Getting distracted by weird noises and listening to data from car tires / 2019-11-16

2019-11-16 Getting distracted by weird noises and listening to data from car tires 3 weeks ago
I was tuning across the 70cm amateur band and heard lots of weird noises around 433.92 MHz. Which is logical: that's the ISM band (industrial, scientific and medical) so lots of unlicensed low-power signals there.

That triggered me to update rtl_433 and see what I could receive. The answer after some searching how to build a running version: a lot. Including tire pressure monitoring sensors (TPMS) on a nearby car:

time      : 2019-11-16 15:33:25
model     : Toyota       type      : TPMS          id        : fb8c8bf9
status    : 128          pressure_PSI: 38.500      temperature_C: 6.000
mic       : CRC
There is indeed a Toyota parked across the street. I see three different values for 'id' suggesting that three wheels are 'awake' and reporting tire pressure data about every two minutes. According to eavesdropping the wheels, a close look at TPMS signals the sensors should only activate when the car is going faster than 40 km/h or when a special LF signal is active.

Update: The three sensors are even active when there isn't a Toyota brand car parked in the street. I guess someone is doing something interesting with the sensors.

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