Newsgroups: comp.robotics
Path: brunix!sgiblab!spool.mu.edu!howland.reston.ans.net!usenet.ins.cwru.edu!news.csuohio.edu!dpalmer
From: dpalmer@csuohio.edu (Darryl Palmer)
Subject: Re: PWM of Servos
Message-ID: <1994Jul23.032945.221@news.csuohio.edu>
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Date: Sat, 23 Jul 1994 03:29:45 GMT
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Brian Van Mondfrans (brianvm@halcyon.com) wrote:
: Jeff and I have run into problems with the twelve servos we need to control 
: for our walking robot.  There is no software solution to creating the PWM 
: for all the servos with a 6.270 board and still have processor time left 
: over.  The high pulse is just too small for any of my solutions.

: We have some solutions that may solve the problem.

:      1.  PWM chips.  I have found some chips that might create the PWM for 
:          controlling servos.The first is a Regulating pulse width modulator 
:          (SG3524).  My hope would be you could send some info to the chip 
:          and it would create the necessary waveform to position the servo.  
:          The other choice is a AM9513APC System Timing Contoller appears 
:          that is may also create the waveforms I need.  Any information on 
:          these chips would be very helpful because this method would be the 
:          cheapest.

:      2.  Our other method would be to network some Bot-Boards together with 
:          the 6.270 board.  Using this method I would need some information 
:          on using the SPI port to network the boards.

: If anyone has any other suggestions, information on the chips, 
: or information on networking with the HC11 it would be greatly appreciated.

: -----------------------------------------------
: Brian Van Mondfrans, North Thurston High School Graduate, Olympia, WA
: Email: brianvm@halcyon.com

If you have a PIC programmer, I would recommend trying to program a 
PIC chip to do the job.  I needed a PWM generator for 2 motors, feedback from
optical encoders for both motors, and RS232 support.  I used one PIC16C57 to
do everything.  If you run it with a 20Mhz clock, you get 200ns instruction
cycles and you could easily have more than 16 signals be generated with
different waveforms.  The 16C57 might be overkill for your application 
because it can hold 7FF instructions (Whatever that is in decimal) but for
only 20 odd bucks, Di$ikey price, it is a good buy.


Darryl Palmer
