LaCrosse TX4-868

Added by uw almost 5 years ago

Hello dear JeeLink fellows

I have a couple of unused LaCrosse TX4-868 outdoor temperature/humidity sensors lying around. Is there any chance they could be recognized by a JeeLink Classic?

Thank you for any support!

Replies (13)

RE: LaCrosse TX4-868 - Added by jstsch almost 5 years ago

Sorry to hijack your thread, but I may be looking for the same thing. I’m trying to get the TFA THX502 remote sensor to work with my JeeLink V3. Seems to be a nice temperature/humidity sensor, for just 16 euros.

The sensor is 868MHz, but I’m not receiving anything. I don’t know if the THX502 is FSK or OOK, does anyone know? What I tried:

  • Listening with the RF12Demo sketch. Only getting other sources/noise. I did try tuning the receiving frequency a bit.
  • Listening with the WeatherstationFSK sketch, no luck unfortunately.

My next step would be to listen with the RFM12B_OOK sketch and use one of my regular JeeNodes where I can connect the FSK/DATA/nFSS signal pin. I don’t feel as comfortable doing the capacitor replacement though…

Suggestions? :)

RE: LaCrosse TX4-868 - Added by uw over 4 years ago

no problem here with hijacking…

From what I have figured out so far the TX4-868 are using OOK modulation. The JeeLink Classic has a RFM12B wireless radio module which is not compatible with OOK. I have ordered the newer JeeLink (v3c) that has the RFM69CW module which should be able to do OOK/FS20 send and receive.

Hope I am right with my assumptions….

RE: LaCrosse TX4-868 - Added by JohnO over 4 years ago

The classic has the most extensive OOK but typically these are 433Mhz devices. The hardware at 868Mhz can do OOK just fine.

RE: LaCrosse TX4-868 - Added by SevenW over 4 years ago

Both mentioned devices are 868Mhz. The Lacrosse TX4-868 may use the same protocol as the 434Mhz TX3. Documented here:\_signals.php

It may well be that RFM12B_OOK sketch contains the right decoder. At least it should be able to decode it.
The mentioned wheatherstation sketch is FSK (not OOK).

I was not able to find info on the THX502 so quickly. First thing to figure out is if it is OOK or FSK. Worst case you have to do the reverse engineering yourself. One way is to open the device and post pictures of the PCB.


RE: LaCrosse TX4-868 - Added by SevenW over 4 years ago

BTW, JeeLink with RFM69 is perfectly fine now I ported most OOK SW.


RE: LaCrosse TX4-868 - Added by jstsch over 4 years ago

I got a few pics of the insides :)

Some things I could decipher:

  • There is some text on the radio IC, but hard to decipher and partly scratched off: 730 42101 223…
  • There is a P/N on the PCB: 200-87270000-000-9V2
  • There is a date on the PCB: 2012.07.22
  • There is a little sticker: 12L2\_IMG\_2889.jpg\_IMG\_2895.jpg\_IMG\_2896.jpg

RE: LaCrosse TX4-868 - Added by SevenW over 4 years ago

After some googling on 10-pin 868MHz chips, I think it is a Amiccom A7302D

The MCU puts the to be send bit pattern on pin 2. It is most likely 868.4 MHz. It can either be ASK (OOK) or FSK. There is a capcitor connected to pin 9, so most likely it is FSK.

Most likely this device is not reverse engineered.

Feel like reverse engineering this? I may be able to give some pointers.



RE: LaCrosse TX4-868 - Added by jstsch over 4 years ago

Yeah, great! I’ve captured about 15 minutes of data at 868.4000MHz with the RFM12Demo sketch:

 _ i31* g212 @ 868 MHz c1 o1680 x1
868.4000 MHz
 ?X 0028EFF8F981B0CA6D8128B7DB9E41FFB8EC0B2F9B
 ?X D492F7026EC881D8009005BEF3B27B045E1008245F
 ?X FFF63FEEBE722011B649886D7BC0F09FC1A5C00029
 ?X A0128C59FB671CF751F2613FFEE17F05D99FA06C7D
 ?X C41717FF5CCEA31B3F3B4B10AF60FFE200233D9271
 ?X FF806FC0100000C0E7B73DBAC228DB7E6000F05F14
 ?X 8840CFF9B7BE3BFFFBDF8C61311BFF7FE340080277
 ?X F2B48C8927DF4088E0
 ?X E766B5C6DFFFF8A1E34061C431FFDD7F3FBF00B9F7
 ?X 80EEE39E3E502833DCFFDE7DFFBE608A0822206E9F
 ?X 00008040F1EFB060F08AC0B080E9FFFD617054A65F
 ?X 50FC0287335320C0408003AD66B7400758D7F265EB
 ?X 2881D8022840E3B5D647FC1D19A49741043226014E
 ?X 4004A014
 ?X 4C4CA7F3D7A15195FDD07E7DF368FFD49D1A17B87D
 ?X C71FF7E04000F039EED61B6F77C01C0025FF52E057
 ?X 1810D08051992691B09EB14483B17E67FD3483BFFC
 ?X 4F7EC403BFF5EF25F810055C43EF4B041E97D00B7D
 ?X 404DB3DC54802307B1F0301BBEAC100F98C0306798
 ?X B73B789ADDFC1FF9001904B1F56FB8C070C8EFBE43
 ?X C0E7FFCB42001B61E00FC33E768F1FFF0F7A785FC6
 ?X 60FFF6262CFE3BD7B339509001806ACA00217FB8BB
 ?X A800034FFFC69CAA0079900200CEB71C16018462F9
 ?X DCBDD0039AEF7FB4E1F67E7198C0388276EE7D0311

Hard to discern any pattern…

RE: LaCrosse TX4-868 - Added by jstsch over 4 years ago

The crystal used is 13.56875MHz, so the frequency would indeed be 868.4Mhz, although I saw that the chip is able to be tuned +/-12,5KHz.

I also saw in the datasheet that a baud rate of 1-20KBps is used. How can I figure it out? Should I just cycle through all the data rates using rfm12_control(C6NN)?

RE: LaCrosse TX4-868 - Added by jstsch over 4 years ago

Also some noise/data from the WeatherstationWS1600FSK sketch, but I presume we’re listening with the wrong data rate.

nok  29 C4 1D 73 38 03 C1 EE 38 2A CF 10 03 08 41 4F
nok  7A C1 00 20 04 B1 18 83 40 3F F3 DF EA 0C FF 95
nok  21 60 3E 0F 78 61 C3 C7 FE 01 63 C9 ED BE 5D BF
nok  EF 7C 1E 6F 99 3F 00 09 91 F8 7C F4 E2 7E DE 3C
nok  20 74 28 18 F0 DA 11 71 3A 4F A7 1D C9 7B 1D 9F
nok  4A 79 F2 31 ED 89 7F CC 30 FE 31 9F E0 FF 81 3C
nok  F3 37 C1 7E F3 C7 A8 1D F8 0F E1 7F FD 3C F1 B9
nok  00 7F D7 FB 60 01 39 EC 35 B0 DD F7 1B FC 09 9F
nok  F8 98 39 19 7E 90 81 FB 4E 1F FF CC 3C CC 7F DD
nok  F8 0C 87 80 0E 4F 7E 50 0C 77 26 88 10 0E F2 CD
nok  01 1F E4 08 7F 87 7D 43 BF 52 C7 EB F0 FB FF E4
nok  8F 7C 77 E7 0E F9 E7 68 19 FE 7D FC F7 2E E5 EF
nok  00 7F FF 3B FF CF F8 BB 17 98 7E 79 F3 FF E7 5D
nok  00 70 60 9F 1F C6 FF FC E7 3F F4 EC C6 02 01 C6
nok  00 D9 1C A4 48 99 E2 65 FA 08 42 11 E1 17 3D 40
nok  46 1C EE DA 88 47 8C 7C 02 39 A0 5A 01 E1 3D C4
nok  78 1B 60 18 60 D8 0F 8F C5 98 4C 40 DF 78 13 F8
nok  93 72 6B 23 C4 F5 79 83 5B F3 37 EC F0 5E 18 3A
nok  00 EF C5 BC 73 C6 4B FD 07 EC 0D E1 5F FF 3A 67
nok crclen 11: BC F8 3B 87 B1 C1 87 BC 8F 2C 40 40 87 30 08 77
nok  44 46 3F BE 0F E0 7B 16 37 D0 68 3F 9A FE FE 0F
nok  00 CB D0 3E 8A 70 70 E0 53 E1 70 85 84 1F 21 C7
nok  3B F1 39 37 2C 8B 0E FA 27 1F 7E F0 E3 FF 74 C1
nok  C7 F8 F0 78 AD FE F0 DF 01 D3 1B 9A 03 97 C0 7F
nok  01 EC F0 BF 19 77 6D 80 1F 41 6C 10 48 C0 98 08
nok  EE 1D FA 67 A0 FF C5 80 03 71 FD 81 CE C8 09 DC
nok  89 FE CE FE F7 03 07 9A BE 00 78 50 74 6C 3F C7
nok  1E 1C 00 E0 FF 98 0E 83 10 0F A3 84 E3 EE 1A 13

RE: LaCrosse TX4-868 - Added by SevenW over 4 years ago

Some years back, people on this forum decoded another unknown FSK device. Thomas Schulz has written a test program. It has several modes (commands), documented in the code. Some of them are really specific to the EC3K target device, but others are at the lower level of packet reception. Maybe you can start experimenting with that. I think it can log any signals received, including RSSI. If your device is at a meter of the receiver, your signal is strong. You should be able to figure out which one.

In this program you may be able to start sweeping bitrate to see if you find something.

I just happened to have ported those old sketches today to the latest arduino IDE. You can download them from here:

take the RF12test14 or 15.


RE: LaCrosse TX4-868 - Added by joop over 4 years ago

Was for old LaCrosse protocol.

RE: LaCrosse TX4-868 - Added by jstsch over 4 years ago

Hi SevenW, thanks a lot! Sorry for the late reply, work took all my time during the week.

So I’ve been playing a bit with the RF12test15 sketch. Getting a lot of noise! :)

Some questions:

1) I can’t seem to find a command how to adjust the bitrate of the transmission. Or is the RFM12B bitrate agnostic?
2) When I do for instance the pulse check: P 690 6 3 2, the sketch seems to crash immediately. What’s going on?

The frequency scan seems to work correctly, although it’s a bit difficult with the THX502 transmitting only every 2 minutes :)