Quote Originally Posted by dhouston View Post
I will stay with 3V3 and make it necessary for the end user to verify the supply voltage and solder in a jumper as needed. I will look at adding the footprints for a regulator and necessary caps, etc. but these will be SMT (there's limited free space) so neophytes will be better off with a 3V3 main board (Amicus18 or compatibles).
The last post was written shortly after returning from several medical appointments. After, I had a bit of rest and then looked at what is involved, i think it will be a simple matter to add a 3V3 LDO (low dropout regulator) and and just one jumper arrangement so the user can solder in a wire based on wehether the system voltage is 3V3 or 5V.

For Connect One, none of the three modules have 5V tolerant inputs and 3V3 may not be seen as logical high by the MCU running on system power of 5V so I will need to add level conversion to the RX, TX & RESET lines. I'll use transistors for this and the same circuit will work at 3.3V as well, meaning no additional jumpers are required.

For the Tibbo shield, the EM500 inputs are 5V tolerant and its output circuitry is such that merely adding a pull-up to 5V works on TX. This also will work equally well whether the system voltage is 5V or 3V3 so, again, no additional jumpers.

I think this is about as straightforward as is possible. I want to use just solder pads rather than a jumper/header so the user will have to think a bit and focus in order to understand the why and wherefore before installing the semi-permanent wire jumper and, hopefully, reduce the possibility of users quickly inserting a jumper on a header in error and blowing a ConnectOne module worth $30-60. But, I'll leave the final decision to Xino and anyone else who wishes to build & distribute these.