# Thread: Wireless USB TPMS Review

1. I and folks from my team are willing to volunteer the Linux (nghost) integration. We are doing for some development for this frontend right now, so may try to help on sensors kit.
Anyway, I am planing to get 2 kits for myself, for 2 cars and until the second one is installed - we can use for the development.
How many people would be interesting in this?

The question - if I need to have a kit with 5, what will be the price then?
Could I purchase just sensors later, if I need to add to spare tires?

2. I would like to know if these tpms kits are good for north america regarding frequency of the senders and what is turnaround time for shipping, i have tried to send private message regarding this matter to lok but no reply. hopefully the shipping is not like the replies SNO

3. Finally got the sensors kit, run smooth in Windows.
So now the question regarding the Linux integration - would anyone did any progress on it already?
If not - we can put the basic stuff together and share for all, but I would like to see if it is possible to get original TPMS developers help on defining HID interface between the receiver and PC. Possible?

This is what we have discoverer so far:

Raw Data Buffer

Byte 0: Pressure Byte (Bar)
Scaling = 0.025 Bar/LSB
Zero Point = 0x28
Formula:
P = (PB - 40)*0.025
Samples:
0x26 = -0.05 Bar
0x27 = -0.025 = -0.03 Bar
0x28 = 0.00 Bar
0x6D = 1.725 = 1.73 Bar
0x7B = 2.075 = 2.08 Bar

Byte 1: Temperature Byte (Celsius)
Scaling = 1 C/LSB
Zero Point = 0x28
Formula:
T = TB -40
Samples:
0x2D = 5 C
0x2E = 6 C
0x3E = 22 C
0x40 = 24 C

Byte 2: Battery Level Byte
Relative level of battery. I think the range is from 0x00… 0xFE.
For the manipulation of this byte to actual “V” I need to know lowest battery voltage on which the sensor could work and type of the battery.

Byte 3: Sensor Mode Byte
It sounds like this byte represents status of the sensors, as per below table (Sensor Modes).
NormalMode = 0x01

Sensor Modes
http://www.mp3car.com/vbulletin/port...erface-19.html

Mode Description
Storage Mode
If the pressure is below 1.5 bar, pressure is measured every 60 seconds but no data is sent. If the pressure increases above 1.5 bars, the sensor shifts into the Initial mode.
Initial Mode This mode occurs if the pressure increases above 1.5 bar from Storage mode. In this mode, pressure is measured every 0.85 seconds and data is sent every 0.85 seconds. This sequence is repeated 256 times. After the sequence is repeated 256 times, the sensor shifts into the Normal mode only if pressure is above 1.5 bar. If the pressure is below 1.5 bar, the sensor will shift into the Storage mode.

Normal Mode
Pressure is measured every 3.4 seconds and data is transmitted every 60 seconds. If the measured pressure differs by more than 200 mbar from the reference taken every 60 seconds, the sensor enters a Pressure Alert mode.

It is the same measurement and transmitting pattern as the Initial mode.

If the temperature exceeds 120°C, the sensor device enters into the same measurement and transmitting pattern as the Initial mode.

------------------------------------------------

HID Protocol
To poll a sensor data:
1. Host writes one byte to device with required sensor number coded as 0x20 + SensorIndex. First Sensor index equals to 1.
2. Host reads the four bytes buffer from device. Structure of buffer is explained above.

Thanks

5. I like it,but i'm in china,how can i get this?

6. from the store.

http://store.mp3car.com/USB_TPMS_Ver..._p/com-090.htm

or you can get the TPMS system direct from the manufacturer Third Eye which is based a lot nearer you. And then get the CarPC adapter kit from Dejan

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