Protocol decoder:easymatic

From sigrok
Jump to navigation Jump to search
Description Asynchronous, serial bus, differential
Status planned
License GPLv2+
Source code decoders/easymatic
Input uart
Output easymatic

The easymatic protocol decoder can decode the thermostat Easymatic bus protocol used by De Dietrich.


Differential link

The easymatic is linked to the boiler with two wires. This link can feed power to the easymatic. Easymatic can have two R4 accu in order to save data if the power is cut.

Boiler power is a 24V modulated with communication power.

Communication is always working.

[To be confirmed]

The hardware is similar to OpenTherm Specifications:

  • differential link
  • about 24V
  • tension modulation for boiler
  • intensity modulation for thermostat (easymatic)?

In order to capture data with a logic analyzer an interface must be created (to reduce the voltages to levels the respective logic analyzer can handle).

Electrical coding

[To be defined]

Idle state

[To be defined]


Uart based

Whereas OpenTherm uses Manchester code, the easymatic seems to be based on Universal Asynchronous Receiver Transmitter (UART):

  • 1200 baud
  • 8 data bits (LSB-first)
  • even parity
  • one stop bit


[To be discovered and detailed]

Frames are repeated twice.

To be defined: how an order is send

All frames consist of 6 bytes.

Boiler frames begin with a byte in 01, 03, 05, 07, 09, 0B, 0D. Thermostat frames begin with a "boiler beginning frame +1": 02, 04, 06, 08, 0A, 0C, 0E.

Frame description

Frame (first byte) Equipment 2nd byte 3rd byte 4th byte 5th byte 6th byte Comments
0A Easymatic ? ? ? ? ?
0B Boiler ? ? ? T°C outside Example: 70.0°C = 700 = 0x02bc
0C Easymatic 00? T°C max boiler Set point frost protection T°C outside
0D Boiler 00? 00? 00? T°C outside
0E Easymatic Hour Day Minutes FF? FF?
01 Boiler 40? T°C drink water T°C boiler water
02 Easymatic C1? Set point room T°C day Set point room T°C night
03 Boiler 00? ? ? ? ?
04 Easymatic 05? Set point frost protection room T°C Set point T°C drink water
05 Boiler Boiler bits command ** *** ? ? outside T°C ***confirmation received order ?
06 Easymatic Boiler bits command ** *** ? ? ? ? ***order ?
07 Boiler Alarm ? ? ? outside T°C
08 Easymatic 00? ? ? ? ?
09 Boiler 00? ? ? outside T°C

(**) bits signification?: Boiler pump/Hydraulic valve Close//Hydraulic valve Open/Burner 1,2/Burner 1,1