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STM8Sxxx three-phase BLDC motor control software library V1.0

1. Name out8 VDEV_OUT8_LED_1 command Description This call is used to drive the virtual LED 1 this is mapped to a real HO pin of the evaluation board The command can take the following values LED_ON Set a high state to the output turning on the related LED LED_OFF Set a low state of the output turning off the related LED LED_TOGGLE Perform a toggle on the output switching on if it is off and vice versa out8 VDEV OUT8 LED 2 command Same as above but related to virtual LED 2 H1 pin of the evaluation board out8 VDEV OUT8 LED 3 command Same as before but related to virtual LED 3 H2 pin of the evaluation board out8 VDEV OUT8 LED 4 command Same as before but related to virtual LED 4 H3 pin of the evaluation board inp8 VDEV INP8 USER INPUT none This call is used to get the input from the user interface Joystick and Key button 4 2 3 Drive structure The drive structure contains the variable and parameters related to the motor and the drive The BLDC drive structure is show in Table 6 Table 6 BLDC Drive structure Name bSpeed Control Mode bCurrent Control Mode Type Variable enum Variable enum Description It specifies the speed control mode It can be of two type open loop or closed loop It specifies the current control mode It can be of two type current mode or voltage mode hMeasured rotor speed Variable 16 bits It contains the
2. drivelnit driveldle driveStartUplnit driveStartUp driveRun driveStop driveWait driveFault BLDC Drive GetSpeed 01HZ BLDCDelayCoefComputation Doc ID 15773 Rev 1 ky UM0708 Library functions drivelnit Synopsis Description Input Returns Note driveldle Synopsis Description Input Returns Note driveStartUplnit Synopsis Description void drivelnit pvdev device t pdevice This function initializes local pointers to the virtual registers drive structure and the other variables of interest required for the other module functions The pointer to the drive structure is retrieved using the Get BLDC Struct function of MC BLDC Motor module The function initializes the low level drive module by calling the dev drivelnit pdevice function The other variables of interest are Hertz to RPM conversion factor based on motor poles pairs local pointer of speed PID structure sampling time duration It also starts the BLDC CONTROL TIMER virtual timer which calls the BLDC Drive function every sampling time period see Section 4 5 pdevice pointer to a structure containing virtual registers None It is called by the relative state machine function void driveldle void The purpose of this function is to call the low level function relative to this state and to update the local state variable DriveState None None It is called by the relative state machine function
3. BEMF SAMPLING TON the BEMF detector is configured to perform the sampling only during the on time of the PWM signal applied see Section 2 4 BEMF SAMPLING MIXED the BEMF detector is configured to perform the dynamic selection of the sampling method based on the value of the duty cycle to be applied This selection is allowed only if the firmware is configured in Voltage mode define SAMPLING POINT DURING TOFF This define statement is used when the BEMF sampling is performed during PWM off time to define the sampling point This parameter sets the advance of the BEMF sampling point before the turn on of the PWM signal It is expressed in nanoseconds A minimum time of 1 5 ms is required to perform the BEMF sampling using the STM8Sx ADC peripheral define SAMPLING POINT DURING_TON This define statement is used when the BEMF sampling is performed during PWM on time to define the sampling point This parameter sets the delay between the turn on of the PWM signal and the BEMF sampling point It is expressed in nanoseconds Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library Note 1 This delay is used as time filter for the turn on noise commutation and must be set accordingly to the hardware It is possible to set a minimum PWM T on time by configuring properly the ETR filter when the current limitation or regulation is set see Section 5 1 8 The MC BLDC Drive Param h contain
4. C71 UM0708 J User manual STM8Sxxx three phase BLDC motor control software library V1 0 June 2009 Introduction This user manual describes the brushless direct current motor BLDC scalar software library a scalar control firmware library for 3 phase permanent magnet PM motors developed for the STM8Sxxx microcontrollers ST STM8Sxxx 8 bit microcontrollers come with a set of peripherals that makes them suitable for performing both PM and AC induction motor scalar control The present document describes the STM8Sxxx software library developed to control trapezoidal driven PM motors in both open loop and speed control mode These motors may be equipped with three Hall sensors or may be sensorless The control of an AC induction motor equipped with tachogenerator is described in the UMO712 user manual The BLDC motor software library is made of several C modules and is fitted out with STVD workspace It is used to quickly evaluate both the MCU and the available tools In addition when used together with the STM8 128 MCKIT motor control starter kit and a PM motor a motor can be made to run in a very short time The BLDC library also eliminates the need for time consuming development of low level drive and speed regulation algorithms by providing ready to use functions that let the user concentrate on the application layer Moreover it is possible to get rid of any speed sensor thanks to the sensorless algorithm for rotor position
5. define TIM2 CH3 REMAP This define statement allows to remap TIM2 channel 3 define HALL FILTER This define statement configures the filter applied to the Input capture filter used for the Hall sensor signal This filter is used to avoid false commutations caused by noise glitches Table 13 gives the values of the allowed filters Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library Table 13 Hall sensor filters Filter for Filter for define HALL_FILTER value F_CPU 16 MHz F_CPU 24 Mhz in uis in us HALL_FILTER_NOFILTER 0 0625 0 0417 HALL_FILTER_F_N2 0 1250 0 0833 HALL_FILTER_F_N4 0 2500 0 1667 HALL FILTER F N8 0 5000 0 3333 HALL FILTER F2 N6 0 7500 0 5000 HALL FILTER F2 N8 1 0000 0 6667 HALL FILTER F4 NG 1 5000 1 0000 HALL FILTER F4 N8 2 0000 1 3333 HALL FILTER F8 N6 3 0000 2 0000 HALL FILTER F8 N8 4 0000 2 6667 HALL FILTER F16 N5 5 0000 3 3333 HALL FILTER F16 NG 6 0000 4 0000 HALL FILTER F16 N8 8 0000 5 3333 HALL FILTER F32 N5 10 0000 6 6667 HALL FILTER F32 NG 12 0000 8 0000 HALL FILTER F32 N8 16 0000 10 67 5 2 Setting up the system when using a brake resistor a To make the MB459 board suitable for the management of a brake resistor additional components must be soldered on its wrapping area Figure 49 gives an example of circuit used for brake hardware implementation Doc ID 15773 Rev 1 73 85 D
6. e In open loop current mode this is the current reference set by the user in the sub menu e In voltage mode it is not used for the drive Figure 27 Current measurement DC bus voltage level and heatsink temperature The sub menu shown in Figure 28 displays the measured DC bus voltage level BUS DC and the heatsink temperature Heatsink BUS DC is the rectified input voltage express in Volt while Heatsink is the temperature expressed in C and measured by the negative coefficient temperature NTC resistor placed on the power stage close to the heatsink of the power switches Figure 28 DC bus voltage and heat sink measurements 3 6 7 Additional options fast demagnetization toggle mode and auto delay Additional options have been implemented in the firmware e Fastdemagnetization e Toggle mode e Auto delay These options can be enabled or disabled in real time through the user interface Doc ID 15773 Rev 1 33 85 Running the demonstration program UM0708 34 85 Fast demagnetization The sub menu shown in Figure 29 can be used to enable disable the fast demagnetization FastDemag option The following steps are required 1 Press the joystick UP or DOWN to select the FastDemag field 2 Then press JOYSEL to activate it 3 Push the joystick UP or DOWN to switch the option from enabled to disabled and vice versa Refer to Section 2 5 for more information concerning fast demagnetization Toggle mode To en
7. Figure 44 Figure 45 and Figure 46 In this case it is possible to use the default values of HALL SENSOR STEPS CW xxx and HALL SENSOR STEPS CCW xxx Otherwise the user should edit the ky Doc ID 15773 Rev 1 63 85 Designing an application using the BLDC software library UM0708 64 85 HALL SENSOR STEPS CW xxx and HALL SENSOR STEPS CCW xxx commutation tables according to its own configuration define HALL SENSOR STEPS CW xxx and HALL SENSOR STEPS CCW xxx These define statements set the Hall sensor commutation tables required for the drive Refer to Section 4 3 3 for details on the commutation table define HALL MAX SPEED 01H2 Defines the rotor mechanical frequency above which speed feedback is not realistic This function can be used to discriminate glitches define HALL MIN SPEED 01H2 Defines the rotor mechanical frequency below which speed feedback is not realistic This function can be used to discriminate too low frequencies define HALI CAPT TIMEOUT MS Defines the duration of the Hall sensor signal timeout in order to detect the zero speed define HALL MAX ERROR NUMBER Defines the number of speed error measurement occurrences before signaling the error on speed feedback Control stage parameters MC ControlStage param h The MC ControlStage param h header file contains the parameters related to the control stage These settings must be modified if the firmware is used with a customized hardware differen
8. MC FuncRetVal t driveStartUpInit void The purpose of this function is to reset the local drive variables to update the local state variable DriveState and to call the low level function relative to this state The local drive variable are Validation of the measured speed flag bValidatedMeasuredSpeed Speed PID integral sum Drivestatus this variable is used to report a fault condition coming from the BLDC Drive function Doc ID 15773 Rev 1 77 85 Library functions UM0708 Input Returns Note driveStartUp Synopsis Description Input Returns Note driveRun Synopsis Description Input Returns Note None The returned value is the one coming from the low level function FUNCTION RUNNING no state change is required by this function FUNCTION ENDED the state change is requested by this function FUNCTION ERROR an error condition occurs and must be reported It is called by the relative state machine function MC FuncRetVal t driveStartUp void The purpose of this function is to call the low level function relative to this state and to update the local state variable DriveState None The returned value is the one coming from the low level function FUNCTION RUNNING no state change is required by this function FUNCTION ENDED the state change is requested by this function FUNCTION ERROR an error condition occurs and must be reported It is
9. Name Type Description This virtual timer is used for two purposes It counts the duration of the welcome message It counts the time interval for the key repetition function When the joystick is set in one position or the button is VTIM KEY Polling pressed a fixed delay time KEY HOLD TIME 300 ms is respected before repeating this function KEY REPEAT TIME 100 ms This can be used to increase or decrease a field value by keeping the joystick pressed UP or DOWN VTIM DISPLAY BLINK Polling This virtual timer is used to count the cursor blinking frequency DISPLAY BLINKING TIME 300 ms VTIM DISPLAY REFRESH Polling This virtual timer is used to count the LCD refresh frequency DISPLAY REFRESH TIME 300 ms Doc ID 15773 Rev 1 53 85 Getting started with the STM8S BLDC firmware UM0708 Table 10 BLDC virtual timers continued Name Type Description This virtual timer is used to count the delay time between the VTIM USER INTERFACE REFRESH Polling visualization of the error messages when several faults occur simultaneously This delay is set by 1 s by the firmware This virtual timer is used to call the BLDC drive function see Section 4 5 DEV DUTY UPDATE TIMER Automatic This virtual timer is used to update the low level register BLDC CONTROL TIMER Automatic This virtual timer is used for three purposes It counts the duration of the bootstrap phase see Sectio
10. Table 7 TIM1 channel output configurations Output configuration High side Low Side Type of outputs Phase floating Off Off PWM signal applied to the high side PMM ai Independent PWM signal applied to off PWM the low side High side active On Off Complementary Low side active Off On The ability of TIM1 to generate complementary or independent channel outputs has been used Independent or complementary channel outputs To generate independent outputs the right channel outputs must be enabled This is done by setting CCxE and CCxNE bits in the Capture compare enable registers TIM1_CCERx registers as shown in Table 8 The PWM mode is selected by setting the OCxM 2 0 bits of the Capture compare mode registers TIM1_CCMRx to PWM mode 1 active in up counting until the counter reaches the compare register Note When two outputs of a timer channel are independent one of the two outputs must be off In this case the pin output is no more driven by the timer and the pin polarity cannot be configured by the OCxP bits In this case the polarity of the correspondent GPIO pin must be set according to the polarity required by the hardware Table 8 Capture compare enable bit register configuration High side Low side CCxE CCxNE Off Off 0 0 PWM Off 1 0 Off PWM 0 1 ki Doc ID 15773 Rev 1 43 85 Getting started with the STM8S BLDC firmware UM0708 4 3 2 44 85 To genera
11. and to get 100 of duty cycle high speed Figure 9 Dynamic BEMF sampling method implementation PhA VVV Ph B Ph C Sampling during T off off time Sampling during T on on time 20 85 Doc ID 15773 Rev 1 ky UM0708 Introduction to STM8S BLDC control 2 5 Fast demagnetization The reverse voltage on the winding can be increased to speed up the floating phase demagnetization This is achieved by applying the PWM signal to the appropriate high or low side switch transistor If the PWM signal is not applied to the right transistor the free wheeling diode applies a voltage in the same direction as the current to be demagnetized thus slowing down the demagnetization process Refer to application note AN1129 referenced in Section 1 5 Reference documenis The following description assumes that the three phase bridge is similar to the one shown in Figure 10 and that the difference between the forward voltage drop of the free wheeling diode and the conduction drain source voltage drop of the power switches is negligible Figure 10 Three phases bridge and stator windings Figure 11 shows the transition between step 1 T1 T4 closed and step 2 T1 T6 closed In this case the current that flows out of phase B has to be demagnetized Phase B terminal will be clamped to HV by the free wheeling diode D3 The neutral point is HV 2 during T on If the PWM signal is applied to the high side s
12. define Rising Fmin and define Falling Fmin Defines the delay coefficients applied for rotor speeds lower than or equal to the minimum frequency Freq Min All the delay coefficients are expressed as 1 256 of the step time e define F 1 Defines the motor speed for the first intermediate value of the curve see Figure 13 It is expressed in rpm define Rising F 1 and define Falling F 1 Defines the delay coefficients for the first intermediate value of the curve e define F 2 Defines the motor speed for the second intermediate value of the curve It is expressed in rpm define Rising F 2 and define Falling F 2 Defines the delay coefficients for the second intermediate value of the curve e define Freq Max Defines the maximum frequency of the rotor speed curve It is expressed in rpm define Rising Fmax and define Falling Fmax Defines the delay coefficients applied for rotor speeds higher than or equal to the maximum frequency Freq Max 5 1 4 Hall sensor parameters MC hall param h The MC hall param h header file contains the parameters related to the Hall sensors These settings are used only in sensored configuration e define HALL SENSORS PLACEMENT Defines the Hall sensor distribution It can be setto DEGREES 60 orto DEGREES 120 The user can select the required sensor distribution and arrange the hall sensors connection in order to reproduce the configuration described in the corresponding figure Figure 43
13. point reconstruction while keeping the compatibility with the power board present in the kit UM0379 It is possible to design a common voltage divider for bus voltage and motor neutral point based on the final application and use only one sampling 46 85 Doc ID 15773 Rev 1 ky UM0708 Getting started with the STM8S BLDC firmware Figure 40 Asynchronous conversions PWM out Asynchro sampling l l l l nous If Bus voit Heat Sink Neutral P Use BUS Volt I I I I I I I Start of conversion 1 1 The start of 4 3 3 conversion depends on the conversion and execution time of the first synchronous conversion Hall sensor management When the firmware is configured for sensor drive the rotor position and speed control are performed by Hall sensors These measurements are performed using the input capture feature of the STM8S 16 bit general purpose timer TIM2 see Figure 41 Before starting the drive the status of the three Hall sensor inputs is read and the appropriate step to be applied is selected according to this configuration The polarity expected edge of the input signals is set as follows if the value of the Hall sensor signal is high then the expected edge corresponding to this sensor is a falling edge otherwise it is a rising edge Figure 41 TIM2 peripheral used for Hall sensor management Hall H1 Hall H2 TI M2 Hall H3 During each further c
14. 4 Getting started with the STM8S BLDC firmware 37 4 1 Application state machine 0 000 ee 37 4 1 1 Description of the states ee 37 4 1 2 Description of the state machine operation 38 4 2 Library architecture 1 aaa e x RR ER RR REA EURO s 39 4 2 1 Virtual registers seso 0 0 ce eee 40 4 2 2 Virtual VOS e nga ee iaga kr ceed eau deed eee PR eee dade rs 40 4 2 3 Drive structure 2 2 02 ee 41 4 3 Low level control 52 na paaa Rh RR Rr debt ERR RR be eee 42 4 3 1 Using the advanced control timer peripheral TIM1 42 4 3 2 Using the ADC i e cox ae these GR ex oe eee e Eke bind Set 44 4 3 3 Hall sensor management 0 ee 47 4 3 4 Dissipative brake poorer eee 51 4 4 High level control aag feats secre es NEW MICRO bee hese KINANA PA 52 4 4 1 BLDC scalar control 000 c eects 52 4 5 Virtual timers s4v hes tkiow ae TAGAHANGA DBP EGRE Ea3eEX ae hea e E 53 4 5 1 Using BLDC virtual timers 0 00000 cece ee 53 4 5 2 Virtual timers related functions AA 54 5 Designing an application using the BLDC software library 55 5 1 Customizing the BLDC software library parameter file 55 5 1 1 BLDC configuration file MC BLDC confh aa 55 5 1 2 BLDC motor parameters MC BLDC Motor Param h 56 5 1 3 BLDC drive control parameters MC BLDC Drive Param h 56 5 1 4 Hall sensor parameters MC hal
15. DEBUGx PIN string by the same number as in DEBUGx PIN This setting is not used if the debug feature is not enabled define C D DEBUG PORT and define C D DEBUG PIN These define statement can be used to set the mapping between the C D event debug signal see Section 5 1 3 and the test pins see Section 5 1 9 The first define statement specifies the test pin by replacing the x character in the DEBUGx_PORT string by the proper number For instance if the debug pin used is pin 0 set DEBUGO_PORT The second define statement also specifies the test pin used by replacing the x character in the DEBUGx_PIN string by the same number as in the first define statement This setting is not used if the debug feature is disabled define AUTO SWITCH PORT and define AUTO SWITCH PIN These define statement can be used to set the mapping between the debug Auto switch signal see Section 5 1 3 and the debug pins see Section 5 1 9 The first define statement specifies the test pin by replacing the x character in the DEBUGx_PORT string by the proper number For instance if the test pin used is pin 0 set DEBUGO_PORT The second define statement also specifies the debug pin by replacing the x character of the DEBUGx_PIN string with the same number as in the first define statement This setting is not used if the debug feature is disabled define PWM ON SW PORT and define PWM ON SW PIN These define statement define the mapping between the BEMF samplin
16. FWLIB Each part is in turn divided into is divided in three sublevels like shown in Figure 34 e Inc folder containing the prototype definitions h files e Src folder containing the implementation files c files e Param folder containing the configuration files h file The configuration files contains all the required define statements allowing to customize the motor control drive Param folder is not present for the STM8 FWLIB Figure 34 STM8S BLDC library organization a STM8 STVD COSMIC stw E MG FWLIB SCALAR gt Ep ed 1 Inc T fq Param et J Inc anand fai Param es eens Src Doc ID 15773 Rev 1 39 85 Getting started with the STM8S BLDC firmware UM0708 The high level modules contain the device independent algorithms while the low level modules contain the hardware dependent code It means that only the low level modules interact directly with the peripherals and the interrupt service routines of the microcontroller The high level modules interact with the low level modules mainly through three interfaces see Figure 33 e The virtual registers e The virtual I Os e The drive structure 4 2 1 Virtual registers The virtual registers are composed of two sets of 8 bit and 16 bit registers Refer to Table 4 for a description of the virtual registers implemented in the BLDC firmware Table 4 Virtual registers Name Size Description VDEV REG8 HEATSINK TEMPERATURE 8 bits C
17. Firmware compatibility with STM8S motor control builder GUI see Section A 3 ky Doc ID 15773 Rev 1 11 85 Features UM0708 e Required ROM RAM Table 1 gives the ROM and RAM requirements These values include non motor control related code implemented for demonstration purposes such as ADC management or software time bases They serve as a rough guide since the code size produced can be smaller or larger depending on the chosen memory model Table 1 ROM and RAM requirements Configuration ROM Kbytes RAM bytes Sensorless open loop 7 08 310 Sensorless closed loop 7 62 324 Sensor open loop 6 92 314 Sensor closed loop 7 46 328 1 4 Development tools The BLDC software library has been fully validated using the STM8 128 MCKIT motor control starter kit This kit also includes a Raisonance R Link hardware debugger which makes it an ideal solution to start a project and evaluate with the BLDC software library As a consequence it is recommended to acquire the STM8 128 MCKIT to quickly implement and evaluate the BLDC library 1 4 1 Toolchains The BLDC library has been compiled using COSMIC C toolchains running under ST Visual development release 4 1 2 STVD Free IDE and demonstration versions of third party toolchains can be found at http www st com mcu under Support Downloads A complete software package consists of e Anintegrated development environment IDE interface STVD free download ava
18. a voltage level beyond the threshold is present in the bus voltage If this condition occurs and the brake management is enabled in the firmware the Over voltage fault is not more generated instead the break control pin is driven to turn on the external brake resistor in order to dissipate the extra energy If the brake resistor is active it is expected that the bus voltage level will decrease so its value monitored always with the ADC conversion to detect the dissipative brake action condition to stop If the value falls below a threshold the dissipative brake is stopped In order to adda hysteresis between the switching on and off the turn off threshold is reduced compared to the turn on threshold See Section 5 1 6 for details on the enabling or disabling of this feature and Section 5 2 for details on the hardware setup required to use that feature Doc ID 15773 Rev 1 51 85 Getting started with the STM8S BLDC firmware UM0708 4 4 4 4 1 52 85 High level control This section explains how to implement a high level BLDC drive algorithm independently from microcontroller resources and peripheral BLDC scalar control The high level BLDC drive algorithm interacts with the low level control to get the value and reliability of the rotor frequency and to set the control variables duty cycle and current reference and the delay coefficient if the Auto delay option is enabled The core of the high level BLDC drive con
19. applied to the high side switch the motor neutral point becomes equal to ground so that the BEMF value can be directly converted by using the ADC ST patented method The sampling point inside the PWM period is set by using TIM1 channel 4 to trigger the ADC conversion The detection of the zero crossing point is performed by comparing the converted value of BEMF to a fixed threshold The default value of this threshold is 0 2 V Figure 8 gives a description of the sampling during T off sequence Doc ID 15773 Rev 1 19 85 Introduction to STM8S BLDC control UM0708 Figure 8 Sampling during off time 300V 300V PWM ON PWM OFF I A GND 5V C bemf bemf ADC T4 always ON T4 always ON A GND bii voltage clamping Current in A amp B Phases Current in A amp B Phases when T1 ON when T1 OFF ON PWM signal Trig signal ADC will be started by rising edge of the trigger 2 4 3 Dynamic BEMF sampling method If the value of the duty cycle to be applied is known in advance for instance when no current regulation or limitation is required the sampling method to be applied Sampling during T off or T on can be set on the fly according to the duty cycle value This is achieved by using three voltage dividers driven by GPIO pins as shown in Figure 9 This method allows both to minimize BEMF partitioning Sampling during off time for low duty cycle applied low speed
20. bit value adjustable from 0 to 32767 This parameter is used only if a PID controller has been selected define SPEED KP DIVISOR This define statement is used to configure the scaling factor of the proportional gain for the speed regulation loop 16 bit power of two value define SPEED KI DIVISOR This define statement is used to configure the scaling factor of the integral gain for the speed regulation loop 16 bit power of two value define SPEED KD DIVISOR This define statement is used to configure the scaling factor of the differential gain for the speed regulation loop 16 bit power of two value This parameter is used only if PID controller has been selected define SPEED OUT MAX This define statement sets the positive saturation value of the speed controller output This value should be equal to the maximum value applicable for the control variable For Voltage mode SPEED OUT MAX should be equal to the maximum value of timer counter It is related to the PWM frequency and CPU frequency see Equation 3 Equation 3 Maximum timer counter in Voltage mode _ CPUFreq Hz MaxtimerFreq PWMFreq Hz For Current mode SPEED OUT MAX should be set to the CURRENT LIMITATION value Doc ID 15773 Rev 1 61 85 Designing an application using the BLDC software library UM0708 62 85 Optional features initial values and parameters define FAST DEMAG Defines the starting configuration of the fast demagnetization opti
21. called by the relative state machine function MC FuncRetVal t driveRun void The purpose of this function is to call the low level function relative to this state and to update the local state variable DriveState The DriveStatus is checked to detect fault condition coming from the low level functions If this condition is detected the return value is FUNCTION ERROR otherwise the returned value is the one coming from the low level function None FUNCTION RUNNING no state change is required by this function FUNCTION ENDED the state change is requested by this function FUNCTION ERROR an error condition occurs and must be reported It is called by the relative state machine function Doc ID 15773 Rev 1 ky UM0708 Library functions driveStop Synopsis Description Input Returns Note driveWait Synopsis Description Input Returns Note driveFault Synopsis Description Input Returns Note MC FuncRetVal t driveStartUp void The purpose of this function is to call the low level function relative to this state and to update the local state variable DriveState None The returned value is the one coming from the low level function FUNCTION RUNNING no state change is required by this function FUNCTION ENDED the state change is requested by this function FUNCTION ERROR an error condition occurs and must be reported It is called by the relative sta
22. crossing Z and commutation C has been dedicated for the current measurement During this interval the direct current that flows into the motor is not affected by the switching between two steps and current sampling is performed during the on time The remaining interval between the commutation C and the end of demagnetization D it is left for the user It is called user defined synchronous conversion Figure 39 Synchronous conversion Phase current Z Zero Crossing C Commutation D End of demagnetization zZ User defined synchronous sampling Asynchronous conversion There is no guarantee that asynchronous conversion is performed during the T on or T off and it is not possible to set a delay with respect to commutations As a consequence asynchronous conversions are used for conversions that do not require sampling to be performed at a specific point inside the PWM period such as bus voltage level or the heatsink temperature measurement see Figure 40 A list of asynchronous conversions has been defined in the current firmware implementation It includes bus voltage sampling heatsink temperature sampling motor neutral point sampling plus one user defined conversion called user defined asynchronous sampling Note Two distinct bus voltage dividers and samplings bus voltage and motor neutral point have been implemented in the current implementation to maximize the resolution of the neutral
23. first three steps a 14 Shinano motor BEMF signal cece ett 14 Current mode AA AA 16 Step time measurement sensorless drive a 17 BEMF and phase current synchronization auaa cee eee 17 Demagnetization time 0 0 een ee 18 Sampling during the on time 2 2 0 2 tetas 19 Sampling during off time liliis 20 Dynamic BEMF sampling method implementation lille 20 Three phases bridge and stator windings llli elles 21 Demagnetization between step 1 and step2 elles 22 Demagnetization between step 2 and step3 ee 23 Rising Falling delay computation accordingly a specified curve 24 Alignment phase 0 0 0 nett 25 Starting Sequence 1 2 tetas 26 Menu structure and navigation 0 0 cee eee ee 27 BLDC drive welcome message 2 20 00 cect tee eee 28 ARA scien ahs 29 Main menu Target speed and measured speed eee eee eee eee 29 Selecting the target speed 0 0 cette 29 User interface sub menu 21 tees 30 Field selected for edition 1 0 0 eects 30 Changing rising and falling delays llis 31 Control variables 2l hh 31 Configuring the speed regulator proportional and integral terms 32 Configuring the speed regulator tuning derivative term demagnetization time 32 Current measure
24. strategy is applied e In speed closed loop configuration the speed regulation is not applied until the measured rotor speed reaches the required threshold The control variable remains constant until this condition is met see Figure 15 The startup output condition is validated only when the minimum rotor speed is measured e In speed open loop configuration the startup output condition is validated when the drive is switched to auto commutation mode If no BEMF zero crossing is detected until the end of the synchronous sequence the Startup failed fault message is displayed on the LCD see Section 3 6 8 Before each motor startup a bootstrap sequence ensures that the bootstrap capacitor used by the high side driver will be recharged This operation is performed by closing the three Doc ID 15773 Rev 1 25 85 Introduction to STM8S BLDC control UM0708 2 8 Caution 26 85 low side switches for the time required to charge the capacitors In the BLDC firmware a duration of 5 ms is implemented Figure 15 Starting sequence Rotation speed rpm 2000 closing the regulation loop 1000 I j synchronous waiting for BEMF 7 sequence Pi I I enabling aNto 1 2 3 time s commutated molle I Control variable 1 I imposed 1 Active brake The BLDC firmware features the Active brake option This function switches on the active brake of the motor by injecting a DC current into
25. the converted values The precision of the measurement can also be improved by setting EXPECTED MCU VOLTAGE to the appropriate value For example if the microcontroller measured power supply voltage is 5 1 V it is possible to set Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library 4 EXPECTED MCU VOLTAGE to 5 1 to maximize the precision in the computation of the converted values define MAX BUS VOLTAGE and define MIN BUS VOLTAGE These two values expressed in Volt set the bus DC voltage range If the bus voltage exceeds OVERVOLTAGE THRESHOLD V or is below UNDERVOLTAGE THRESHOLD V the corresponding error event is generated and is kept as long as the bus voltage remains outside the allowed range In addition if DISSIPATIVE BRAKE is defined an overvoltage event will be handled by activating the brake resistor and the corresponding error message will not be issued define NTC THRESHOLD C and define NTC HYSTERIS C These two values expressed in C are used to set the power device operating temperature range measured at heatsink If the measured temperature exceeds NTC THRESHOLD C the corresponding error event is generated and is kept as long as the measured temperature remains above NTC THRESHOLD C NTC HYSTERESIS C define TEMP SENS ALPHA define TEMP SENS BETA and define TEMP TO These three values are used to characterize the transduction curve between temperature sen
26. two groups contain functions related to the microcontroller while the first group contains hardware independent functions as described in Section 4 2 High level MC modules The high level MC modules are stored under the folder MC FWLIB SCALAR They are composed if the following modules e MC BLDC Drive this module contains all the functions related to the electrical drive and engine control see Section MC BLDC Drive c module e MC BLDC Motor this module is the holder of the drive structure It contains all the function used to interact retrieve or set parameters directly with the BLDC drive structure or to provide the reference of that structure for other modules e MC BLDC User Interface this module is the holder of the user interface specific to the BLDC drive It contains a function used to provide the reference of this structure for other modules The interaction with this structure is managed also by MC User Interface c MC User Interface this module is used to manage the user interface The user interface has been implemented using a joystick a button and an LCD display see Doc ID 15773 Rev 1 75 85 Library functions UM0708 Note 76 85 Section 3 6 It interacts with MC keys and MC display modules The user interface is adapted to the drive by the MC BLDC User Interface module MC dev this module makes the interface between high level and low level modules For instance it initializes the low
27. vector This configuration is not an ordinary position but itis the intermediate position between two steps for example between step 6 and step 1 if you want to start the next phase with step 1 Moreover this configuration has the particularity to energize the three windings to generate a more important flux see Figure 14 Doc ID 15773 Rev 1 ky UM0708 Introduction to STM8S BLDC control Usually the high side switch T1 is controlled by a PWM signal with a duty cycle that increases following a ramp The current limitation sets the maximum current that flows into the motor during the alignment phase Figure 14 Alignment phase 300V DC T1 T4 T6 2 7 2 Note Ramp up phase The second phase is the ramp up phase It is performed to accelerate the motor up to the required speed that allows the BEMF zero crossing detection To do this an asynchronous sequence of steps must be applied to the motor This sequence of steps generates a rotating stator field that will accelerate the rotor up to the target speed The strength of the applied torque is usually controlled applying a fixed duty cycle or controlling the direct current that flows into the motor When the rotor speed is sufficient to detect the BEMF zero crossing the synchronization mechanism is enabled This mechanism it is also called auto commutation mode Then according to the configuration of the speed loop regulation one of the following
28. 16 0000 10 67 define MCI CONTROL PINS define MCI CONTROL DDR and define MCI CONTROL DR When the firmware runs on a customized hardware these define statements can be used to configure the control pins which enable the dividers used for the BEMF sampling during T on see Section 2 4 The first define statement specifies the pins used for OR ing the BITx which are used for example BIT4IBIT5IBIT6 The second define statement specifies the port used by replacing the x character in the GPIOI 2 DDR string by the appropriate letter If the port used is port I set GPIOI gt DDR The third define statement also specifies the port used The value should be identical to the second define statement and the x character in the GPIOI gt ODR string should be replaced by the same letter of above Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library Note Three different pins must be used on the same port define Z DEBUG PORT and define Z DEBUG PIN These define statement can be used to set the mapping between the Z event debug signal see Section 5 1 3 and the test pins see Section 5 1 9 The first define statement specifies the test pin which is used by replacing the x character in the DEBUGx PORT string by the proper number For instance if the debug pin used is pin O set DEBUGO PORT The second define statement also specifies the test pin by replacing the x character of the
29. It analyzes the zero crossing of the floating phase BEMF signal to establish the commutation point The match between the BEMF signal of the floating phase with respect to the motor neutral point or star point is used to generate the commutations between two consecutive steps in order to achieve the rotor synchronization Rotor speed regulation In addition to the synchronization with the rotor the BLDC drive can control the rotor speed to compensate for eventual load variations In this case the drive it is called closed loop drive If the BLDC synchronous drive does not perform rotor speed control the drive is named open loop drive In this case the final rotor speed is affected by load variations Bus voltage modulation Normally the BLDC drive is performed by applying a PWM signal to modulate the bus voltage This is implemented by using one of the following control method e Current mode The control variable is the phase current Current regulation is achieved by setting the current level through a PWM signal and by using an external RC filter to set the comparator threshold A dedicated microcontroller input driven by the output of the comparator is used to switch off the PWM signal used for current regulation The turn on is synchronized with then PWM period see Figure 3 e Voltage mode The control variable is the phase voltage Voltage regulation is achieved by fixing the duty cycle of the applied PWM signal Current limit
30. LIMITATION Defines the value of the current limitation expressed in mA This parameter is used both in Voltage and Current mode to set the maximum allowed DC current This parameter is not used during the alignment and ramp up phases define STARTUP CURRENT LIMITATION Defines the value of the current limitation expressed in mA used during the alignment and ramp up phases This parameter is used both in Voltage and Current mode to set the maximum allowed DC current Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library Type of speed PID controller sampling time and initial values define SPEED PID TYPE This define statement is used to configure the type of speed controller There are two possible setting PI sets the proportional integral regulator PID sets the proportional integral derivative regulator define SPEED PID SAMPLING TIME This define statement is used to select the speed regulation loop frequency It is expressed in milliseconds define SPEED KP This define statement is used to configure the proportional constant of the speed loop regulation 16 bit value adjustable from O to 32767 define SPEED KI This define statement is used to configure the integral constant of the speed loop regulation 16 bit value adjustable from O to 32767 define SPEED KD This define statement is used to configure the derivative constant of the speed loop regulation 16
31. M 10 bit ADC timers UART SPI I2C Datasheet STM8S105xx Access line 16 MHz STM8S 8 bit MCU up to 32 Kbytes Flash integrated EEPROM 10 bit ADC timers UART SPI I C Datasheet STM8S20xxx Performance line 24 MHz STM8S 8 bit MCU up to 128 Kbytes Flash integrated EEPROM 10 bit ADC timers 2 UARTs SPI IPC CAN Datasheet STM8S903K3 16 MHz STM8S 8 bit MCU up to 8 Kbytes Flash 1 Kbyte RAM 640 bytes EEPROM 10 bit ADC 2 timers UART SPI I2C User manual UM0379 MB459 motor control evaluation board User manual UM0712 STM8S three phase ACIM motor software library V1 0 PM0044 STM8 CPU programming manual User manual UM0144 ST Assembler Linker User manual UM0036 ST Visual Develop STVD User manual UM0482 STM8 128 EVAL evaluation board UM0709 STM8S MCKIT motor control starter kit Doc ID 15773 Rev 1 13 85 Introduction to STM8S BLDC control UM0708 2 Introduction to STM8S BLDC control 2 1 Introduction to BLDC theory A brushless three phase motor is composed by a fixed part made of a set of three windings called stator and a mobile part containing an internal permanent magnet called rotor In BLDC motor control the electrical cycle is subdivided into six commutation steps For each step the bus voltage is applied to one of the three phase windings of the motor while the ground is applied to a second winding The third winding remains open The successive steps are executed in the same way e
32. T define KEY LEFT BIT define KEY RIGHT PORT define KEY RIGHT BIT define KEY UP PORT define KEY UP BIT define USER BUTTON PORT define USER BUTTON BIT When the firmware runs on a customized hardware these define statements can be used to configure the ports and pins used for the user interface input signals joystick and button Define the port by setting the xxx PORT define statements to GPIOx where x specifies the port For instance set GPIOH if port H is used Define the pin by setting the xxx BIT define statements to GPIO PIN x where x with specifies the pin For instance set GPIO PIN 1 if pin 1 is used define DISSIPATIVE BRAKE PORT define DISSIPATIVE BRAKE BIT When the firmware runs on a customized hardware these define statements can be used to configure the port and pin used for the dissipative brake signal see Section 4 3 4 In the first define statement set the port by replacing the x character in the GPIOx string with the proper letter For instance set GPIOH if port H is used In the second define statement specify the pin by replacing the x character in the GPIO_PIN_x string with the proper number For instance set GPIO_PIN_1 if pin 1 is used Hall parameter microcontroller interfaces MC_stm8s_hall_param h The MC_stm8s_ hall param h header file contains the define statement related to the definitions of the pins and ports used to configure the Hall sensors The pins are related to TIM2 inputs
33. T3 Step 5 T5 T2 Current B from bridge to motor Low side T2 Step 6 T5 T4 Current A from motor to bridge High side T5 Setting the delay coefficient accordingly a specified curve It is important to select the most adequate delay coefficients to run a BLDC motor in standalone closed loop mode and achieve a given target speed For each target speed these values should be recorded in a table which will be used by the STM8S firmware It is recommended to collect data for four speeds the minimum and maximum speeds specified plus two intermediate speeds The STM8S firmware then makes a linear extrapolation of delay coefficients between the four specified speeds to ensure smooth operation Once the data are collected edit the MC BLDC drive h file and fill in the fields dedicated to the rising falling delay coefficients calculation see Section 5 1 3 BLDC drive control parameters MC_BLDC_Drive_Param h Once the motor runs rising falling delay coefficients are computed following a linear curve between Freq_min and F_1 F_1 and F_2 F_2 and Freq_max see Figure 13 Doc ID 15773 Rev 1 23 85 Introduction to STM8S BLDC control UM0708 2 7 2 7 1 24 85 Figure 13 Rising Falling delay computation accordingly a specified curve Rising_Fmax Falling Fmax Rising F 2 Falling F 2 Rising F 1 Falling F 1 Rising Fmin Falling Fmin Freq min F 1 F2 Freq max 1 Freq min F 1 F 2 and Freq max a
34. able disable the toggle mode use the same sub menu and sequence as for fast demagnetization see Figure 29 When the toggle mode is enabled the absolute value of the target speed is kept but with a complemented sign to allow the user to run the motor alternatively in clock wise and counter clock wise direction each time the motor is restarted Figure 29 Enabling disabling fast demagnetization and toggle mode options Auto delay The sub menu shown in Figure 30 can be used to enable or disable the auto delay option Refer to Section 2 6 for more information regarding this option Figure 30 Auto delay option Doc ID 15773 Rev 1 ky UM0708 Running the demonstration program 3 6 8 Fault messages This section provides a description of the fault messages that can be displayed on the LCD screen when using the BLDC firmware together with the STM8 128 MCKIT There are seven different fault sources when using the BLDC firmware in conjunction with the STM8 128 MCKIT Overcurrent A low level was detected on the PWM peripheral dedicated pin BKIN This means that either the hardware overtemperature protection or the hardware overcurrent protection has been triggered Overtemperature An overtemperature was detected on the dedicated analog channel The threshold NTC THRESHOLD C and the related hysteresis NTC HYSTERESIS C are specified in the MC PowerStage Param h header file Bus overvoltage An ov
35. apture the step time measurement the change of polarity of the expected new capture of this channel and the selection of the appropriate steps redundancy resynchronization are performed As for sensorless drive the capture of the Hall sensor signal is called Z capture The speed measurement is performed using a software counter that increases each PWM period stores its value each time a input Z capture occurs and computes the rotor speed starting from the delta between these values see Section 2 2 Rotor speed measurement and Figure 42 The BLDC sensored drive is based on a commutation table that indicates the related step configuration for each combination of the Hall sensor signals represented by bits H1 H2 and H3 see Figure 42 The BEMF signal is related to the Hall sensors signals To achieve a maximum efficiency the step configuration must be synchronized with the Hall sensor configuration This synchronization is performed by the firmware accordingly to the commutation table Doc ID 15773 Rev 1 47 85 Getting started with the STM8S BLDC firmware UM0708 Figure 42 Step time measurement for sensored drive Phase current Z Zero Crossing C Commutation Software counter l Z j Step time measurement The Shinano motor is provided with three Hall sensors spatially distributed at 120 to each other with a phase shift electrical delta angle between maximum BEMF of phase A and H1 risin
36. ate the DAC values if required None None This function is automatically called by the BLDC_CONTROL_TIMER virtual timer at each sampling time period see Section 4 5 u16 GetSpeed_01HZ void The purpose of this function is to compute the measured rotor speed using the values coming from the low level function These values are stored inside the virtual register of the related sensor see Section 4 3 and Table 4 None Measured electrical rotor speed value express in tenth of Hz The value returned by this function is not already validated BLDCDelayCoefComputation Synopsis Description Input Returns Note void BLDCDelayCoefComputation u16 Motor Frequency The purpose of this function is to compute the delay coefficient accordingly the predefined curve see Section 2 6 Mechanical rotor speed express in rpm None The values computed are stored in the drive structure Doc ID 15773 Rev 1 ky UM0708 Library functions MC vtimer modules vtimer SetTimer Synopsis void vtimer SetTimer VtimerName t name timer res t msec void pCallback Description The purpose of this function is to initialize the virtual timer Input name is the reference to the virtual timer to be initialized It can be a mnemonic or a relative number msec is the duration of the virtual timer expressed in milliseconds pCallBack is the pointer to the function to be executed at the end of the counting It must be set to 0
37. ation level is set either by an external resistor voltage divider or by a PWM signal filtered by the RC circuit Doc ID 15773 Rev 1 15 85 Introduction to STM8S BLDC control UM0708 Figure 3 Current mode to inverter current reference low side i Operational Amplifier Comparator Current clock 4 4 Motor Voltage 1 D L H I 7 step time i step time Gain TT Programmable current i Ta Po setting limit or current O reference 2 2 Rotor speed measurement When the motor is running the rotating magnetic field of the rotor induces a BEMF signal in the stator windings If the motor is intrinsically sinusoidal or trapezoidal the induced BEMF signals are periodic and their frequency is proportional to the frequency of the motor turns The proportional coefficient is the number of motor pole pairs The motor speed can consequently be calculated by measuring the frequency of the BEMF signals as shown in Equation 1 Equation 1 BEMFfreq x 60 Moto rpm Borepairs The measurement of the rotor speed is performed by counting the time delay between two consecutive zero crossings of the BEMF signal This computation is also called step time measurement It is implemented in the BLDC firmware by means of a software counter managed by the timer update interrupt service routine TIM1 UPD ISR The TIM1 UPD ISR routine is executed during each PWM period The pre
38. ation program UM0708 36 85 Figure 31 Fault message shown in case of undervoltage To indicate the fault which occurred to the user the FAULT OCCURRED message remains displayed even if the source of the fault has disappeared The FAULT CONDITION message is displayed only when the fault condition is present If several fault events occur simultaneously they are displayed in the LDC one after the other If all fault sources disappear pressing the KEY button causes the main state machine to switch from the fault to the idle state Doc ID 15773 Rev 1 ky UM0708 Getting started with the STM8S BLDC firmware 4 Getting started with the STM8S BLDC firmware 4 1 Application state machine The motor control firmware library was developed around the state machine showed in Figure 32 The state machine is implemented in MC StateMacchine c module it is composed by the following states Reset Idle Start init Start Run Stop Wait Fault and Fault over 4 1 1 Description of the states Reset The system is in Reset state once after the main reset It is used to perform the main initialization Idle When the state machine goes into Idle state the motor is stopped and the system waits for a startup to be executed Start init The Start init state is executed at every restart of the motor It is used for specific initialization Start In this state the motor ramps Run After the end of the startup phase the moto
39. cision of the step time measurement is always proportional to the PWM period since zero crossings are sampled only once during each PWM cycle with the resolution of the closest cycle 16 85 Doc ID 15773 Rev 1 ki UM0708 Introduction to STM8S BLDC control Figure 4 Step time measurement sensorless drive Phase current Nh SS SS SS SS SSS SS SS SSS Step time measurement 2 3 Commutation delay and demagnetization time Since the BLDC drive is a synchronous drive the main objective of the drive is to ensure that the rotor position remains synchronized with the stator magnetic field It is possible to demonstrate that the maximum efficiency of the drive is obtained by keeping the magnetic field of the stator with a 90 degree spatial advance with respect to the rotor magnetic field This can be achieved by keeping the zero crossing in the middle of each step see Figure 5 Figure 5 BEMF and phase current synchronization BEMF Phase Current Commutation delay Zero crossing The commutation delay is the delay equal to a half step time between the zero crossing and the step commutation The BEMF signal can be measured only after the current of the floating phase has reached zero Otherwise the free wheeling diode would clamp the floating terminal voltage or the bus voltage to ground depending on the current direction As a consequence a delay time called demagnetization time must be respec
40. conf h The purpose of this file is to declare the compiler conditional compilation keys that are used throughout the entire library compilation process to select which speed position sensor is actually used If this header file is not edited appropriately no choice or undefined choice you receive an error message when building the project Note that you do not receive an error message if the configuration described in this header file does not match the hardware that is actually in use or in case of wrong wiring Doc ID 15773 Rev 1 55 85 Designing an application using the BLDC software library UM0708 5 1 2 56 85 The following define statement are used to choose Hall sensors or sensorless drive depending on your application requirements define HALL Uncomment this define statement when three Hall sensors 60 or 120 distribution are used to detect rotor position and speed Also fill MC hall prm h andMC stm8s hall param h as explained in Section 5 1 4 and Section 5 1 10 define SENSORLESS Uncomment this define statement when the BEMF detector is used to detect rotor position and speed BLDC motor parameters MC BLDC Motor Param h The MC BLDC Motor Param h header file contains the parameters related to the motor define MOTOR POLE PAIRS Defines the number of motor pole pairs define MAX SPEED RPM Defines the maximum rotor speed expressed in rpm BLDC drive control parameters MC BLDC Drive Pa
41. ction is triggered by a high logic level of the dissipative brake control signal DISSIPATIVE BRAKE ACTIVE LOW the braking action is triggered by a low logic level of the dissipative brake control signal define BUS VOLTAGE MEASUREMENT This define statement is used to configure the firmware to perform DC bus voltage measurement If the hardware does not support bus voltage measurement or if you want to disable this feature leave this define statement uncommented The bus voltage will not be measured by the firmware and will be assumed constant and equal to the value specified in the next define statement define BUS VOLTAGE VALUE Defines the constant value of the bus voltage if the bus voltage measurement feature has been disabled This setting is not used if the bus voltage measurement function is enabled define BUS ADC CONV RATIO Defines the DC bus voltage partitioning ratio performed by the hardware to allow the bus voltage measurement This setting is not used if the bus voltage measurement function is disabled define EXPECTED MCU VOLTAGE Defines the reference value of ADC conversions ADC conversions are usually performed using a voltage reference that is identical to the microcontroller power supply voltage 5 V To increase the resolution it is possible to design a customized hardware that uses a lower ADC reference value In this case EXPECTED MCU VOLTAGE contains the required value used for the computation of
42. d the user interface is automatically switched to the main menu regardless of which menu is selected 28 85 Doc ID 15773 Rev 1 ky UM0708 Running the demonstration program Figure 18 Help menu HELP MENU 1 HELP MENU 2 HELP MENU 3 3 5 Main menu target and measured rotor speed To enter the main menu press the joystick RIGHT one more time from the Help menu 3 The main menu allows to set the target rotor speed and display the measured speed see Figure 19 The main menu function is the same as the other sub menus except that the system is automatically switched to the main menu when the motor is started or stopped Figure 19 Main menu Target speed and measured speed 1 To set the target rotor speed press JOYSEL when the Targ rpm function is active gt displayed and blinks 2 After pressing JOYSEL the arrow changes in to a double arrow 1 to indicate that the value can be changed see Figure 20 3 Press the joystick UP and DOWN to increase and decrease the value Figure 20 Selecting the target speed When the motor is still enter a negative target speed to run the motor in the opposite direction ki Doc ID 15773 Rev 1 29 85 Running the demonstration program UM0708 3 6 3 6 1 30 85 User interface sub menus Sub menu overview Each sub menu of the user interface is composed of two fields which are in turn composed of one label one value and the corres
43. ding 9 high sink outputs A Highly robust I O design immune against current injection e Development support Embedded Single Wire Interface Module SWIM for fast on chip programming Non intrusive debugging 1 3 BLDC software library V1 0 features CPU running at 16 MHz The BLDC software library source code is available free of charge if it is used in an end application based on ST products The main library features are the following e ics BLDC modes trapezoidal 6 step method Sensorless mode back EMF voltage on the non energized phase is monitored and used to trigger the commutation events Sensor mode Hall sensors trigger the commutation events Voltage mode PWM duty cycle is set directly via 16 bit PWM generator Current mode internal current loop and external voltage reference are used jointly to maximize the current in motor windings The PWM duty cycle is automatically managed by the current feedback loop output Open loop operation Closed loop operation Proportional integral PI regulator 1 to 255 ms sampling time DC bus voltage measurement DC bus brake resistor management Heatsink temperature measurement Fault handling including overcurrent shunt resistor network required DC bus overvoltage undervoltage heatsink overtemperature User interface with LCD and joystick Two channel virtual DAC functionality for real time tracing of software variables
44. dingly if needed The following steps are required to perform these tasks 1 Gather all the information regarding the hardware motor parameters power device features speed position sensor parameters current sensors transconductance 2 Use an IDE to edit the following high level parameters files present in the folder STM8 MC KITMC FWLIB SCALARflparam see Figure 34 MC BLDC conf h see Section 5 1 1 MC BLDC Motor Param h see Section 5 1 2 MC BLDC Drive Param h see Section 5 1 3 3 If the drive is performed using the Hall sensor edit Mc hall param h parameter header files see Section 5 1 4 4 Edit using an IDE the following parameter header files if you hardware is different from the STM8 128 MCKIT MC ControlStage param h see Section 5 1 5 MC PowerStage Param h see Section 5 1 6 5 t may be necessary to edit also the low level parameters header files present in the folder STM8 MC_KIT STM8_MC_FRAMEWORK param MC stm8s clk param h see Section 5 1 7 MC stm8s BLDC param h see Section 5 1 8 MC stm8s port param h see Section 5 1 9 MC stm8s hall param h see Section 5 1 10 6 Re build the project and download it on the STM8Sxx microcontroller These modifications can be performed automatically using the STM8S MC Firmware Library builder see Section A 3 Customizing the BLDC software library parameter file BLDC configuration file MC BLDC
45. e not used for other purposes inside the firmware and are not configured as outputs define CURRENT FILTER This define statement is used to configure the filter applied to the ETR signal The ETR signal is used to manage the current limitation regulation in the BLDC drive see Section 4 3 1 This filter is used to prevent unwanted shutdown of the PWM signal which may be caused by glitches Using a larger filter may lead to a less precise current control It can also be used to define the minimum T on of the PWM signal required for BEMF sampling see Section 2 4 Table 12 gives the values of the allowed filters Doc ID 15773 Rev 1 69 85 Designing an application using the BLDC software library UM0708 70 85 Table 12 External filters Filter for Filter for define CURRENT_FILTER value F_CPU 16 MHz F_CPU 24 Mhz in ps in ps CURRENT_FILTER_NOFILTER 0 0625 0 0417 CURRENT_FILTER_F_N2 0 1250 0 0833 CURRENT_FILTER_F_N4 0 2500 0 1667 CURRENT_FILTER_F_N8 0 5000 0 3333 CURRENT_FILTER_F2_N6 0 7500 0 5000 CURRENT_FILTER_F2_N8 1 0000 0 6667 CURRENT_FILTER_F4_N6 1 5000 1 0000 CURRENT_FILTER_F4_N8 2 0000 1 3333 CURRENT_FILTER_F8_N6 3 0000 2 0000 CURRENT_FILTER_F8_N8 4 0000 2 6667 CURRENT_FILTER_F16_N5 5 0000 3 3333 CURRENT_FILTER_F16_N6 6 0000 4 0000 CURRENT_FILTER_F16_N8 8 0000 5 3333 CURRENT_FILTER_F32_N5 10 0000 6 6667 CURRENT_FILTER_F32_N6 12 0000 8 0000 CURRENT_FILTER_F32_N8
46. e will be taken into account if the corresponding mode is not selected Configuring the speed regulator When the firmware is configured in speed closed loop mode the user can adjust the speed regulator parameters while the motor is running The speed regulator implemented can be a proportional integral P1 or a proportional integral derivative PID regulator The regulator Doc ID 15773 Rev 1 31 85 Running the demonstration program UM0708 Note 3 6 5 32 85 acts on the control variable minimizing the error between the target speed and the measured speed Figure 25 shows the speed regulator sub menu It allows to change the proportional term Speed KP and the integral term Speed KI of the speed controller Figure 25 Configuring the speed regulator proportional and integral terms The speed regulator type PI or PID can be selected using the following define statement included in the MC BLDC Drive Param h header file define SPEED PID TYPE PI unit none Select a PI speed regulator define SPEED PID TYPE PID unit none Select a PID speed regulator In this case the derivative term is set through the Speed KD field of the sub menu shown in Figure 26 Figure 26 Configuring the speed regulator tuning derivative term demagnetization time Changing the Speed KD field has no effect if the speed controller is of PI type Changing the Speed KP Speed KI Speed KD has
47. ements 00 cee ete 12 Fast demagnetization table eee 23 Document conventions 0 000 hh 28 Virtual registers csse Eke a ek eee RR x RR de Ros Ren a ee ACA BANG kapa 40 Viral OS i ngaa eise x e nor aon x aea ioc BING ga a ee a Rd OU o 40 BLDC Drive structure 0 0 0 cc eh rr 41 TIM1 channel output configurations 0 0 0 0 0 cee eee 43 Capture compare enable bit register configuration liliis 43 Hall sensor commutation table for Shinano motor lesen 50 BLDC virtual timers lille rr 53 Debug pins description llle I naai 62 External fiets was iiia ea a a a dn a a aa hh 70 Hall sensor filters arosi ran aed eae aa va Te Dee ae Re dae NGA 73 lieder PTT 83 Document revision history llieleeeeeeee mr 84 Doc ID 15773 Rev 1 5 85 List of figures UM0708 List of figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Figure 35 Figure 36 Figure 37 Figure 38 Figure 39 Figure 40 Figure 41 Figure 42 Figure 43 Figure 44 Figure 45 Figure 46 Figure 47 Figure 48 6 85 BLDC motor control sequence
48. ervoltage was detected on the dedicated analog channel The threshold MAX BUS VOLTAGE is specified in the MC PowerStage Param h header file This fault message is available only if the DISSIPATIVE BRAKE define statement is commented default status in MC PowerStage Param h If the DISSIPATIVE BRAKE define statement is uncommented it is assumed that a resistor with a high power dissipation capability was connected in parallel to the bus capacitors through a switch In this case the over voltage does not generate a fault event because the resistor is supposed to be able to dissipate the excess of voltage across the bus capacitors For more detailed information on brake resistor management see also section Section 4 3 4 Dissipative brake Bus undervoltage The DC bus voltage is below 18 V DC This threshold is specified in the MC PowerStage Param h header file by the MIN BUS VOLTAGE parameter Startup failed This fault message displays only when SENSORLESS is uncommented It signals that no startup output condition was detected during motor ramp up Refer also to Section 2 7 Startup strategy in sensorless mode Speed feedback error An error on the speed position feedback was detected Motor running error This fault can occur if the firmware is configured in sensor mode It will be reported if the user tries to start the motor when it is not still Figure 31 shows a typical error message Doc ID 15773 Rev 1 35 85 Running the demonstr
49. esigning an application using the BLDC software library UM0708 Figure 49 Brake resistor circuit 15V 15V Vbus R3 R1 100 ohm 20W 1k Q1 He BC557B R6 Z1 6 8k A STGF7NC60HD R4 Q2 BRAKE CPI O PORT BRAKE CPI O PI N 1k R7 BC547B 100k 1 The resistor should be carefully dimensioned in terms of both resistance and sustainable power 2 Inthe MB459B the pin 23 of the MC connector J7 that carries the signal for brake implementation is positioned close to the wrapping area a 74 85 Doc ID 15773 Rev 1 UM0708 Library functions 6 6 1 6 2 6 2 1 Library functions Function description conventions Functions are described in the format given below Synopsis Lists the prototype declarations Description Describes the functions specifically with a brief explanation of how they are executed Input Gives the format and units Returns Gives the value returned by the function including when an input value is out of range or an error code is returned Note Indicates the limits of the function or specific requirements that must be taken into account before implementation Some of these sections may not be included if not applicable for example no parameters or obvious use Modules description The firmware is composed of a set of modules that are logically subdivided in three groups e High level motor control MC modules e Low level MC modules e Standard library The last
50. g during on time debug signal see Section 5 1 3 and the debug pins see Section 5 1 9 The first define statement specifies the debug pin by replacing the x character in the DEBUGx PORT string by the proper number For instance if the debug pin used is the pin O set DEBUGO PORT The second define also specifies the debug pin used by replacing the x character of the DEBUGx PIN string by the same number of the first define statement This setting is not used if the debug feature is disabled Doc ID 15773 Rev 1 71 85 Designing an application using the BLDC software library UM0708 5 1 9 5 1 10 72 85 Port pins definition parameters MC_stm8s_port_param h The MC stm8s port param h header file contains the define statements related to the definitions of the pins and ports used for the motor control related signals define DEBUGx PORT and define DEBUGx PIN When the firmware runs on a customized hardware these define statements can be used to configure the ports and pins used for the debug signals The first define statement specifies the port replace the x character in the GPIOx string by the proper letter For instance set GPIOH if port H is used The second define statement specifies the pin replace the x character in the GPIO PIN x string with the proper number For instance set GPIO PIN 1 if pin 1 is used define KEY UP PORT define KEY UP BIT define KEY DOWN PORT define KEY DOWN BIT define KEY LEFT POR
51. g edge of 60 The corresponding graph of quantities of interest is given in Figure 43 Figure 43 is used as starting point to extract Table 9 e The first column is the index of the table It is made up of the seven configurations of the three Hall sensor It corresponds to the H status of Figure 43 e The second column is shown for clarity but is not included in the final table It corresponds to H1 H2 and H3 configurations of the H status see Figure 43 e Thethird column is the related step coming from the relation between H status and Step to be applied coming from Figure 43 For example if the configuration of the Hall sensor signals is H1 High H2 High and H3 Low the H status is 6 and the step to be applied is step 2 Depending on the spatial distribution of the Hall sensors some configurations may not be allowed such as configuration 000 and 111 In this case the related step of the commutation table will be Invalid see Table 9 See Section 5 1 1 and Section 5 1 4 for information on how to customize Hall sensors The same procedure can be followed to compute the Hall sensor commutation table required for counter clockwise direction or for any other kind of sensor distribution such as 60 see Figure 43 Figure 44 Figure 45 and Figure 46 48 85 Doc ID 15773 Rev 1 ky UM0708 Getting started with the STM8S BLDC firmware Figure 43 Shinano motor Hall sensor configuration 120 clockw
52. igning an application using the BLDC software library UM0708 68 85 not be measured by the firmware and will be assumed constant and equal to the value specified in the next define statement define HEAT SINK TEMPERATURE VALUE Defines the constant value of the heat sink temperature if the heat sink temperature measurement feature has been disabled This setting is not used if the heat sink temperature measurement function is enabled define PWM LOWSIDE OUTPUT ENABLE Comment this define statement to enable the control of the low side switches using standard GPIOs instead of TIM1 outputs In this case the GPIOs that are used must be defined by changing the following define statements in MC stm8s BLDC param h file define LS A PORT define LS A PIN define LS B PORT define LS B PIN define LS C PORT define LS C PIN Figure 48 Transduction curve between the temperature sensor and the ADC converted ADC converted TO Temperature C This curve represents Equation 4 where a is defined using TEMP SENS ALPHA p is defined using TEMP SENS BETA and TO is defined using TEMP TO Equation 4 Transduction equation ADC a xt B axTg Microcontroller clock definition MC stm8s clk param h The MC stm8s clk param h header file contains the define statements dedicated to the microcontroller and its peripherals define STM8 FREQ MHZ This define statement is used to set the CPU frequency express i
53. ilable on internet e Athird party C compiler Cosmic a free 16K size limited evaluation versions can be obtained upon request This version is sufficient to compile all standalone firmware configurations The choice of the C toolchain is left to the appreciation of the user Only COSMIC compilers are fully supported and the dedicated workspace compatible with STVD can be directly opened in the root of the library installation folder STM8 STVD COSMIC stw STM8 STVD COSMIC BLDC stp In addition the STM8S motor control builder GUI allows to customize these libraries according to your application see Section A 3 This makes the first implementation of this library significantly easier see Section 5 Designing an application using the BLDC software library 1 4 2 Programming tools In order to program an MCU with the generated S19 file you should also install the ST Visual Programmer software STVP and use a SWIM programming interface Raisonance RLink The STVP tool provides an easy way to erase program and verify the code programmed in the MCU Go to http www st com for information on STVP and RLink 12 85 Doc ID 15773 Rev 1 1677 UM0708 Features 1 5 Reference documents Application note AN1129 PWM management for BLDC motor drives using the ST72141 Reference manual RM0016 STM8S microcontroller family Datasheet STM8S103xxx Access line 16 MHz STM8S 8 bit MCU up to 8 Kbytes Flash integrated EEPRO
54. ime 0000e eee 19 2 4 3 Dynamic BEMF sampling method 000 eee eee eee 20 2 5 Fast demagnetization AA eee 21 2 6 Setting the delay coefficient accordingly a specified curve 23 2 7 Startup strategy in sensorless mode cee eee eee 24 2 7 1 Alignment phase sesse recriar 0c eect ete 24 2 7 2 Ramp up phase 0 eee 25 2 8 Active brake 00 0 cc tees 26 3 Running the demonstration program ees 27 3 1 User interface structure 2 0000 eee eens 27 3 2 Document conventions 000 eens 28 3 8 Welcome message 2 cee ees 28 3 4 Pelp menus er eles ia bie ind kah GA KAG HULI DAD HUG a Nh 28 2 85 Doc ID 15773 Rev 1 ky UM0708 Contents 3 5 Main menu target and measured rotor speed 29 3 6 User interface sub menuS 0 eee eee 30 3 6 1 Sub menu overview 00 000 cee ns 30 3 6 2 Changing rising and falling delays lille 31 3 6 3 Setting the current reference and duty cycle 31 3 6 4 Configuring the speed regulator 0 0 0 cece eee eee 31 3 6 5 Changing the demagnetization time a 32 3 6 6 Displaying the measured current DC bus voltage and heatsink temperature on ee ed Eee ERG RR EE Rd De bee RE ee EE FER 33 3 6 7 Additional options fast demagnetization toggle mode and auto delay 33 3 6 8 Fault messages 0 00 cee es 35
55. imitation Current feedback TIM1_CH4 TIM1 ETR TIM2 CH2 Fixed voltage divider Daughter board jumper setting Using the ADC The STM8S 10 bit analog digital converter ADC is used to achieve sensorless motor control by performing BEMF zero crossing detection The BEMF sampling method implies that ADC sampling is performed at a specific position inside the PWM period see Section 2 4 This is essential not only to perform BEMF signal sampling during on or off time but also to specify the stabilization time between the sampling and the turning on and off the PWM to avoid commutation noises This is done by synchronizing the STM8S ADC conversion with the PWM generated by TIM1 TIM1 channel 4 is used to trigger the start of the ADC conversion see Figure 37 Doc ID 15773 Rev 1 1677 UM0708 Getting started with the STM8S BLDC firmware Figure 37 Synchronization between TIM1 and ADC ADC Trigger TRGO OC4REF PhA BEMF PhB BEMF PhC BEMF When the conversion is complete the related interrupt routine is serviced This routine compares the converted value with threshold to determine if a zero crossing occurred e BEMF conversion during T off the threshold is fixed and can be customized by the user using define statements see Section 5 1 3 BLDC drive control parameters MC BLDC Drive Param h e BEMF conversion during T on the sampling value it is compared with the motor neutral v
56. ines the maximum applicable duty cycle Maxduty to allow the BEMF sampling during off time see Equation 2 Equation 2 Maximum applicable duty cycle for off time BEMF sampling EWM FREQUENCY Hz Maxduty 100 x 1 MINIMUMogerime 10 Doc ID 15773 Rev 1 59 85 Designing an application using the BLDC software library UM0708 Note 60 85 If the BEMF SAMPLING MIXED is selected as BEMF method then the DUTY CYCLE TH TON must be lower than the maximum applicable duty cycle defined by this parameter define ALIGN DUTY CYCLE Defines the value of the duty cycle percentage applied during the alignment phase define RAMP DUTY CYCLE Defines the value of the duty cycle percentage applied during ramp up define ALIGN DURATION Defines the duration in millisecond of the alignment phase define ALIGN SLOPE Defines the slope of the duty cycle in milliseconds during the alignment phase The duty cycle applied during the alignment phase starts from zero up to ALIGN DUTY CYCLE incremented each ALIGN SLOPE milliseconds The increment is automatically computed from the other parameters define FORCED STARTUP STEPS Defines the number of forced steps which are always performed during ramp up before starting the BEMF sampling Current regulation parameters define CURRENT REFERENCE Defines the initial value of the current reference expressed in mA This parameter is used only in Current mode define CURRENT
57. insertion Hardware fault protection Break input Flexible synchronization 8 bit basic timer with 8 bit prescaler Auto wake up timer 2 watchdog timers Window watchdog and independent watchdog Doc ID 15773 Rev 1 ky UM0708 Features e Communications interfaces High speed 1 Mbit s active CAN 2 0B interface UART with clock output for synchronous operation LIN master mode LIN 2 1 compliant UART master slave mode automatic resynchronization SPI interface up to 10 Mbit s PC interface up to 400 Kbit s e 10 bit analog to digital converter ADC with up to 16 multiplexed channels e l Os Up to 68 I Os on a 80 pin package including 18 high sink outputs A Highly robust I O design immune against current injection e Development support Embedded Single Wire Interface Module SWIM and Debug module DM for fast on chip programming Nonintrusive debugging ky Doc ID 15773 Rev 1 9 85 Features UM0708 1 2 Access line STM8S features 10 85 Core 16 MHz advanced STMB8 core with Harvard architecture and 3 stage pipeline Extended instruction set Memories Program memory up to 32 Kbytes Flash with 20 year data retention at 55 C after 10 kcycles Data memory up to 1 Kbytes true data EEPROM with 300 kcycle endurance RAM up to 2 Kbytes Clock reset and supply management 8 0to 5 5 V operating voltage Flexible clock control 4 master clock sources Low power c
58. ion occurred for example Start gt Stop The optional jumps are symbolized by blue lines in Figure 32 e Error condition a fault condition occurred for example Startup failed overtemperature The error conditions ar symbolized by red lines Each state machine function make calls to the related drive functions to the user interface interaction functions and to the error check functions It executes the action on the basis of the outputs of these functions Figure 32 Main motor control state machine User interface STOP End of START INIT Fault Fault User interface condition START Fault Si condition NG Fault Restart Fault condition Comm condition User interface End of m mm Next state Wika CSTOPD mm Error condition Optional Jump End of CWAIT WAIT 38 85 Doc ID 15773 Rev 1 ky UM0708 Getting started with the STM8S BLDC firmware 4 2 Library architecture The STM8S BLDC library has been logically divided in three different parts e MC FWLIB SCALAR containing the high level motor control modules e STM8 FWLIB containing the STM8 standard libraries e STM8 MC FRAMEWORK containing the low level motor control routines Figure 33 Firmware architecture high level low level interface High level no is sonum FWLIB SCALAR Device independent Device dependant Virtual I Os f Virtual registers Low level STM8 MC FRAMEWORK STM8
59. ise direction 5 T Sp pod l l Curr PhA i l l l l l Hall H1 i i L HallH2 l l l H Status 1 5 4 6 2 3 1 Phase current mmm BEMF Sensor signal Figure 44 Shinano motor Hall sensor configuration 120 counter clockwise direction Step Curr PhA Hall H1 Hall H2 Hall H3 H Status 1 3 2 6 4 5 1 Phase current BEMF Sensor signal Doc ID 15773 Rev 1 49 85 Getting started with the STM8S BLDC firmware UM0708 Figure 45 Hall sensor configuration 60 clockwise direction Step Curr PhA Hall H1 Hall H2 a 1 1 o 1 H Status 1 3 7 6 4 0 1 Phase current BEMF Sensor signal Figure 46 Hall sensor configuration 60 counter clockwise direction Step 3 4 Curr PhA Hall H1 Hall H2 Hall H3 H Status 1 0 4 6 7 3 1 Phase current BEMF Sensor signal Table 9 Hall sensor commutation table for Shinano motor H status H1 H2 H3 Step 0 000 Not valid 1 001 5 2 010 3 3 011 4 4 100 1 5 101 0 6 110 2 7 111 Invalid 50 85 Doc ID 15773 Rev 1 UM0708 Getting started with the STM8S BLDC firmware 4 3 4 Caution Dissipative brake Because of its physical construction the BLDC motor is able to transform kinetic energy into electrica
60. l energy just like a dynamo Under a limited number of conditions this property of BLDC motors has to be taken into consideration to avoid possible damage to the hardware system For instance a dangerous situation could arise when e The six inverter switches are opened and the motor is running at a speed higher than the nominal one In this case the amplitude of the line to line BEMF generated is higher than the nominal bus voltage e The control tries to brake The energy is transferred from the load to the board Unless the used power system has regenerative capabilities in both of these situations the inverter bulk capacitor is charged Furthermore depending on the rotor speed with reference to the first situation or on the amount of energy transferred with reference to the second situation the voltage across the bulk capacitors could increase to a destructive level A strategy for somehow dissipating the generated electrical energy is thus necessary Different methods could be implemented to do so but one of them in particular the utilization of a brake resistor is supported by the library presented in this user manual If the motor is operated beyond the rated speed it is mandatory to use a regenerative power converter or a brake resistance to prevent bus over voltage from damaging your board In the firmware this strategy has been implemented using the analog to digital conversion of the bus voltage value to determine if
61. l param h leues 63 KYT Doc ID 15773 Rev 1 3 85 Contents UM0708 5 1 5 Control stage parameters MC ControlStage param h 64 5 1 6 Power stage parameters MC PowerStage Param h 66 5 1 7 Microcontroller clock definition MC stm8s clk param h 68 5 1 8 Microcontroller specific BLDC drive parameters MC stm8s BLDC param h eere 69 5 1 9 Port pins definition parameters MC stm8s port param h 72 5 1 10 Hall parameter microcontroller interfaces MC stm8s hall param h 72 5 2 Setting up the system when using a brake resistor 73 6 Library functions 1 5 ick ac me e Cl OCC CR Re a ae 75 6 1 Function description conventions lille 75 6 2 Modules description apa paa Ina RR RR RREXTEGEG ERR KE I EAR 75 6 2 1 High level MC modules 6 0000 cece eres 75 6 2 2 Low level MC modules 00 000 e eens 81 Appendix A Additional information 000 0c eee ee 83 A 1 DAG configuration o ee esaat Ear AA 83 A 2 Motor control related CPU load liiis elsi 83 A 3 STM8 motor control builder GUI liliis 83 Revision BISTOFV 2220 tert ioa a a Rect e ed d NAKAGAWA 84 4 85 Doc ID 15773 Rev 1 ky UM0708 List of tables List of tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Table 11 Table 12 Table 13 Table 14 Table 15 ROM and RAM requir
62. level modules by calling each specific initialization functions dev clklnit dev portlnit etc MC display this module manages the display of the information on the 15 rows x 2 lines LCD This module is developed over the low level virtual I Os functions see Section 4 2 MC Keys this module manages the button and joystick 4 directions plus a center button This module is developed over the low level virtual I Os functions see Section 4 2 MC pid regulators this module manages all the application regulators They can be either PID or PI regulators It is used to instantiate a regulator structure and to execute it MC StateMachine this module manages the main application state machine through the StateMachineExec function that is used to execute the state machine MC vtimer this module is used to manage the virtual timers as explained in Section 4 5 2 Main this is the main application firmware module It is used to execute the state machine in a infinite loop The exhaustive description of the high level MC modules is out of the scope of this user manual Only the functions of the MC BLDC Drive and MC vtimer modules will be described in details MC BLDC Drive c module The high level BLDC drive module manages the calls to the state machine functions and interacts with the low level modules through the virtual registers and the drive structure The MC BLDC Drive c functions are listed in the MC drive h header file
63. measured rotor speed express in rpm hTarget rotor speed Variable 16 bits It contains the target rotor speed express in rpm hDuty cycle hCurrent reference Variable 16 bits Variable 16 bits It contains the control variable for voltage mode Duty cycle express in timer counts It contains the control variable for current mode Current reference express in mA hCurrent measured Variable 16 bits It contains the measured value of DC current express in mA bFalling_Delay Variable 8 bits It contains the falling delay coefficient express in 1 255 of the step time bRising_Delay Variable 8 bits It contains the rising delay coefficient express in 1 255 of the step time bDemag_Time Variable 8 bits It contains the demagnetization time express in percentage of step time ky Doc ID 15773 Rev 1 41 85 Getting started with the STM8S BLDC firmware UM0708 Table 6 BLDC Drive structure continued Name Type Description hMinimumOffTime Variable 16 bits It contains the minimum off time express in ns hBusVoltage Variable 16 bits It contains the measured DC bus voltage express in Volt bHeatsinkTemp Variable 8 bits i anis the measured heat sink temperature express in bFastDemag Variable on off It is used to enable or disable the fast demagnetization option bToggleMode Variable on off It is used to enable or disable the t
64. ment 0 0000 cee ae 33 DC bus voltage and heat sink measurements 0 0000 eee nes 33 Enabling disabling fast demagnetization and toggle mode options 34 Auto delay option aaau auaa tenets 34 Fault message shown in case of undervoltage 0 6 eee ee 36 Main motor control state machine ren 38 Firmware architecture high level low level interface lille 39 STM8S BLDC library organization liliis eh 39 Timer output control signals lt siis rasis reresesidircdky RII 43 Current regulation limitation tae 44 Synchronization between TIM1 and ADC sees 45 Synchronous and asynchronous ADC conversion 0c cece eee eee eee 45 Synchronous conversion 00 0c 46 Asynchronous conversions llle hr 47 TIM2 peripheral used for Hall sensor management 0 0 cee eee 47 Step time measurement for sensored drive 0 cc llle 48 Shinano motor Hall sensor configuration 120 clockwise direction 49 Shinano motor Hall sensor configuration 120 counter clockwise direction 49 Hall sensor configuration 60 clockwise direction cece eee 50 Hall sensor configuration 60 counter clockwise direction 50 High level BLDC drive 0 0 00 ccc hrs 52 Transduction curve between the temperature sensor and the ADC converted 68 Doc ID 15773 Rev 1 ky UM0708 Li
65. n 2 7 It counts the interval of the alignment ramp MTC ALIGN RAMP TIMEOUT 4 ms This means that the duty cycle is incremented each 4 ms starting from 0 up to DEFAULT ALIGN DUTY CYCLE during the alignment phase It counts the duration of the active brake if that function is enabled MTC ALIGN RAMP TIMER Polling This virtual timer is used to count the duration of the alignment MTC ALIGN TIMER Polling phase see Section 2 7 This virtual timer is used to update the firmware variables ADC SAMPLE TIMER Automatic related to the ADC sampled values ADC sampling is performed every 10 ms This virtual timer is used to identify the rotor stall condition HALL CAPT TIMEOUT TIMER Automatic when no more signal coming from the Hall sensor This allows to set the zero speed 4 5 2 Virtual timers related functions Refer to Section 6 2 1 for the description of the functions using the virtual timers a 54 85 Doc ID 15773 Rev 1 UM0708 Designing an application using the BLDC software library 5 Note 5 1 5 1 1 Designing an application using the BLDC software library Setting up an operational evaluation platform with a drive system based on the STM8 128 MCKIT and a permanent magnet motor is quite easy The BLDC software runs on the STM8S microcontroller on which the STM8 128 MCKIT is based This section explains how to quickly configure your drive system and customize the library accor
66. n MHz It can be set to 16 or 24 When it is set to 24 MHz the firmware is configured to use the external Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library oscillator with 1 wait state Flash latency Otherwise the internal oscillator is used with 0 wait state 5 1 8 Microcontroller specific BLDC drive parameters MC stm8s BLDC param h The MC stm8s BLDC param h header file contains the define statements related to the BLDC drive define RAMP VALUExx Defines the values of the ramp up step durations These values are pre computed They are expressed in PWM periods They can be customized through the STM8S MC Firmware Library builder see Section A 3 define PHASE A BEMF ADC CHAN define PHASE B BEMF ADC CHAN and define PHASE C BEMF ADC CHAN When the firmware runs on a customized hardware these define statements allow to configure the channels used to perform the BEMF samplings Note Make sure that these pins are not used for other purposes inside the firmware and are not configured as outputs define ADC CURRENT CHANNEL define ADC USER SYNC CHANNEL define ADC BUS CHANNEL define ADC NEUTRAL POINT CHANNEL define ADC TEMP CHANNEL and define ADC USER ASYNC CHANNEL When the firmware runs on a customized hardware these define statements allow to configure the channels used to perform the other ADC samplings see Section 4 3 2 Note Make sure that these pins ar
67. no effect if the firmware is configured in speed open loop The controller coefficients actually applied are the ratio between the values ranging from O to 255 configured by the user through the sub menus and the division factors defined in the MC BLDC Drive Param h header file define SPEED KP DIVISOR 128 unit none define SPEED KI DIVISOR 512 unit none define SPEED KD DIVISOR 16 unit none Changing the demagnetization time To adjust the demagnetization time use the sub menu shown in Figure 26 It is recommended to set a demagnetization time high enough to allow the discharge of the current inside the floating phase This parameter is a percentage of the step time see Section 2 3 Commutation delay and demagnetization time Doc ID 15773 Rev 1 ky UM0708 Running the demonstration program 3 6 6 Displaying the measured current DC bus voltage and heatsink temperature The firmware measures several power stage output characteristics see Section 4 3 2 Using the ADC e The direct current that flows into the motor e The DC bus voltage level e Theheatsink temperature Direct current The sub menu shown in Figure 27 displays the measured value of the direct current together with the current reference The Curr ref field assumes different meanings according to the configuration of the firmware e Inclosed loop current mode it corresponds to the current reference computed by the speed regulator
68. ode 16 6 A 3 STM8 motor control builder GUI The STM8 motor control builder GUI is not part of the motor control kit Please check http www st com mcu inchtml pages stm8 html for availability ky Doc ID 15773 Rev 1 83 85 Revision history UM0708 Revision history 84 85 Table 15 Document revision history Date 25 Jun 2009 Revision 1 Initial release Changes Doc ID 15773 Rev 1 UM0708 Please Read Carefully Information in this document is provided solely in connection with ST products STMicroelectronics NV and its subsidiaries ST reserve the right to make changes corrections modifications or improvements to this document and the products and services described herein at any time without notice All ST products are sold pursuant to ST s terms and conditions of sale Purchasers are solely responsible for the choice selection and use of the ST products and services described herein and ST assumes no liability whatsoever relating to the choice selection or use of the ST products and services described herein No license express or implied by estoppel or otherwise to any intellectual property rights is granted under this document If any part of this document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products or services or any intellectual property contained therein or considered a
69. oggle mode option bAutoDelay Variable on off It is used to enable or disable the Auto delay option bMotor_Pole_Pairs Constant 8 bits It expresses the number of motor poles pairs hMax_Speed Constant 16 bits It expresses the motor maximum speed in rpm hPWM_Frequency Constant 16 bits It expresses the PWM signal frequency in Hz bSpeed_PID_sampling_time Constant 8 bits It expresses the PID regulator interval of action in milliseconds pPID_Speed Constant pointer Pointer to the speed PID structure hCurrent_Limitation Constant 16 bits It contains the value of the current limitation express in mA 4 3 Low level control This section describes the implementation of the low level drive which is interfaced with the microcontroller peripheral memory 4 3 1 Using the advanced control timer peripheral TIM1 The BLDC drive can be achieved by using STM8S 16 bit advanced control timer TIM1 peripheral to generate the control signals for the inverter power switches as described in Figure 35 The OCx output is connected to the high side switch while the OCNx output is connected to the low side switch For a given step four configurations are possible for each TIM1 channel output see Table 7 42 85 Doc ID 15773 Rev 1 UM0708 Getting started with the STM8S BLDC firmware Figure 35 Timer output control signals TIM1 CHx
70. oltage The motor neutral voltage it is reconstructed starting from the bus voltage and using a different ADC conversion Since the STM8S microcontroller features one single ADC peripheral it is necessary to configure it to perform all the remaining conversions plus extra conversions that may be requested by the application This is done by performing two ADC conversions for each PWM period see Figure 38 e The first conversion is called synchronous sampling It is triggered by the TIM1 OCREF4 signal to set the sampling point at the desired position inside the PWM period e The second conversion is called asynchronous sampling It starts at the end of the interrupt routine executed after the first conversion Figure 38 Synchronous and asynchronous ADC conversion I PWM Period I MA PWM dt ldcy ADC co Loot O l LI It l ll 1 ISR Start 1 End 1 conversion conversion Start 2th End 2 conversion conversion ki Doc ID 15773 Rev 1 45 85 Getting started with the STM8S BLDC firmware UM0708 Synchronous conversion Inside each step between C and C on Figure 39 the synchronous conversion is used for different purposes It is dedicated for BEMF zero crossing detection only between the end of demagnetization D and the effective zero crossing instant Z During the remaining time intervals the synchronous conversion can be used for other purposes inside each step The interval between zero
71. on see Section 2 5 1 Fast demagnetization enabled 0 Fast demagnetization disabled define TOGGLE MODE Defines the starting configuration of the toggle mode option see Section 3 6 7 1 Toggle mode enabled 0 Toggle mode disabled define ACTIVE BRAKE Uncomment this define statement to enable the active brake function see Section 2 8 define BRAKE DURATION If the active brake function is enabled use this define statement to specify the duration in milliseconds of the active brake action define BRAKE DUTY If the active brake function is enabled use this define statement to specify the percentage of the applied duty cycle define AUTO DELAY Defines the starting configuration for the Auto delay option If this function is enabled the value of the delay coefficients are computed starting from a predefined curve see Section 2 6 1 Auto delay feature enabled 0 Auto delay feature disabled define RISE FALL DELAY LINK Comment this define statement to change the rising and falling coefficients independently When left uncommented the two coefficients are linked and have the same value if changed by the user This setting is not used if the Auto delay function is enabled define DEBUG PINS Uncomment this define statement to enable the debug pins When this feature is enabled the test pins are configured to generate in real time dedicated function of the drive such as C D Z Auto switch BEMF detection d
72. ontains the measured heat sink temperature Contains the step time measured with the Hall VDEV REG16 HALL COUNTS 16 bits sensors It is expressed as a number of PWM periods Contains the step time measured with the BEMF VDEV REG16 BEMF COUNTS 16 bits detector It is expressed as a number of PWM periods VDEV REG16 BLDC DUTY CYCLE COUNTS 16 bits Contains the number of timer counts of the control variable VDEV REG16 BOARD BUS VOLTAGE 16 bits ee the measured bus voltage expressed in VDEV REG16 HW ERROR OCCURRED 16 bits Each bit represent an error condition which occurred VDEV REG16 HW ERROR ACTUAL 16 bits Each bit represent an actual error condition 4 2 2 Virtual I Os The virtual I Os are low level functions called by the high level modules For instance if an high level module want to set a GPIO high level output as test pin it should call the virtual l Os outS VDEV OUT8 LED 1 LED ON instead of driving directly the microcontroller register The virtual I Os are summarized in Table 5 Table 5 Virtual I Os Name Description out8 VDEV_OUT8_DISPLAY_FLUSH none This call is used to invoke a refresh of the LCD screen out8 VDEV_OUT8_DISPLAY_PRINTCH none This call is used to refresh only the cursor displayed on the LCD for example blinking 40 85 Doc ID 15773 Rev 1 ky UM0708 Getting started with the STM8S BLDC firmware Table 5 Virtual I Os continued
73. ponding unit see Figure 21 The field can either be editable or read only e An editable field can be selected and modified by the user when the cursor B is displayed near the field e A read only field is used to display a value The user can neither select it nor modify it Figure 21 User interface sub menu Editable field Read only field Labels max 8 char Field active when blinking To select and modify and editable field the following steps are required 1 Press the joystick UP or DOWN to navigate between the editable fields of the sub menu The cursor blinks when the field is active 2 Then press JOYSEL to select the active field The cursor changes to 1 Change the value by pressing the joystick UP or DOWN see Figure 22 4 To exit from edit mode press JOYSEL again or change sub menu Figure 22 Field selected for edition Editable field Read only field Selected field Press the joystick LEFT or RIGHT to navigate between sub menus Each sub menu is related to a specific issue of BLDC motor control The following sections provide a detailed description of the sub menus Users with less experience in BLDC motor control are advised to jump to Section 4 Getting started with the STM8S BLDC firmware Doc ID 15773 Rev 1 ky UM0708 Running the demonstration program 3 6 2 3 6 3 Note 3 6 4 Changing rising and falling delays To enter this sub menu press
74. ppendix A Additional information A 1 DAC configuration The DAC functionality is implemented by using two PD2 and PDO pins TIM3 output compare channels and by modulating the duty cycle of the generated 62 5 kHz PWM signal To properly filter the generated signals without introducing important delays on the waveforms it is recommended to use a appropriate first order low pass filter e g with a 1 kQ resistor and a 33 nF capacitor The two DAC outputs are used to monitor the measured rotor speed and the control variable controller output The DAC outputs can also be used to monitor two user defined variables such as user vari or user var2 see example below The MC BLDC Drive c file must be modified as follows ifdef DAC FUNCTIONALITY dev DACUpdateValues DAC CH 1 u8 user varl dev DACUpdateValues DAC CH 2 u8 user var2 endif Assuming that the DAC implemented has an 8 bit resolution a suitable scaling factor should be applied to user defined variables Note The DAC cannot be used together with the dissipative brake function See Section 5 1 5 for details on how to enable the DAC A 2 Motor control related CPU load Table 14 gives the percentage of the microcontroller workload required by the BLDC firmware for the specified configuration Table 14 Workload Configuration Workload Sensorless closed loop voltage mode 3296 Sensorless closed loop current mode 2796 Sensor closed loop current m
75. r is in normal Run state The user can interact with the system change parameters in real time or issue a stop request Stop The motor is in Stop state each time the motor needs to be stopped Wait The system is in Wait state when the motor is stopped It remains in this state till the required condition for a new restart is present Fault The system goes into Fault state when an error condition occurs It remains in this state as long as the fault condition is present Fault over When the fault condition has disappeared the system remains in Fault over state to indicate which error occurred and waits for a user action Note The states marked with an asterisk are executed continuously until an event occurs user action or fault condition Doc ID 15773 Rev 1 37 85 Getting started with the STM8S BLDC firmware UM0708 4 1 2 Description of the state machine operation Each state corresponds to the execution of the related state machine function The change of state is performed according to the value returned by that state machine function The returned value of a state machine functions can be one of the following e State remain no change in the state is required by the state machine function e Next state the natural flow of the state machine is followed for example Idle gt Init start gt Start gt Run The natural flow is symbolized by green lines in Figure 32 e Optional jump a path deviation caused by user act
76. ram h The MC BLDC Drive Param h header file contains the parameters related to The general drive configuration and parameters The BEMF detector configuration and parameters The current regulation parameters Speed PID controller type sampling time and initial values The optional features initial values and parameters The linear variation of delay coefficients according to the mechanical speed Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library Note General drive configuration and parameters define SPEED CONTROL MODE CLOSED LOOP Uncomment this define statement to enable the speed closed loop operation define SPEED CONTROL MODE OPEN LOOP Uncomment this define statement to enable the speed open loop operation define CURRENT CONTROL MODE VOLTAGE MODE Uncomment this define statement to select the Voltage mode drive see Section 2 1 for details define CURRENT CONTROL MODE CURRENT MODE Uncomment this define statement to select the Current mode define TARGET ROTOR SPEED Defines the mechanical rotor speed set point expressed in rpm at startup in closed loop mode define PWM FREQUENCY Defines the switching frequency expressed in Hz of the applied PWM signal for all configurations define DUTY CYCLE Defines the duty cycle percentage of the applied PWM signals in open loop mode define FALLING DELAY and define RISING DELAY Defines the values of falling and
77. re electrical frequencies with 0 1 Hz resolution For example F 1 1234 means F 1 123 4 Hz 2 Rising and Falling curve can be different Startup strategy in sensorless mode To perform sensorless control the BEMF signal inducted by the rotor field in the stator windings must reach a detectable amplitude Since the amplitude of the BEMF signal is proportional to the rotor speed the motor cannot be synchronized using the BEMF detection strategy if the rotor speed is lower than a specific threshold It is important to underline that the detection is performed on the BEMF zero crossing and not on the BEMF peak value However to achieve a good zero crossing detection precision the BEMF signal slope must be sufficiently steep during the zero crossing The BEMF level increases proportionally with the speed As a result the BEMF signal slope becomes more and more steep in the proximity of the zero crossing and the synchronous driving using the BEMF detection can be applicable It is consequently important to implement an asynchronous startup strategy that brings the motor up to the required speed A classical BLDC motor startup sequence consists of 2 phases 1 The Alignment phase 2 The ramp up phase Alignment phase During the alignment phase the rotor is put in a specified position before running the motor To do this the power switches must be set to a specific configuration corresponding to a predetermined position of the stator
78. reconstruction based on BEMF detection A prerequisite for using this library is basic knowledge of C programming PM motor drives and power inverter hardware In depth know how of STM8Sxxx functions is only required for customizing existing modules and for adding new ones for a complete application development Doc ID 15773 Rev 1 1 85 www st com Contents UM0708 Contents 1 Features coraa en AA AKA ABA ARAB Da fe ence ANA a 8 1 1 Performance line STM8S features nunan 0000 cece eee 8 1 2 Access line STM8S features 00 00 e eee eee 10 1 3 BLDC software library V1 0 features CPU running at 16 MHz 11 1 4 Development OCIS exea x hee PERESRERSLECRPREFETeE RREGRERE ERG 12 1 4 1 Toolchains 2 uote rh dence mar m eR Dh Re 12 1 4 2 Programming tools 0 ccc eren 12 1 5 Reference documents cece eee eee eee nets 13 2 Introduction to STM8S BLDC control 14 2 1 Introduction to BLDC theory 0 00 eee 14 2 1 1 Rotor synchronization reeni yir eien eee 15 2 1 2 Rotor speed regulation 0 cee tee 15 2 1 3 Bus voltage modulation 0 0 0 eee 15 2 2 Rotor speed measurement 00 00 eee ee 16 2 3 Commutation delay and demagnetization time 17 2 4 Detection of BEMF zero crossingS cece ee eee eee 18 2 4 1 Sampling during PWM signal on time 0000 eae ee 18 2 4 2 Sampling during PWM signal off t
79. reset define ENABLE OPTION BYTE PROGRAMMING Comment this define statement to disable in application option byte re programming Disabling this option allows to decrease the firmware size In this case the option bytes can be programmed off line by using the STVP tool Doc ID 15773 Rev 1 65 85 Designing an application using the BLDC software library UM0708 5 1 6 Power stage parameters MC PowerStage Param h The MC PowerStage param h header file contains the parameters related to the power stage These settings must be modified if the firmware is used with a customized hardware different from the one of the kit or to enable disable unused library features 66 85 define RS M Defines the value of the power board shunt resistor in MQ used for the current management define AOP Defines the value of the voltage gains of the power board amplification stage used for the current management define DISSIPATIVE BRAKE Uncomment this define statement to enable the dissipative brake function see Section 4 3 4 The next define statement must be edited when this feature is enabled define DISSIPATIVE BRAKE POL This define statement is used to set the polarity of the dissipative brake signal It should be set according to the dissipative brake hardware implementation This setting is not used if the dissipative brake function is disabled There are two available options DISSIPATIVE BRAKE ACTIVE HIGH the braking a
80. rising delay coefficients These values are expressed in 1 256 of the step time For example the value should be 128 50 of 256 to set the delay coefficient to 50 of the step time The MC_BLDC_Drive_Param h contains two sections to set these parameters one for the sensorless configuration and one for the Hall sensor configuration It is recommended to edit the proper section to avoid undesired behaviors define DEMAG TIME Defines the duration of the demagnetization time It is expressed as a percentage of the step time define MIN SPEED 01HZ Defines the minimum speed of the measured rotor speed Sensorless configuration at which the closed loop is validated and the loop closed using the speed controller This parameter is used only for closed loop operations It is expressed in tenth of Hz of the electrical frequency define ADC SAMPLE TIMEOUT Defines the frequency of the update of additional ADC conversions Bus voltage heatsink temperature express in milliseconds See Section 4 3 2 Doc ID 15773 Rev 1 57 85 Designing an application using the BLDC software library UM0708 Note 58 85 BEMF detector configuration and parameters define BEMF SAMPLING METHOD This define statement is used to configure the BEMF sampling method There are three possibilities BEMF SAMPLING TOFF the BEMF detector is configured to perform the sampling only during the off time of the PWM signal applied see Section 2 4
81. rtual timers are high level hardware independent general purpose counters These counters are used to manage the execution of the code performed at specified time intervals such as speed regulation The implementation of these virtual timers is based on a physical layer that uses the STM8S resources the virtual timers are implemented using the TIM4 peripheral TIM4 is configured to generate an interrupt each millisecond and is used as time base to update each Virtual timer It is possible to use the virtual timers in two modes e Polling mode In this case the end of counting has to be check using a specific function call and the execution of the code is subject to the value returned by this function e Automatic mode At the end of counting the specified function is automatically executed The virtual timers are implemented in one shot This means the counting must be restarted each time whatever the mode A set of virtual timers is implemented inside each drive firmware Each virtual timer is dedicated to specific operations and is identified by a name VTIMx where x is the number of the virtual timer The virtual timer names can be customized through a define statement Example As an example timer number 0 can be named VTIM KEY by using the following define statement define VTIM KEY VTIMO Using BLDC virtual timers The list of virtual timers used by the BLDC drive is given in Table 10 BLDC virtual timers
82. rystal resonator oscillator External clock input Internal user trimmable 16 MHz RC Internal low power 128 kHz RC Clock security system with clock monitor Power management Low power modes Wait Active halt Halt Individual peripheral clock switch off Permanently active low consumption power on and power down reset Interrupt management Nested interrupt controller with 32 interrupts Up to 37 external interrupts on 6 vectors Timers 2x 16 bit general purpose timers with 2 3 capture compare channels input capture output compare or PWM Advanced 16 bit control timer 4 capture compare channels input capture output compare PWM edge or center aligned mode single pulse output mode 3 complementary outputs with adjustable dead time insertion Hardware fault protection Break input Flexible synchronization 8 bit basic timer with 8 bit prescaler Auto wake up timer 2 watchdog timers Window watchdog and independent watchdog Communications interfaces UART with clock output for synchronous operation Smartcard IrDA and LIN mode LIN 2 1 compliant UART master slave mode automatic resynchronization SPlinterface up to 8 Mbit s fCinterface up to 400 Kbit s Analog to digital converter ADC Doc ID 15773 Rev 1 ky UM0708 Features 10 bit 1 LSB ADC with up to 10 multiplexed channels scan mode and analog watchdog e 1 Os Up to 38 I Os on a 48 pin package inclu
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84. s two sections to set these parameters one for the Voltage mode configuration and one for the Current mode configuration It is recommended to edit the proper section to avoid undesired behaviors define BEMF RISING THRESHOLD V and define BEMF FALLING THRESHOLD V Defines the voltage thresholds used by the BEMF detector for the sampling during of time method The first statement is used for the rising edge detection while the second is used for the falling edge detection define BEMF SAMPLE COUNT Defines the numerical filter used by the BEMF detector This means that ADC conversions must cross N times N being BEMF SAMPLE COUNT the threshold before validating the zero crossing event define DUTY CYCLE TH TON Defines the threshold of the duty cycle percentage used by the BEMF detector to choose dynamically the sampling method This parameter is used only if BEMF SAMPLING MIXED method is selected If the instantaneous value of duty cycle if above this threshold the BEMF sampling during on time is applied Otherwise the sampling during off time is applied define MINIMUM OFF TIME Defines the value of the minimum off time in nanosecond required for the BEMF sampling during the off time This parameter is related to the hardware and motor It depends on The stabilization time between the turn off of the switch till the end of commutation noise The duration of ADC sampling minimum 1 5 us This parameter also def
85. sequence phase A winding will be demagnetized with an equivalent PWM voltage between HV 2 and GND If the PWM is applied to the low side switch T6 during T off the neutral point will be clamped to HV by the D5 free wheeling diode Phase A windings will consequently be demagnetized with an equivalent PWM voltage between HV and HV 2 The reverse voltage applied to the windings is higher than in the first case The PWM control signal should consequently be applied to the low side switch T6 to speed up the demagnetization of A windings between step 2 and step 3 In conclusion to accelerate the demagnetization the PWM signal should be applied to the low side switch during the step when the demagnetizing current is flowing from the bridge to the motor phases Refer to Table 2 for a description of the firmware implementation Doc ID 15773 Rev 1 ky UM0708 Introduction to STM8S BLDC control 2 6 Figure 12 Demagnetization between step 2 and step 3 HV GND B 4 T1 GND GND Step 3 Toff PWM on Hem side GND Step 2 Step 3 Ton Step 3 Toff PWM on Low side Table 2 Fast demagnetization table Switches T PWM applied for fast Step HS LS Demagnetizing current demagnetization Step 1 T1 T4 Current C from bridge to motor Low side T4 Step 2 T1 T6 Current B from motor to bridge High side T1 Step 3 T3 T6 Current A from bridge to motor Low side T6 Step 4 T3 T2 Current C from motor to bridge High side
86. sists of a 16 bit PID speed controller The speed measurement block makes the interface between the low level and the high level drive Starting from the feedback coming from the low level drive it provides the rotor speed and the related reliability When a sensorless control is performed the speed measurement is not immediately reliable at startup and the drive operates in speed open loop with control variables configured through by the user interface As soon as the rotor speed measurement becomes reliable the speed loop is closed using the PID output Starting from that control variable the low level generates the output signal to drive the motor to the required speed according to the value of the duty cycle to be applied in voltage mode or the level of current reference in current mode The synchronization between the BLDC motor stator and rotor is also performed by the low level drive In addition the high level drive computes the delay coefficients starting from the predefined curve see Section 2 6 and using the measured rotor speed if it has been configured Figure 47 High level BLDC drive Fixed User Control var interface A Control var B Low level gt C PID Output Delay coeff Speed Delay coeff measurement computation Target speed To the user interface Doc ID 15773 Rev 1 ky UM0708 Getting started with the STM8S BLDC firmware 4 5 4 5 1 Table 10 Virtual timers Vi
87. sor value expressed in C and the ADC converted value This curve is assumed to be linear see Figure 48 define BKIN POLARITY When the firmware runs on a customized hardware these define statements allow to configure the polarity of the Break input The polarity can be set to ACTIVE HIGH or ACTIVE LOW define PWM U LOW SIDE POLARITY define PWM U HIGH SIDE POLARITY define PWM V LOW SIDE POLARITY define PWM V HIGH SIDE POLARITY define PWM W LOW SIDE POLARITY and define PWM W HIGH SIDE POLARITY When the firmware runs on a customized hardware these define statements allow to configure the polarity of the PWM output The polarity can be set to ACTIVE_HIGH or ACTIVE_LOW define PWM U HIGH SIDE IDLE STATE define PWM U LOW SIDE IDLE STATE define PWM V HIGH SIDE IDLE STATE define PWM V LOW SIDE IDLE STATE define PWM W HIGH SIDE IDLE STATE define PWM W LOW SIDE IDLE STATE When the firmware runs on a customized hardware these define statements allow to configure the status of the PWM output during the idle state The status can be set to ACTIVE or INACTIVE define HEAT SINK TEMPERATURE MEASUREMENT This define statement is used to configure the firmware to perform heat sink temperature measurement If the hardware does not support this feature or if you want to disable it leave this define statement uncommented The heat sink temperature will Doc ID 15773 Rev 1 67 85 Des
88. st of figures Figure 49 Brake resistor circuit Doc ID 15773 Rev 1 7 85 Features UM0708 1 Features 1 1 Performance line STM8S features e Core 8 85 Advanced STM38 core with Harvard architecture and 3 stage pipeline fcpu up to 24 MHz setting O wait state at fopy x 16 MHz Extended instruction set Maximum 20 MIPS performance at fcpy 24 MHz Memories Program memory up to 128 Kbytes Flash with 20 year data retention at 55 C after 10 kcycles Data memory up to 2 Kbytes true data EEPROM with 300 kcycle endurance RAM up to 6 Kbytes Clock reset and supply management 2 95 to 5 5 V operating voltage Flexible clock control 4 master clock sources Low power crystal resonator oscillator External clock input Internal user trimmable 16 MHz RC Internal low power 128 kHz RC Clock security system with clock monitor Power management Low power modes Wait Active halt Halt Individual peripheral clock switch off Permanently active low consumption power on and power down reset Interrupt management Nested interrupt controller with 32 interrupts Up to 37 external interrupts on 6 vectors Timers 2x 16 bit general purpose timers with 2 3 capture compare channels input capture output compare or PWM Advanced 16 bit control timer 4 capture compare channels input capture output compare PWM edge or center aligned mode single pulse output mode 3 complementary outputs with adjustable dead time
89. switch the motor neutral voltage becomes 0 V see Section 2 4 2 The zero crossing can consequently be detected both during the on and the off time of the applied PWM signal Refer to Section 2 4 1 and Section 2 4 2 for a detailed description of sampling methods during PWM signal on and off time Sampling during PWM signal on time It is recommended to perform the sampling during the T on when 100 of the duty cycle applied is required During T on of the PWM signal applied to the high side switch the motor neutral point is equal to the bus voltage 2 If this value is above the maximum voltage allowed by the STM8S ADC converter it is necessary to divide the phase voltage before feeding the signal into the ADC and to convert the bus voltage to reconstruct the neutral point This value is used as a threshold for the zero crossing see Figure 7 Detection of the zero crossing is performed by comparing the BEMF converted scaled value with the converted scaled value of the bus voltage neutral point reconstruction Doc ID 15773 Rev 1 ky UM0708 Introduction to STM8S BLDC control 2 4 2 Figure 7 Sampling during the on time 300V l T1 PWM ON A 5V ADC bemf T4 always ON GPIO Current in A amp B Phases when T1 ON oN PWM signal l nm Trig signal ADC will be started by rising edge of the trigger Sampling during PWM signal off time During T off of the PWM signal
90. t from the one of the kit or to disable some library features in order to reduce code size and CPU occupation define DISPLAY Uncomment this define statement to select the control board LCD as display define DAC FUNCTIONALITY The DAC functionality is a debug option which can be used to analyze the behaviors of up to two variables inside the code The variables to be analyzed should not vary more than 20 kHz See Section A 1 for details on how to customize it Doc ID 15773 Rev 1 ky UM0708 Designing an application using the BLDC software library Note Note The DAC functionality cannot be set together with the dissipative brake option define TIM1_CHxN REMAP Uncomment this define statement to remap the TIM1 CH1N TIM1 CH2N TIM1 CH3 N and TIM1_ETR pins This remapping is necessary if the STM8S features less than 80 pins define BKIN Comment this define statement to disable the emergency input feature of the advanced control timer define JOYSTICK Comment this define statement to disable the joystick input define SET TARGET SPEED BY POTENTIOMETER Uncomment this define statement to use the potentiometer RV1 available on the MB631 This potentiometer allows to set the target rotor speed In this case the rotor speed cannot be modified using the joystick define AUTO START UP Uncomment this define statement to disable the KEY button management The motor is start to run automatically few second after the
91. te complementary channel outputs both outputs must be enabled This is done by setting both CCxE and CCxNE bits in CCERx registers Since no PWM is required on these signals the OCxM 2 0 bits must be configured to forced active or forced inactive to activate the high side or the low side respectively Refer to STM8S reference manual RM0008 for a detailed description of TIM1 operation Current regulation limitation Current regulation and limitation have been implemented using the clear enable feature of STM8S TIM1 advanced control timer This feature allows the asynchronous turn off of the PWM applied if a triggering signal is present on the dedicated ETR pin external trigger This pin is driven by an external comparator that generates the trigger event when the measured DC current is higher than the threshold The value of comparator threshold used for current regulation or limitation can be selected using two jumpers in the daughter board See Figure 36 Three different sources can be configured e TIM2 CH 2 output for sensorless control current reference or current limitation e TIM1 CHA output for sensored control current reference or current limitation e Fixed voltage divider for both control current limitation only So it is possible to free the resource needed to drive the threshold if only a current limitation is required Voltage mode setting the fixed voltage divider Figure 36 Current regulation l
92. te machine function MC FuncRetVal t driveStartUp void The purpose of this function is to call the low level function relative to this state and to update the local state variable DriveState None The returned value is the one coming from the low level function FUNCTION RUNNING no state change is required by this function FUNCTION ENDED the state change is requested by this function FUNCTION ERROR an error condition occurs and must be reported It is called by the relative state machine function MC FuncRetVal t driveStartUp void The purpose of this function is to call the low level function relative to this state and to update the local state variable DriveState None FUNCTION ENDED is always returned indicating that a state change is requested It is called by the relative state machine function Doc ID 15773 Rev 1 79 85 Library functions UM0708 80 85 BLDC Drive Synopsis Description Input Returns Note GetSpeed 01HZ Synopsis Description Input Returns Note void BLDC_Drive void The purpose of this function is to Update the speed measurement calling the GetSpeed_01HZ function Validate it Convert it into rpm Manage the rotor direction based on the sign of the target speed Call the delay computation BLDCDelayCoefComputation function if required Execute the speed regulation if required Refresh the control variables Upd
93. ted after the commutation to wait for the floating phase current to reach zero The method used to manage the demagnetization time is usually called software demagnetization It consists ky Doc ID 15773 Rev 1 17 85 Introduction to STM8S BLDC control UM0708 Figure 6 in adding a delay between the commutation instant and the end of the demagnetization start of next BEMF zero crossing detection The demagnetization delay is expressed as a percentage of the step time see Section 3 6 2 It is computed using the mean value of two successive step time measurements Demagnetization time Phase c rrent VACA AAA Ee eS see usce a nn a eee ees Z Zero Crossing C Commutation D End of demagnetization Software counter PWM period IC Dj zi d D gt Zi iz pla l le pa gt Commutation Demagnetization Commutation Demagnelization delay time delay time 2 4 2 4 1 18 85 Detection of BEMF zero crossings Zero crossing points must be identified to achieve sensorless BLDC drive Zero crossing points indicate the instant when the BEMF signal becomes equal to the motor neutral voltage During the on time T on of the PWM signal applied to the high side switch the motor neutral voltage becomes equal to the bus voltage 2 see Section 2 4 1 During the off time T off of the PWM signal applied to the high side
94. the application and not related to motor control drive The interrupt service routines used by the motor control firmware are defined inside each module MC stm8s clk this module sets the microcontroller clock MC stm8s DAC this module manages the digital to analog function implemented for debugging purposes It uses TIM3 as described in Section A 1 MC stm8s display this module contains the low level functions that interact with the LCD display This module has been developed on top of MC stm8s 1cd module The exported function is dev displaylnit used to configure the hardware for the LCD display dev displayClear that clears the LCD screen dev displayFlush that outputs on the LCD the data already formatted by MC display module and dev displayPrintch used to refresh the cursor MC stm8s keys this module is used only to initialize the hardware dev keyslnit since the low level functions that manage the keys are implemented inside the vdev ios MC stm8s port this module is used only to initialize the GPIOs of the microcontroller that are used by the application MC stm8s vtimer this module is used to manage the low level virtual timers It is used only for the initialization of the hardware dev vtimerlnit and contains the TIM4 interrupt service routine vdev ios this module is used to manage the low level input output functionality see Table 5 Virtual I Os Doc ID 15773 Rev 1 ky UM0708 Additional information A
95. the joystick RIGHT from the main menu This sub menu allows to set the falling and rising delay coefficients expressed in 1 255 of percentage 255 correspond to 100 of the step time If the auto delay function is enabled this sub menu displays the current values of the delay coefficients applied Contrarily to the main menu in which only the Targ rpm field is editable both fields can be selected and modified Figure 23 Changing rising and falling delays Setting the current reference and duty cycle The current reference and the duty cycle are the control variables related to the current mode and voltage mode respectively Refer to Section 2 1 for a detailed description of the control variables This sub menu features two fields e The current reference The current reference is expressed in Ampere using a 2 1 fixed point format This field is used To set the current reference in open loop current mode configuration To display the applied current reference in closed loop current mode e The duty cycle This field is used To set the applied duty cycle in open loop voltage mode To visualize the applied duty cycle in closed loop voltage mode Figure 24 Control variables These fields can be modified only if the related control method current mode for current reference and voltage mode for duty cycle is enabled in the firmware and the closed loop is not set Modifications in current reference or duty cycl
96. the motor phases This is performed by applying the same configuration as during the alignment phase see Figure 14 The high side switch T1 is controlled by a PWM signal with a fixed duty cycle Current limitation is always performed to prevent the current flowing through the motor to exceed its maximum value The active brake is kept for a fixed time that can be configured through the firmware If the active brake is switched on while the motor is running the extra energy generated by the motor is flowed into the bus voltage and may cause overvoltage In this case it is recommended to use the active brake in conjunction with the dissipative brake function see Section 4 3 4 Doc ID 15773 Rev 1 ky UM0708 Running the demonstration program 3 3 1 Running the demonstration program The BLDC motor control software library includes a demonstration program which allows driving a Shinano motor in sensorless mode A user interface has been developed to display drive variables and customize the application by changing parameters and disabling enabling options in real time The interface is composed of e A 2x15 character LCD screen e A joystick see Table 3 for the list of joystick actions and conventions e Apush button Key button User interface structure The demonstration program user interface is based on a circular navigation menu with submenus item selection and back capability Figure 16 shows the menu str
97. ucture To navigate the help menus and sub menus perform the following actions as required e RIGHT navigates to the next menu or sub menu on the right e LEFT navigates to the next menu or sub menu on the left Figure 16 Menu structure and navigation WELCOME MESSAGE HELP MENU 3 Start stop motor LEFT RIGHT LEFT RIGHT LEFT Speed regulator KD PID only DemagTim sub menu ai15592 eps q Doc ID 15773 Rev 1 27 85 Running the demonstration program UM0708 3 2 Document conventions Table 3 Document conventions Keyword User action UP Joystick pressed up DOWN Joystick pressed down LEFT Joystick pressed to the left RIGHT Joystick pressed to the right JOYSEL Joystick pushed KEY Press the KEY push button 3 3 Welcome message After the MB459B is powered on or reset a welcome message is displayed on the LCD screen to inform the user about the release of the firmware code loaded on board Refer to Figure 17 for the BLDC drive welcome message Figure 17 BLDC drive welcome message 3 4 Help menus After a few seconds the LCD screen displays the first help menu see Figure 18 The user can then navigate to the next help menu by pressing the joystick RIGHT or go back to the previous help menu by pressing the joystick LEFT The KEY button can be pressed anytime to start and stop the motor When the KEY button is presse
98. uring on time events This is very useful when debugging the application Table 17 shows the signal output on the test pins when the debug option is enabled See also Section 5 1 8 for details on how to configure the test pins Table 11 Debug pins description Name Default pin Description Z Event HO This signal toggles each time a zero crossing event is detected In sensorless configuration this signal shows a rising edge for C D Events H1 each commutation and a falling edge at the end of demagnetization Doc ID 15773 Rev 1 1677 UM0708 Designing an application using the BLDC software library Table 11 Debug pins description continued Name Default pin Description This signal becomes high when the drive switches to Auto PEN SWE H2 commutation mode see Section 2 7 This signal becomes high when the BEMF sampling mode is H3 performed during the on time Otherwise it is performed during the off time BEMF sampling during on time Linear variation of delay coefficients according to mechanical speed If the Auto delay function is enabled then the rising and falling coefficient will be computed starting from a predefined curve This curve is set by the user using the following defines These settings will not be used if the Auto delay function is disabled see Section 2 6 define Freq Min Defines the minimum frequency of the rotor speed curve It is expressed in rpm
99. viously supplied The ST logo is a registered trademark of STMicroelectronics All other names are the property of their respective owners 2009 STMicroelectronics All rights reserved STMicroelectronics group of companies Australia Belgium Brazil Canada China Czech Republic Finland France Germany Hong Kong India Israel Italy Japan Malaysia Malta Morocco Philippines Singapore Spain Sweden Switzerland United Kingdom United States of America www st com ky Doc ID 15773 Rev 1 85 85
100. when the Virtual timer operates in polling mode Returns None vtimer TimerElapsed Synopsis u8 vtimer TimerElapsed VtimerName t name Description The purpose of this function is to check the end of counting of a virtual timer operating in polling mode Input Name is the reference to the virtual timer to be checked It can bea mnemonic or a relative number Returns 0 if the time interval has not elapsed 1 at the end of the counting of the requested virtual timer vtimer KillTimer Synopsis void vtimer KillTimer VtimerName t name Description This function stops a Virtual timer operating in automatic mode An automatic Virtual timer can be used to call a function at regular time intervals To do this inside the called function the Virtual timer must be reinitialized The vtimer KillTimer function is used to exit from this loop Input Name is the reference to the virtual timer to be stopped It can bea mnemonic or a relative number Returns None KY Doc ID 15773 Rev 1 81 85 Library functions UM0708 6 2 2 82 85 Low level MC modules The low level MC modules are stored in the folder STM8 MC FRAMEWORK They are composed of the following modules MC stm8s BLDC drive this module contains all the functions related to the low level electrical drive and engine control MC stm8s BLDC it this module contains all the interrupt service routines defined inside the interrupt vector available for
101. witch T1 during the T off the neutral point will be clamped to GND by the D2 free wheeling diode As a consequence the phase B winding will be demagnetized with an equivalent PWM voltage between HV and HV 2 If the PWM is applied to the low side switch T6 during T off the neutral point will be clamped to HV by the D5 free wheeling diode The phase B windings will consequently be demagnetized with an equivalent PWM voltage between HV 2 and GND The reverse voltage applied to the windings is lower than in the first case To speed up the demagnetization of B windings between step 1 and step 2 the PWM control signal should consequently be applied to the high side switch T1 Doc ID 15773 Rev 1 21 85 Introduction to STM8S BLDC control UM0708 22 85 Figure 11 Demagnetization between step 1 and step 2 HV D2 HV HV D3 m Las HV T6 T1 n A I GND D3 Step 2 Toff PWM on High side HV B B C HV v 2 s14 T6 HV T1 GND GND D5 Step 1 Step 2 Ton D3 61O HV Step 2 Toff PWM on Low side Figure 12 shows the transition between step 2 T1 T6 closed and step 3 T3 T6 closed In this case the current that flows through phase A has to be demagnetized Phase A terminal will be clamped to GND by the free wheeling diode D2 The neutral point is HV 2 during T on If the PWM is applied to the high side switch T3 during T off the neutral point will be clamped to GND by the D4 free wheeling diode As a con
102. xcept that the motor phase winding changes to generate a rotating stator field see Figure 1 A BLDC motor has a trapezoidal BEMF Back electromagnetic force induced into the motor phase windings The BLDC drive is also called trapezoidal control because of the shape of the phase current The maximum performance in terms of efficiency and minimum torque ripple is achieved if the motor is intrinsically built as BLDC Figure 2 shows the BEMF signal for the BLDC Shinano motor included in the STM8 128 MCKIT Figure 1 BLDC motor control sequence first three steps V Bus V Bus gt gt gt V Bus GND GND pa GND Step 1 Step 2 Step 3 Figure 2 Shinano motor BEMF signal EN ir 1 zi 1 1 Ng c WAS 50 0ms 100 0ks s 10 0us pt 14 85 Doc ID 15773 Rev 1 ky UM0708 Introduction to STM8S BLDC control 2 1 1 Rotor synchronization The BLDC drive is a synchronous control drive This means that the maximum of the efficiency is achieved if the commutation between two consecutive steps is performed only when the rotor is in the right spatial position This corresponds to the position where the BEMF signal and the phase current are synchronized Two methods can be implemented to perform the rotor synchronization e Sensored drive The first method uses position sensors usually Hall sensors to measure the rotor position e Sensorless drive The other method is based on the BEMF

STM8Sxxx three-phase BLDC motor control software library V1.0

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