Thread: Custom USB tyre pressure monitoring interface

You can build a simple 433.92 MHz antenna with a thin 50Ω coaxial cable as shown in this picture:

Robby, Do i have to unsolder the original antena or can i solder that peice directly onto the existing one? Also I used the doctor application yesterday and did a master reset. Now the doctor appllication is unable to see any changes in the tire presure.

I am glad to hear that WAECO is compatible! Increases chance of finding replacement sensors when batteries are out. On WAECO (was not Waeco some kind of suicidal sect?) it says that their sensors have 7 year service interval. Does that implicate that batteries can be replaced or charged?

I found Waeco kit at €85 on ebay.

Hello Guys,
a Few people have asked for some pics about where/how to cut the RF-Rx from the poriginal board, mounting it, etc.

Below a quote from a post I made in my worklog.

Kind regards,
MrBean

Hello Guys,

Originally Posted by MrBean

Extras:
I have just received my Tyre Pressure Monitoring kit from my supplier, and I am 90% complete removing the wireless receiver, and integrating it via a custom PIC-Micro into my Carputer - all the temperature, and pressures, from each wheel will be displayed in realtime on CentraFuse frontend, with adjustable alarm-limits to warn of excursions.

In my mind, this is a very important part of having this carputer in the 1st place, it is an added safety factor when doing serious travelling with a 500+ HP (on the wheels) UTE

Ok, as promissed, a few detailed pictures of how to do the TPMS setup, based on RobbyBMW's PIC USB interface, and the 3rd Eye TPMS kit.

Here's the kit as it will arrive, all neatly packed, in an eye-catching box - no pun intended:




Taking a close-up between the RF receiver, which is the unit with the LCD display combination, one of the 5 tyre pressure sensors, the unit in the front, and the PIC micro USB to PC interface board.



Another shot, showing the rear, with the serial number in this case, of the RF module.



I decided to get her naked, and expose her innermost secrets to the salivating masses out there....



And take off some of her clothes, actually, completely strip her - lol...



Well, I got lost for a moment there, soz about that....

Here is a pic showing how I desoldered the LCD board, and ending up with the RF/PSU combination board, and the LCD/Decoder board.



And here is a shot of the same from the back, the piece on the bottom, right, is what we are interested in - the RF Receiver, repsonding to frequencies at 433,92Mhz.



So, we need to do a bit of dremmelling, and end up with this - be very, very careful of firstly, statics, and secondly, to cut just to the left of the little divider line on the PCB - the larger portion must be the RF Receiver part!



And here is the connections to be made, they will be soldered to pins on the PIC USB interface pcb:



to give us an end result, looking something like this (hopefully yours do too):



and here:



I just thought I'd post a good guide on how-to do this mod, as it's not as simple as it seems by reading Robby's thread, and, if you're not familiar with electronics, and do not owe a good, fine-tipped soldering iron, don't attempt this, as you would ruin a perfectly good TPMS unit.

What do we acheive by doing the above mod?

Well, now we can display our tyre temps, and pressures directly onto our Carputer Frontend - the plugin for Roadrunner is ready, and working, and the Centrafuse one is nearly Beta, the developer will notify me as soon as it is.

For now, I have tested mine with Robby's test applet, and it works very well.

Nice, and a good safety feature to add to your carputer setup.

Now you can start to understand why I opted for the very powerful Core 2 Duo based solution

Enjoy this thread, I hope it is helpful.

edit: One thing I did not add, and which is not visible in the photos - I added a piece of supporting foamrubber under the RF board, so it will sit firm on the USB-pcb, with no fear of vibrations causing any harm/loose connections.

Something to keep in mind.

Originally Posted by a__l

Hi Robby.
Thanks. Would like to confirm that WAECO device is fully compatible(including CRC) with your investigation and realization (I used my own program and ATmel device but based on your research. The only thing is the rate for getting pressure. In my case the formula is a little bit different[pressure = 2.38*RAW data(from sensor) - 70 but to get BAR] but the idea is the same) :-) By the way have you thought also about displaying the signal strength coming from sensors?

Glad to hear this, but are you sure about the formula to get the pressure?
2.38 is a strange value.

As for the signal strength, I had initially thought to it, but since the data packet sent from the sensors is too fast (about 11,2 ms) there isn't sufficient time to perform a reliable reading, also it would be necessary to modify the 3rdEye receiver to pickup the signal strength (i think it is available on the pin 26 of the TDA5200) and make an A/D conversion of this last.

Originally Posted by goosey2099

Robby, Do i have to unsolder the original antena or can i solder that peice directly onto the existing one? Also I used the doctor application yesterday and did a master reset. Now the doctor appllication is unable to see any changes in the tire presure.

You have to remove the original antenna and to solder the center core of the coaxial cable, you need also to solder the shield of the coaxial cable to GND, for example on JP3.

About the master reset, it is normal, now you need to perform again the learnig procedure for each sensor.