Custom USB tyre pressure monitoring interface

**Robby BMW** · 11-08-2007, 12:47 PM

Originally Posted by mrbean_phillip

@ Robby BMW: Is there a Microchip HCS515 decoder anywhere on the circuitry? Any of the boards?

No, there are only a PIC 16C621A used for handling and decoding the received signal, a PIC 16C926 used to drive the LCD display, an EEPROM 24C02W6 I think used to store the data and of course a TDA 5200 used in the RF part.

**inh** · 11-08-2007, 12:56 PM

Looks like the receiver board from the third eye just spits out the raw data, and robby's PIC decodes it..

Which means we buy the TDA5200's, build the board and robbys circuit, and then order $100 worth of in-wheel sensors =] There! We've already cut costs in half!

**LYHTSPD** · 11-08-2007, 02:02 PM

I would much rather see a home-grown solution anyway. The problem with taking the pre-built unit and hacking it is that makes you dependant on the manufacture and supplier of the other unit. Plus, you are buying a $250 item and not using half of it.

I mentioned earlier that I can get a hold of a couple of different TPMS reciever units. I can get an 08 Honda, 08+ Kia, and a few others. Robby, if you want me to send you some of them, just let me know. This may help in developing our own version of this thing.

**vicky_obee** · 11-08-2007, 02:15 PM

Well if some 1 can get me the whole working module/kit at a reasonable price i would like to have 1 as well pls

**turbocad6** · 11-08-2007, 02:38 PM

what I think would be sweet would be if you were able to do robbies interface & still have the display too, is this possible? tap into the data instead of diverting the data?

just curious, def not a deal breaker, but that would be cool to for some installs I think...

**mrbean_phillip** · 11-08-2007, 04:37 PM

Originally Posted by inh

Looks like the receiver board from the third eye just spits out the raw data, and robby's PIC decodes it..

Which means we buy the TDA5200's, build the board and robbys circuit, and then order $100 worth of in-wheel sensors =] There! We've already cut costs in half!

Exactly

That's why I want to do it this way, it would help in saving costs...

Originally Posted by turbocad6

what I think would be sweet would be if you were able to do robbies interface & still have the display too, is this possible? tap into the data instead of diverting the data?

just curious, def not a deal breaker, but that would be cool to for some installs I think...

From an electronic perspective this would be easy, as you can intercept the datastream where it heads into the factory decoder pic, and divert it to Robby's solution......then you have the best of both worlds.

Originally Posted by robbybmw

No, there are only a PIC 16C621A used for handling and decoding the received signal, a PIC 16C926 used to drive the LCD display, an EEPROM 24C02W6 I think used to store the data and of course a TDA 5200 used in the RF part

Thanx Robby, I could actually read the code of one of your pictures, the TDA5200 part that is.

I know the 16C926 fairly well as an integrated LCD driver pic, so they must use the 16C621A for decoding then.

Well, this really confirms then that we need to find TPMS receivers running 433.92Mhz, making use of FSK - so it narrows the field down a lot.....even the 315Mhz USA version receivers should work just fiine - generally 433.92Mhz is used in the EU, and 315Mhz receivers in the USA.

Just something to look at for, but it is generally just a case of changing the onboard crystal oscillator to a different speed rating, and maybe changing the 64x or 128x freq multiplier on the chip to either ground or floating....

Easy enough.

Well, I will do some reading on this on the weekend, and notify you guys of anything interesting.

Kind regards,
Beanie.

**turbocad6** · 11-08-2007, 04:44 PM

Originally Posted by mrbean_phillip

From an electronic perspective this would be easy, as you can intercept the datastream where it heads into the factory decoder pic, and divert it to Robby's solution......then you have the best of both worlds.

thanks, that's the route I'm going to take with this, so the data stream won't be hurt by being tapped & feeding 2 different pics at the same time? if that's the case then this is really cool & worth the extra for the whole kit I think..

**mrbean_phillip** · 11-08-2007, 05:18 PM

Hey Turbocad6,
Being a digital stream it should be ok, it is the same as if sitting ontop a RS-comms link and snooping data, or, for a better example, consider a standard ethernet netowork

The data is available to anyone, but only those that needs to respond will.....so, in this case, you send the data down the link, and whoever is "authorized" to listen can.....

**juve021** · 11-08-2007, 05:30 PM

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