Hi,
First I want to thank everyone for this excellent project. Especially @hek.
I succeeded in making work an electric heater thermostat. But changes were necessary on lines 97 and 98 L_Arduino.lua. (Development Branch)

Original code:
HEATER = {21, "urn:upnp-org:serviceId:HVAC_UserOperatingMode1", "ModeStatus", "" },
HEATER_SW = {22, "urn:upnp-org:serviceId:SwitchPower1", "Status", "" },

Modified code:
HEATER = {21, "urn:upnp-org:serviceId:TemperatureSetpoint1_Heat", "CurrentSetpoint", "" },
HEATER_SW = {22, "urn:upnp-org:serviceId:HVAC_UserOperatingMode1", "ModeStatus", "" },

Can someone verify and upload these changes?
I can confirm it works fine with my Vera Lite(UI6).
Thank you.