I have been working on some projects that require WiFi connectivity and for that I am using ESP32 chips. I started off by purchasing an off-the-shelf development board from an Aliexpress store, the TTGO board with an LCD screen and a debug controller connected to the USB port.
I used the Arduino IDE to test a few examples, then designed a custom board. Most esp32 development boards use UART connection for debug. This works OK but is slower than the JTAG protocol. There is a JTAG interface on esp32 chips which can be used for faster programming and debug. So I wired this up on my custom board based on the esp-prog board design and ordered an esp-prog unit from an Aliexpress store as well.
When I got my custom boards, I was able to debug using the esp-prog but it had a few hiccups. First the 1.27mm cable connectors on the esp-prog board are very poor quality and don’t fit well even with the supplied ribbon cable. So I removed them and soldered some good quality connector I had from digikey.com. Next, the JTAG uses 4 protocol pins and power and ground, a total of 6 pins. But the board uses a 10 pin connector so 4 out of those 10 are connected to ground, one is left floating, one is connected to power and the other 4 to JTAG pins. The UART connection is on a different connector requiring another 4 pin ribbon cable. I think this multitude of connectors on the esp-prog are great to serve all kinds of use cases, but I want a smaller custom jtag unit with a single 10 pin cable.
So I designed the esp-jtag, as I call it. It is a direct copy of the esp-prog, from the schematic with a few customizations. It is done in KiCad so that more people can be able to customize it for their own use, and possibly share back using pull requests as the project files are available on a github repo. The HTML BOM is in there, LCSC part numbers filled but no Digikey part numbers yet.
The debug connector is connected as:
So if you plan to use this debug probe to debug your esp32 custom board, you need to add a 10-pin 1.27mm connector matching this pinout. The only downside with this board cost-wise, the FT2232H chip costs more than $6 on LCSC.com and on Digikey.com.