Hi All,

I think that PIC16F877 may be easily used to build a digital oscilloscope
with "random repetitive sampling" (well, with ca. 200 kps it can be usefull
only for hobbyists...). However I've some doubts.

  I can generate the waveform driving the external S/H, using the PWM module.
The position of TRIG pulse may be found with CCP module. However AFAIK
there is no way to have CCP & PWM working with the same timer. Am I wrong?
If not - I should use two timers running synchronously, but I can not
start them synchronously. Probably it is possible to compensate the delay,
writing different values to both counters. (I'll try to ilustrate it
with the pseudocode below).

 timer1 = 0
 timer2 = comp_val
 GIE=0
 enable_timer1
 enable_timer2

Does anybody can share his experience with such problems? Is it supposed
to work?
Another solution could be driving both timers from external gated clock.

Additionally I'd like to position the TRIG pulse with higher precision using
the time/voltage converter, or time expander circuit. However for this
purpose I'd need to output the waveform driving both timers. At the moment I
don't see such possibility... so maybe the external gated clock is the right
solution, but it destroys the simplicity of the design...

I'd appreciate any suggestions. I think that such Open Source/Open Hardware
design would be usefull for all of us ;-).

--
                                TIA & Greetings
                              Wojciech M. Zabolotny
        http://www.ise.pw.edu.pl/~wzab  <--> wzab@ise.pw.edu.pl

http://www.debian.org  Use Linux - save your data and time

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