As a reminder on how to do the OpenDTU-OnBattery code upgrade with "tiny" ESP32-WROOM-32U let me remind myself to do it like this:
https://github.com/hoylabs/OpenDTU-OnBattery
PS C:\Users\user\AppData\Local\Arduino15\packages\esp32\tools\esptool_py> C:\Users\user\AppData\Local\Arduino15\packages\esp32\tools\esptool_py\4.9.dev3\esptool.exe --chip auto --port COM4 --baud 115200 --before default_reset --after hard_reset write_flash -z --flash_mode dio --flash_freq 40m --flash_size 4MB 0x0 'C:\Users\user\Documents\2025\opendtu backup 06\opendtu-onbattery-2025.06.11-generic_esp32_4mb_no_ota.factory.bin'
esptool.py v4.8.1
Serial port COM4
Connecting.....
Detecting chip type... Unsupported detection protocol, switching and trying again...
Connecting....
Detecting chip type... ESP32
Chip is ESP32-D0WD-V3 (revision v3.0)
Features: WiFi, BT, Dual Core, 240MHz, VRef calibration in efuse, Coding Scheme None
Crystal is 40MHz
MAC: a8:42:e3:4b:f3:1c
Uploading stub...
Running stub...
Stub running...
Configuring flash size...
Flash will be erased from 0x00000000 to 0x0027efff...
Compressed 2616400 bytes to 1567250...
Wrote 2616400 bytes (1567250 compressed) at 0x00000000 in 137.9 seconds (effective 151.8 kbit/s)...
Hash of data verified.
Leaving...
Hard resetting via RTS pin...
PS C:\Users\user\AppData\Local\Arduino15\packages\esp32\tools\esptool_py>
