This repo contains several subprojects for this hardware module :
There appear to be several versions of this module. Differences appear to be both functional and technical :
This is also visible on the board itself : the 20 pin connector on the PCB has those four GPIOs exported just above the GND pins - see pin map in the middle of the PCB picture :
Please note that there's an unsoldered header for programming the board at the right of the PCB (see the DEBUG label), exporting GND, EN, IO0, RX, TX, 3V3, 5V. It is perfectly possible to program this board from the 20-pin socket that is already on the board, as all those signals are present on it too.
Obviously the connectivity required is as described in the esp documentation :
ESP pin | Serial pin |
GND | GND |
5V | 5V |
RX | TX |
TX | RX |
EN | RTS |
GPIO0 | DTR |
so a 6 wire flat cable will do.
Note that the connector has 2mm pitch, not the standard 2.54mm. A double-row curved connector such as this one can be used :
If you would want to solder wires to it, it's recommended to pry out the pins, solder them separately, and put them back in.
Some links :