dannable:
Shouldn't you have 5v into HV and 2.8v into LV?
I was trying to figure out why you had a wire going from the 4.9v supply to your home made level shifter... I think my understanding of how a level shifter works is wrong. I thought that you put in high voltage into the HV pin along with the rx and tx wires again on the high side and the level shifter downs the voltage to 2.8 as well as corrects the signal, i didn’t think you had to also supply power into the LV pin.