I want to use a PIC16F877A (I have a boot loader on it) to control the speed of an electric motor. I also want to use the PIC for a few other things not related to this problem so I want to program it in assembly for better programming control (and for the fun of it). Motor speed will be controlled using a potentiometer as input in a voltage divider. The voltage will be measured using RA0/AN0 (or which ever) of the analog pins on the PIC . The measured voltage will used to set the value of a PWM signal that will go to an H-bridge. My oscillator is 16 MHz.
How can I program the PIC16F877A in assembly code to measure voltage at one of the analog pins and output a PWM signal to an H-bridge? I've managed to put together some code from what I remember and have been able to get from the internet but I'm sure that it needs correcting. What else do I need to add or correct?
LIST P=16F877A
INCLUDE P16F877.INC
org 0x1F00 ; For the boot loader
__CONFIG _WDT_OFF
Start
; 01 = B1
bsf STATUS, RP0
bcf STATUS, RP1
; Set PORTA to input
movlw B'11111111'
movwf TRISA
; Set PORTE to input
movlw B'11111111'
movwf TRISE
; Justify left the A2D inputs
; All possible pins are analog, VREF+ = VDD, VREF- = VSS
clrf ADCON1
; 00 = B0
bcf STATUS, RP0
; Fosc / 8, RA0/AN0, AD on
movlw B'01000001'
movwf ADCON0
; 00 = not used, 11 = LSB, 1100 = PWM
movlw B'00111100'
movwf CCP1CON
; Goto Main
goto Main
; Move the new values from the A2D, ADRESH and ADRESL,
; to the PWM values, CCPR1H and CCPR1L, respectively
SetPWM
movf ADRESH, CCPR1H
movf ADRESL, CCPR1L
return
; Get the AD measurement
GetAD
bsf ADCON0, GO
Pause
btfsc ADCON0, GO
goto Pause
return
Main
call GetAD ; Get the AD measurement
call SetPWM ; Set the PWM values
goto Main ; Loop back
end
How can I program the PIC16F877A in assembly code to measure voltage at one of the analog pins and output a PWM signal to an H-bridge? I've managed to put together some code from what I remember and have been able to get from the internet but I'm sure that it needs correcting. What else do I need to add or correct?
LIST P=16F877A
INCLUDE P16F877.INC
org 0x1F00 ; For the boot loader
__CONFIG _WDT_OFF
Start
; 01 = B1
bsf STATUS, RP0
bcf STATUS, RP1
; Set PORTA to input
movlw B'11111111'
movwf TRISA
; Set PORTE to input
movlw B'11111111'
movwf TRISE
; Justify left the A2D inputs
; All possible pins are analog, VREF+ = VDD, VREF- = VSS
clrf ADCON1
; 00 = B0
bcf STATUS, RP0
; Fosc / 8, RA0/AN0, AD on
movlw B'01000001'
movwf ADCON0
; 00 = not used, 11 = LSB, 1100 = PWM
movlw B'00111100'
movwf CCP1CON
; Goto Main
goto Main
; Move the new values from the A2D, ADRESH and ADRESL,
; to the PWM values, CCPR1H and CCPR1L, respectively
SetPWM
movf ADRESH, CCPR1H
movf ADRESL, CCPR1L
return
; Get the AD measurement
GetAD
bsf ADCON0, GO
Pause
btfsc ADCON0, GO
goto Pause
return
Main
call GetAD ; Get the AD measurement
call SetPWM ; Set the PWM values
goto Main ; Loop back
end
