MOST Bus exploration using a raspberry pi

[Rhys_Morgan]

I’ve been working on getting some kind of integration to the MOST bus on my jaguar XF and Land Rover Freelander 2, thought it might be of interest here



A bit of back history, for a long time I’ve been trying to replace the factory head unit (3 years and counting project so far!) in that time I’ve moved between developing an app integrating canbus, to developing react-CarPlay to be able to run CarPlay on Linux based systems. Throughout the entire thing the MOST bus has been a massive blocker, no hardware or projects are really out there that have tackled it, so finally a couple of months ago I set about it.



It started with a hacked up breadboard with a repurposed os8104 and MOST transceiver, then moved to a v1 of a custom PCB.





This one was very much experimental, but it worked, so I started writing the multi layer drivers for it (all written in nodeJs at this point)



Using the breakout header at the bottom I managed to get audio injection working using i2s from the pi. The beauty of this is it doesn’t use the awful clocks on the pi, but rather the clock source comes from the MOST network, running at 48khz on the jlr brand.



This then gave birth to v1.1






Which now has the header removed and traces run to the i2s GPIOs, it also has a can channel running too.



Currently implementing the standard fblocks for cd player, amfm tuner etc and hopefully a final version of the board which will handle power on/off based on most network activity in low power mode. Quick example video below of it integrating the OEM cd player

[jakesmith]

I thought Dension used to make a MOST interface
Audison still do, expensive tho, google the Audison Bit DMI

[Rhys_Morgan]

Yeah there are a few bits of hardware out there that can handle extracting audio for external amps, mobridge also do similar. Whilst this can handle that, it also gives access to all the control on the network, and also being able to grab microphone input etc etc

[jrb43]

Very well done. Also a problem in Porsche. Please keep us informed of progress - you won't sell millions but there is a market!

[Bodo]

Nice work. In the early days of my first full time job, I've developed MOST oPHY applications for fibre optics. Both yours look like MOST 25.

[tim2100]

jrb43 said:

Very well done. Also a problem in Porsche. Please keep us informed of progress - you won't sell millions but there is a market!

Was thinking the same. I am amazed there hasn't been an alternative solution for this.

[carbonblack]

Really interesting stuff. It’s quite frustrating that all of the very limited MOST equipment you can buy seems to be pretty much limited to a decoder to use with aftermarket amps….


This looks really cool!

[Rhys_Morgan]

Bodo said:

Nice work. In the early days of my first full time job, I've developed MOST oPHY applications for fibre optics. Both yours look like MOST 25.

Very interesting! Have you retained any of it??

Small update in the board itself, finally managed to get power from 12v converted down to the pi. When it detects activity on the MOST network it powers the Pi up, then when activity drops off, it then powers off the Pi, 30 seconds later it cuts the power, standby current at 0.5ma.

[dvs_dave]

Audi/VW/Porsche generally have a decent MOST bus aftermarket. Best ones currently are the Mr12volt interfaces. Wireless CarPlay/android auto that sit on the MOST bus ring with factory infotainment and steering wheel control integration and video “injection” into the OEM screen. Excellent bits of kit.

If you’re handy with this sort of thing it probably wouldn’t be difficult to hack it to work with JLR systems.

https://www.mr12volt.com/