esp12_trivial_programmer

Trivial programming addons for an ESP-12.

This is designed as a low-cost method to add basic programming features to an ESP8266 embedded in a device.

Hardware Design

This is designed to add FTDI serial cable programming to most bare-bones ESP8266 boards, specifically the ESP-12e / ESP-12f boards from AI Thinker.

The hardware design is based upon the final circuit posted here: https://hallard.me/esp8266-autoreset/ with minimal addons to turn it into a complete solution.

Essentially it consists of the following elements:

1. GPIO15 and GPIO2 are pulled to ground and +3.3v to (partially) set the device into the correct mode
2. Charles Hallard's circuit is used to auto-reset the board and put it into program mode by controlling EN (CH_PD) and GPIO0 with the DTR signal
3. A 3.3v FTDI USB to Serial converter is used as the actual interface with the programming computer

A Note on cheap FTDI serial cables / programmers

Many "3.3v compatible" FTDI boards / cables actually provide a 5v power source, not 3.3v.

As such, it's strongly recommended that you power the board from an external power source instead of from the FTDI cable.

Attached software

This repository also contains a trivial WiFi access point and webserver as a "hello world" project to test this.

It contains configuration to be build and programmed using PlatformIO however main.cpp should work in the Arduino IDE with ESP8266 addons without major modifications.

Compatibility

This works with esptool without any special commandline arguments or tweaks however esptool uses the RTS line to hard-reset the ESP8266 after it's finished which doesn't work because standard "FTDI" cables don't have that pin broken out.

Using the device with this circuit attached

1. Build and upload the software using PlatformIO or your IDE of choice
2. Make sure that either the serial programmer is disconnected or the DTR pin is low
3. Reset the ESP8266 device by either removing and restoring power or pulsing the reset pin
4. The uploaded code should run

Licensing and Copyright

The auto-reset circuit is copyright Charles Hallard as stated on his blog. He does not specify a license.

The remaining hardware design and instructions are copyright Julian Calaby 2019-2020 and licensed under the Creative Commons Attribution-ShareAlike 4.0 International License.

The PlatformIO files and related software are trivial and are released to the public domain: To the extent possible under law, I have waived all copyright and related or neighboring rights to the software in this repository.