Thanks all for the help. I used a Teensy 3.0 bord from the drawer and it
works great. I am reading a 2khz signal from the parport and converting
it to a 40khz signal. Duty cycle is from 0% to 99%.
I have not checked the AVR but most micro controllers have timers with
hardware support or duty cycle measurement. XMC4xxx or STM334 devopment
boards have high resolution timers equal to a frequency about a few
gigahertz.
On Tue, 25 Aug 2015 21:09:08 +1000
Erik Christiansen <[email protected]> wrote:
On 25.08.15 10:30, Marius Liebenberg wrote:
> I have a couple of Teensy 3.0 boards in the drawer here and they
are
> pretty fast enough I think.
> I am a bit allergic to the USB interface when one uses high current
> switching devices on the machine. The USB interface is not that
> reliable.
It would not be hard to use one Arduino timer in capture mode to
measure
M/S ratio of a low frequency PWM input (from LinuxCNC), then
replicate
the ratio on a higher frequency output on another timer. If the ratio
of
input and output frequencies were a binary multiple, then dividing
the
input mark to fit the higher frequency output would only be a right
shift of the requisite number of bits. (The AVR does not have
hardware
multiply, but software multiply would be OK, if preferred, if the PWM
ratio doesn't change at a crazy high rate.)
An interrupt on "capture complete" would be infinitely more efficient
than any polling hack, for input PWM measurement. The output timer
would
just run with auto-reload, responding to a new M/S ratio in the next
cycle
after it is written to the hardware register.
A 20 MHz part could run 10 bits of count at 20 kHz, giving 0.1%
resolution. Go for something like 9 bits, 40 kHz, and 0.2%, maybe?
But mebbe you have all that figured, already.
Erik
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