After much pulling my hair and pounding my head I finally
recovered my OS. I tried loading a bunch of different binaries
that supported OTA updates but none would work to update
the OS firmmware. I tried the Arduino IDE which loaded
binary images OK but none that were useful.
I finally loaded “OpenGarage” which worked properly and
presented an update screen at 192.168.4.1/update.
To load the OpenGarage firmware I executed:
esptool.py –port /dev/ttyUSB0 write_flash 0x0 ~/Downloads/og_1.1.0.bin
Clearly there is something in the OpenSprinkler firmware
that is not clearing some area of the flash and causing
a read fault and then a reset. Likely an invalid pointer.
Loading OpenGarage seems to clear that condition.
It is likely that OpenSprinkler is sensitive to something
in it’s configuration data. This is the data that is not
over-written when a new version is flashed during the update
process.