In my previous post, I talked about how I assembled my first PCB that came in and that the Attiny85 programmer/breakout design works great. Unfortunately, the 74HC595 shift register breakout does not. I haven’t found the source of the problem yet but I wanted to leave a few notes on what I’ve looked at so far.
I went through the schematic again in Eagle and it looks fine. All of the connections appear to be made properly. I do not think the circuit design is the problem.
Some ideas I’ve had on what could be wrong are burnt shift registers during soldering, programming errors, or something wrong with the traces (shorted or opened). I do not believe the shift registers are burned out, nor do I believe there is an issue with programming. If I disconnect Vcc and Ground and poke both with the Ground wire, the pattern will run once and then stop. I’ve also noticed that when I touch an area on the back of the board, all of the LEDs will latch on. That makes me believe there’s an issue with a trace somewhere.
I plan on soldering another shift register board later today, reusing the parts I used on this board. I’ll try with just one shift register first and then add a second one if it works. I’ll post the results when that’s done!