On Sep 11, 2008, at 3:59 PM, Martin Peach wrote: > > > >> From: Derek Holzer <[EMAIL PROTECTED]> >> To: [email protected] >> Subject: [PD] OT: PWM frequency of Arduino >> Date: Thu, 11 Sep 2008 21:09:33 +0200 >> >> Hi all, >> >> using Pduino as a CV generator for my modular. First problem is to >> make >> a low pass filter circuit to remove the PWM noise and get smooth >> DC out. >> Might be helpful to know the default PWM frequency. I know it's >> set in >> the firmware, but I've read everything from 450 Hz to 32 Khz, and >> several other numbers in between out there in Googleland. I'm using >> Arduino 0011 and the Arduino NG board (ATMega8 controller). Anyone >> have >> the definitive answer? >> > > The atmega168 data sheet gives the frequency for Timer1 in phase- > correct > pwm mode as > fclk_I/O/(2*N*TOP) > where N is prescaler (set to 64 in init() in wiring.c), TOP is set > to 255 in > init() in wiring.c, and fclk_I/O is equal to the crystal frequency > (16000000), so it should be about 490.2Hz. (I have a motor > connected to it > now and it sounds about that pitch at low duty cycles.) > > On the atmega168, Timer0 is used in fast pwm mode and runs at twice > that > frequency.
I have 30kHz burned in my brain, but I don't have a reference. You could try setting the PWM at 50% duty cycle, hooking it up via big capacitor (to filter the DC) to a speaker. Then compare the sound to a square wave generated by Pd. .hc > > Martin > > > > _______________________________________________ > [email protected] mailing list > UNSUBSCRIBE and account-management -> http://lists.puredata.info/ > listinfo/pd-list ------------------------------------------------------------------------ ---- ¡El pueblo unido jamás será vencido! _______________________________________________ [email protected] mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
