Thursday, August 6, 2015

Work resumes on SAC Interface box


It is time to turn back to the interface box and its debugging. Thanks to Richard Stoffer, I have a Ztex board which can boot from flash, unlike my two boards. Before I turned on power, I decided to carefully check all the wiring to be sure there is no error in my cabling that might connect to unintended pins on the board.

I checked all the wires for the cable to the AB connector, which were fine. In addition to finishing CD later tonight, I have to carefully modify the method I used to hook up diagnostic LEDs, as the current method could get connected to undesirable pins quite easily. That is because the connector for the lights is only a subset of the unused pins on the board - if I don't count correctly when inserting them, I could affect something important.

If the new board, which does store bitstreams in flash and boots from them, continues to work properly for bootup after I run the SAC Interface box for a while, then I can feel confident that whatever caused the problems with my old boards is not going to hit the new board.

I owe Richard Stoffer a new working board, which will come from the vendor in Germany. Richard had a great idea about a test mechanism that would immediately show me that the board will work properly. There is a demo program from the vendor called 'lightshow' that I asked the maker to install in flash before shipping the board to me. As long as it flashes the LEDs on powerup, I know the newly received board is good. If it doesn't, and my problem is a result of quality variations, I will know to immediately return the board.

Once all the cabling was checked and my LED plugs were attached with the new safe method, I powered the board up and found it booted itself from the flash. Everything looked good, so I can do two tests tomorrow - first, that I can modify and load a new bitstream into flash so that it boots, then power up the 1130 and continue refining the logic in the interface box. 

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