Hi folks,

I'm a new person to pics. By background I'm a software guy with a smattering
of hardware many years ago. Lately I've been tasked to look for alternatives
to a data capture board. We think we can make something cheaper and much
better than what we have.

The gadget I have to interface with has the following traits:
	-A pulse-width-modulated signal coming out at 80MHz
	-Three analog lines
	-An encoder on a spinning wheel.

The pulse signals come along at up to about 5KHz. When a pulse happens, I
need to 
	-Grab the width, measured with an 80MHz clock
	-Grab the three analog values
	-Grab the encoder value

This data must be buffered and streamed out to a host.

I've been reading data sheets and it seems a dsPIC33FJ128MC710 might be a
decent choice: Quadrature encoder, decent amount of RAM to buffer stored
data, and enough A/D to easily get the analog data. 

However, it's only running at 40 MIPS, and my signal is 80MHz. As I'm
reading the data sheets, I see reference to running the Type A Timer in
asynchronous mode from an external source. I haven't found anything that
tells me if this external source can be 2x the CPU clock speed.

So.... Can someone tell if this is a valid approach (or tell me which
documentation I should be reading to determine that)? If this won't work I
assume I could add an external timer- would this be a reasonable approach
for this soft of signal?

My hope is to demonstrate the validity of this approach using the
downloadable Microchip tools. If that works I can get an electronics type
with appropriate hardware background to support me in this project.

It's been quite a while since I looked at PICs for any projects. I'm
impressed with what's out there and the clock speeds- my last glance into
this area only low-speed chips were available.

Thanks,

Les Elkins


Les Elkins
Spatial Integrated Systems, Inc.
Rockville, MD
www.sisinc.org 
les.elkins@sisinc.org
301 610 7965 x107



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