MicroPython Forum (Archive)

I made myself PCB based on pyboard. when I powered the board by USB, it can work well, but if I powered it by external power, it will not work, and the LEDR2 will flash for a moment and then stop. The serial terminal can execute the program well. Why?

Hello @wwsehldons, I think we all need more details to understand your problem.
a) how do you supply PyBoard, at which pins and which suplly voltage.
b) is there an additional circuitry on you PCB.
c) Do you have statements in boot.py and main.py that start your code at power-up?
d) What do you mean with "The serial terminal can execute the program well. "
The facts that LEDR2 flashes shortly is a good sign. That's how it should be. That looks if PyBiard starts
Generally, the board should be supplied through the Vin and GND conection(s) with at least 5V DC. A capacitor of about 100µF close to the board is always helpful. If you connect both USB and an external power supply, the may be interdependencies, and you may need a diode in ther external supply path to block that, like the one on PyBoard.
Best Regards

a) how do you supply PyBoard, at which pins and which suplly voltage.
b) is there an additional circuitry on you PCB.

a) the power of board supplied by LM317, which will change 24V to 5V, then MCP1802 change 5V to 3.3V.
do you give me a email? I can send the schematic to you , thank you