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EMS-Telegram-Types.md

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Tip

Another good source of EMS and EMS+ investigation look at https://github.com/Th3M3/buderus_ems-wiki_

A2

This message is a EMS 1.0 message

Display code and Cause

(00:28:29.966) Thermostat -> all, type 0xA2 telegram: 10 00 A2 00 00 00 00 00 00 (CRC=CA) #data=5
data position (0..n) in decimal description format notes
0-2 Display code 3 bytes HEX To Decimal
3-4 Cause Code 2 bytes HEX To Decimal

3E, 48, 52, 5C

These are EMS1.0 type broadcasted from an RC35 compatible thermostat (typically with a device ID of 0x10) as a Heating Controller Monitor Message. The data block is 16 bytes. We use this telegram to read the current room temperature, the setpoint temperature for up to 4 Heating Controllers 0x3E (HC1), 0x48 (HC2), 0x52 (HC3) and 0x5C (HC4)

Examples:

<  header   > < 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15> (data block)
 10 0B 3E 00   00 00 00 7D 00 00 00 00 00 00 00 00 00 11 05 04
 10 00 48 00   00 00 00 00 E4 00 00 00 00 00 00 00 00 11 05 04
 10 0B 52 00   00 00 00 00 00 00 00 00 00 00 00 00 00 11 00 00
 10 0B 5C 00   00 00 00 00 00 00 00 00 00 00 00 00 00 11 00 00

in night mode:

 10 00 3E 00   04 03 00 7D 00 00 00 00 00 00 00 00 00 11 05 00
 10 00 48 00   00 00 10 00 E9 00 00 00 00 00 00 00 00 11 05 00

in day mode:

 10 0B 3E 00   04 03 00 7D 00 00 00 00 00 00 00 00 00 11 05 00
 10 0B 48 00   00 00 10 00 E8 00 00 00 00 00 00 00 00 11 05 00

in auto day mode:

 10 00 3E 00   04 03 00 7D 00 00 00 00 00 00 00 00 00 11 05 00
 10 0B 48 00   04 03 00 00 EB 00 00 00 00 00 00 00 00 11 05 00

deciphering each data element from 0 to 15

data #n description format notes
0 settings1 1 byte as a bit mask bit 2 is automatic mode, bit 7 is manual mode, bit 5 is holiday mode
1 settings2 1 byte as a bit mask bit 0 if in summer mode, bit 1 if in daytime
2 setpoint room temperature 1 byte * 2
3 + 4 current room temperature 2 bytes * 10 has value 0x7D00 if switched off
13 switch state 1 byte as a bit mask always 11?
14 calculate setpoint flow temperature 1 byte this looks wrong
15 settings3 1 byte as a bit mask we see two values 0 and 4

Questions:

  • how to determine if a heating circuit is not active? Check for data #14 if its 0 ?
  • when to ignore the setpoint temperature being 0? This depends on the bit masks in data #1 and #2 somehow
  • data #0 is sometimes 04 (b0100) always with data#1 being 3 (b0011). This means DWH priority is set and daytime mode, according to https://emswiki.thefischer.net/doku.php?id=wiki:ems:telegramme#wwbetriebsart. Is this correct since one of the examples we're in nightmode?