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hardware:vaillantvrt340f_protocol [2017/05/05 18:19] reinholdhardware:vaillantvrt340f_protocol [2017/05/11 21:28] (aktuell) reinhold
Zeile 84: Zeile 84:
 Why least significant bit first? That took me a while, too, and it stems from the way the checksum is calculated. Why least significant bit first? That took me a while, too, and it stems from the way the checksum is calculated.
  
-Our sixteen base signals from above now become:+Our sixteen base signals from above now become (again using a [[https://github.com/kainhofer/vaillant-calormatic340f/blob/master/Vaillant_decode_bitstuff_hex.c|little self-written utility]]):
  
 ^Heat.^Wat.^Rep.^Bat.| ''Byte1\ 2\ \ 3\ \ 4\ \ 5\ \ 6\ \ 7\ \ 8\ \ 9\ 10\ 11\ 12\ 13\ 14\ 15\ 16'' | ^Heat.^Wat.^Rep.^Bat.| ''Byte1\ 2\ \ 3\ \ 4\ \ 5\ \ 6\ \ 7\ \ 8\ \ 9\ 10\ 11\ 12\ 13\ 14\ 15\ 16'' |
Zeile 150: Zeile 150:
  
 ==== UPDATE: Making sense of the 0xFD byte 13 ==== ==== UPDATE: Making sense of the 0xFD byte 13 ====
-The byte 13 with unknown constant value 0xFD kept bothering me, and a few days after I understood the checksum byte I figured out its meaning too: As I mentioned, bytes 4-12 together with the checksum byte 14 summed up always yielded 0x0300. It seemed strange to me that the 0x03 byte of the sum was somehow ignored, until I realized that 0xFD is actually the binary complement of 0x03, i.e. the checksum is actually just byte 14, but the two-byte value of bytes 13 and 14. So, our assumption that bytes 13 with a value of 0xFD is some kind of End-Of-Data or separator byte was simply wrong, and it being constant is just a coincidence.+The byte 13 with unknown constant value 0xFD kept bothering me, and a few days after I understood the checksum byte I figured out its meaning too: As I mentioned, bytes 4-12 together with the checksum byte 14 summed up always yielded 0x0300. It seemed strange to me that the 0x03 byte of the sum was somehow ignored, until I realized that 0xFD is actually the binary complement of 0x03, i.e. the checksum is actually not just byte 14, but the two-byte value of bytes 13 and 14. So, our assumption that bytes 13 with a value of 0xFD is some kind of End-Of-Data or separator byte was simply wrong, and it being constant is just a coincidence.
  
-In short, bytes 13 and 14 are simply the binary negative of the sum of bytes 4-12, with most significant byte first, i.e. bytes 13+14 interpreted as a signed integer is -sum(byte 4-12). As we are summing up only 9 bytes, there will be no overflow, either (which was what was bothering me with the 0x03 when one understood only byte 14 as the checksum).+In short, bytes 13 and 14 are the binary negative of the sum of bytes 4-12, with most significant byte first, i.e. bytes 13+14 interpreted as a signed integer is -sum(byte 4-12). As we are summing up only 9 bytes, there will be no overflow, either (which was what was bothering me with the 0x03 when one uses only byte 14 as checksum).
  
  
Zeile 191: Zeile 191:
  
 Let's print all observed values of the heating byte in correlation with the difference between target and current room temperature:{{:hardware:vaillant_calormatic340f:vaillant_calormatic340f_heatingbyte_tempdifference.png?direct|}} Let's print all observed values of the heating byte in correlation with the difference between target and current room temperature:{{:hardware:vaillant_calormatic340f:vaillant_calormatic340f_heatingbyte_tempdifference.png?direct|}}
 +
 The values of this chart were observed for room temperatures of 22, 22.5, 23, 23.5 and 24°C, but the current room temperature has no influence on the heating byte, only the difference to the target temperature. As observed above, the same temperature difference can lead to different heating bytes, but apparently, the possible intervals for each temperature difference are not overlapping. This is an indication that the wireless control displays the temperature only in 0.5°C steps, but measures the current room temperature (and thus the difference to the target) in higher accuracy. The values of this chart were observed for room temperatures of 22, 22.5, 23, 23.5 and 24°C, but the current room temperature has no influence on the heating byte, only the difference to the target temperature. As observed above, the same temperature difference can lead to different heating bytes, but apparently, the possible intervals for each temperature difference are not overlapping. This is an indication that the wireless control displays the temperature only in 0.5°C steps, but measures the current room temperature (and thus the difference to the target) in higher accuracy.
  
Zeile 238: Zeile 239:
  
 Each signal is first sent with byte 9 set to 0x00 and shortly afterwards repeated with byte 9 set to 0x01 (and the checksum updated correspondingly). Each signal is first sent with byte 9 set to 0x00 and shortly afterwards repeated with byte 9 set to 0x01 (and the checksum updated correspondingly).
 +
 +==== Setup Mode: RF detection ====
 +Playing around with the operator and installation modes of the Vaillant VRT340f, all signals I found fit perfectly well into the protocol described in the last section, except for one signal: RF detection:
 +
 +''0x00 00 7E FF FF 00 FF 00 F0 FF FF 6D F6 20 00 02 00 F8 90 FF 00\\
 +0x00 00 7E FF FF 00 FF 00 F1 FF FF 6D F6 20 00 02 00 F8 8F FF 00''
 +
 +As one can see, the signal is longer, but it still follows the same pattern of the begin and end of frame bytes. Also, bit-stuffing is still used, and the checksum is calculated just like in all other packets. However, there are some differences: the Device ID does not appear at the beginning of the data, but somewhere in the middle. Instead the device ID is 0xFF FF, which probably indicates a broadcast. All other values are completely unknown to me, as they never change.
 +
 +^Byte ^^ Value ^Description ^ 
 +^1-2  || 0x00 00 | Preamble (square wave to synchronize clocks with the receiver) |
 +^3    || 0x7E    | Begin of frame/data (Constant) |
 +^ 4-19 || Data content of the frame with 2-byte checksum attached ||
 +| ^4-5  | 0xFF FF | Indicates broadcast | 
 +|::: ^6-8  | 0x00 FF 00 | Unknown (constant) |
 +|::: ^9    | 0xF0/F1 | Repeat: 0xF0 for original signal, 0xF1 for repeat signal (bit 1, bits 5-8 always set) |
 +|::: ^10-11  | 0xFF FF | Unknown (constant) |
 +|::: ^12-13  | 0x6D F6 | Device ID of searching control (Constant for each device) | 
 +|::: ^14-17  | 0x20 00 02 00 | Unknown (constant) |
 +|::: ^18-19 | 0xF8 .. | 2-byte Checksum (signed integer): negative of the sum of bytes 4-17 |
 +^20 || 0xFF | End of Signal indicator |
 +^21 || 0x00 | Epilogue (no data any more) |
 +
 +
  
 ====== Implementing support for the device in rtl_433, rflink and/or OpenHAB ====== ====== Implementing support for the device in rtl_433, rflink and/or OpenHAB ======
  
 Now that we understand both the physical layer of the signal, as well as the structure of the protocol, we can go on to [[hardware:vaillantvrt340f_implementing|implementing support for it in applications like rtl_433 (part of GNUradio), rflink or OpenHAB in part 3 of our series]]. Now that we understand both the physical layer of the signal, as well as the structure of the protocol, we can go on to [[hardware:vaillantvrt340f_implementing|implementing support for it in applications like rtl_433 (part of GNUradio), rflink or OpenHAB in part 3 of our series]].
hardware/vaillantvrt340f_protocol.1494001194.txt.gz · Zuletzt geändert: 2017/05/05 18:19 von reinhold

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