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Thread: Control of E39 DSP system via iBus - fantasy?

  1. #1
    Join Date
    Jul 2016
    Location
    Kent, UK
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    3
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    2002 BMW E39 M5

    Question Control of E39 DSP system via iBus - fantasy?

    Hi folks, I am thinking of doing the NBT retrofit into my E39 M5. I have the DSP audio system and I understand that after the NBT retrofit the audio should still work although I will lose control of the DSP itself.

    I'm new to hacking BMWs, but I have a question for the audio/iBus gurus out there.

    I'm sure I read somewhere that the DSP is controlled by iBus messages, so would it be feasible to capture these messages from a working car with DSP, and then build a simple device to allow sending these messages when the old head unit has been disconnected?

    This might allow independent control of the DSP even when a non-standard head unit is installed.

    I have just got Rolf Resler's USB iBus interface (not connected yet) and I was wondering if that could be used to sniff the iBus messages being sent to the DSP.

    Does this sound feasible?

    Cheers,

    Charlie

  2. #2
    Join Date
    Sep 2008
    Location
    West London/Heathrow - UK
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    6,342
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    03 530dT - Ex Police Car
    Hi Charlie,

    Anything is possible given enough money! related to that, given enough time, effort and feasibility.

    In this 'idea' then I'd say it's not worth it at all. 'DSP' or 'Digital Signal Processing' became popular in consumer electronics in the mid 90's. It'd be things like Church, Stadium, jazz club type 'sound effects' it was commonly used for. This is when the E39 was being designed, so they included it. By the late 90's DSP for those sound effects had fallen out of fashion generally speaking. However, for the E39, these audio modules remained in the cars and now, 16+ years later, car's like yours still have them working! Due to the relative 'few' E39's which came with DSP, nothing from the quality and reputable car hifi aftermarket specialists was ever made due to that low level of demand. Over time, the oem DSP amplifiers become more flaky and faulty, and the oem DSP speaker drivers deteriorate with UV exposure and temperature and humidity extremes. They weren't exactly great when brand new either.

    So your idea here is of course possible, but practically, it's going to be very expensive to develop and test to make sure it works properly. Building a 'simple device' is easy to write/type/speak, but the reality is it's still going to be a complex project which will require a deep level understanding of the protocol required. There's quite a number of amateur BMW enthusiasts who perhaps do know and can perhaps work/make something for you, but you'll have a uphill struggle to convince them to work on the project. An easier way around that is to perhaps pay them a decent consulting rate for doing the R&D and building a prototype etc.

    The 'best' route for you and perhaps other's considering this NBT retrofit to earlier BMW's, is to use a dedicated high quality sound processor and then similar high quality amplifiers to then drive upgraded much better sounding speakers. All the products exist, are excellent quality and you'll also get a significant increase in sound quality compared to the 'idea' you are thinking.

    So, units like processors from JL Audio, Audiocontrol, Alpine, Audison, JBL, Rockford Fosgate amongst others will take the audio output from the NBT (I'm currently assuming the NBT unit has a built in amplifier) and it'll 'clean' that output by removing the factory pre-set Equalization curve, boost the output voltage and ensure a non clipping signal no matter how much into distortion you drive the oem in built amplifier. That 'clean' signal is then fed to your choice of either a 4 channel amplifier and a mono subwoofer amplifier or a single 5 channel amplifier. The output from there would go to upgraded 2 way component speakers in the front of the car and 2 way co-axial speakers on the back shelf. The subwoofer channel would go to perhaps an 8/10/12 inch subwoofer in a small sealed enclosure to fit up against the rear seat bulkhead and 'fire' the output through the ski hatch - this would give you 100% bass transmission into the cabin of the car, no rattles or vibrations of the bootlid/number plate.

    You'll not have the church and stadium effect settings going the route above though!

    Cheers, Dennis!

  3. #3
    Join Date
    Jul 2016
    Location
    Kent, UK
    Posts
    3
    My Cars
    2002 BMW E39 M5
    Hi Dennis,

    Thanks for the reply.

    This would only be a hobby project for me, I'm a software developer who likes tinkering, so the only real costs are my time and maybe some small amounts of hardware.

    Reading around iBus a bit more it sounds like it might work, so I'll be playing around with my Resler interface to see if I can control the DSP from my laptop and if that works then I might look into a dedicate Arduino-based solution.

    All I'm after is a few buttons to allow sending basic commands to the DSP, it might fill in some of the missing features when using a non-standard head unit.

    After all, I can always come back later and replace the whole DSP/speaker setup, but something like this might allow more enjoyment of the existing setup for a while first.

    Cheers,

    Charlie

  4. #4
    Join Date
    Sep 2008
    Location
    West London/Heathrow - UK
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    03 530dT - Ex Police Car
    Hi Charlie,

    Thanks for the update from your side and thoughts!

    I will drop you a PM via bmw5 !

    Cheers, Dennis!

  5. #5
    Join Date
    Jun 2015
    Location
    Dallas
    Posts
    13
    My Cars
    TBD
    arduino to ibus is fairly easy. I recommend the L9637D interface chip for connecting the microcontroller i/o to the iBus lines. I believe the audio is unbalanced consumer line level so interfacing to phone/mp3 players is simple

  6. #6
    Join Date
    Dec 2018
    Location
    California
    Posts
    1
    My Cars
    BMW E39 528i
    Did the Resler interface ever work to spoof the DSP so that you could get audio out of your aftermarket head unit?

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