gnupic: PWM Fun
Subject:
Re: PWM Fun
From:
Declan Moriarty ####@####.####
Date:
23 Jan 2003 09:18:59 -0000
Message-Id: <03012309105301.00198@genius.chateau.dec>
On Wednesday 22 January 2003 19:45, somebody wrote
> I'm working on a device to emulate some old game console controllers.
> To support everything I want, I need 4 individually timed PWM
> outputs. I'm not an electronics expert, so I thought I'd ask here to
> find some alternatives.
>
> The PIC16F877 I've been using is too busy for me to figure a way for
> it to output the PWM. I've considered using 2 PIC's so one can
> concentrate on PWM. I can see how to do it, but it does make things a
> bit more complex. I've also considered using an Atmel megaAVR
> controller that can manage 4 PWM outputs in hardware, but the part I
> was considering (ATmega128) doesn't seem to be supported by gcc yet,
> and I have no desire to code everything in assembly.
>
> Are there any other ways I can make this happen that I haven't
> considered?
>
> Thanks for the help!
Some pic somewhere has a pwm module. If it's any help to you, you can
do it in a variety of ways.
Some guy from New Zealand designed a 50hp 3 phase inverter with OPAMPS
& thyristors back in the early 'eighties: he made a sine & cosine wave,
from which he got 3 phases, and had all the bells & whistles running
through (a lot of LM1458s). I suffered with that project as it
gradually went belly up. At the heart of the business end, you have the
waveform you want out compared with a triangle wave. That's the only
bit you need. A pot, a triangle wave and a comparator at it's simplest
for dc output.
The next generation used a 16 bit cpu to calculate everything. The cpu
ran flat out and just managed to do 50 hertz without tripping over
itself. Then they realised they were twits, and put in a lookup table,
and an 8 bit cpu :-). That ran sweetly.
If none of that keeps you happy Analog Devices did do an inverter on a
chip for 3 phase sinewaves to drive fets or inverters.
Why not mystify yourself with the instructions for the pic first?
--
Regards,
Declan Moriarty.
