Saturday, January 2, 2016

Chasing odd issue with virtual 2310 adapter in SAC Interface Box


Continued use of the typewriter while testing the virtual 2310 is loosening up more crud (residual lubricants) and improving type quality slightly. Won't fix everything wrong with the 1053 but it helps.


The flaw I was debugging was an apparent failure to reset the last XIO command code as it was read by the Python program, so that when it next requested the last XIO, it got XIO IR again instead of code 000. As much as I stared at the logic to handle this in the FPGA, I couldn't see how it would fail to do the right thing. The answer was some careful instrumentation to flag whether my process to handle this is stalling somehow.

I also tossed in some special instrumentation in Python to warn me if I do receive a second IR command code without having first received some other value, either 000 or a Sense DSW which is how the op complete interrupt condition is reset.

I do see signs of double delivery of the XIO IR command but the FPGA side looks good. I will look over the Python code to see if there is any way I can get this condition due to an overlooked path in the code. I suppose I may have a race hazard occurring but this happens far too often to be something like that. It is puzzling.

I decided to make several changes to the involved logic in both sides, just in case there was a defect I couldn't see. When I retest tomorrow I will see if things improve.

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