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Control a BLDC motor with PIC16F877A

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Ttelmah

Joined: 11 Mar 2010
Posts: 19540

Posted: Mon Dec 17, 2012 9:35 am

No guarantees.
This was the original code I generated from the application note. However I never used it on this chip, switching to a PIC18, and then having to do a lot of changes (fault with AN3 on the chip, and the CCP behaves differently from a PIC16 one), so this was never tried:

Code:

//Code based on AN857 for BLDC

#include <16F877.h>
#device adc=16 //Left justify the ADC
#FUSES NOWDT, HS, NOBROWNOUT, NOLVP
#use delay(clock=16MHz)

#define ManThresh (0x3F) //Change to 0xFF for manual mode - 0x3F else - using 44 - almost immediate
#define AutoThresh (0x100-ManThresh)
int8 flags=0;
#bit DriveOnFlag=flags.0
#bit AutoRPM=flags.1
#bit FullOnFlag=flags.4
#bit Tmr0Ovf=flags.5
#bit Tmr0Sync=flags.6

int8 PhaseIndx=6,Drive,RPMIndex;
int8 ADCRPM;
int8 PWMThresh=0;
int8 ADCOffset;
int8 Vsupply;
int8 DeltaV1,DeltaV2;
int16 CCPSave,CCPT2;
int8 RampTimer;

#define AccelDelay 100
#define DecelDelay 10

#bit BEMF1Low=DeltaV1.7
#bit BEMF2Low=DeltaV2.7
#bit ADCneg=ADCOffset.7

enum {RPMSetup,RPMRead,OffsetSetup,OffsetRead,Vsetup,Vidle,Vread,BEMFSetup,BEMFIdle,BEMFRead,BEMF2Idle,BEMF2Read,Inval} STATE=RPMsetup;

#use fast_io(C)

/*
ADC channels are wired as:
AN0 = RPM I/P voltage
AN1 = Offset
AN3 = sense on OP/A BEMF etc..
*/

#define RPM (0)
#define OFFSET (1)
#define BEMF (3)

//Drive word definitions
#define OffMask (0B11010101)
#define Invalid (0B00000000)
#define Phase1 (0B00100001)
#define Phase2 (0B00100100)
#define Phase3 (0B00000110)
#define Phase4 (0B00010010)
#define Phase5 (0B00011000)
#define Phase6 (0B00001001)

//ADC switching definitions
//Each assumes the ADC is in a defined previous state, and changes it to the next
#define ADC0to1 (0B00001000)
#define ADC1to3 (0B00010000)
#define ADC3to0 (0B00011000)
#byte ADCON0=getenv("SFR:ADCON0") //0xFC2 //("SFR:ADCON0")
#byte ADRESH=getenv("SFR:ADRESH") //0xFC4 //("SFR:ADRESH")
#bit GO=ADCON0.1
#byte STAT=getenv("SFR:STATUS")
#bit CARRY=STAT.0
#bit ZERO=STAT.2
#byte TMR0=getenv("SFR:TMR0")
#byte CCP1CON=getenv("SFR:CCP1CON")
#bit SPECIAL_EVENT=CCP1CON.0

#include "T1Tableold.h" //You will need to use the code as shown and build this for your motor
//format is const int16 Timer1Table[256] = {xxx,xxx...};

int save_w;
#locate save_w=0x7f
int save_status;
#locate save_status=0x20

#byte status = 3
#bit zero_flag = status.2
#bit t0if = 0xb.2

#INT_GLOBAL
void timer_0_int(void) {
#asm
//store current state of processor
MOVWF save_w
SWAPF status,W
BCF status,5
BCF status,6
MOVWF save_status
// Save anything else your code may change
// You need to do something with PCLATH if you have GOTOs

// remember to check to see what interrupt fired if using more than one!!

// code for isr
#endasm
Tmr0Ovf=TRUE;
Tmr0Sync=TRUE;
clear_interrupt(INT_TIMER0); //fastest possible int handler - relies on instructions not changing flags etc..

#asm
// restore processor and return from interrupt
SWAPF save_status,W
MOVWF status
SWAPF save_w,F
SWAPF save_w,W
#endasm
}

const int8 OnTable[]={Invalid,Phase6,Phase5,Phase4,Phase3,Phase2,Phase1,Invalid};
void DriveMotor(void);
void LockTest(void);

void commutate(void) {
//Commutation triggered by CCP1IF
if (SPECIAL_EVENT) {
//Here special event trigger is set
clear_interrupt(INT_CCP1);
if (--PhaseIndx==0) PhaseIndx=6; //Handle 'bottom of table'
Drive=OnTable[PhaseIndx];
DriveMotor();
}
}

void DriveOff(void) {
set_adc_channel(RPM); //Changing to start with my current reading
STATE=RPMSetup;
}

void main(void)
{
int8 temp;
output_c(0); //Motor drivers off to start....
set_tris_c(0);
//setup_adc_ports(sAN0|sAN1|sAN3);
setup_adc(ADC_CLOCK_DIV_32);

set_adc_channel(RPM);
setup_spi(FALSE);
setup_timer_0(T0_DIV_2);
enable_interrupts(INT_TIMER0);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_4);
setup_ccp1(CCP_COMPARE_RESET_TIMER);
clear_interrupt(INT_TIMER0);
enable_interrupts(GLOBAL);

do {
if (interrupt_active(INT_CCP1)) commutate();
DriveOnFlag=TRUE;
if (!FullOnFlag) {
temp=(int8)PWMThresh+TMR0;
if (!CARRY) DriveOnFlag=FALSE;
DriveMotor();
}
LockTest();
switch (STATE) {
case RPMSetup:
if (Drive==Phase1) {
output_high(PIN_A4);
read_adc(ADC_START_ONLY);
set_adc_channel(OFFSET); //Offset default
STATE++;
Tmr0Sync=FALSE;
output_low(PIN_A4);
}
break;
case RPMRead:
if (adc_done()) {
ADCRPM=ADRESH;
}
break;
case OffsetSetup: //Wait for Phase2 ADC Go RA3->ADC
if (Drive==Phase2) {
read_adc(ADC_START_ONLY); //Trigger ADC
set_adc_channel(BEMF);
STATE++;
}
break;
case OffsetRead:
//Wait for ADC Read ADC->ADC Offset
if (adc_done()){
ADCOffset=ADRESH ^ 0x80; //Generate +/- offset
PWMThresh=ADCRPM+ADCOffset;
if (!bit_test(ADCOffset,7)) { //Offset is +ve
if (CARRY) PWMThresh=0xFF;
}
else {
if(!CARRY) PWMThresh=0;
}
if (ZERO) {
DriveOff();
break;
}
FullOnFlag=FALSE;
if (PWMThresh>0xFD) FullOnFlag=TRUE; //Fixed full on threshold
STATE++;
}
break;
case Vsetup:
//wait for phase4
if (Drive==Phase4) {
CCP_1=Timer1table[RPMIndex]; //Table from spreadsheet
STATE++;
}
break;
case Vidle:
//Wait for Drive ON, wait Tacq, set ADC go
if (DriveOnFlag) {
delay_us(8); //Tacq
read_adc(ADC_START_ONLY);
STATE++;
}
break;
case Vread:
if(adc_done()) {
//ADC has finished
Vsupply=ADRESH;
STATE++;
Tmr0Sync=FALSE;
}
break;
case BEMFSetup:
if(Drive==Phase5) {
if (Tmr0Sync) {
if (bit_test(PWMThresh,7)!=0) {
if (DriveOnFlag==FALSE) break;
}
//BEMFS1
SPECIAL_EVENT=FALSE; //Turn off event on compare
CCPSave=CCPT2=CCP_1; //Save two copies of CCP
CCPT2/=2; //1/2 Phase time
CCP_1=CCPT2/2; //1/4 phase time into CCP_1
STATE++;
}
}
break;
case BEMFIdle:
if (interrupt_active(INT_CCP1)) {
DriveOnFlag=TRUE;
DriveMotor();
Delay_us(8);
read_adc(ADC_START_ONLY);
CCP_1+=CCPT2; //add 1/2 phase time to give 3/4 phase time
clear_interrupt(INT_CCP1);
STATE++;
}
break;
case BEMFRead:
if (adc_done()) {
DeltaV1=ADRESH-(Vsupply/2);
STATE++;
}
break;
case BEMF2Idle:
if (interrupt_active(INT_CCP1)) {
DriveOnFlag=TRUE;
DriveMotor();
delay_us(8);
read_adc(ADC_START_ONLY);
set_adc_channel(RPM);
CCP_1=CCPSave; //Full time
clear_interrupt(INT_CCP1);
SPECIAL_EVENT=TRUE; //enable event on compare
STATE++;
}
break;
case BEMF2Read:
if (adc_done()) {
DeltaV2=ADRESH-(Vsupply/2);
STATE=RPMSetup; //Changing to start with current reading
}
break;
case Inval:
STATE=RPMSetup;
//Status=0;
set_adc_channel(RPM);
break;
}
} while(TRUE);
}

void DriveMotor(void) {
if (DriveOnFlag) {
output_c(Drive | 0x80);
}
else {
output_c(Drive & OffMask);
}
}

void LockTest(void) {
if(Tmr0Ovf==TRUE) {
if (bit_test(PWMThresh,7)){
//On longer than off
if (DriveOnFlag==FALSE)
return;
}
//Here drive is either on, and on>off, or drive off, and off>on - LT05
Tmr0Ovf=FALSE;
if (--RampTimer!=0)
return;
AutoRPM=TRUE;
if (ADCRPM<=ManThresh) {
AutoRPM=FALSE;
}
if (BEMF1Low) {
//LT10
output_low(PIN_B6);
output_high(PIN_B7); //ahead of lock
RampTimer=AccelDelay;
if (AutoRPM==FALSE) {
//Manual code
RPMIndex=ADCRPM;
return;
}
if (RPMIndex==0xFF) {
return;
}
RPMIndex++;
return;
}
//LT20 - else
RampTimer=DecelDelay;
if (!BEMF2Low) {
output_low(pin_B6);
output_low(PIN_B7); //behind lock
if (AutoRPM==FALSE) {
//Manual code again
RPMIndex=ADCRPM;
return;
}
if (RPMIndex>0) --RPMIndex;
return;
}
//Showlocked
output_high(PIN_B6);
if(AutoRPM==FALSE) {
//Manual code
RPMIndex=ADCRPM;
}
}
}

You'll have to use the spreadsheet in the application note, to build a a T1Tableold.h, to match your motor requirements.

You'll also have to add the instructions to save the registers to int_global (look at ex_glint.c), I'd already started assuming I was going to use the PIC18, which saves the critical registers automatically.

Have done this for you now....

Best Wishes

SherpaDoug

Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA

Posted: Tue Dec 18, 2012 6:20 pm

A_L_E_X wrote:

Quote:

Have a look at Microchip AN857, which shows how to have a 877A, handle a BLDC motor, including reading a pot to set the speed.

I did that but the code is in ASM and i don't know ASM. Is there a version in c ? It doesn't have to be for CCS, just c.

If you are going to do this sort of intense optimized embedded processor programming in C or any other language you MUST have at least a familiarity with ASM for the chip you are using. Spend some time exploring the instruction set and registers. It will be a good investment.
_________________
The search for better is endless. Instead simply find very good and get the job done.

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Tue Dec 18, 2012 7:22 pm

If you want to Google for CCS code, then try a search string like this:

Quote:

18F4431 OR PIC18F4431 BLDC "#use delay"

You can also try it with PICs in the same family, such as the 18F2331,
18F2431 and 18F4331.

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