TTL to RS-232 power issue on Electron

I’m having an issue with a MAX3232 not working with the Electron on battery. I don’t know for sure that it’s a power issue because a MAX3232 is supposed to work on 3.3-5V. When the Electron is plugged in via USB and battery is connected, it works great and I can see the RS-232 data coming into Serial1. I really need this to work on battery only for field operations. Thanks in advance.

Looking at the Electron schematic, I believe the Vin does not source power for your project when solely on battery power. Your Max323 board is not receiving any power when only on battery. You should probably power your Max323 board from the 3.3V pin instead.

Stating another way: When you have the Electron plugged into USB, essentially the Max323 board is receiving it’s power only from the USB power rail, not from the Electron. When you disconnect the USB, power does not flow from the battery back onto the Vin pin.


Oh man your absolutely right, and I remember reading that a while back the vin switches when powered over USB. Thanks for the reminder.

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