Back dated August 10th 2017
So there are some bugs with the first assembled PCB. I'm glad now for the decision to make the PCB design as close to the breadboarded prototype as possible, because we have a reference to work with.
It turns out I left a connection off of the ESP pins: CH_PD was left disconnected and needs to be pulled to Vcc for the ESP to work the way we want it. A small wire soldered in fixes that:
But now that we can see the microcontroller serial output from the ESP, the ATmega boot loop is still there :-/
Again it was pretty fast to find the issue: The PCB has a new ESP8266 on it, with stock esp-link firmware, the GPIO pin that controls our ATmega's reset line wasn't configured, and so it was creating spurious resets. With that config change, the resets stopped and we could finally start testing wireless transmit!