Flashing documentation for S31 does not result in valid connection

[Ryanf55]

Hello!

I'm trying to flash a Tasmota S31 according to the documentation. I tried a few years ago and it not work. I tried again with the latest tools (Tasmota Web Flasher and esptool.py).

Neither connection method works to flash. I have a sparkfun 3.3V FTDI that works great for tons of other projects. TX and RX are crossed, and I tried flipping them. The power is 3.3V and the S31 blinks on boot.

Attached is a logic analyzer capture of the connection handshake.

• Channel 5 is from the FTDI RX connected to the S31 RX
• Channel 7 is from the S31 TX connected to the FTDI RX

Pressing the GPIO before boot has no effect on the handshake.

S31.zip

I cannot determine the baud of channel 7 (the data from the S31). It doesn't match any of the common ones.

ryan@B650-970:~/Dev$ esptool.py -p /dev/ttyUSB0 read_mac
esptool.py v4.7.0
Serial port /dev/ttyUSB0
Connecting......................................

A fatal error occurred: Failed to connect to Espressif device: Invalid head of packet (0x28): Possible serial noise or corruption.
For troubleshooting steps visit: https://docs.espressif.com/projects/esptool/en/latest/troubleshooting.html

The message about serial noise or corruption makes sense - it's trying to read data at the wrong baud likely.

Are there any troubleshooting steps to try, and any specific time the button needs to be released to get it to flash?