I forgot to post the pinout for the 100-way connector...here it is
Arn.
Many thanks for the pinout!
I built the board from the Hackaday site and used the pin numbers on that board.
However, the scope wouldn't boot with the card inserted and I just couldn't understand what I had done wrong.
But then found your pinout here and realized the pin numbering used on the Hackaday board is different/wrong.
After resoldering the wires using your drawing, everything worked like a charm.
For everyone's reference, the "tabs" I've used on the Hackaday board are:
U1 - pin 1 -----> board tab #63
U1 - pin 11 ---> board tab #64
U1 - pin 12 ---> board tab #67
U1 - pin 13 ---> board tab #68
U1 - pin 14 ---> board tab #71
U1 - pin 15 ---> board tab #75
U1 - pin 16 ---> board tab #76
U1 - pin 17 ---> board tab #79
U1 - pin 18 ---> board tab #80
U1 - pin 19 ---> board tab #59