RAK3172 Custom PCB Windows device malfunctioned error

[kefecik (K)]

Hello, I made a custom board using RAK 3172 based on the evaluation board using CH340E for the USB controller. When I plug it in for the first time It says that the device has malfunctioned.

I manually installed CH340 drivers and checked that the IC is getting 3.3V. The only thing that I am thinking that could be wrong is that the board is supposed to be powered by 12V so there is a switching regulator that takes 12V to 5V and then a LDO to take it down to 3.3V. I have the VBUS tied to 12V line via a diode since I am just using USB to program it.

I am not too familiar with USB protocol but could it be possible that CH340 is missing the device descriptor request because it takes too much time for 3.3V bus to come alive from VBUS since I am only powering it from USB? Any help is appreciated.

J2 is the micro USB port.

[IGtti (Iaran Gadotti)]

Hi @kefecik ,

Standard VBUS from USB is 5V.
Check your power supply lines, best with an osciloscope, to confirm both (+5V and +3V3) are stable.

For debug you can also power your board with an external supply, not using the VBUS.

[kefecik (K)]

D+ and D- were reversed on CH340E…