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eaton · Joined: 02 Oct 2004 Posts: 22 Location: cleveland

Hello,
I was wondering if anybody had a link to better explanation of using the compare module to output a PWM string of pulses for communication.
microchips AN594 tries to explain it but the code is ASM and its not my strong suit. I'm really on the hunt for something similar written in C.

Thanks

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

These CCS driver and example files have C source code that uses the
PWM module in Compare mode:

c:\Program Files\PICC\Examples\EX_CCP1S.C
c:\Program Files\PICC\Drivers\SERVOS.C
c:\Program Files\PICC\Drivers\EM4095.C

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

What sort of communication are you trying to do with the PWM? It is usually used for analog output or power control, not communication.
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dmendesf · Joined: 31 Dec 2005 Posts: 30

I don´t know what he´s doing, but i´ve used the PWM for generating a diferential manchester signal. It´s very easy and works OK.

eaton · Joined: 02 Oct 2004 Posts: 22 Location: cleveland

I'm trying to communicate to a car using the SAE J1850 PWM protocol.
each bit is 24us long. a 1 is high for 8us and low for 16us while a zero is high for 16us and low for 8us. This sounded like a job for a PWM signal.
33% for a 1 and 66% for a zero. But it's not working out.

any help would be appreciated