Re: PWM signal to step/direction signals

Howard,
I looked at the robot sites and did not see an RC PWM to step and
direction driver. There are many H Bridge and speed controller
circuits available. I will keep an eye out as I'm sure I spotted
a
few one time as cheap robot drivers.

The basic decode is not very difficult with a micro controller such
as the AVR or PIC, I use AVR's for doodling.

To do this I would use the MCU's capture interrupt. This gives
you
an interrupt for each PWM pulse and a latched timer count value for
the pulse width. The typical RC PWM seems to be centered around 1.5
ms with a 1ms or so range. At 8 Mhz you will get up to 8000 clock
counts over the range, not bad. Now you just add an absolute move to
position algorithm keeping internal count and slew limits.

What flops is there is no feedback from the stepper so you have to
center the device some way at turn on, say by seeking a limit or
center spring etc.

Otherwise you could use a DC gear motor, power amp and follow up pot
skeebed into an old servo's guts .

Brian
BSP