My next (hopefully final) iteration of the newton 2×00 serial board is on the way from the PCB manufacturer now. Moved some things around so two different chip types can be used (in case you find the one or the other) and added a switch to override Newton control of the serial transceiver.
This way you can turn it on, install the control software, and then flip the switch the other way to let the Newton control it. Should hopefully not affect battery life too much.
Need to order the switches and some more serial ports. Unfortunately I haven’t found a source for surface-mount circular serial ports so that means I get to have the fun of snipping the leads down to less than 0.6mm (PCB thickness) to avoid bending the case of the Newton.