CAN Bus in BMW: How to Guide

Hello there,

Möchte mich mal hier als neuer User vorstellen, mit einem etwas ungewöhnlichem Tuning Projekt für meinen BMW E36 24V Bj 92.

UOkay, I'm planning to install a new speedometer in my car. Currently, I'm considering either a CAN-bus speedometer from an Audi A3 with Maxidot or a very new speedometer from a BMW salvaged vehicle (year 2006).

I've driven an Audi A3 8P TDI before and have some experience working on its CAN-gateway, so I have some basic knowledge. That's why I'm leaning towards the Audi option, as I'm not sure if BMW uses CAN-bus or only ODB.

Interestingly, the Audi A3 speedometer fits almost perfectly into my BMW. I already know which analog signals I need to tap from my BMW.

Are there any possibilities or existing projects for such a solution? I was thinking about using an Atmel or PIC microcontroller circuit.

What do you think?

Best regards,
Sany.Now that I've already driven an Audi A3 8P TDI and have tinkered with the CAN gateway, gaining some basic knowledge in the process, I thought about taking the Audi because I'm not sure if BMW even uses CAN or just ODB.

It was interesting to see that the Audi A3 speedometer almost fits perfectly into my BMW... I already know which signals I need to tap from my BMW (analog).

Is there a way to do this, or are there any existing projects for such a solution? I'm thinking about an Atmel or PIC circuit.

What do you think?

Best regards,
SanyI found it amusing that the Audi A3 speedometer almost perfectly fits into my BMW... I already know which signals I need to tap from my BMW's wiring (analog).

Is there a way, or are there any existing projects, for such a solution? I'm thinking of an Atmel or PIC circuit.

What do you think about this?

Best regards,
SanyI found it amusing that the Audi A3 speedometer almost perfectly fits into my BMW. I already know which signals I need to tap into from my BMW's wiring harness (using analog connections).Is there a way to achieve this, or are there already projects that implement such a solution? I'm thinking of something like an Atmel or PIC circuit.Best regards.

Hello there,
Now that I've already driven an Audi A3 8P TDI and have tinkered with the CAN gateway there, gaining some basic knowledge in the process, I thought I might as well take the Audi. I'm not sure if BMW even uses CAN or just ODB.


What have you done with a CAN gateway besides perhaps changing a coding using VAG-COM?


I'm not familiar with BMWs, but what is ODB? In the world of Windows, I understand ODB to be a database interface. Perhaps you're confusing it with OBD in the automotive world, which isn't actually intended for constant data exchange between control units, but rather for diagnostics.

How familiar are you with the CAN protocol? Do you know how a CAN message is structured? I'm asking this in a simple way so I can understand the best way to explain it to you.

Regards,
Markus.

Hello,

Sorry, I misspelled it; I meant 'OBD' (lowercase). :)

Also wie CAN Funktioniert weiß ich schon, hab dazu auch schon komplett den Artikel in eurem Forum gelesen.
I also have experience with ATMEL CAN interfaces, etc.

However, I believe your project could be realized using an Atmel microcontroller with a CAN interface and an A/D converter.?But surely my plan can be realized using an Atmel microcontroller with CAN functionality and an AD/DA converter?

Kurz und knapp gesagt, ja hab auch schon in einen golf2 einen golf5 tacho spasseshalber angeschlossen(attiny 2313 + mcp2515) und konnte drehzahl und geschwindlichkeit anzeigen lassen.

an deiner stelle würde ich so vorgehen, deine schlatung mit den atmel machen, und dann erst mal testbotschaften an einen can tool oder so senden.
Okay, next I would connect the CAN interface to the future speedometer (outside the car) and see if you can simulate the speed (the ID for the speed is available on this forum).

Then, you'll need to figure out what functions are required (ABS, airbag, oil sensor, etc.). Most of these things aren't documented on the forum, so you'll have to find a VW, log its data, and identify the corresponding IDs.

After that, it gets interesting: use an oscilloscope to see what signals appear on the analog lines of the BMW.

I wouldn't recommend using an ATtiny2313 like I did, because you would also need to program the SPI interface for the CAN module. Instead, use an ATMega or even better, the AT90CAN128. And always remember to make sure these devices are sufficiently automotive-grade (voltage spikes, short circuits, etc.).)'First, you need to figure out what functions are required (ABS, airbag, oil sensor, etc.). Most of this information isn't available in the forum, so you'll have to find a VW and log its data to determine the IDs.

Then things will get interesting: use an oscilloscope to see what signals appear on the analog lines of the BMW.

I wouldn't recommend using an ATtiny2313 like I did, because you would also need to program the SPI interface for the CAN module. Instead, it's best to use an ATMega or even the AT90CAN128. And always remember to make sure these devices are sufficiently automotive-grade (voltage spikes, short circuits).' 'Soon it will get really exciting. Now I'm going to use an oscilloscope to find out what signals are present on the analog lines in the BMW.

I wouldn't recommend using an ATtiny2313 like the one I used, because you would also have to program the SPI interface for the CAN module. Instead, it's best to use an ATMega or even the AT90CAN128. And always remember to make sure these devices are sufficiently automotive-grade (resistant to voltage spikes and short circuits).'I wouldn't recommend using an ATtiny2313 like the one I used because you would also have to program the SPI interface for the CAN module. Instead, it's best to use an ATMega or even the AT90CAN128. And always remember to make sure these devices are sufficiently automotive-grade (resistant to voltage spikes, short circuits, etc.).

Hello there,

Thank you very much for your contribution; fortunately, there are still crazy people in the world with the same idea .

I have been described as 'crazy' in several forums.


Okay, I already know that the speed and tachometer readings can be displayed. The only thing I might have trouble with is in the FIS (multifunction display) with the general warning indicators like brake or ABS, which light up on the display when something is broken.

I was also thinking about using the ATmega328P. The rest of the functions, like headlights/high beams, could actually be controlled quite easily with an I2C interface. Of course, you could then implement it in great detail .

Okay, in my BMW, I'm mostly getting resistance signals, which I've already measured.

100 Ohms: tank empty
255 Ohms: tank half-full
455 Ohms: three-quarters full, etc.

Could I process these values using an Atmel microcontroller like this?

Hey, how's it going?

According to the Atmel website, can the AT90CAN128 be programmed directly via USB, or do I still need an FTDI USB chip to program the Atmel via USB? I haven't found any information about this in the datasheet.

Desweiteren hab ich eine Microkontroller Karte gefunden, die mir auch noch eine I2C Bus Funktion ermöglicht... was hälst du von der?
And specifically, the following: <!-- m --><a class='postlink' href='http://www.microcontroller-starterkits.de/index.html?d_1067_Bausatz_ATMegaEvoBoard_mit_AT90CAN128184.htm'>http://www.microcontroller-starterkits. ... 128184.htm</a><!-- m -->.R}And specifically the following: }}} ... 128184.htm}}

Den CAN128 kann man per ISP und JTAG programmieren.
Für Downloads via CAN oder UART brauchst du einen passenden Bootloader.
To use USB, you need the FTDI chip.

The evaluation board looks quite interesting.

SGMThe evaluation board looks quite interesting.

also den fdti chip braucht man um vom urat auf usb kommt, programmieren geht wie maxx schon gesagt hat über spi (isp bedeuted eigendlich bloss, das es 'im system programmiert' werden kann, dh ohne den chip auszulöten).

I would build you such an adapter if you could provide me with a storage oscilloscope, a good digital analyzer, and a suitable BMW for two weeks, including an A3 speedometer.R}I would build you such an adapter if you could provide me with a storage oscilloscope, a good digital analyzer, and for two weeks, a suitable BMW including an A3 speedometer .

...about SPI (SPI actually just means that it can be 'programmed in the system', i.e., without desoldering the chip).

I probably made a typo. My natural SPI .