Karl Schmidt wrote: > On 07/20/2012 11:47 AM, Jon Elson wrote: > >> Charles Steinkuehler wrote: >> >>> My current plan is to bit-bang GPIO pins based on code from the parallel >>> port driver, but >>> adding a bit of electronics would probably make things much easier. >>> > > What would the "bit of electronics" look like? Most of the single chip uP > have hardware pulse > generators built in that could easily generate the stepper pulses without > jitter. No, the problem is you need to COUNT your pulses. There is no way for the CPU to know exactly when a pulse gets issued without counting them, due to slight variations in timing. Now, on the ARM chips with everything in one, and all clocked off the same crystal, it MAY be possible to keep some kind of sync on the whole system, but it might take some revision of the way LinuxCNC works. If the rates are not perfectly synched between the pulse generator and the software, small errors could accumulate to cause large position errors.
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