Thread: M-Bus CD changer adapter for car pc integration

I'd like to see this i have a volvo v50 do you know how hard a job it woul be?

Originally Posted by palta

I do not think a MOST adapter is very feasable. It is not easy to interface to an optical network and I'm not sure people driving those fat BMWs and mercedeses are the people who will add a custom made device to their car.
However jbors, if do decide you are going to make an interface and if you need any help pm me because I do have quite a lot of experience with MOST.

BTW personally I want to know more about the bus used by Toyota.

Patrick

Hi Palta

Thanks for this

It was the disruption of the ring that was my concern when reading Volvo's technical specs and dependencies on the system. I figured if this was not done 100% it may impact on other systems including the maintenance system I read about that goes round checking the components of the BUS. Would this be the case?

My concern is that any non Volvo specified component that may effect the other components on the system would be recorded and effect the warranty of the vehicle. Does this seem feasible?

I know that there is an iPOD interface coming soon to the UK and this is available in the US. My other thought was to get a PC to emulate the iPOD interface and connect into the Volvo iPOD interface similar to other ideas put forward on this thread.

Originally Posted by palta

It will be dificult and a lot of work.

First of all you need connector with a builtin optical to electrical convertor. This is not something you can make yourself because the transmittor and receiver need to be properly alligned (it is not so critical as glass fiber but still). Futhermore the sender must not transmit to much light and the receiver must sensitive enough.
Then you need to decode the datastream which is 25 MBit (biphase coded) containing up to 60 audio channels (44.1 khz 8 bit) or 15 audio channels (44.1 16 bit stereo), it can also contain async data (but that is probably not used in a car system) and control messages. You need to decode but this is not possible with a simple ucontroller/PC. People are busy making FPGA implementation but I do not know how far they are. Best is probably buying some IC which is able to do this. There are standalone transceivers and micrcontrollers with builtin MOST, DSP, uC, ADC/DAC (the original designer of MOST Oasis makes these part, but othe companies are also busy). I do not know it is possible to get single parts of these components.
You also need to make software to commicate with your radio. This is possible as the specification of the protocol is standard and can be found on the internet. This will take time but not impossible.
Some warning is in place: MOST is a bus system so you have to take care that your device behaves properly (especially on a hardware level) because it is possible the desturb the ring. It is however not very easy to break the other components permenantly.

Feel free if you want more details.

Patrick

Sorry my only experience of MOST is from Volvo's Service application VADIS

They state that there is a maintenance packet sent around the system that checks on the system. I was concerned that there may be components in the system like the seat belts which are connected to the system and maybe the airbags that might be connected. I know that you recieve messages from the MOST BUS on an LCD that reports seat belt information so I presume that airbags may be on the same system. This being the case? If the adapter caused issues under testing would simply disconnecting it and restarting the car cause any issues to go away?

I see you say that it only happens during the time that the device is connected so that should mean that my worries above are for no reason. However will the MOST BUS record the connection of that device.

I'd like to see a PC adapter for MOST and would be willing to pay? how much would you say that a retail version would go for?

Thank you for your response and please excuse my delayed response and lack of knowledge on the MOST BUS. I am very interested in it's design and functionality.

Originally Posted by palta

Hello,
If the hardware you use is ok and the software you use doesnot behave too bad (like sending too much messages) the other component will work ok. If your hardware is not ok it is possible to influence the other components because it breaks the ring. There should be no critical systems on the bust (like ABS) only multimedia components. I'm not sure what you mean with maintenance system. The MOST master will check the bus if it gets desturbed to check where the ring broke but if you added a new component it should just use it.

In the MOST function catalog there are functions available that give you the data of the manufacturer of a device (but that you have to implement yourself ofcourse). So they could record the connection of other devices. MOST is designed to be a standard so you should be able to connect other devices. I do not think you can void the warrenty of your vehicle by connecting something to your audio system (that is illegal). Futhermore you cannot break devices by connecting something in the optical ring only desturb it during the time the device is connected.

With respect to the ipod interface you can find the information here:
http://www.oasis.de/files/Newsletter...r_V_I-2005.pdf
As you can read in the newsletter the reference design is free of royalties but I do not think Oasis would like single users to contact them. Futhermore you still need the components I mentioned in an earlier post.
Oasis also has MOST PC-cards but I do not really remember the price (I think it is more than 500 Euro).

Patrick

This sounds just how it works with the Volvo. I believe that Volvo does have a recording device for something as they state very clearly that any issues with the car that are recorded could be given to authorities if they should request them ... in so many words.. Unless this is another part of the system again separate from the MOST BUS. I do not know I am makeing assumptions from watching vehicle operations, Reading VADIS and the car manual.

I will follow up your link I'm desparate for a module I can plug in and get the PC connected... but I'll make do with FM for the time being.

Thanks for the help Palta! appreciated

Originally Posted by palta

I have experience with the MOST bus but do not know exactly how Volvo uses it.

With respect to the safety belts, airbags and other critical devices; MOST is not developed to control these. I think they are only connected to a device in the MOST ring to be able to display messages.
Problems you cause by experimenting with the MOST bus should go away when you disconnect the device. The MOST bus doesnot record anything. It possible to create a device that can record these events and store them in some kind of memory but I do not think this will be the case (what will the company gain with this effort?)

There are some interfaces used for development of MOST devices (.e.g. http://www.oasis.de/eng/content/view/181/228/ ) but I do not know what they cost (it is certainly more than 200 Euro because that costed a driver update if I remember correctly) and if they will sell these things to private persons.
I'm not sure if there is a big market for a MOST interface but if somebody wants to build one I can help.

Patrick

I did not try that circuit but pretty sure it works.
You can grab schematics for my adapter somewhere in this thread and it works for sure
If you just want the adapter and no wires then it will be pretty small package. I think will be $8 and adapter itself $40.
BTW: I can send you the pic program as well.