Thread: BMW 540i Project Part 2

thats just gorgeous!!!!!!!

that's really sleek, I like that... do you know what size lcd is in there? would you mind sharing what you've learned of the data packets?

cool install

Thanks for the compliments, everyone. I'm actually not interfacing with the car's ibus, but instead, simulating the ibus enough to operate the screen. All it takes is a pull-up resistor (10K) to twelve volts. I finished the screen wiring this afternoon - used a single Cat 6 cable to run both the video and the "simulated" ibus from the PC in the trunk. The LCD itself is a 6.5" but it requires RGsB at NTSC or PAL timings. I use an old Matrox G200 and Powerstrip to generate the right signal. Mostly since the G200 will also output the required Sync on Green natively. As for data packets there are only a few relevant ones. First, the monitor needs 80 xx bf 11 01 xx - which is a general bus-wide wakeup (key on). Then you can use 3b xx f0 4f 11 11 xx and 3b xx f0 4f 01 01 xx to turn the video on and off respectively. The monitor also needs a keep alive packet sent every 18-20 seconds - 3b xx 46 01 xx. I send it every 10 or so just to be safe - the count resets everytime it receives the message. And finally, to turn the monitor off, send 80 xx bf 11 00 xx (key off). For those who arent' familiar the packets are structured like so:

aa bb cc yy yy yy yy yy xx

aa - sending device address
bb - total packet length
cc - receiving device address
yy - data
xx - checksum

When the monitor is active, the button on the right will open or close it and the button on the left changes the angle in one degree increments. The buttons do not work unless monitor has received the wakeup packet and the keep alive pings. It will also internally store the last position and return to it automatically the next time it's used.

Here's a quick pic I took last night when I was testing the wiring. It's not very good, but you get the idea, anyway.

wow man, that is realy sweet, thanks for the tips too... do you happen to have any pictures showing the actual mechanisim?... I would want this for the housing alone, & rescreen it.... just wondering if I could rewire it too, maybe loose the micro adjustments, but open & close would still be pretty cool without the ibuss comunication end of it... either way, even with that, really cool... keeping my eyes open for one of these...

No pics, but I can take some after work today - I have another unit from ebay that arrived with part of the gearing mechanism broken. You'll get the idea from the pictures, though. There's not much to it really.

that's what I'm thinking, if theres not much to it, then it may not be too difficult to eliminate the need for buss communication entirely.... I briefly looked around on ebay, but haven't seen any of these at the moment... I'll keep these in mind, & if I can get my hands on one I really want to play with it

turbocad6 - sorry this took so long, been busy at work lately.

Here's a picture of the bottom of the unit. Vehicle wiring comes in through the left, passes through the screen housing itself, and then pops out on the motor side. You can see that the button wiring goes directly to the motor side.



Here's a shot of the motor side, you can see a bit of the gearing, etc.



Underneath the motor cover, there is a small board that attaches to the motor itself. The PCB contains two ICs - one is a very low drop voltage regulator from STI (LE80) and the other is a stepper motor controller (L9935). There are eleven lines coming into the header on the PCB. I imagine by studying the L9935 datasheet and following the PCB traces, it should be possible to figure out exactly what is needed to operate the motor independent of the ibus controller (it must be inside the actual screen housing). I also suspect that the ibus controller doesn't do much more than supply power to this control board when appropriate.



Of course, now the trick will be actually getting one. In the past month, there were several on ebay, but they seem to have dried up for the moment.

Okay, I take that back a bit. I looked up the L9935's datasheet and it's a stepper motor driver - it uses a serial input and controls the motor based on the data it receives. I would *guess* there's another chip responsible for this inside the monitor housing. So it probably isn't that simple to control independently as you would have to devise some software. It most likely would be much easier to leave the ibus controller intact inside the screen housing and use a PIC to send the key on/key off/stay alive packets.

Here's a short vid of the monitor operating - Z4 Monitor (changed servers - save target as)

It's not the best since I shot it at night using a worklight to provide some more light. I'll shoot another during the day at some point. Still have to fabricate a home for the powermate, but the software is working great!