@btaillandier The tarball is at https://github.com/robert-hh/Shared-Stuff.git. It's name is: LoPy4-1.20.2.rc11_invert.tar.gz You call the inversion with e.g. from machine import UART uart=UART(1, 1200, invert=UART.INV_RX) there is also UART.INV_TX, UART.INV_CTS and UART.INV_RTS, to be or'ed if required.

@RichardBH The Pycom development modules are supplied by the Vin Pin. The 3.3V Pin of the modules is the output of the internal regulator. AFAIK, this is an LM3281 device with an absolute maximum input voltage of 6V. Between the Battery plug and the Vin pin is the charge chip and some switching circuitry. They should not cause a major voltage drop. So: If you are absolutely sure that the battery voltage is never above 6V, you could connect it. But typically, the voltage of a fully charged/fresh battery is above its nominal voltage. Like: 6V Lead battery, full charged 7.2V, 1.5 V Alkaline: fresh ~1.6V, ... So you will need some means to limit or lower the input voltage.