{"NAME":"Shelly 3EM","GPIO":[1,1,288,1,32,8065,0,0,640,8064,608,224,8096,0],"FLAG":0,"BASE":18}

** Before installing Tasmota make sure to retrieve a copy of the calibration data from your device! **

Download file calib.dat from http://<your_shelly3em>/calib.dat

Search your Shelly 3EM firmware dump for calib.dat

• Edit the file to become a single line. Notice the removal of unneeded data to make the string as short as possible:

    {"rms":{"current_a":3166385,"current_b":3125691,"current_c":3131983,"current_s":1756557,"voltage_a":-767262,"voltage_b":-763439,"voltage_c":-749854},"angles":{"angle0":180,"angle1":176,"angle2":176},"powers":{"totactive": {"a":-1345820,"b":-1347328,"c":-1351979}},"freq":0}
  

• Install Tasmota and use the above template.
• In addition to possible rules add a rule containing the calib.dat string from above like:

  rule3 on file#calib.dat do {"rms":{"current_a":3166385,"current_b":3125691,"current_c":3131983,"current_s":1756557,"voltage_a":-767262,"voltage_b":-763439,"voltage_c":-749854},"angles":{"angle0":180,"angle1":176,"angle2":176},"powers":{"totactive": {"a":-1345820,"b":-1347328,"c":-1351979}},"freq":0} endon
  

• Powercycle the Shelly 3EM with Tasmota and obeserve that the results seem calibrated as Tasmota now uses the information from calib.dat

Pinout

GitHub Discussion