Protocol decoder:Easymatic

easymatic

Name	EASYMATIC
Description	Asynchronous, serial bus, differential
Status	planned
License	GPLv2+
Source code	decoders/easymatic
Input	uart
Output	easymatic
Probes	—

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

Hardware

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]

Protocol

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)
• odd parity
• one stop bit

Details

[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 exterior		Example: 70.0°C = 700 = 0x02bc
0C	Easymatic	00?	T°C max boiler		Set point frost protection T°C exterior
0D	Boiler	00?	00?	00?	T°C exterior
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 ** ***	?	?	exterior T°C		***confirmation received order ?
06	Easymatic	Boiler bits command ** ***	?	?	?	?	***order ?
07	Boiler	?	?	?	exterior T°C
08	Easymatic	00?	?	?	?	?
09	Boiler	00?	?	?	exterior T°C

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

Resources

• Wikipedia: Universal asynchronous receiver/transmitter
• De Dietrich information