Post by thread:[PIC] Simple 16C73 PWM routine?

Hi Graham: In which programming language? Asm or C? Ismael. Graham North wrote: {Quote hidden}> Hi > > I am just starting to play with the 16C73, and would like to use the PWM > outputs. > I have read the data book but I am afraid it has gone straight over my head > (I have > not implemented any PWM outputs before). > > If anyone has a simple program to get me started I would be very grateful. > > Thanks > > Graham > > (I just don't know where to start!) -- ------------------------------------------------------------------ Ismael M. Khangane, Specialist in Robotics. Automatic Control & Systems ( Bsc in Eng.) Instituto de Automatica Industrial IAI-CSIC Madrid, Spain. Tel: (34) 91 871 1900 Fax: (34) 91 871 7050 E-mail: spam_OUTimkespTakeThisOuTexcite.com ; .....ismaelmKILLspam@spam@iai.csic.es ------------------------------------------------------------------

Graham, Here's a short bit of code that sets up the PWM and sets the PWM to ~50% duty cycle I copied it from some code that works, Its been a while since I wrote it so, I may have forgot to copy something. Try it and let us know. MOVLW 0xFF ; 00 --> W BSF STATUS, RP0 ; Select bank 1 MOVWF PR2 ; Load PR2 with period info ; at 20MHz PR2=FF gives a 1.22KHz ; at 4MHz PR2=FF gives a 3.906KHz BCF STATUS, RP0 ; Select bank 0 MOVLW 0X80 ; Load W with 0X80 MOVWF CCPR1L ; Duty Cycle is ~50% of PWM 1 Peroid MOVWF CCPR2L ; Duty Cycle is ~50% of PWM 2 Peroid BSF T2CON, T2CKPS1 ; Set the TMR2 prescale value BSF T2CON, T2CKPS0 ; Set the TMR2 prescale value BSF T2CON, TMR2ON ; Enable timer2 MOVLW 0X0F ; MOVWF CCP1CON ; SET low two bits of PWM 1 and turn it on MOVWF CCP2CON ; SET low two bits of PWM 2 and turn it on ; PWM has 10-bits of resolution Matt

Asm if possible. -----Original Message----- From: Ismael M. Khangane [SMTP:ismaelmKILLspamIAI.CSIC.ES] Sent: 19 May 2000 15:39 To: .....PICLISTKILLspam.....MITVMA.MIT.EDU Subject: Re: [PIC] Simple 16C73 PWM routine? Hi Graham: In which programming language? Asm or C? Ismael. Graham North wrote: > Hi > > I am just starting to play with the 16C73, and would like to use the PWM > outputs. > I have read the data book but I am afraid it has gone straight over my head > (I have > not implemented any PWM outputs before). > > If anyone has a simple program to get me started I would be very grateful. > > Thanks > > Graham > > (I just don't know where to start!) -- ------------------------------------------------------------------ Ismael M. Khangane, Specialist in Robotics. Automatic Control & Systems ( Bsc in Eng.) Instituto de Automatica Industrial IAI-CSIC Madrid, Spain. Tel: (34) 91 871 1900 Fax: (34) 91 871 7050 E-mail: EraseMEimkespspam_OUTTakeThisOuTexcite.com ; ismaelmspam_OUTiai.csic.es ------------------------------------------------------------------

Thanks for the program. Am I right by looking at the program that the input from the 10k pot should be connected to RA0? Which port is the output? <Snip> BCF TRISC,2 ;MAKE PIN OUTPUT Is it port C? All 8 leds connected. Sorry for the dumb questions. Thanks Graham -----Original Message----- From: RAYMOND WILLCOX [SMTP:@spam@markwillcox56KILLspamhotmail.com] Sent: 20 May 2000 17:50 To: KILLspamGRAHAM.NORTHKILLspamLANDINST.COM Subject: Re: [PIC] Simple 16C73 PWM routine? Graham Here is a simple A/D - PWM code (from Toni Nixon), it works well. It drives an eight bit bar-graph display or 8 LED's. It uses a 10k pot on the input. Real simple and quite self explanitory. Have fun - Mark

Graham North wrote: > > Thanks for the program. > > Am I right by looking at the program that the input from the 10k pot should > be connected to RA0? > > Which port is the output? > > <Snip> BCF TRISC,2 ;MAKE PIN OUTPUT > > Is it port C? All 8 leds connected. > > Sorry for the dumb questions. > > Thanks Graham Graham, there are no such thing as dumb questions, only dumb answers. I am not referring to the other replies to your email of course :). I did not see the program that Tony wrote, but it should be very similar to this A/D to PWM test program below (I modified the tutorial A/D program for the ICD, bit rough, but it works). To answer your questions: The 10K pot is connected to RA0 and the pin is set up to be an analogue input. BCF TRISC,2 is the CCP1 output on PortC which is set up to be the PWM1 output. Get the Mid-Range MCU Family Reference Manual from Microchip. It will give you a bit more info (You can also get it from Microchip's web with each chapter as a separate download, get the CCP section). To do PWM: Set up TMR2, switch TMR on and set prescaler (16 in this case). Set TMR2 period in PR2. Default is 0x0FF. You should only change this setting lower if you want a faster PWM period (together with the prescaler), but then you start meddling with resolution. Clear TMR2 interupts in PIR2 and PIE2 (You don't need them for simple PWM) Should be cleared as default. Do the calculations (in the data books) to see if your duty cycle is not longer than the period. The above settings should keep you in spec. Set CCP1CON to be PWM. Write your PWM duty cycle to CCPR1L (8 MSB) and CCP1CON, 5 and 4 (2 LSB) and away you go! Hope this helps Quentin ;A/D input on RA0 to PWM output on RC2 Start banksel PORTC clrf PORTC ;Clear PORTC movlw B'01000001' ;Fosc/8, A/D enabled movwf ADCON0 banksel OPTION_REG movlw B'10000111' ;TMR0 prescaler, 1:256 movwf OPTION_REG clrf TRISC ;PORTC all outputs movlw B'00001110' ;Left justify,1 analog channel movwf ADCON1 ;VDD and VSS references banksel PORTC MOVLW B'00000111' ;switch on TMR2 and set prescaler to 16 MOVWF T2CON MOVLW B'00001100' MOVWF CCP1CON ;select CCP1 to be PWM output Main btfss INTCON,T0IF ;Wait for Timer0 to timeout goto Main bcf INTCON,T0IF bsf ADCON0,GO ;Start A/D conversion Wait btfss PIR1,ADIF ;Wait for conversion to complete goto Wait DO_PWM movf ADRESH,W ;Write A/D result to PWM MOVWF CCPR1L BCF CCP1CON,4 ;do the LSB BCF CCP1CON,5 BSF STATUS,RP0 MOVF ADRESL,W BCF STATUS,RP0 MOVWF TEMP1 BTFSC TEMP1,6 BSF CCP1CON,4 BTFSC TEMP1,7 BSF CCP1CON,5 goto Main ;Do it again