====== Tasmota on the JR-TM05S Water Supply Timer ======
I recently bought a wifi enabled water supply timer [[https://www.banggood.com/Wifi-Controller-Garden-Water-Timers-Intelligent-Phone-Remote-Control-Irrigation-Timer-p-1628955.html?rmmds=myorder&ID=514833&cur_warehouse=CN|JR-TM05S on Banggood]]. i hoped that this device would be ESP8266 based so that icould run [[https://tasmota.github.io|tasmota]] on it and integrate it into my smarthome via MQTT.. 

I was lucky, it is based on ESP8285 which is 100% compatible with ESP8266 but has more memory! the necessary 4 pins are even routed to some contacts where you just need to plug-in a pin-header and solder it down, to comfortably program the device! the only slightly annoying part is, that the unit is covered in silicone to waterproof it. i think they have done a good job at that.. but we have to peel it off to get to the pin headers. 

{{ ::esp:jr-tm05s.png?nolink&600 |}}

luckily the only button on the board is connected to GPIO0 which makes it also the flash-mode switch :)

so to prepare the unit, remove the big front-cover sticker and unscre the four screws in the corner, this will split open the case

{{ ::esp:jr-tm05s_1.png?direct&400 |}}

now remove the board by carefully cutting away some of the white silicone from the back and also remove the silicone where the pi header next to the button is

{{ ::esp:jr-tm05s_2.png?direct&400 |}}

Pin header next to the button is used to re-program. the pinout is as follows (from pin closest to the outside edge of the board towards the inside of the board): 
1.) GND
2.) TX
3.) RX
4.) 3.3V

connect those 4 to a programmer, no additional power supply is needed 

press the button on the device while you plug-in the usb programmer, this will start the programming mode

install ''esptool.py''
  pip3 install esptool 
make a {{ ::esp:jr-tm05s.zip |backup of original firmware}} 
  esptool.py -p /dev/ttyUSB0 read_flash 0x00000 0x100000 JR-TM05S.bin
re-start programming mode and erase the flash 
  esptool.py -p /dev/ttyUSB0 erase_flash
re-start the programming mode again and flash the tasmota binary from the latest release
  esptool.py -p /dev/ttyUSB0 write_flash -fs 1MB -fm dout 0x0 ../Downloads/tasmota.bin 

unplug and power back on using the power cable that came with the unit, take your cellphone and connect to the tasmotaxyz wifi to configure tasmota

open a web browser and enter http://192.168.4.1

and there you go.. even the gpio pre-config seems to work right away, the button still opens and closes the valve and the toggle button on the web interface does the same :) 

for the re-assebly i put the board back into the case and then sealed it again with some electronics-silicone. I sealed it so that the 4 pins would still stick out the back. After the silicon had dried, i bent the 4 pins 90° as otherwise the valve would not fit into the housing anymore. but by bending the pins that was taken care of, and they still remain accesible should i ever need them again