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Originally Posted by seanwitte
Another option is to use a counter with synchronous serial output. You can tie the data and clock lines from all of the accumulators to two RC pins, then have one dedicated RC pin for the Chip Select on each accumulator. The code to shift in the bits would be easy to implement but I think Kevin Watson has already written it.
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My original design was to use an 8 bit counter and shift register for each axis but I decided that the increased complexity in circuit and software was not worth saving a few pins. (Save the pins for what, anyway?) I did look for a counter with shift register combined, and the only one I (think I) found is
http://www.digikey.com/scripts/DkSea...sus.dll?Filter The reason I say think is because the datasheet is very unclear (no truth tables or anything). Additonally, it is only 4 bit, so I would either have to poll it outside the main loop using a timer interrupt or cascade it. Again, the complexity was prohibitive.
I will soon post pictures of my counters and sensors (which I think should void any of this discussion because of their simplicty.) Everything has been tested except for the robustness of the sensors on a running robot.