I have been thinking about the parallel port being too slow as a signal
generator. FPGA cards are really fast, but they are way too hard (for me
at least) to hack (,too closed). So I was wondering, what would be a
very small next step up from the parallel port? I played with an ATtiny
and got it to talk to the parallel port so that I could possibly send a
few or more command bytes per servo period. So I thought, what next? Now
I can send commands that would have the AVR create fast signals, of
which steps and PWM are pretty much what is needed. I have also been
playing with an L298 h-bridge and how it could be used for both steppers
and DC servos, but also micro-steppers and BLDC. So, it really boils
down to just PWM signals because step signals could be thought of as 0%
and 100% duty cycles, but who wants simple steps if you have PWM and
therefore micro-stepping for free?
So my system is starting to look like
EMC2
-> Parallel Port(s)
-> AVR Fast(ish) PWM generators
-> H-bridges
-> Stepper Motors (incl. micro-stepping, 2ea. PWM + and -)
-> DC Brushed Motors (PWM + and -)
-> BLDC Motors (3-phase PWM)
-> AVR Fast(-ish) Encoder Counters
-> AVR Analog inputs
-> Slow digital I/O handled by plain parallel ports
I went through the AVR ATmega (because mostly 5V) device list and found
15 PWM channels on the ATmega2560, which happens to be in the
Arduino2560 (around $60, cheaper than FPGA's). So all's I need are
shield like thingies to connect to; a parallel port, multiple individual
h-bridges of a range of power with feedback, encoders, and analog input.
Oh, and a bit of software to make it all work, without losing HALscope's
ability to see everything that's going on in every dark corner.
Am I on acid?
--
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/index.html
California, USA
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