Using the USI I2C Code Library (Rev. A)
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1. 1 0x01 int RxCallback unsigned char RxData Received data byte is stored in flash FCTL3 FWKEY FCTL1 FWKEY WRT unsigned char ptr_rx RxData ptr rxt FCTL1 FWKEY FCTL3 FWKEY LOCK return TI_USI_STAY_LPM int TxCallback int TxDataPtr Data byte to be transmitted is passed through reference to the library unsigned char TxDataPtr unsigned char ptr tx ptr_txt Increment tx pointer return TI_USI_STAY_LPM Stop watchdog Set DCO Enable P1 0 as output Enable flash erase Flash timing setup Disable lock Dummy write to erase flash Diasble flash write enter LPM enable interrupts start received turn LED on Enable flash write Write data to flash Increment Rx pointer Disable flash write stay in LPM stay in LPM Using the USI PC Code Library SLAA368A September 2007 Revised May 2009 Submit Documentation Feedback 5 INSTRUMENTS www ti com Slave Library The USI I2CSlave h must be included to initialize variables and functions when using the library from a C program The TI USI 12 Slavelnit function needs to be called only once at the start to initialize the USI module in slave mode The slave program example slave430interface c runs on the dedicated slave MSP430 while the master program example master43O0interface c runs in2. or received and also store the received data for application use Figure 2 is a high level flow diagram explaining the state transitions in an 12 slave routine No Initialize State Machine Invoke Start Callback Function Receive Slave Address and R W Bit Device Address Correct Perform Read No Invoke Receive Callback Function Send ACK Restart Condition Received No Yes Operation No v Invoke Transmit Callback Function Transmit Byte Receive ACK NACK Received Restart Condition Received Yes Figure 2 Program Flow for Slave Code Library SLAA368A September 2007 Revised May 2009 Submit Documentation Feedback Using the USI Code Library Slave Library 3 1 10 Usage From C TEXAS INSTRUMENTS www ti com void main void WDTCTL WDTPW WDTHOLD BCSCTL1 CALBC1_1MHZ DCOCTL CALDCO 1MHZ PIDIR 0x01 P1OUT 0 FCTL1 FWKEY ERASE FCTL2 FWKEY FSSEL 2 FNO FCTL3 FWKEY unsigned int 0x1000 0 1 FWKEY FCTL3 FWKEY LOCK Initialize USI module in Slave mode TI USI I2C SlaveInit OwnAddress StartCallback RxCallback TxCallback while 1 disable interrupt SR register LPMA bits GIE no operation void StartCallback
3. SlaveAddress This is the device address of the slave unsigned int Length This value is the number of bytes to be received unsigned char Multi This variable is used to suppress the generation of I C stop condition if the user wants to leave the channel open for further transactions void RxData This pointer variable points to the memory location where the received data should be stored The function returns a zero if the operation was successful and a nonzero value if a NACK was received at any time during the IC transaction It is valid only when no callback function is provided Otherwise the function returns immediately and the IC transaction takes place in the background TI USI l2CWrite This function implements block write master transmitter functionality The parameters passed as arguments are unsigned char SlaveAddress This is the device address of the slave unsigned int Length This value is the number of bytes to be transmitted unsigned char Multi This variable is used to suppress the generation of C stop condition in case the user wants to leave the channel open for further transactions void TxData This pointer variable points to the memory location of the data to be transmitted The function returns a zero if the operation was successful and a nonzero value if a NACK was received at any time during the 2 transaction It is valid only when no callback function is provided Otherwise the function re
4. WRT amp FCTL1 3 mov w FWKEY amp FCTL3 mov w amp RxFlashPtr R6 mov b R12 0 R6 H mov w FWKEY amp FCTL1 mov w FWKEY LOCK amp FCTL3 amp RxFlashPtr mov w 0 R12 A ret Initialize stackpointer Stop WDT Load DCO calibration constants P1 0 and 1 1 as output Set erase bit Set flash timing Clear lock bit Dummy write to start Flash erase Initialize Rx pointer Initialize Tx pointer Address of slave StartCallback fn ptr Tx Callback fn ptr Rx Callback fn ptr 2 Slave initialize compensate stack pointer enter LPM enable interrupts start received LED on pass data to be transmitted to the library increment tx pointer stay in LPM Set WRT bit Clear lock bit Move rxed byte to flash location lock flash stay in LPM In assembly the usage of the library is the same as in C Arguments are passed using the C calling convention making the library functions compatible for both C and assembly usage The first two parameters are passed using registers R12 and R14 all others are pushed onto the stack 2 12 Using the USI PC Code Library SLAA368A September 2007 Revised 2009 Submit Documentation Feedback I TEXAS INSTRUMENTS www ti com Code Size 3 3 Function Description The following functions are defined in the slave code library 3 3 1 TI USI I2C Slavelnit This is the slave initialization function The following parameters a
5. not generate stop call TI_USI_I2CRead receive stream 1 2 add w 4 SP compensate SP on return bis w LPMO GIE SR enter LPM enable interrupts 6 Using the USI Code Library SLAA368A September 2007 Revised May 2009 Submit Documentation Feedback TEXAS INSTRUMENTS www ti com Master Library StopTransaction call TI_USI_I2CStop Stop 2 transactions CheckResult mov w Receive store received data location Glr b R4 Compare cmp b R4 0 R6 j Increment data valid continue clr b amp P1OUT data invalid LED off jmp EndProgram Increment R4 inc w R6 cmp b 10 R4 jnz Compare if all 10 bytes are correct bis b 0x01 amp P1OUT 22 turn on LED EndProgram jmp program ends here AcknowledgePoll mov b 0x50 R12 Slave address call TI USI I2CSelect Ack polling function ret StatusCallback mov w 1 R12 wake up on exit ret In assembly the usage of the library is the same as in C Arguments are passed using the C calling convention making the library functions compatible to both C and assembly usage The first two parameters are passed using registers R12 and R14 all others are pushed onto the stack 2 2 3 Function Description The following functions are defined in the master code library 2 3 1 TI USI I2C Masterlnit The function initializes the USI module for 2 communication The parameters passed as arguments unsigned char ClockConfig This
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7. parallel on the dedicated master MSP430 device The slave device uses the Info D segment 0x1000 to 0x104F to emulate an EEPROM with 64 byte data storage On reception of the start condition from the master the StartCallback function is called This function can be used to refresh data pointers before a transmit or a receive operation In the previous example the StartCallback function turns on the LED to indicate that the IC transaction has started The master MSP430 transmits 16 bytes of data and then reads it back from the slave 5 430 On the reception of each data byte the RxCallback function is called The received data byte is passed as an argument to this function and the return value is used to modify the low power mode The TxCallback function is called before each transmit operation The function passes the data byte to be transmitted indirectly using a reference pointer It also returns a zero if the existing low power mode should be maintained or a nonzero value if the low power mode should be exited The data can be validated by viewing the Info D segment of flash Note If C callback functions are used the library needs to preserve additional CPU registers C scratch registers across the callback function call as these registers could be affected by the callback function If it can be ensured that the callback function does not modify the C scratch registers they need not be preserved Preserving the C scratch register
8. value contains the clock select frequency divider and clock polarity bits that are to be loaded onto the control register USICTLO int StatusCallback unsigned char This function is called on the transmission reception of the last byte in the communication stream The result of the previous operation ACK NACK is passed as an argument to this function The function returns a zero if the existing low power mode should be maintained or a nonzero value if the low power mode should be exited 2 3 2 TI USI 12CSelect This function detects the presence of a slave by addressing it and determining if the slave responds with an ACK NACK The following parameter is passed as an argument unsigned char SlaveAddress This is the device address of the slave The return value is the result of the operation The function returns a zero if the slave is present and has acknowledged and it returns a nonzero value if the slave is absent or not ready to acknowledge For example this function can be used to poll slower slave devices like EEPROM while waiting for it to complete an internally timed write cycle SLAA368A September 2007 Revised May 2009 Using the USI Code Library 7 Submit Documentation Feedback 5 INSTRUMENTS PC Master Library www ti com 2 3 3 2 3 4 2 3 5 2 4 TI USI 2 This function implements block read master receiver functionality The parameters passed as arguments are unsigned char
9. 430 master transmits a stream of data to the 24C02 a two wire serial EEPROM device The device requires an 8 bit data word address following the device address before data bytes can be written to it The internal word address counter of the EEPROM maintains the last address accessed during the previous data transmission Hence before a read the internal counter needs to be reinitialized by transmitting to the required data word address At the end of every write operation the EEPROM enters an internally timed write cycle and does not respond until the write operation is complete At this time it can be polled by the master device for an acknowledge ACK using the TI USI I2CSelect function This function returns a nonzero value if the slave sends a No Acknowledge NACK Once the slave has acknowledged the data is ready to be read from the EEPROM The transmitted and received data are compared and if found to be valid the LED is turned on The data can also be viewed in the memory through a watch window The callback function is used to modify the low power mode for the next operation The result of the previous operation is passed as an argument to the callback function A zero indicates that the previous operation was successful An additional example application to communicate with a dedicated slave MSP430 device is provided in the file example master430interface c Note If C callback functions are used the library needs to preserve add
10. 5 LED toggles until slave ACKS 11 dec w R5 jnz L1 Poll 0 call AcknowledgePoll Slave device present cmp b 0 812 Is result zero ACK jnz SlaveDetect Loop until device acknowledges clr b amp PlOUT Slave acknowledged LED off TransmitCall 1 mov w 0x50 R12 Slave address mov w 9 R14 length 9 push w Transmitl pointer to data buffer push w 0x00 generate stop call TI_USI_I2CWrite transmit data stream 1 add w 4 SP compensate SP on return bis w LPMO GIE SR enter LPM enable interrupts Poll 1 call AcknowledgePoll Device ready for next transfer cmp b 0 812 Is result zero ACK jnz Poll 1 Loop until device acknowledges TransmitCall 2 mov w 0x50 R12 Slave address mov W 3 R14 length 3 push w Transmit2 pointer to data buffer push w 0x00 generate stop call TI_USI_I2CWrite transmit data stream 2 add w 4 SP compensate SP on return bis w SR enter LPM enable interrupts Poll_2 call AcknowledgePoll Device ready for next transfer cmp b 0 R12 Is result zero ACK jnz Poll 2 Loop until device acknowledges TransmitCall 3 mov w 0x50 R12 Slave address mov W 1 R14 length 1 push w Transmitl pointer to data buffer push w 0 01 generate stop call TI USI I2CWrite transmit to reset internal counter add w 4 SP compensate SP on return bis w SR enter LPM enable interrupts ReceiveCall mov w 0x50 R12 Slave address mov w 10 R14 length 10 push w Receive pointer to data buffer push w 0 01 do
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12. I TEXAS Application Report INSTRUMENTS SLAA368A September 2007 Revised 2009 Using the USI FC Code Library Priya Thanigai MSP430 Applications ABSTRACT This document serves as an overview of the master and slave code libraries for 12 communication using the USI module as found on MSP430F20xx The USI 12 master and slave libraries encapsulate all the functions necessary to transmit and receive multiple bytes The functions are written in assembly and can be accessed by any C program that includes the required header files Related source files can be downloaded from http www ti com lit zip slaa368 Contents 1 INMOGUCHON Pes 2 2 2 Master Library 2 3 Slave cart e 9 4 Code SIZE e EET 13 5 iie tte E 13 List of Figures 1 Program Flow for Master Code 241422222 22 1 3 2 Program Flow for Slave Code Library 9 List of Tables 1 enin 13 All trademarks are the property of their respective owners SLAA368A September 2007 Revised May 2009 Using the USI FC Code Library 1 Submit Documentation Feedback 1 5 INSTRUMENTS Introduction www ti com Introduction The USI module provides the basic functionality needed to support synchronous serial communication When configured in the IC mode the USI module i
13. ating in the nonblocking mode callback function provided the I C function returns immediately and communication takes place in the background In this mode the result of the operation ACK NACK is passed as an argument to the callback function In the blocking mode no callback function provided the functions in the library are executed exclusively without parallel application code and provide a valid return value in the end The return value reflects the result of the operation Also the CPU operating mode can be changed or modified using callback functions defined at the application level Figure 1 is a high level flow diagram explaining the state transitions in an 2 routine Using the USI Code Library SLAA368A September 2007 May 2009 Submit Documentation Feedback 5 INSTRUMENTS www ti com Master Library Initialize State Machine Transmit Slave Address and R W Bit Did Slave Acknowlege Yes Recieve One Byte Byte CTR 0 Perform Read Operation Transmit One Byte Receive ACK NACK From Slave Did Slave ACK Yes No Invoke Callback Function Byte CTR 0 Prepare for Stop Figure 1 Program Flow for Master Code Library SLAA368A September 2007 Revised May 2009 Using the USI FC Code Library 3 Submit Documentation Feedback 5 INSTRUMENTS Master Library 2 1 Usage From C www ti c
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15. itional CPU registers scratch registers across the callback function call as these registers could be affected by the callback function If it can be ensured that the callback function does not modify the C scratch registers they need not be preserved Preserving the C scratch registers consumes additional code space and execution cycles Therefore the end user is given the option of using a predefined macro within the library to preserve the C scratch registers USE C CONTEXT SAVE is included or leaving the registers as is USE C CONTEXT SAVE is commented out See the compiler documentation for more details regarding C calling conventions 2 SLAA368A September 2007 Revised May 2009 Using the USI FC Code Library 5 Submit Documentation Feedback Master Library 2 2 Usage From Assembly TEXAS INSTRUMENTS www ti com RESET mov w SFE CSTACK SP Initialize stackpointer StopwDT mov Ww WDTPW WDTHOLD amp WDTCTL Stop WDT SetupDCO mov b amp CALBC1_1MHZ amp BCSCTL1 Load DCO calibration constants mov b amp CALDCO 1MHZ amp DCOCTL SetupPx bis b 0x01 amp P1DIR P1 0 amp 1 1 as output bic b 0x01 amp P10UT InitCall mov b OxEA R12 USIDIV_7 USISSEL_2 USICKPL mov w StatusCallback R14 Callback fn pointer call TI USI I2C MasterInit Initialize USI master SlaveDetect xor b 0x01 amp P1OUT Detect if slave is present mov w OxFFFF R
16. om Void main void WDTCTL WDTPW WDTHOLD Stop watchdog BCSCTL1 CALBC1_1MHZ Load DCO constants DCOCTL CALDCO_1MHZ PIDIR 0x01 P1 0 as output LED P1OUT 0x00 Initialize USI module clock SMCLK 128 TI_USI_I2C_MasterInit USIDIV_7 USISSEL_2 USICKPL StatusCallback Acknowledge polling function LED blinks continuously until slave device provides an ACK TI_USI_I2CSelect unsigned char SlaveAddress while TI_USI_I2CSelect 0x50 100 0x01 Toggle LED for i 0 lt 0x3000 i Delay P1OUT 0 Slave acknowledged LED off Transmit data to the EEPROM device prefixed by page address 0x01 TI USI I2CWrite SlaveAddress Length Multi TxData disable interrupt TI USI I2CWrite 0x50 9 0 TxData0 bis SR register LPMO bits GIE Acknowledge polling function loops continuously until slave device provides an ACK while TI USI I2CSelect 0x50 Transmit data to the EEPROM device prefixed by page address 0x08 TI USI I2CWrite SlaveAddress Length Multi TxData disable interrupt TI USI I2CWrite 0x50 3 0 TxDatal bis SR register LPMO bits GIE Acknowledge polling function loops continuously until slave device provides an ACK while TI USI I2CSelect 0x50 T Reset address counter of the EEPROM device by transmit
17. p ftp iar se WWNWfiles msp430 guides oc430 pdf 3 FC Bus Specification and User Manual NXP Semiconductors 2007 http www nxp com acrobat usermanuals UM10204 3 pdf SLAA368A September 2007 Revised May 2009 Using the USI Code Library 13 Submit Documentation Feedback Revision History TEXAS INSTRUMENTS www ti com Revision History Revision Comments SLAA368 Initial release SLAA368A Updated associated zip file slaa368 zip no changes to document NOTE Page numbers for previous revisions may differ from page numbers in the current version 14 Revision History SLAA368A September 2007 Revised May 2009 Submit Documentation Feedback IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries reserve the right to make corrections enhancements improvements and other changes to its semiconductor products and services per JESD46 latest issue and to discontinue any product or service per JESD48 latest issue Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete All semiconductor products also referred to herein as are sold subject to Tl s terms and conditions of sale supplied at the time of order acknowledgment TI warrants performance of its components to the specifications applicable at the time of sale in accordance with the warranty Tl s terms and
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19. re passed as arguments to this function unsigned char OwnAddress This is the address of the slave MSP430 device int StartCallback void This function is called on the detection of the start condition int RxCallback unsigned char This function is called on the reception of a data byte The received data is passed as an argument to the function The function returns a zero if the existing low power mode should be maintained or a nonzero value if the low power mode should be exited int TxCallback int This function is called before the transmission of a data byte The data byte to be transmitted is stored at the location provided as an argument to this function The function returns a zero if the existing low power mode should be maintained or a nonzero value if the low power mode should be exited 3 4 Included Library Files USI_I2CSlave s43 This library file includes all the functionality necessary for an 12 slave device to transmit and receive single and multiple bytes USI I2CSlave h This header file has the necessary definitions and functions for the slave library and must be included in any C program that uses the library 4 Code Size Table 1 shows the code size for the master and slave code libraries in IAR Table 1 Code Size IAR CODE LIBRARY USE C CONTEXT SAVE SIZE bytes 0 616 Master 1 628 0 408 Slave 1 444 5 References 1 MSP430x2xx Family User s Guide SLAU144 2 IAR MSP430 C C Compiler Reference Guide ft
20. s 8 bit shift register that can output a stream of serial data With minimal software it can be used to setup a master slave relationship to implement serial communication A software IC library is especially useful for lower pin count devices that do not include hardware module dedicated to 12 communication The USI 2 libraries offer the functionality needed to configure the MSP430 as either a master or a slave device capable of transmission and reception of multiple bytes The library functions are capable of servicing interrupts while allowing transactions to take place in the background without interfering with user applications The definitions of the interrupt service routines however prevent the master and slave libraries from existing on the same device The example files include a master MSP430 interface to a slave EEPROM device and to a slave MSP430 device Note Internal pullup resistors are enabled on the MSP430F20xx to support C communication Master Library The I C master initiates data transfer and generates the clock signal SCL It can be used in two modes e Master transmit e Master receive The master code library provides the necessary functionality to support multiple byte and word transmission and reception It allows the user to switch between transmit and receive operations on the fly using a repeated start condition The library can execute in both blocking and nonblocking modes While oper
21. s consumes additional code space and execution cycles Therefore the end user is given the option of using a predefined macro within the library to preserve the C scratch registers USE C CONTEXT SAVE is included or leaving the registers as is USE C CONTEXT SAVE is commented out See the compiler documentation for more details regarding C calling conventions 2 SLAA368A September 2007 Revised May 2009 Using the USI Code Library 11 Submit Documentation Feedback Slave Library 3 2 Usage From Assembly TEXAS INSTRUMENTS www ti com RESET mov w SFE CSTACK SP 4 StopWDT mov w WDTPW WDTHOLD amp WDTCTL SetupDCO mov b amp CALBC1_1MHZ amp BCSCTL1 mov b amp CALDCO_1MHZ amp DCOCTL SetupPx bis b 0x03 amp P1DIR EraseFlash FWKEY ERASE amp FCTL1 mov w FWKEY FSSEL_2 FNO amp FCTL2 mov w FWKEY amp FCTL3 E mov w 0 amp 0x1000 mov w FWKEY amp FCTL1 mov w FWKEY LOCK amp FCTL3 mOV W 0x1000 amp RxFlashPtr mOV W 0x1000 amp TxFlashPtr H SlaveCall mov b 0x48 R12 mov w StartCallback R14 3 push w TxCallback push w RxCallback 11 TI_USI_I2C_SlavelInit H add 4 SF bis w LPM4 GIE SR jmp StartCallback bis b 0 01 68 100 H ret TxCallback mov w amp TxFlashPtr R6 mov b R6 0 R12 inc w amp TxFlashPtr H mov w 0 R12 ret RxCallback mov w FWKEY
22. ting the page address to be read from 0x00 Dummy write TI USI I2CWrite SlaveAddress Length Multi TxData disable interrupt TI USI I2CWrite 0x50 1 1 TxData0 bis SR register LPMO bits GIE Read data from the EEPROM device starting at page address 0x00 TI USI I2CRead SlaveAddress Length Multi RxData Using the USI Code Library SLAA368A September 2007 Revised 2009 Submit Documentation Feedback 5 INSTRUMENTS www ti com Master Library disable interrupt TI USI I2CRead 0x50 10 1 RxData bis SR register LPMO bits GIE This function can be used to end any open I2C transaction Use only if I2C transaction was left open previously by setting stop condition bit 1 TI USI I2CStop check data for validity for j 0 3 lt 10 if RxData j j while 1 data invalid stay in loop 100 0x01 data valid LED on while 1 program ends here int StatusCallback unsigned char return TI_USI_EXIT_LPM Exit active for next transfer The USI I2CMaster h must be included to initialize variables and functions when using the library from a program The TI USI I2C Masterlnit function needs to be called only once at the start to initialize the USI module in master mode In the previous example example the MSP
23. turns immediately and the IC transaction takes place in the background TI USI I2CStop This function generates the 12 stop condition and can be used to end an open C transaction It is typically not used as both transmit and receive functions generate a stop condition by default It can be used in conjunction with a read or write function when the Multi parameter has a nonzero value Included Library Files USI 2 543 This library file includes all the functionality necessary to transmit and receive single and multiple bytes as an IC master device It also contains the acknowledge polling function which polls for the presence of a slave device USI 2 This header file has the necessary definitions and functions for the master library and must be included in any C program that uses the library Using the USI FC Code Library SLAA368A September 2007 Revised 2009 Submit Documentation Feedback 5 INSTRUMENTS www ti com 3 Slave Library Slave Library The 2 slave does not control the clock and can be used two modes e Slave transmit e Slave receive The slave code library allows for multiple byte transmission and reception The library executes in a nonblocking manner and allows for the 2 transactions to take place in the background Callback functions are provided to allow the user to modify the CPU operating mode after each byte is transmitted
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