depending on the ROM function called Parameters Table 4 24 void mma9559 rom command parameters Field Description func id Specifies the ROM functions to be executed addr Gives the address of the parameter block used for the ROM function MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 88 Freescale Semiconductor Inc 4 6 IIR filter The MMA9559L firmware includes an optimized Direct Form I Nth order Infinite Impulse Response IIR filter function that can be accessed by user code A Direct Form I IIR filter is calculated using a general formula than can be extended to an Nth order filter See the following equation Yin bO X n b1 X n 1 a1 Y n 1 b2 X n 2 a2 Y n 2 Eqn 4 1 Where e X n is the current input e X n N is the input from N cycles earlier e Y n is the current output e Y n N is the output from N cycl
85. re is not used directly because it does not have any data buffer space Instead users should create the FIFOs they need using the FIFO STRUCT macro and include a correctly sized data buffer The contents of the structure should not be accessed directly by user code but accessed by MMAO9559L firmware functions See also intmma9559 fifo init volatile mma9559 fifo t fifo ptr events t events unsigned int max entries unsigned int bytes per entry intmma9559 fifo pop volatile mma9559 fifo t fifo ptr uint8 data ptr unsigned int entries define FIFO STRUCT max entries bytes per entry struct uint32 rsvd 2 uint8 data max entries bytes per entry Fields Table 4 15 mma9559 fifo t fields Field Description events t events Events to signal when the FIFO has data uint8 read index Index for the next entry to be read uint8 maximum entries Maximum number of elements in the FIFO uint8 number of entries Number of entries currently in the FIFO uint8 bytes per entry Number of bytes in each data element uint8 data Configurable size buffer for FIFO data MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 75 4 4 3 Functions 4 4 3 1 int mma9559 fifo init volatile mma9559 fifo t fifo ptr events t events unsigned int max entries unsigned int bytes per entry This function
86. sing the mma9559 afe offsets set function and read back using the mma9559 afe offsets get function The user specified offset values are treated as values in the 8g range and adjusted automatically to the appropriate g range when the g range is changed with the mma9559 afe csr set function The user specified offset values can be determined by putting the device into the 8g mode reading the accelerometer values without the effects of gravity and then negating these values The user offset values are reset whenever the device is reset 2 3 3 Stop mode control When there is no further software processing required the CPU can be put into STOP mode to reduce the power consumption The MMA955xL hardware enables additional power savings by also enabling the system clock rate to be controlled Three different stop clock modes are supported Stop Fast Clock The CPU is stopped and the clock tree is still running at the normal rate of 8 MHz Stop Slow clock The CPU is stopped and the clock tree is running at a reduced rate of 62 5 kHz Stop No Clock The CPU is stopped and the clock tree is disabled There are some limitations on which clock rate can be used and they vary with the hardware functionality being used For example When the AFE is converting a data sample then the clock must remain at 8 MHz fast therefore the Stop Fast Clock mode must be used when stopping the CPU but not Stop Slow Clock or Stop No Clock e If the fram
87. space and overflowing the FIFO The entries value is only correct at the time it is read If any other tasks such as interrupt handlers are using the FIFO there may be more or less space in the FIFO when the user code actually accesses the FIFO Example 4 22 free entries mma9559 fifo entries free mma9559 fifo t amp fifol pointer to the FIFO structure Return The number of entries in the FIFO that are currently available to store more data Parameter fifo ptr Address of the FIFO data structure MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 81 4 5 Other functions This section describes additional firmware functionality that does not fit into the previous functional categories 4 5 1 Enumerations 4 5 1 1 enum boot options t This sets the execution path for a startup other than power on reset When the device first powers up the boot mode is loaded with the FOPT settings from the flash location at Ox3FFE This is set in the flash code image On subsequent resets the FOPT settings are not reloaded from the flash location Instead the register settings are used directly This function enables users to modify the FOPT setting for the execution path in order to set the operation next time the device resets See also void mma9559 boot options set boot options t option Enumerators Table 4 19 enum boot options t enumerators
88. ster Vector Table and the user and supervisor stack pointers The firmware enables interrupts and switches to User mode and jumps to the function whose address is stored in the flash location 0x0000 0800 If the user flash memory is blank the Freescale firmware resets back to the ROM command interpreter e Exception vector handler This code provides a thin handler that is called whenever an exception occurs other than a Trap instruction This handler saves the state of the volatile registers disables masks the interrupts switches to User mode and then calls a user supplied exception handler function MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 11 The user written user exception handler code returns a bit field that sets bits in the mma9559 vars t events field This can be used to control a simple execution loop in the user firmware Trap vector handler Traps are software triggered exceptions that can be issued by user firmware This code provides a set of functions that can be called by the user firmware A set of four trap exceptions are reserved for the user firmware that can register user supplied trap handlers for each of them The contents of the mma9959 h header file may be used by customer firmware but this file should not be modified 2 2 Memory and CPU usage The Freescale firmware uses 2 KB of the MMA9559L device s 16 KB of flash memory and 3
89. storing data temporarily during the times when the long execution task runs so that that data can be retrieved from the FIFO and processed when shorter tasks run The MMA9559L firmware includes simple FIFO functionality that enables multiple user configurable FIFOs to be created by the user code For each of the FIFOs the FIFO buffer size is configured in terms of the maximum number of entries that can be stored and the size of each entry All entries within a FIFO are the same size although different FIFOs may have a different fixed entry size The size of each FIFO entry should be determined by the data being stored in it For example if a FIFO is storing AFE samples the entry size might be sizeof mma9559 afe data t The maximum number of entries should be determined according to the maximum delay that may be caused by the long execution tasks The FIFO functions also can use the event functionality When a FIFO is initialized the event bit field is specified that defines the events associated with the FIFO Typically there is either zero or one event associated with a FIFO If there are any events associated with a FIFO when data is pushed into the FIFO the associated events are signaled When the FIFO becomes empty either because the last data was popped out of the FIFO or the FIFO is reset the associated events are cleared This can be used in conjunction with the simple event scheduling capability to trigger processing to occur whe
90. t easier to set the parameter values Parameters Table 4 11 int mma9559 user trap0 parameters Parameter Description d0 First integer parameter user defined meaning d1 Second integer parameter user defined meaning d2 Third integer parameter user defined meaning a0 First pointer parameter user defined meaning al Second pointer parameter user defined meaning MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 70 Freescale Semiconductor Inc 4 3 4 10 int mma9559 user trapt int dO int d1 int d2 void a0 void a1 This function issues a trap instruction that calls the function registered in the firmware variables structure entry user trap handler 1 The parameter variables are passed to the trap function and their usage is determined by the user trap handler function Return The integer value returned by the user trap handler function NOTE The user trap handler can be called directly using the asm trap TRAP USER 1 instruction This function makes it easier to set the parameter values Parameter Table 4 12 int mma9559 user trap1 parameters Parameter Description d0 First integer parameter user defined meaning d1 Second integer parameter user defined meaning d2 Third integer parameter user defined meaning a0 First pointer parameter user defined meaning al Second pointer parameter user defined meaning
91. ta t raw data Variable to hold the semi trimmed AFE data case VectorNumber Vconversion complete AFE conversion complete exception mma9559 afe raw sensor data get raw data data Read semi trimmed AFE data mma9559 fifo push mma9559 fifo t amp afe fifo uint8 raw data data 1 store in a FIFO break In the main execution loop mma9559 afe data t raw data Variable to hold the semi trimmed AFE data mma9559 afe data t afe data Variable to hold the trimmed AFE data case EVENT AFE FIFO Get the semi trimmed data from the FIFO mma9559 fifo pop mma9559 fifo t amp afe fifo uint8 raw data data 1 mma9559 afe raw sensor data trim afe data data raw data data and trim it continue processing with the trimmed AFE data A more complete description of the FIFO operation is given in FIFOs on page 24 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 16 Freescale Semiconductor Inc The trim process modifies the gain and offset of the X Y Z and temperature sensor values using part specific trim values that were measured and calculated during the manufacture of the device The trim process also applies a set of three user specified offsets to the X Y and Z axes that can be set to user configured values by adding them to the results of the normal trim calculation The user specified offsets can be set u
92. ter int16 input const mma9559 coef t coef 5 ouod errira ed Tr m 91 pc IG pi aR KEE Apos 0 Wed dco Re deo edo Ubi UP AER e D ADU ond 92 4 6 3 1 typedef struct mma9559 coef t mma9559_coef_t 92 Appendix A Revision History A 1 Changes Between Revisions 0 and 0 1 ii 93 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 5 Freescale Semiconductor Inc Chapter 1 About this Document 1 1 Overview 1 1 1 Purpose This reference manual describes the features architecture and programming model of the MMA9559L Intelligent Motion Sensing Platform This device incorporates dedicated accelerometer MEMS transducers signal conditioning data conversion and a 32 bit programmable microcontroller For information about the device s hardware see the MMA955xL Intelligent Motion Sensing Hardware Reference Manual MMA955xLRM See References on page 10 1 1 2 Audience This document is primarily for system architects and software application developers who are using or considering use of the MMA9559L device in a system 1 1 3 Document structure This document combines a firmware overview with detailed functional documentation and sample user code Firmware Overview Provides an overview of the device s memory configuration and firmware requirements and explanations of the firmware s basic functional blocks User Co
93. tes in each data entry The max entries nd bytes per entry fields normally match the values used in the FIFO STRUCT macro to create the FIFO variable Other values may be used however as long as the product of the max entriesand bytes per entry values used in the mma9559 fifo init function is not larger than the product of the values used by the FIFO STRUCT macro to determine the FIFO data buffer size NOTE There is no automatic validation of the max entries and bytes per entry values The user must ensure that these values are consistent with the FIFO STRUCT usage MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 76 Freescale Semiconductor Inc See also define FIFO STRUCT max entries bytes per entry struct uint32 rsvd 2 uint8 data max entries bytes per entry e Initialize FIFO on page 25 Return Error status e Ifthe max entries Or bytes per entry values are greater than 255 or less than 1 then 1 is returned e Otherwise O is returned on success Parameters Table 4 16 int mma9559 fifo init parameters Field Description fifo ptr Address of the FIFO data structure to be initialized events Bit field of events signaled when the FIFO contains data max entries Maximum number of entries that can be stored bytes per entry Bytes per FIFO entry MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev
94. the flash location Instead the register settings are used directly This function enables users to modify the FOPT setting for the execution path to set the operation next time the device resets Once the execution path has been set using the mma9559 boot options set function a reset can be generated by writing to the Assert Software Reset ASR bit of the user accessible Reset Control and Status Register RCSR Resets caused by anything other than the POR also follow the execution path set with this function The following example resets the device back to the ROM Command Interpreter Example 4 23 mma9559 boot options set BOOT TO ROM Set next reset boot path to ROM RCSR ASR 1 Issue software reset NOTE The MMA955xL EVM board issues a reset to the MMA955xL device whenever it connects to the device to ensure that the correct IPC SPI connection selection is used If the user code already has set the boot path to ROM using mma9559 boot options set BOOT TO ROM the part always runs the ROM Command interpreter when the PC connects to the part through the MMA955xL EVM board This problem is avoided by not setting the boot path to ROM until a reset to ROM is desired Parameter option Selects the execution path on the next non POR reset MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 86 Freescale Semiconductor Inc 4 5 3 2 int mma9559 device info get int length mma9559 d
95. the user exception handler oruser trap handler functions e When interrupts are disabled using the interrupts disable function e Using the mma9559 idle use stop config function MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 29 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 30 Freescale Semiconductor Inc Chapter 3 User Code Example The functionality of the device is determined by the user firmware This section shows sample code that can be used as a template for creating that firmware The following code usually would be contained in a single file The code is split into four sections e Header e User exception handler User trap handler e User main Each of the sections is required except the user trap handler which is optional and usually not needed 3 1 Header The user code should include the mma9559 n header file instantiate the key global variables assign event bits and set the FOPT value that is loaded from address Ox3FFE Example 3 1 finclude derivative h include peripheral declarations include mma9559 n include mma9559 firmware functions User assignment of event bits 0 to 31 define EVENT AFE DATA 0 AFE conversion is complete define EVENT SLAVE PORT 1 write to the slave port mailboxes completes Set Flash Options
96. tion The AFE can operate in 2g 4g or 8g range e Fourth Conversion The X Y and Z accelerometer channels are measured using three out of the four ADC channels The fourth ADC channel can be disabled or used to measure the temperature or external input e Conversion mode The ADC can perform a 10 12 14 or 16 bit conversion A higher bit conversion gives more resolution in the result but takes longer to complete and consumes more power The significance of the most significant bit remains the same in all conversion modes If the conversion mode is less than 16 bits the least significant bits of the raw sensor value is 0 The AFE CSR setting value is normally constructed by OR ing one entry from each of the three sections and casting it to the correct type as shown in the following example Example 4 7 Configure the AFE Control and Status Register mma9559 afe csr set afe csr options t AFE CSR GRANGE 2G Use 2 g range AFE CSR C4MODE TEMP Measure X Y Z and Temperature AFE CSR CMODE 10BIT Use 10 bit conversion Parameter options Configuration option to be loaded into the AFE CSR MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 52 Freescale Semiconductor Inc 4 2 4 8 afe csr options t mma9559 afe csr get void This function reads the configuration bits from the AFE CSR register Example 4 8 afe csr options t csr
97. to enable boot from Flash word flash opt 0x3FFE 0x0337 FOPT BF MASK This bit is inverted so leave blank for boot from flash FOPT CHECKB MASK Do not perform Flash CRC FOPT PW MASK PROTB writable FOPT PROTB MASK Flash Array NOT protected FOPT SSW MASK Security State Writable FOPT SSC MASKj Security State Unsecured Instantiate global variables Use a pointer to access the MMA9559 firmware variables mma9559 vars t mma9559 vars ptr MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 31 The following variables are useful if working with the slave mailboxes to record the mailbox read and write status bits before they are cleared in the user exception handler vuint32 sp reads vuint32 sp writes 3 2 User exception handler The user firmware normally contains a single user exception handler function that is similar to Equation 3 2 on page 33 This example lists all of the exception vectors that are specific to the MMAO955xL device For additional information on the exception sources see the MMA955xL Intelligent Motion Sensing Hardware Reference Manual MMA955xLRM See References on page 10 The MMA9559L firmware handles the exception masks the interrupts and saves the volatile registers Then it switches to User mode with interrupts still masked and calls the user except
98. ue returned by the matching mma9559 interrupts disable function call e f user code does not support nested critical sections then the status parameter may be set to 0 to re enable interrupts No other values should be used Only the interrupt priority mask bits of the status parameter are used If any of the interrupt priority mask bits are set then the interrupt priority mask is set to 7 to disable mask all interrupts otherwise the interrupt priority mask is set to 0 to enable unmask the interrupts For example code using the mma9559_interrupts_restore function see the description of the int mma9559 interrupts disable void function See also intmma9559 interrupts disable void e Interrupts and critical sections on page 22 Parameter status Interrupt status state to be restored MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 69 4 3 4 9 int mma9559 user trapO int dO int d1 int d2 void a0 void a1 This function issues a trap instruction that calls the function registered in the firmware variables structure entry user trap handler 0 The parameter variables are passed to the trap function and their usage is determined by the user trap handler function Return The integer value returned by the user trap handler function NOTE The user trap handler can be called directly using the asm trap TRAP USER O instruction This function makes i
99. used by the Freescale firmware MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 12 Freescale Semiconductor Inc The first section of RAM is reserved for use by the Freescale firmware to store variables used by the firmware and the ROM functions The second section of 1664 bytes is available for use by the user firmware This includes space for global variables the heap and the user stack The Freescale firmware initializes the entire user variable and heap region with the value 0 so that all global variables are initialized to 0 The last section of RAM is reserved for the Freescale firmware to store the supervisor stack which is used whenever the firmware is running The user exception handler andthe user trap handler functions are called from the Freescale firmware but are run in User mode using the user stack space rather than using the supervisor stack space 2 2 3 Supervisor stack usage The MMA955xL devices use a ColdFire v1 core as the CPU This CPU contains a set of user registers and a set of supervisor registers When executing in User mode only the user registers are accessible but when running in Supervisor mode all registers are accessible The ColdFire CPU enables separate stacks to be used for User and Supervisor modes The MMA9559L firmware operates in Supervisor mode but switches back to User mode when executing any user firmware The ColdFire CPU uses the A7 and alternat
100. ver the device has no further CPU processing to perform the Freescale firmware can put the CPU into Stop mode until the next interrupt occurs However the appropriate clock speed mode must be used The mma9559 idle function selects the clock speed based on the two fields in the mma9559 idle t structure fuse stop fc is not zero then use StopFastClock mode Else if use_stop_sc is not zero then use StopSlowClock mode e Else use StopNoClock mode The 32 bits in each field are split into 16 bits that are reserved for use by Freescale firmware and 16 bits that user code can allocate to different activities that are impacted by the clock rate so that the activities can each independently control the selection of the Stop mode clock speed The Freescale firmware already uses two of the reserved bits DLE BITS CKOSC is used by the frame interval counter to prevent the use of StopNoClock when the frame interval counter is being used MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 28 Freescale Semiconductor Inc DLE BITS AFE is used by the AFE to force the use of StopFastClock when the ADC is performing a conversion The use stop fcanduse stop sc fields may be modified inside the user exception handler function While these functions can be read anywhere any code that modifies the functions should only be executed when interrupts are disabled This can be achieved in three ways e Within
101. ves the state of the interrupts at the start of the critical section This form also restores the interrupts to the same state masked or unmasked that they were at the start of the critical section See the following example Example 2 8 int status mma9559 interrupts disable start critical section disable interrupts mma9559 interrupts restore status restores previous interrupt mask state The mma9559 interrupts disable function changes the Interrupt Priority Mask in the ColdFire Status Register to 7 that masks all interrupt sources Any exceptions that occur while the interrupts are disabled are not lost but remain pending in the hardware Those pending interrupts are serviced as soon as the interrupt level is restored at the end of the critical section Since interrupts are delayed the critical section should be kept as short as possible to avoid unnecessarily increasing the interrupt latency The mma9559 interrupts restore function does not just enable interrupts by changing the Interrupt Priority Mask back to 0 It also restores the mask to the state supplied in the status parameter which the user should have saved from the result of the mma9559 interrupts disable function call This distinction enables the interrupt functions to work correctly even when interrupts are nested accidentally or deliberately The mma9559 interrupts restore function uses only the interrupt priority mask bits of the supplied
102. w The MMA9559L device is a member of the Freescale MMA955xL intelligent motion sensing platform family Unlike the other members of the MMA955xL family where the factory programmed firmware provides out of the box operation the MMA9559L only provides a lightweight infrastructure and requires user programmed firmware for the device to run anything other than the internal ROM command line interpreter This approach reduces the factory programmed firmware on the MMA9559L to only 2 KB of flash memory leaving the other 14 KB for customer firmware After an introduction to the firmware file this chapter provides an overview of the firmware and related hardware topics The information is divided into the following functional categories Memory and CPU usage e Hardware support e Events and scheduling e FIFOs e Power These same categories are used in the following chapter that provides functional details 2 1 Firmware elements and functionality The mma9559 h file contains the type and function declarations required to build custom user firmware that can be loaded onto the Freescale MMA9559L device In order to use this device CodeWarrior 10 1 or later with the MMA9550 service pack must be installed for development The MMA9559L device s built in firmware provides the following basic functionality Device initialization This code clears the RAM within the MMA9559L and sets up the Exception Vector Base Regi
103. xception vector number Events to be signaled defaults to none Proxy for the INT pin IRQ external interrupt Clear level 5 Software Interrupt first Clear interrupt source Re enable IRQ interrupt TPM Overflow Clear interrupt source TPM Channel 0 Clear interrupt source TPM Channel 1 Clear interrupt source MTIM Modulo Timer Overflow Clear interrupt source PDB_A Clear interrupt source PDB_B Clear interrupt source MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 Freescale Semiconductor Inc 33 case VectorNumber Vsp wake Slave mailbox Save the mailbox read and write status bits if needed for later Sp writes vuint32 amp SP_WSTSO sp reads vuint32 amp SP_RSTSO SP_SCR_ACTIVE_CSR 1 Clear slave port read and write status bits Signal an event to trigger processing in the main execution loop events EVENT BITFIELD EVENT SLAVE PORT break case VectorNumber Vstart of frame Start of Frame FCSR SF 1 Clear interrupt source mma9559 afe conversion start Start a new AFE conversion break case VectorNumber Vconversion complete AFE conversion complete Interrupt source already cleared in the Freescale exception handler Signal an event to enable processing in the main execution loop events EVENT BITFIELD EVENT AFE DATA break case VectorNumber Vmaster i2c I2C Master IICS IICIF 1 Clear interrupt source
104. xplained in Supervisor stack usage on page 13 The user exception handler anduser trap handler functions are always called with interrupts already disabled masked so that they are not interrupted The user firmware should not change the interrupt settings inside these functions Normal user code executes with interrupts enabled unmasked Occasionally there are small sections of code that should not be interrupted by exceptions in order to avoid unintended side effects For example themma9559 vars t events and mma9559 idle t fields may be modified within exception handlers as a result any changes to these fields within normal user code would be protected The mma9559 interrupts disable and mma9559 interrupts restore functions can be used by normal code to create critical sections that cannot be interrupted by exceptions They may be used in either of the following manners MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 22 Freescale Semiconductor Inc In simple implementations where calls to disable interrupts can never be nested a simpler form can be used a shown in the following example Example 2 7 mma9559 interrupts disable start critical section disable interrupts mma9559 interrupts restore 0 enable interrupts If there is any possibility that calls to disable interrupts such as critical sections may be nested a more advanced form can be used that sa
105. ze is in bytes This macro can be used to create FIFOs in two ways Asingle variable instance of a FIFO can be created using the macro as shown in the following example Example 4 15 FIFO STRUCT 5 sizeof uint32 fifol FIFO variable to hold five 32 bit unsigned integers e A typedef can be created for a particular FIFO configuration and individual variable instances of the same configuration created from that typedef as shown in the following example Example 4 16 typedef FIFO STRUCT 10 sizeof uint8 fifol0_t FIFO data type to hold 10 bytes fifolO t fifo2 Instance variable of a FIFO to hold 10 bytes NOTE When creating the FIFO structure this macro calculates the total data buffer size in bytes by multiplying the maximum entries field by the bytes per entry field The two separate values are not needed here but are kept in this format to maintain consistency with the mma9559 fifo init function See also intmma9559 fifo init volatile mma9559 fifo t fifo ptr events t events unsigned int max entries unsigned int bytes per entry e FIFOs on page 24 MMA9559L Intelligent Motion Sensing Platform Software Reference Manual Rev 0 1 74 Freescale Semiconductor Inc 4 4 2 Data structures 4 4 2 1 mma9559 fifo t This structure provides a generic FIFO structure that contains the internal variables used by the FIFO functions and a placeholder for the data buffer This structu

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