Post by thread:[PIC]:servo control with 16F84

Hi, my name is Dave, and I am trying to get a couple of servo's working with a pic16f84, but am not having much luck. I was able to get the servos working with this article http://www.rentron.com/servo.htm but I want to modify the source, and I don't have their c compiler. So, I went about to make my own program, but since this is one of my first pic programs, I am looking for a little help. What I have so far is at the end of this message. (the servo's are modified for continuous rotation). All I am trying to do with this right now is when B1 goes high, start the servo for a period of time, and stop it before the period expires if B0 goes high. But, it doesn't work. That's why I'm mailing the list of course :) Any help would be greatly appreciated..... (Trust me, I've searched the archives plenty, and couldn't find the awnser or any other servo controller that suited my needs....) -Dave watson --------------------------------------------------- LIST P=16F84 ; tells which processor is used INCLUDE "p16f84a.inc" ; defines various registers etc. Look it over. ERRORLEVEL -224 ; supress annoying message because of tris __CONFIG _PWRTE_ON & _LP_OSC & _WDT_OFF ; configuration switches w equ 0 ;in byte instructions, use w & f f equ 1 ; instead of 0 & 1, it s much clearer ;-----------------------------------------------------------------------; ; Here we set up our own registers start at the 1st free address ; ;-----------------------------------------------------------------------; CBLOCK H'0C' dlycount ; counter used in delays speedright speedleft lcnt wcnt tempright templeft d1 d2 ENDC ORG 0 ; start a program memory location zero ;-----------------------------------------------------------------------; ; First we set up all bits of PORT A and B as outputs ; ;-----------------------------------------------------------------------; movlw B'00000000' ; all a output 0,1 are servos tris PORTA ; contents of W copied to PORT A ... movlw B'11111111' ; all b input tris PORTB ; and PORT B movlw B'00000000' ; port B pull-ups active option movwf PORTA movwf PORTB ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;MAIN mainloop: btfss PORTB,1 ;if porta.1 is one, then do this func goto skipa1 movlw B'11111111' movwf speedright movwf speedleft call motor skipa1: goto mainloop ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;MTOTOR function motor: movwf wcnt mloopw: movlw B'00011110' movwf lcnt mloopl: btfsc PORTB,0 goto endmotor movf speedright,w movwf tempright movf speedleft,w movwf templeft bsf PORTA,0 rightmotorl: goto $+1 goto $+1 goto $+1 nop decfsz tempright,f goto rightmotorl bcf PORTA,0 bsf PORTA,1 leftmotorl: goto $+1 goto $+1 goto $+1 nop decfsz templeft,f goto leftmotorl bcf PORTA,1 ;wait ;13625 cycles movlw 0x34 movwf d1 Delay_00 movlw 0x56 movwf d2 Delay_01 decfsz d2, f goto Delay_01 decfsz d1, f goto Delay_00 ;40 cycles movlw 0x0d movwf d1 Delay_10 decfsz d1, f goto Delay_10 ;2 cycles goto $+1 ;end wait decfsz lcnt,f goto mloopl decfsz wcnt,f goto mloopw endmotor: return ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;END of prog END _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Hi Dave, here is a simple servo test program written in CC5X pic C. A free compiler is available. // servo2.c // // Servo control using push buttons or switches JPB 11/12/00 // ******************************************** // For CC5X C compiler // Xtl frequency 4MHz // A simple r/c servo test program. // This version uses switches to control the servo position. // Port B bit 1 is the servo control signal o/p // Port A bit 0 = 0 resets the servo position to center (pulse = 1.5 ms) // Port A bit 1 moves the servo clockwise when taken low. // Port A bit 2 moves the servo anticlockwise when taken low. // // Note the pulse width range is specified as 1ms to 2ms giving a movement // of 180 deg. but the precise pulse width and mechanical range varies from // manufacturer to manufacturer. // // The pulse width range generated by this program has been found to work // well with a range of servos. // // Connect the servo to a 5volt supply and take the control wire to port A // bit 3, you will need a connection from the PSU 0V to the pic circuit // supply 0V. Connect port A bit 0 to 3 to push buttons (with pullups). // Do not leave the servo running at the extreme range of movement if it // is pushing against the end stop. You can tell when this is happening // by watching the current taken from the PSU which will be high if the // servo is stalled. #include "16F84.H" #define CP_off |= 0x3FFF // copy protect off for 16F84 #pragma config CP_off, PWRTE=on, WDTE=off, FOSC=XT /* assign names to ports and pins */ #pragma bit SERVO @ PORTB.1 #pragma bit RESET_S @ PORTA.0 #pragma bit TURN_C @ PORTA.1 #pragma bit TURN_A @ PORTA.2 /* function prototypes */ void delay_min (void); void delay_var (char n); void pause (void); void main( void) { PORTB = 0b.0000.0000; /* initial value */ TRISB = 0b.0000.0000; /* Port B all o/p */ PORTA = 0b.0.0111; /* initial value */ TRISA = 0b.1110.0111; /* xxx0 0001 */ char position=107; // total time 1.5ms center position while(1) // endless loop { SERVO=1; delay_min(); if (position>0) delay_var(position); SERVO=0; pause(); // 20 ms delay before next pulse if ((TURN_C==0)&&(position<255)) position++; if ((TURN_A==0)&&(position>0)) position--; if (RESET_S==0) position=107; // center the servo } } // end of main void delay_min (void) // 750 uS including overhead { char n=248; do ; while(--n>0); nop(); // padding to produce precise time } // delay = 2 + 2 + (n x 3) -1 +1 +2 = 750us @ 4MHz // 2 for call, 2 for preset n, (n x 3)-1 for loop, 1 padding, 2 for return void delay_var (char n) // adc x 7 uS = 1790us max. { do {nop(); nop(); nop(); nop();} while(--n>0); } // delay= 2 + 2 + (t x 7) -1 +2 us @ 4MHz void pause (void) // delay between pulses approx 20 ms { char n; for (n=0;n<26;n++) { delay_min(); // 750 us } } -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> > LIST P=16F84 ; tells which processor is used > INCLUDE "p16f84a.inc" ; defines various registers etc. Look it >over. > ERRORLEVEL -224 ; supress annoying message because of tris > __CONFIG _PWRTE_ON & _LP_OSC & _WDT_OFF ; configuration switches You failed to mention what speed you are running. If you're trying to control a servo, you need some fairly precise timing, otherwise you'll end up with so much jitter that your servos will be unusable. Your timing in your routines looks like it's 4MHz, but I'm guessing. >; First we set up all bits of PORT A and B as outputs ; >;----------------------------------------------------------------------- I'm not sure if the TRIS instruction defaults to bank 1, but I always do it manually anyways. You should select bank 1 before you access the TRIS registers. bsf STATUS, RP0 ; > movlw B'00000000' ; all a output 0,1 are servos > tris PORTA ; contents of W copied to PORT A ... > movlw B'11111111' ; all b input > tris PORTB ; and PORT B bcf STATUS, RP0 ; select Bank 0 for PORTA/B access > movlw B'00000000' ; port B pull-ups active > option > movwf PORTA > movwf PORTB Your main routine looks like it times out at 158 seconds, which should be plenty to run the servos around. But your servo timing seems to be off a little. Servos run from 1.0ms to 2.0ms with 1.50ms being centered. I doubt whether the comparator inside the servo can differentiate signals greater than 2.0ms. In your routines, you're running a value of 0xFF through a 10us loop (@4MHz) which would create a high servo pulse of 2.55ms. I think this is your problem. Try reducing your initial loop counters to a value less than 200 decimal. Also, try to stick with a 50Hz pulse timing (which is not so critical, by the way) to operate the servos. Your delay counters for the low pulse cycle total 13.667ms instead of 18ms. This MAY not be a problem, but there's no reason you can't get precisely 18ms. This should give you an 18ms delay at 4MHz, and a servo cycle of 50Hz if you're using a 2.0ms high pulse: movlw 0x12 ; 18 times through @ 1ms per loop movwf Counter Delay_Start movlw 0x07 ;249 cycles * 4us per cycle + 4us = 1.000ms Delay addlw 0x01 btfss STATUS, Z goto Delay decfsz Counter goto Delay_Start Hope this helps. --Andrew {Quote hidden}> movf speedright,w > movwf tempright > movf speedleft,w > movwf templeft > > bsf PORTA,0 >rightmotorl: > goto $+1 > goto $+1 > goto $+1 > nop > decfsz tempright,f > goto rightmotorl > > bcf PORTA,0 > > bsf PORTA,1 >leftmotorl: > goto $+1 > goto $+1 > goto $+1 > nop > decfsz templeft,f > goto leftmotorl > > bcf PORTA,1 > > ;wait > ;13625 cycles > movlw 0x34 > movwf d1 >Delay_00 > movlw 0x56 > movwf d2 >Delay_01 > decfsz d2, f > goto Delay_01 > decfsz d1, f > goto Delay_00 > > ;40 cycles > movlw 0x0d > movwf d1 >Delay_10 > decfsz d1, f > goto Delay_10 > > ;2 cycles > goto $+1 > ;end wait > > decfsz lcnt,f > goto mloopl > decfsz wcnt,f > goto mloopw >endmotor: > return _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Check out my home site at http://www.webhome.idirect.com/~bine . I have not updated it for some time now but my source code might help. At 07:23 AM 12/18/2000 -0000, you wrote: {Quote hidden}>Hi, my name is Dave, and I am trying to get a couple of servo's working with >a pic16f84, but am not having much luck. I was able to get the servos >working with this article > >http://www.rentron.com/servo.htm > >but I want to modify the source, and I don't have their c compiler. So, I >went about to make my own program, but since this is one of my first pic >programs, I am looking for a little help. What I have so far is at the end >of this message. (the servo's are modified for continuous rotation). All >I am trying to do with this right now is when B1 goes high, start the servo >for a period of time, and stop it before the period expires if B0 goes high. > >But, it doesn't work. That's why I'm mailing the list of course :) > >Any help would be greatly appreciated..... > >(Trust me, I've searched the archives plenty, and couldn't find the awnser >or any other servo controller that suited my needs....) > > >-Dave watson >--------------------------------------------------- > > LIST P=16F84 ; tells which processor is used > INCLUDE "p16f84a.inc" ; defines various registers etc. Look it >over. > ERRORLEVEL -224 ; supress annoying message because of tris > __CONFIG _PWRTE_ON & _LP_OSC & _WDT_OFF ; configuration switches > >w equ 0 ;in byte instructions, use w & f > >f equ 1 ; instead of 0 & 1, it s much clearer > > >;-----------------------------------------------------------------------; >; Here we set up our own registers start at the 1st free address ; >;-----------------------------------------------------------------------; > CBLOCK H'0C' > dlycount ; counter used in delays > speedright > speedleft > lcnt > wcnt > tempright > templeft > d1 > d2 > ENDC > > ORG 0 ; start a program memory location zero > >;-----------------------------------------------------------------------; >; First we set up all bits of PORT A and B as outputs ; >;-----------------------------------------------------------------------; > movlw B'00000000' ; all a output 0,1 are servos > tris PORTA ; contents of W copied to PORT A ... > movlw B'11111111' ; all b input > tris PORTB ; and PORT B > movlw B'00000000' ; port B pull-ups active > option > movwf PORTA > movwf PORTB >;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >;MAIN > >mainloop: > btfss PORTB,1 ;if porta.1 is one, then do this func > goto skipa1 > movlw B'11111111' > movwf speedright > movwf speedleft > call motor >skipa1: > goto mainloop > >;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >;MTOTOR function >motor: > movwf wcnt >mloopw: > movlw B'00011110' > movwf lcnt >mloopl: > btfsc PORTB,0 > goto endmotor > > movf speedright,w > movwf tempright > movf speedleft,w > movwf templeft > > bsf PORTA,0 >rightmotorl: > goto $+1 > goto $+1 > goto $+1 > nop > decfsz tempright,f > goto rightmotorl > > bcf PORTA,0 > > bsf PORTA,1 >leftmotorl: > goto $+1 > goto $+1 > goto $+1 > nop > decfsz templeft,f > goto leftmotorl > > bcf PORTA,1 > > ;wait > ;13625 cycles > movlw 0x34 > movwf d1 >Delay_00 > movlw 0x56 > movwf d2 >Delay_01 > decfsz d2, f > goto Delay_01 > decfsz d1, f > goto Delay_00 > > ;40 cycles > movlw 0x0d > movwf d1 >Delay_10 > decfsz d1, f > goto Delay_10 > > ;2 cycles > goto $+1 > ;end wait > > decfsz lcnt,f > goto mloopl > decfsz wcnt,f > goto mloopw >endmotor: > return >;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >;END of prog > END >_________________________________________________________________ >Get your FREE download of MSN Explorer at http://explorer.msn.com > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads