Page 1 of 3 123 LastLast
Results 1 to 20 of 55

Thread: Understanding the factory CD and boot amp

  1. #1
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     

    Post Understanding the factory CD and boot amp

    Hi folks, this thread is intended to piece together information from fellow club members, other enthusiast forums and personal research. It is a work in progress and will be amended as time goes on.

    Part 1
    As some of you are aware, a small percentage of 8G VR-4's left the factory with an upgraded in-car entertainment system which comprised of a 10-disc CD changer, 4.1 amplifier and an 8" subwoofer, all of which located in the boot. @phosty took some excellent photos here.

    For those (un)lucky enough to have come into ownership of these cars, upgrading the head unit to an aftermarket model is fruitless without either installing an aftermarket 3ch/4ch amplifier or worse, running cables to all the individual speakers.

    The reason for this is because (on these particular) variants of the VR-4, the speaker wires do not terminate behind the centre console like in every car, they terminate in the boot under the spare wheel cover. You can buy a Mitsubishi-to-ISO loom and it will power up the radio, however you will have no sound. I found this out the hard way recently when I tried to upgrade to a Kenwood single DIN stereo.

    In these particular variants, the audio is sent separately to the amp in the boot by a 13-pin DIN connector like the following (rightmost connector);

    Mitsubishi Legnum Head Unit connectors.jpg

    After a bit of playing about, it became clear that audio from these factory upgraded head units was being sent to the amp in the back via a 13-pin DIN cable, so out came the multimeter and I started to try and find a way to replace this unit. This is what I found;

    === This information is incomplete!! ===

    1. Right Channel Audio
    2. N/C
    3. Left Channel Audio
    4. Audio Ground
    5. N/C
    6. N/C
    7. Remote amp (+12V when radio is on, GND when not)
    8. N/C
    9. +5V (data signal)
    10. +5V (data signal)
    11. Gnd (possibly for above)
    12. N/C
    13. +5V (data signal)

    === This information is incomplete!! ===

    So the first thing I thought of was "Can I feed audio into the amp if I power it up manually?", the answer was sadly no, even though I could hear the speakers quietly clicking when I turned the amp on and off with Pin 7, nothing came out. That's when I started to think about the serial lines.

    This is further reinforced by the fact that the audio coming from Pins 1, 3 & 4 was unaffected by the volume control / tone control / fader / balance. It was a constant line level output whilst the head unit was on (specifically the radio input but I imagine it would be the same for the tape).
    Last edited by foxdie; 11-11-2015 at 10:51 PM. Reason: Amended pin-out
    Want your car tuning? Here's my pricing
    Have questions about performance upgrades and ECU tuning? Before PM'ing me, Check this thread first
    Please support CVR4 & become a Full member, you get a full years access to guides, games, chat & much more!

  2. #2
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Part 2

    So after the events of the first post, I started messing around to try and build a line-in cable, I had some scraps (previous 13 pin DIN male-male loom and a newly purchased 13 pin DIN socket from ebay) and one iteration of this cable (with an incorrect pin layout) resulted in mono sound (or more specifically, that hollow sound from having stereo audio with no ground, each channel cancelling out the common part of the sound). What was interesting however was when I fiddled with the balance (or any of the controls) there was a rhythmic pulsing / clicking, further reinforcing the thought that there was some serial communication going back and forth between the head unit / amplifier / CD changer.

    After that, I started to do some deeper research. I managed to find a nice Google hit which outlines pinouts for a similar Mitsubishi head unit from a 3000GT / GTO which is as follows;

    === This information is not applicable to our cars!! ===

    WireHarnessMit121003.jpg

    === This information is not applicable to our cars!! ===

    Although this closely tallies up there is at least one difference; The ACC / Remote is Pin 7 on ours and Pin 6 on the above pinout for the 3000GT head unit.

    Mini-update: After picking up an oscilloscope for a good price from a friend, I definitely managed to establish the fact that there's some 5v TTL serial communication going back and forth between the head unit and the amp;

    sillyscope.jpg sillyscope2.jpg
    Last edited by foxdie; 11-11-2015 at 10:54 PM.

  3. #3
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Part 3

    Okay so the research lumbers on, I started today by trying to strip the head unit down to try and identify it's manufacturer, unfortunately the screws in the side of the head unit are virtually welded in place, even with the correct size screwdriver I managed to start to strip one of the screw heads, so before I did more damage I decided to skip.

    I did however take some photos where I could jam my camera phone, these are attached;

    head-unit-1.jpg head-unit-2.jpg
    head-unit-3.jpg head-unit-4.jpg

    Moving on, as you can see in the later replies I built a break-out cable to let me start debugging the protocol, unfortunately I haven't yet gotten the logic analyser but I did spend a bit of time playing around with the Oscilloscope and got something meaningful from it;

    amp-protocol-1.jpg

    Ch1 was connected to (I believe) pin 9 and Ch2 was connected to pin 13. The above graphs are taken whilst turning the volume up one notch, you can see that both channels start pulsing 5 times before going quiet again. After aligning with one of the messages...

    amp-protocol-2.jpg

    and then zooming in...

    amp-protocol-3.jpg

    we can see that Ch1 has a regular pulse and Ch2 has an irregular pulse. To me, this says that Ch1 is a clock base for transmission and Ch2 is the message being transmitted.

    Further digging into this protocol revealed this website (since gone offline but the Internet Archive has a copy) which starts to describe how the transmissions work but the protocol differs (theirs focuses on the Alpine implementation of M-Bus, ours may be Pioneer at this point).

    By the looks of it, we've got 8 bits being transmitted so 5 bytes, here's all of the messages in sequence;

    amp-protocol-4.jpg amp-protocol-5.jpg amp-protocol-6.jpg amp-protocol-7.jpg amp-protocol-8.jpg

    From what I can tell, the messages are as follows;

    Seq / Binary / Hex / ASCII

    1. 01101111 = 0x6F = o
    2. 11100101 = 0xE5 = å
    3. 01001000 = 0x48 = H
    4. 01111101 = 0x7D = }
    5. 11001111 = 0xCF = Ï

    Means nothing right now but sure it'll become clear with further investigation.

    Update: I've gotten the Logic Analyser working nicely and started to export the decoded data to a Google Spreadsheet here: VR-4 Head Unit to Amp to CD Player Protocol
    Last edited by foxdie; 18-11-2015 at 09:23 PM.

  4. #4
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Reserved for part 4.

  5. #5
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    i had a sub in the boot of my legnum but a previous owner had done the conversion to a standard single din head unit and they had discannected the sub abd amp in the boot and just cut the speaker wires and run cable directly to the individual speakers.
    i think this is the most straight forward way to do it, and if you want to connect the sub up in the boot you can run a pair wires from the head unit directly to the sub as most modern head units have a sub out connection on the back of them.
    if you want to run wires from the head unit to the boot, tape the new wires to the old 13 pin din cable before you pull the old cable out, then you will pull the new wires through to the boot as the old wire comes out.

    it all depends on if you want to reuse the old amp in the boot to drive the speaker, or replace it for a more modern amp.

    Bye for Now!

  6. #6
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Part 2 has been added.
    @Davezj yep that'll be the simplest option but isn't as fun as working out a puzzle or making use of something that can still do a good job with a bit of coercing

  7. #7
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    it is good to have a fun puzzle to solve. wish i had more info in it to help you on you way.

  8. #8
    Atik's Avatar

    Offline
     
    Name
    Atik
    Join Date
    May 2007
    Last Online
    04-03-2024
    Posts
    7,231
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    RVR HSGR
     
    Quote Originally Posted by foxdie View Post
    Part 2 has been added.
    @Davezj yep that'll be the simplest option but isn't as fun as working out a puzzle or making use of something that can still do a good job with a bit of coercing
    Jason, you are going to end up spending days and days working this out only to end up going and doing it the easy way
    1997 Mitsubishi RVR HSGR : 2.0 4G63T, 4 seats and the seating position from a truck
    2009 Ford Mondeo : 2.2TDCi, 4 wheels, some plastics, some metal and some seats
    Former owner of The Mongrel (RIP 2011) and The Rednum (RIP 2014)

  9. #9
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Quote Originally Posted by Atik View Post
    Jason, you are going to end up spending days and days working this out only to end up going and doing it the easy way
    Well, probably yeah, but as I've only got a budget of 600 quid to spend on the car I've gotta at least try

  10. #10
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Updated part 2 with a couple of photos

  11. #11
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    nice scope, show your waveforms, show me your waveforms.

    You can't hand my waveforms.

  12. #12
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Updated to reflect pin-out updates in Part 1 and remove incorrect information in Part 2.

    My car now has a working line-in by connecting some wire to pins 1, 3 and 4 above and using a bit of trickery;

    I connected a stereo Bluetooth receiver and was able to play music through, unfortunately there is no 'quiet' input so we can send audio without interference. Without a cassette tape, playing Bluetooth audio with the radio input on results in the the radio being mostly muted (Bluetooth audio overrides it, doesn't well mix it as one would expect) and the CD player input doesn't take any sound feed from the head unit whatsoever.

    I did find a nifty workaround though, you can trick the head unit into thinking a tape is present by doing the following;

    1. Gently lift the tape flap
    2. With the blunt end of a pen, gently and slowly push the tape eject mechanism (located towards the ceiling of the head unit) all the way in until it latches
    3. Then use the pen to gently rotate the closest spindle (the bit that turns the tape) for about a second
    4. That's it! Remove the pen slowly and enjoy

    This workaround even survives the input being changed and the radio being turned off with the ignition, but is totally reversible by just pressing the eject key. Win-win

  13. #13

    Offline
     
    Name
    Tomasz
    Join Date
    Apr 2015
    Last Online
    22-11-2023
    Posts
    508
    Country
    Other
    Location
    Lodz PL
    Car
    Legumina
     
    Looks like the headunit replacement is not possible unless the serial communication is understood and worked around, am I reading this right? You may want to look into acquiring a Logic for that - https://www.saleae.com/
    The more you know, the faster you can go. And I still don't know enough.

  14. #14
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Quote Originally Posted by Grid View Post
    Looks like the headunit replacement is not possible unless the serial communication is understood and worked around, am I reading this right? You may want to look into acquiring a Logic for that - https://www.saleae.com/
    Correct, the amp will not output any audio if you simply turn it on by setting Pin 7 high, it needs to be told what the settings are (volume, tone etc) before it will work, presumably to stop speaker popping.

    As for a Logic Analyser, already got one on order

    Once the protocol is captured, I'm thinking it'll be possible to build a small and cheap PCB with a microprocessor on-board to 'play back' the first init commands to turn the amp on and set the volume to maximum, then use the volume control on the new head unit to control the volume.

    The only potential issue I can foresee is there's no tone nor fader / balance control, I could probably decode the entire protocol and build a replacement controller that could fit in the glasses holder or a single DIN slot without too much effort, I'm thinking of possibly using an ATTINY84 in either case but with that many inputs / outputs I could easily build a front-end

  15. #15

    Offline
     
    Name
    Tomasz
    Join Date
    Apr 2015
    Last Online
    22-11-2023
    Posts
    508
    Country
    Other
    Location
    Lodz PL
    Car
    Legumina
     
    Arduino path is probably right, easiest to jump into. It's worked for me for a few pet projects (unfinished ones... sigh). Exciting stuff! Wish I had a VR-4 amp to play with, but my Regnum came pretty much bog standard from the factory.

    These are the microcontrollers I've dabbled with so far:
    https://www.arduino.cc/en/Main/ArduinoBoardProMini
    http://lowpowerlab.com/moteino/

    This one is a cheap cheap Arduino clone to go with your Logic ;-)
    http://www.aliexpress.com/item/10pcs...277170712.html

  16. #16
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    It is an interesting project but time consuming and costly when you cold buy 10m of speaker wire chop it at the head unit and run the new wire to each speaker. Could be done in about 2 hours realistically,
    But I know what you are like when you get the bit between your teeth Jason .
    Just keep pounding away until you get satisfaction. Lol

  17. #17
    foxdie's Avatar

    Offline
     
    Name
    Jason
    Join Date
    Jan 2008
    Last Online
    Yesterday
    Membership ID
    518
    Posts
    5,030
    Country
    United Kingdom
    Location
    Birmingham, UK
    Car
    Silver PFL VR4
    My Garage
    Visit
     
    Quote Originally Posted by Davezj View Post
    It is an interesting project but time consuming and costly when you cold buy 10m of speaker wire chop it at the head unit and run the new wire to each speaker. Could be done in about 2 hours realistically,
    But I know what you are like when you get the bit between your teeth Jason .
    Just keep pounding away until you get satisfaction. Lol
    I'm not really doing this for me, I'm doing it for future owners who may want to follow my steps




    Okay okay I'm doing it for me

  18. #18
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    sorry mate could not resist it, you have to keep your capacity at max, and dont induce any errors.

    i am so funny it kills me, i get my coat.

    you keep going jason, it is worth getting to the bottm of the issue. and sorting it out, i give you a great sense of achievement.

  19. #19

    Offline
     
    Name
    Tomasz
    Join Date
    Apr 2015
    Last Online
    22-11-2023
    Posts
    508
    Country
    Other
    Location
    Lodz PL
    Car
    Legumina
     
    Dave though to tell the truth this is about demystifying a rarely seen option in a car that's rare as hens teeth itself. Like I said before - exciting stuff!

  20. #20
    Davezj's Avatar

    Offline
     
    Name
    Dave
    Join Date
    Jan 2006
    Last Online
    09-01-2024
    Membership ID
    255
    Posts
    16,245
    Country
    England
    Location
    Manchester
    Car
    VR-4
    My Garage
    Visit
     
    Just thought I would throw this one out there, is the protocol likely to be CANBUS or at least an early form of it.

Page 1 of 3 123 LastLast

Similar Threads

  1. Factory Fitted Amp?
    By n13l pm in forum General / Questions
    Replies: 7
    Last Post: 21-08-2009, 06:06 AM
  2. Factory boot floor protector
    By Hipsi in forum General / Questions
    Replies: 1
    Last Post: 16-04-2008, 08:05 AM
  3. Dog Guard Boot liner & boot liner on ebay
    By peter thomson in forum General Chat
    Replies: 10
    Last Post: 26-07-2007, 11:03 PM
  4. FS: NZ, Factory Wheels & tyres
    By Xeroid in forum NZ Parts for Sale / Wanted
    Replies: 5
    Last Post: 01-10-2004, 06:22 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •