WiFi LoRa 32 V2 - using external power with USB?

#1

Hello!
I’ve searched around but would appreciate some help.

Will I ruin the board by trying this?
I would like to have the board normally powered by 5V (or maybe 3.3V if necessary), while being able to plug/unplug USB.

It doesn’t look like there are any diodes preventing current flow out of the 5V, or out of USB, like I’ve seen mentioned about trying this with other ESP32 variants. So, if they’re mismatched at all, where does it go?
I suppose the next step would be a circuit to switch my power supply on/off at the presence of USB. Am I missing an easier way?

#2

Make USB adapter/separator.
USB cable (or external board with connectors) with power wire cut.
Or you can cut the power wire/trace and put there standard rectifier diode in series.

#3

I have a related question, so I thought I’d post it here rather than start a new topic.

I have a WiFi LoRa 32 V2 board configured with a 5V supply through the 5V pin. The board is being simultaneously powered via a Li-Ion battery, connected through the on-board JST connector. The 5V supply is actually from a USB connection, just not through the on-board USB connector, and my supply also passes through a 6V/500mA fuse, as well as a 1N5819 diode. Looking at the board schematic, I thought that this would be seen [by the battery charging circuit] the same way as a USB [power] connection through the on-board USB connector (the only difference being that my circuit includes the diode).

My problem is this: When I supply power through the on-board USB connector, the battery charging LED illuminates while the battery is charging and then goes out (presumably when the battery is fully charged). When I supply power through the board’s 5V pin, the charging LED never really goes out.

When the battery is disconnected, the charging LED flashes, dimly, constantly. When the battery is reconnected, the charging LED continues to flash dimly but also flashes brightly, although not with quite the same regularity as the dim flashing.

If I unplug the external power connection and supply power through the on-board USB connector, the charging LED goes out. If I disconnect the on-board USB supply and go back to my external supply, the LED starts flashing again.

From the board schematic, I can see no difference between power being supplied through the on-board USB connector and the 5V pin—the 5V pin is connected into the circuit after the on-board fuse. My 5V supply uses exactly the same fuse, but does also include a diode.

So I removed the diode, and the ‘problem’ disappeared—no flashing LED. I thought I was doing the right thing by including the diode for protection, but its inclusion in this case obviously has some impact on the battery management system.

Can anyone offer any insight into what is going on here?