Hi! I have designed a CH340-based Arduino compatible standalone board for my project, I designed two of them, one is powered by 5V directly from USB port, the other is powered by 3.3V from AP2112-3.3V regulator from USB port. The 3.3V powered CH340 works just fine, however the CH340 powered by 5V does not seem to work at all, I hooked it up to Raspberry Pi 3, my dual-boot Ubuntu 18.04, or Windows 10, none recognize the USB device.
What I have tested:
- Different ICs (tested 6 of them, none of them work when supplied by 5V, tried 3 CH340 on my 3v3 board, all work without a hitch)
- Tested the voltages, CH340 receives 5V on VCC and the internal regulator does output 3.3V on the V3 pin
- Checked the connection, USB differential pair, VCC, and GND, all seems to be connected without a problem
- Added bypass capacitor (I forgot to add 5V-GND bypass capacitor in the design, ended up soldering a ceramic 100nF between pin 16 and 1)
- CH340 driver, I have the correct driver, my 3v3 board is detected and works just fine on my Raspberry Pi, dual-boot Ubuntu 18.04 or Windows 10
What I have not tested:
- Supplying 3V3 externally to the V3 pin
Does anyone have experience with this chip and can share something I'm probably missing?
Thanks in advance!