Modify Cactus Micro:
1) convert default serial port to hardware serial (cut/solder)
2) connect Digital pin 5 to ESP8266’s GPIO0 (so arduino sketch at the bottom of this page can pull ESP8266’s GPIO0 to GND – this puts the ESP8266 in program mode to receive firmware update)

Load Arduino programmer sketch – sends computer COM serial straight to ESP8266 hardware serial

Flash firmware. Do NOT use I kept getting this error:

Instead, use the GUI for Node MCU

Click Config tab
Uncheck the internal Node MCU firmware (selected by default)
Browse for espduino 0x00000 bin
Browse for espduino 0x40000 bin

Enjoy espduino!

Important: when using the serial passthrough Arduino sketch, don’t change the default baud rate of espduino – I tried to be smart and set it at 9600 — didn’t work.

Below is the “passthrough” sketch I used to stream the firmware from USB through Arduino serial through ESP8266 hardware serial. It’s ugly and there are many other similar sketches, but I’m saving the one I used here, just in case.

P.S. You’ll probably want this Arduino library next:

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