Can't get it working

[alejandroalis]

Hi!

I've tried running the example on an ESP32 with the 433MHz wheel sensors, but no luck. Communication with the CC1101 is working correctly; it initializes everything, but it doesn’t receive any data. I know the TPMS is sending data because I can read it correctly with the RTL-SDR, and thanks to the rtl_433 utility, I can see readings compatible with the ‘truck’ sensor type. I tried changing the sync bytes to other values based on the readings I had from the SDR, but still nothing. I noticed that when compiling the code, there was an error (a missing ; on line 81 and the setFlag function isn’t declared at the beginning), so I'm wondering if the code was really tested or if you made any changes. Any help would be appreciated!

[unverbuggt]

Hi,

I'm currently working on reading tpms_ford.c devices and I've learned something yesterday: The TPMS sensors send using OOK modulation when triggered by the 250kHz trigger tool and they use FSK while the wheels are spinning.
This is not a big problem for a SDR (Maybe it is possible for rtl_433 to show the used modulation?), but a big problem for the CC1101 chip. You can try adding radio.setOOK(true); in the setup routine. But best is to use Universal Radio Hacker with the SDR and record the signal and then check the modulation.

[alejandroalis]

Hello unverbuggt! I’m using some from Aliexpress for a motorcycle; they only have a pressure sensor, and I noticed they detect when the vehicle moves by changes in the pressure, without an actual motion sensor—pretty clever. Using the RTL-SDR, I can capture the data, but no configuration works with the CC1101. I tried following your example and changing everything, but still nothing… did you ever manage to get it working?

[unverbuggt]

yes, I got it working. I'll fork this repo and share my code in the next days.

Main problem with receiving these signals is the short preamble (the chip needs 16 bits). Also the preamble isn't manchester encoded, which, as I understand it, means we cannot use the manchester decoding on the chip (I don't know how @andi38 got it working, also with the one byte sync word...).
The other problem is that I currently only get stable results if I use the sensor ID as sync word, which means that If sensors start with a different ID, they cannot be received (I got two Ford cars with different generations of sensors, but also with different tyre sizes, so I wouldn't need to mix these).
I'm planning of writing an article about this, but this is going to take some time.

[alejandroalis]

The truth is I spent an entire day on it and couldn’t get it to work. I’m developing a specific tablet for motorcycles from scratch (I’m an electronics engineer) and, honestly, doing it all without help... I hope to launch a Kickstarter in a couple of months. Being able to read directly from standard TPMS sensors would be incredibly useful. If you could give me a hand and share the code that works for you, it would be a huge help—I’m going crazy with everything!... you can check it on www.alsenms.com

[unverbuggt]

I've forked here

[alejandroalis]

Sorry for not replying sooner... I'm in the area affected by the DANA in Spain, and it's been complete chaos. I'll try to get back to this and test the code you shared. Thank you! I'll let you know once I've tried it. :)

[alejandroalis]

Thanks, I’ve tested it, and after analyzing the data, I was able to extract the pressure since the sensors don’t seem to be the "Truck" model but rather a different one. Thanks for the help!

[unverbuggt]

Good to hear. You're welcome.