Custom USB tyre pressure monitoring interface

**meddler** · 12-17-2007, 06:20 AM

Originally Posted by richyrich

I have heard back from them yes... 100 Dollars per unit (so a full kit!) although i have to order a minimum of 200 which is a bit of a pain... Trying to sort out some cash for this!

at $100 per kit, I'll take one. (only 199 left to sell)

**richyrich** · 12-17-2007, 08:35 AM

Just out of curiosity dont you guys over the pond in USA have to run these at 315Mhz and not 433Mhz like we in europe do??

**FMode** · 12-17-2007, 10:28 AM

Hello,

sorry for being absent for while and not reading here...

I noticed this thread just before the question to buy Smarttire sensors again or to change the system to a cheaper one. So I decided to change (my summer-tires also need new sensors...)...
I choose the Waeco TPMS (www.waeco.com) stuff for only 100 Euro and with 4 sensors but without a display (which I, and I guess you guys too, don't need) and it would be good to have a system from a vendor "with a name" (in 5-6 years if you need new sensors - but the batteries could be exchanged easily).

Originally Posted by Robby BMW

...
Discovered this, I’ve noticed that the whole data packet consist of 14 bytes (112 bits) organized in this way:

Preamble (32 bits) - The preamble is a series of 31 logic ‘1’ bits followed by a single logic ‘0’ bit (FFFE in hexadecimal), used to recognize the RF transmission as a valid TX message.

....

no

... the Preamble is 16 bits (FFFE) (your digitrace screenshots also shows only 15 bits at 1)...

The Waeco system also transmits on 433Mhz AM with a differential manchester coding... which looks like (!) that:
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which gives for example a: FFFE 001C40F7 81 30 DA 01 E258
with Robby's findings these can be interpreted to a tire pressure of 2,2bar (I have a normal car!) and 8°C (which perfectly fits into a german winter) and 218 of 255 (new sensors with new batteries!) (How does the CRC fit inside ? I didn't get it to work...)

So I guess the Waeco system is compatible ?

This all sounds too good ? Then have a look at the PCB of the receiver

:

The receiver is this shielded box connected with 7 pins to the main pcb... it gets 5V+ , ANT (external antenna!) and GND and devlievers the signal and the field strength...
easy to desolder ?

no saw needed.. only a soldering iron...

I guess Robby has to send me that PIC quickly

(PayPal!)...

Cheers to Robby !

**DaveDog** · 12-17-2007, 11:15 AM

I purchased one of the VALET tire presure monitoring systems, its available on ebay for less that $100 USD and it uses a separate display from the receiver.

It uses the same receiver PCB as FMode's waeco unit!!!

http://cgi.ebay.com/NEW-Valet-Tire-P...QQcmdZViewItem

I've taken the display and receivers apart to identify the communication protocol between the received and the display, looks like it uses a single wire LIN bus protocol, as the receiver uses a 6258 IC and the display uses a 6259-2 IC.

I noticed the PIC Robby used for his USB interface also supports LIN bus. If we can decode the communication, we might be able to modify Robby's PCB to communicate with this receiver, offering a somewhat affordable solution.

**WuNgUn** · 12-17-2007, 11:23 AM

Okay, how do I get a complete setup, ready to go, minus the wheel sensors? Or do I need a COMPLETE kit with reciever, and piggy-back it on a custom PCB?
You guys have done a tremendous job with this!! I wish I could easily incorporate it into my CarPC

**LYHTSPD** · 12-17-2007, 11:33 AM

I am starting to wonder if the tpms sensors are interchangable. What happens with the Valet unit if you need more sensors? Can you use another sensor from a different company?

I have boxes of OEM TMPS recievers sitting next to me (Honda, Toyota, etc). None of them look like the after-market ones though. All have intergrated boards. But I guess they do not need all the fancy external lcd stuff though since it all goes to the ECM.

**Robby BMW** · 12-17-2007, 11:50 AM

Originally Posted by FMode

no

... the Preamble is 16 bits (FFFE) (your digitrace screenshots also shows only 15 bits at 1)...

Sorry, my bad

, the preamble is 16 bits.
I made a mistake writing, thank you for the correction.
I've just changed it in the first post.

**Robby BMW** · 12-17-2007, 12:04 PM

FMode, the CRC error also match, in fact the CRC of 001C40F78130DA01 is E258 (the last part of your data), so it seems to be 100% compatible.

What about the timing, is the bit length about 100 μs?

**FMode** · 12-17-2007, 02:14 PM

Originally Posted by Robby BMW

FMode, the CRC error also match, in fact the CRC of 001C40F78130DA01 is E258 (the last part of your data), so it seems to be 100% compatible.

What about the timing, is the bit length about 100 μs?

Lol I am stupid... I forget that... certainly the bit length is 100µs...

dammit... I am too stupid to enter the correct values for CRC ??? (Button CCITT?)
http://www.zorc.breitbandkatze.de/crc.html

Originally Posted by DaveDog

I purchased one of the VALET tire presure monitoring systems, its available on ebay for less that $100 USD and it uses a separate display from the receiver.

It uses the same receiver PCB as FMode's waeco unit!!!

http://cgi.ebay.com/NEW-Valet-Tire-P...QQcmdZViewItem

I've taken the display and receivers apart to identify the communication protocol between the received and the display, looks like it uses a single wire LIN bus protocol, as the receiver uses a 6258 IC and the display uses a 6259-2 IC.

I noticed the PIC Robby used for his USB interface also supports LIN bus. If we can decode the communication, we might be able to modify Robby's PCB to communicate with this receiver, offering a somewhat affordable solution.

too much circumstances...
try to connect at the receiver module !
Pinlayout: from left to right looking at the back:
12345 678 90

2 DATA
3 GND
4 5V+ powersupply
5 fieldstrength
6,7,8 not soldered
9 GND
0 Antenna

is your TPMS 433MHz or 315Mhz ? AM or FM ?

You have the option to try your good luck and connect Robby's PIC to Pin2 (without "scopeing before" like me)

**Enforcer** · 12-17-2007, 02:49 PM

Originally Posted by FMode

I noticed this thread just before the question to buy Smarttire sensors again or to change the system to a cheaper one. So I decided to change (my summer-tires also need new sensors...)...
I choose the Waeco TPMS (www.waeco.com) stuff for only 100 Euro and with 4 sensors but without a display (which I, and I guess you guys too, don't need) and it would be good to have a system from a vendor "with a name" (in 5-6 years if you need new sensors - but the batteries could be exchanged easily).!

so where exactly did you get these units for 100Euro?