Friday, August 7, 2015

Work resumes on SAC Interface box

SAC INTERFACE FOR ADDING PERIPHERALS TO THE 1130

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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