I have finished soldering up a prototype for a second CPU-FPGA-Pico project: the HD6309-FPGA-PicoW. The other one I have done is the W65C02S-FPGA-Pico which I have yet to blog about and make more progress on the FPGA side of things. I've made many fewer mistakes on this one than that one. But let me tell you, building an electronic circuit prototype is quite tedious and error prone. Especially if your almost 60 y/o - and your eyes are not (even close) to what they used to be!
The only two mistakes I've made on this one (that I have caught so far) are I had the direction pin (1) on the 3 74LVC245s / U2, U3, U4 chips set to HIGH which sets the direction A to B -- but they need to be set to LOW which sets the direction B to A. And the other mistake was soldering the lane next to the ground pin (11) on the TXB0108 / U5 chip instead of on the actual ground pin lane. Which means the ground was not connected at all.
So after fixing those two mistakes I proceeded to update my hand drawn schematics with the pin-to-pin information.
I still need to label the pins of the jumpers w/ the DE2 FPGA board J0/J1 internal pin labels that must be mapped. And before I populate the chips and start testing, I need to do a last thorough check w/ a continuity tester and check that every chip's pin-to-pin connections are correct and that there are no shorts. Then finally fire it up and see if it works the first time -- or if I have other mistakes to troubleshoot!
Finally I need a good schematic done in KiCAD.