I'm having trouble getting Loopa to connect via USB to load the firmware. I get a red SMD PWR LED on the Waveshare board and that's it. My computer does not recognize that a device is connected, and I don't get the Green LED on the Loopa PCB.
I've tested all of the Waveshare header pins for any adjacent continuity, there is nothing touching (only the adjacent 3.3V pins near PA12 show continuity). I checked all of the 3.3V and the 5V pins and they all show the correct voltages. I've tested continuity between the CPU and the header pins, everything is connected to the CPU. I've tested continuity from PA11 and PA12 to R30 and R31 (near USB port), it's fine. I tried connecting my PC directly to the Waveshare board via the mini USB, it's the same result, unrecognized by the PC (but with the direct mini connection, I do also see the VBUS LED). I've tried multiple different USB cables, Mac and Windows PC.
Update: I read this entire thread, including Altitude's issues and the suggested checks / solutions. Nothing has helped so far. But I did see at one point Peter said "Two red small power LEDs should be lit on the Waveshare board when all is well." -- I am only seeing PWR LED, and not VBUS LED.
Update 2: Removed TVS diode, no change.
I've watched Peter's video a half dozen times and I can't see anything different between his board and mine. I got all my parts from Mouser, and I've done lots of SMD before so I think my work is really tidy. Just to be sure I fluxed and reflowed every connection on the board. It's still the same.
Pics here. Right click on the pic and select "View in new tab" to see the full size 4032x3024
https://imgur.com/a/e5ABpzb
Thanks for any help! I've been troubleshooting this for 3+ hours and can't find anything amiss. I'm happy to try JTAG stuff if someone can guide me through it. I have a STM32f0Discovery board and USBasp programmer and I generally know how to hookup the pins and such, but a bit unsure what software to use to erase and reflash this thing.