Re: Expansion Board Servo timing... At 03:31 PM 4/12/99 -0500, wengd@optionshealthcare.com wrote:

>How sensitive are the exp bd servo routines to many processes running
>concurrently.  My servo works fine in a stand alone test file but when I
>include it in my main code it gets the "nervous shakes", as if the timing
>pulse is fluctuating ( I don't have a scope to verify this).

 I don't know about the servo routines on the HB, but servos *do* start to
jitter when the pulses get much below about 20Hz. This is not due to the
pulse width 'fluctuating', it's because the refresh rate is dropping. It
certainly is possible that the refresh rate drops as the load on the 6811
increases. Perhaps servo control could be offloaded onto a PIC ala. Scott
Edwards SSC (serial servo controller) at:

http://www.seetron.com

If you have a PIC programmer (or a BASIC stamp) it's pretty trivial to
program one to accept serial commands and output the pulses to a few
servos. Scott's is nice because it can handle eight servos and there is
*no* jitter.

Hope this helps, Duncan

