PWM examples in Assembly - Electronic Circuits Projects Diagrams Free

**bryan1** · 30th December 2005, 01:43 AM

Hiya Guy's,
I'm on playing around with a 6 wire steppermotor and a 5804 translator/driver chip and this will be the first time I've used pwm. I'm thinking of using a 16f88 and after looking on the net for over 3 hours I'm still yet to find some examples in assembly to help me get started. I looked at the piclist but that site is so hard to find anything so if anyone has some routines to setup and run on a 16f chip I'll appreciate it as I'm a bit confused just using the datasheet.

Cheers Bryan

Pommie · 30th December 2005, 03:01 AM

I'm not sure if this is what you are looking for or not.

This is part of a PID servo on a 16F819.

The PWM setup is

Code:

;	Set PWM Period by writing to PR2
;	With 8MHz clock this will give a frequency of 31kHz
                movlw   3fh
                bsf     STATUS,RP0
                movwf   PR2
                bcf     STATUS,RP0

;	set PWM value to middle - 50/50 duty
                movlw   1fh
                movwf   CCPR1L

;	Enable timer 2 with prescaler 1
                movlw   B'00000100'
                movwf   T2CON

;	Turn on PWM
                movlw   B'00001111'
                movwf   CCP1CON

The PWM value was set with the following.

Code:

                movwf   PWMVal
                movlw   B'00001111'
                bcf     STATUS,C
                rrf     PWMVal,F;      Get lowest bit
                btfsc   STATUS,C
                iorlw   B'00010000';   Put in bit 4 of CCP1CON
                bcf     STATUS,C
                rrf     PWMVal,F;      and bit 1 to bit 5
                btfsc   STATUS,C
                iorlw   B'00100000'
                movwf   CCP1CON
                movfw   PWMVal;		remaining 6 bits to CCPR1L
                movwf   CCPR1L

The values above only give 8 bit resolution of the PWM. The lower bit are in CCP1CON and so mid point is 31 (1Fh).

This might get you started.

Mike.

**Nigel Goodwin** · 30th December 2005, 09:28 AM

You might try my PWM 'tutorial', basically a simple demonstration of how to set the PWM up on a 16F876 - the 16F88 will be almost identical.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

30th December 2005, 01:43 AM	#1
bryan1	PWM examples in Assembly Hiya Guy's, I'm on playing around with a 6 wire steppermotor and a 5804 translator/driver chip and this will be the first time I've used pwm. I'm thinking of using a 16f88 and after looking on the net for over 3 hours I'm still yet to find some examples in assembly to help me get started. I looked at the piclist but that site is so hard to find anything so if anyone has some routines to setup and run on a 16f chip I'll appreciate it as I'm a bit confused just using the datasheet. Cheers Bryan __________________ " The only way to avoid human error is to avoid the use of humans"

30th December 2005, 09:28 AM	#3
Nigel Goodwin	You might try my PWM 'tutorial', basically a simple demonstration of how to set the PWM up on a 16F876 - the 16F88 will be almost identical. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk