What you are seeing here is the Raspberry Pi Zero W that was part of Dwalin v1 repurposed to fix my damage to Ori. 

The right angle header at the top of the Ori board is new - bringing out 3.3v, gnd, TX, RX. Not actually using 3.3v here (skipped pin). Gnd, TX and RX are connected to Pi GPIO header to appear under Linux on Dwalin as /dev/ttyS0

Built a new copy of the sketch to confirm I'm able to flash this way, copied from Windows machine to Dwalin via SSH over WiFi. From Dwalin using esptool.py to write to the flash on the ESP8266. Showing on the OLED is a visual simplification to confirm successfully flashing. BME280 not presently plugged in so getting error values instead of real readings.

 sudo esptool/esptool.py --chip esp8266 --port /dev/ttyS0 write_flash 0x00000 tempnode-v0.1.ino.bin

From here I should be able to get OTA firmware updates to work.