After the construction of the printer there was a desire to connect it with the outside world. Options with a cable did not suit me. I did not want to become attached to the computer’s surroundings. I also did not want to run around the printer to the computer and back  with SD card. Therefore, from the wireless options that everyone has heard, remained bluetooth and Wi-fi. Wi-Fi bribed the ability to remotely download the job, and when the "ESP3D" firmware was be found at github with a camera connection, the choice became obvious.

The idea to make a module, the size of ESP8266, came to me a long time ago.
In ESP8266, I must say, non-standard pads. In the solder breboard 2.54 patch, so ESP pads could not be simply soldered. At the same time, I didn’t want to add more wires to the already crowded case of the printer. Therefore, the options with aliexpress solutions did not suit me.

I decided to do everything from scratch. I calculated the dc-dc power supply, picked up the chip, inductance taking into account the size restrictions. AMS1117 with its low efficiency did not want to use, so as not to overload the USB when the printer is in hibernation. The dc-dc power supply  placed easily between the terminals of the ESP module. I also put resistors on UART circuits for parallel control through a port terminal / monitor and a web interface.

Module connection is standard, via AUX-1.

In parallel with the design of the board, I was working on a modification of the firmware. Russification added, authorization enabled.

Changed the code to increase the attempts to resume the file upload when the connection is broken, if the printer is away from the access point.

Now the modules is on sale at the ebay.

https://www.ebay.com/itm/173704097750