Troubleshooting the gzload TDO mismatching problem

Now that I have tidied up the messy wiring, and stacked the I2C and SPI hardware.  The next step is troubleshooting the Guzunty Pi.

I have no idea of the cause of the problem of "TDO mismatch".  I don't even know what is the meaning "TDO mistmatch".  Does it mean gz_load tries to loop back from TDI what is output to TDO, and since the TDI is broken (actually I could not successfully read it, though I could write to it).

I tried the test with the shortest connection I could make, using the 26 pin ribbon cable to directly connect GuzuntyPi to RPi through the P1 header, but there is still the problem of "TDO mismatch" after loading (or triing to load) the gz_test.xsvf file for about 2min45sec.

I think I should first google the meaning of "TDO mismatch" before using a scope to check the waveform of TCK, TDO, TDI, TMS etc.

If the scope displays waveforms seemingly OK, then perhaps the RPi's TDI pin is indeed broken.  So I can use another RPi to do the test.  If even the second RPi has the same problem of TDO mismatching, then it is very likely that the Guzunty Pi is deffective.  Perhaps I have made some bad soldering joints somewhere, though I have used a multimeter to make sure there is no careless shorts during soldering.

So I might need to assembly another Guzunty Pi to start all over again.

Since the same problem occurs using the shortest connection, the 26 pin ribbon cable to RPi's P1, I think the connection I2C, SPI, and JTAG should be OK, there is no point using the flat ribbon cable again.  I can instead use the JTAG cable with external 3V3 supply (not the RPi's 3V3).

So I  executed the same load statement again.

pi@raspberrypi ~/Guzunty/Pi/src/gz_test $ sudo gz_load gz_test.xsvf

When the gz_load started, I switched to another job, because I was impatient to wait 2+ minutes to see the same TDO mismatch error message.

But after a while, when I switched back to the  puTTY window, I was very, every surprised to see that there is no error message, but only the success message below.

pi@raspberrypi ~/Guzunty/Pi/src/gz_test $ sudo gz_load gz_test.xsvf
Guzunty loader v5.01, portions courtesy Xilinx, Inc.
XSVF file = gz_test.xsvf
SUCCESS - Completed XSVF execution.
Execution Time = 9.740 seconds

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