Powering an ESP32 with TTL headers

[eisengrau]

Hello,

I would like to "hide" and ESP32-WROOM-32 inside a consumer router/access point (in my case it is the Xioami Redmi AC2100). I have read that it is possible to power the ESP from the routers's TTL ports inside. There I soldered 4 headers to the appropiate locations: VCC, TX, RX, GND. I have measured 3.3V from both VCC and RX. I read on the OpenWRT forums that if I connect the GND, RX and TX with the ESP8266's appropiate ports, it is possible to power it on as such, and also possible to access the ESPs serial console.

For me this does not work, I have tried with both an ESP8266 and the above mentioned ESP32, it does not simply power on... However it does if I connect the VCC and GND.

Question: as stated above I can power it with the VCC -> 3V and GND as such, Is it safe to also connect the TX -> RX, RX -> TX or I will get the "magic smoke"?

I would like to use the OpenWRT router to issue commands / monitor the console of the ESP32. Basically OpenWrt as a screen client.

Nevertheless, it is not a priority, at least the power is working. However it would be a nice feature to be able to flash the ESP with the aid of the router, if they are in a remote location.

[eduperez]

You do not connect VCC when connecting two powered devices, like a router and a TTL-to-USB converted plugged into your computer.

However, your ESP is not connected anywhere else, so you definitively need to power it from VCC.

[markbirss]

@eisengrau
Here is web ap terminal for such use, on a ESP-01 you also need to connect the CH_PD pin to 3.3V

espterm/espterm-firmware

Online Demo
https://espterm.github.io/term.html

[eisengrau]

@eduperez Indeed, I had to connect the VCC as well as RX->TX and TX->RX. The reason why it does not work for me (can't read output from OpenWRT screen command) is most probably specific to my device (Redmi AC2100). Nevertheless getting power does work.

@markbirss That looks like a cool project, similar to esp-link https://github.com/jeelabs/esp-link, but I kind of wanted to achieve the reverse of this: OpenWrt should act as a terminal client for the ESP32's debug messages.

[markbirss]

@eduperez ah ok, i see

you could look at python serial script for this ?

i actually have a serial console to e-paper (esp32)

connected to Raspberry Pi 3A and Zero W currently for hardware flow control serial