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Subaru Radio Digital Control Data Decoded


jazzymt

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Ok - first off - don't get your hopes up. I'm not sure how much farther I will take this, but after years of on & off working on this - being shelved multiple times due to busy life/jobs, etc. Check this out:

 

Using a logic analyzer I decoded the data protocol for the CD changer & radio (this was a royal pain). Then I programmed a microprocessor to read & display the data.

 

2011-11-28_20-54-47_833.jpg

 

Yay - it works!

 

[ame=http://www.youtube.com/watch?v=nPzIBVECkTs]Decoding Subaru Radio Data - YouTube[/ame]

[CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER]
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I'm not sure if no one understand the significance of this or if just nobody cares anymore.

 

For those interested - the reason this is significant is because this can be used to both capture commands (like track fwd/rwd, etc.) and send phony info to the radio (like track time, number, etc.). In short - it can be used to fool the radio - negating the need for a silent CD - and it can be used to control an external device.

 

My plan right now is to continue development using a bluetooth chip so that you can stream music to your stereo with no external wires or soldering. Any device capable of sending audio via A2DP would be compatible. It also wouldn't be very difficult to add a provision for a mic and provide hands-free bluetooth calling capability through the stereo.

[CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER]
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Great work!

 

That also means one could build a fairly basic device that only fools the HU enough so you can use the CD changer port as an aux input. Interfacing to/from an iPod would just be icing.

 

I wonder how many other Subaru HU models use that same protocol.

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Great work!

 

That also means one could build a fairly basic device that only fools the HU enough so you can use the CD changer port as an aux input. Interfacing to/from an iPod would just be icing.

 

I wonder how many other Subaru HU models use that same protocol.

Fooling the headunit so you don't need a silent CD should not be very difficult at this point. I'm still debugging all possible messages (there is one when loading a CD that still interrupts comms that I'm working out) but I'm nearly there. Once it's purring like a kitten, I'll try it out on some Legacy radios I have. I assume they're very similar if not identical - but the MP3 version could be interesting since it has to read a lot more info (and text).

 

A2DP should be fairly straight forward at this point too. I've found a couple combinations of microprocessor/radios that have what I need. It's not the cheapest route to go, but it's the only sensible way for a do-it-yourself project.

 

Interfacing with an iPod is not going to be possible anymore though. A few years ago Apple locked down their products with authentication chips so that you can not develop an accessory for them without paying the Apple tax. If you're an iPod owner - you may recall the sudden need to buy all new adapters & higher prices for all Apple accessories. I wouldn't mind paying that per-item royalty really, but developing a MFI (made for ipod) accessory also has an entry fee of about $20-50k due to the required 3rd party testing prior to Apple's blessing. That ain't gunna happen.

 

I *could* buy a more expensive bluetooth module that has MFi approval so that you could stream music from your iPhone/iPod (bluetooth is also locked down with authentication), but I'll likely just continue with the 3rd party cable I'm using now for Apple users.

[CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER]
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I think I have it running pretty good now. I changed some things up to handle the corrupted packet created when loading a new cd. Showing several radio functions including loading a CD, track up/dn, changer cd's loaded, etc.

 

Maybe this weekend some time I will grab a Legacy radio and see if I'm on the same page there or if I have to start over.

 

Also hoping my bluetooth chip shows up tomorrow and I can get started on that part (A2DP) once the Legacy radio's are in working order. UPS is starting to piss me off though - delayed delivery 2 days in a row now.

 

Until then..

[ame=http://www.youtube.com/watch?v=RvRkGJ-aBl0]Subaru Radio Decode Part2 - YouTube[/ame]

Edited by jazzymt
[CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER]
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Well the overwhelming lack of interest isn't exactly encouraging. Thanks for the couple that have posted. If anyone else is even remotely interested - please say something so I know you're there.

 

Until then - I guess I'll just keep going since I'm actually making progress. Here's a radio you might all recognize a little better. As I suspected - the CD changer module is identical and the communication protocol is too - without any changes I'm reading the Legacy GT CD changer with no problems.

 

Next I'll take a look at an MP3 changer & try to figure out A) How does it communicate title text, etc. B) Is that protocol also universal and can I display text on a non-MP3 radio?

 

[ame=http://www.youtube.com/watch?v=8FFf4-3JJ08]Subaru Radio Decode Part3 - YouTube[/ame]

[CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER]
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How good do you think A2DP sound quality will be compared to the built-in Subaru aux input on 07+ radios? I have A2DP through my iSimple Gateway right now, but I rarely use it because sound quality kind of sucks. :rolleyes: I'd ditch that and get some other A2DP product (e.g. yours) if I can get better sound quality.
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Here's a radio you might all recognize a little better. ...

 

Yeah, baby! Now you're on to something "modern" enough to be interesting! ;)

 

With that HU, your research may solve a problem that some people in Europe have: On EDM models, when you remove the factory HU, the OEM nav display unit stops sending the audio turn-by-turn prompts.

 

EDM models use the 20-pin CD changer bus for that audio (instead of the i88 harness in North America).

 

So your work should provide the starting point for a person to figure out how to "trick" the nav display into thinking the OEM HU is still present. It will probably require "eavesdropping" on that conversation to find out what the HU says to the nav display. I'm hoping it's only something sent at power-up.

 

 

Next I'll take a look at an MP3 changer & try to figure out A) How does it communicate title text, etc. B) Is that protocol also universal and can I display text on a non-MP3 radio?
.

The MP3 data is interesting. Do you know whether the external changer bus has that capability? It may only be the HU's built-in changer that can do that. (Think about how people have complained that the HU doesn't display very much text from the OEM sat radio tuners and iPod interface).

 

I'll bet the non-MP3 HUs will only show basic track #/time.

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Wow - for awhile there I was beginning to think everyone was in hibernation. Thanks for all the posts everyone.

 

Regarding the European (and all other overseas Subaru radios) - they're all manufactured by Kenwood instead of our Panasonic radios so I'm sure everything is different unfortunately..

 

Regarding the A2DP sound quality - I'm not sure what to expect - I'm not even sure what the sound quality is dependent on (transmitter or receiver or both?), but I have heard *very good* quality A2DP and *bad* A2DP so I know good is possible. I'll be sure to thoroughly test and offer my subjective opinion on the module I chose as soon as I can. Also the bluetooth module FINALLY came in from UPS yesterday - and not a moment too soon seeing as it's raining again and my road is already nearly impassible. My dad is also visiting from out of town so I'll probably cool development for a few days, but I am eager to start playing with this little chip and will be sure to post more once I have it up and running.

 

Regarding text - I'm certain the changer is doing all the MP3 decoding and text reading - what I don't know is if when it sends that title info to the radio, it's in some universal format that non-mp3 radios would still understand and be able to display text too...only time will tell. It's possible non-MP3 radios are not programmed to understand the text data, but my hope is that they're all just programmed the same and the only difference is the CD changer. Even without text - basic next/prev control and track data combined with automatic handling of input source would be a nice improvement over the current solutions.

[CENTER][URL="http://legacygt.com/forums/showthread.php?t=18504"]Subaru Plug & Play Aux-in Mod[/URL][/CENTER] [CENTER][URL="http://www.jazzyengineering.com"]www.jazzyengineering.com[/URL][/CENTER]
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A2DP sound quality is definitely dependent on the transmitter. With my iSimple, iphone 4 sounds horrible over A2DP. But with Atrix it sounds just as good as using the factory aux-in.

 

It would be interesting to have a bluetooth module that isnt as clunky as the iSimple. The iSimple supports AVRCP for remote commands, but does not allow metadata for displaying song info, which I would love to have.

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A2DP sound quality is definitely dependent on the transmitter. With my iSimple, iphone 4 sounds horrible over A2DP. But with Atrix it sounds just as good as using the factory aux-in.

 

It would be interesting to have a bluetooth module that isnt as clunky as the iSimple. The iSimple supports AVRCP for remote commands, but does not allow metadata for displaying song info, which I would love to have.

 

The AVRCP is also a little buggy, from my experience. Whenever I shut off the car (i.e. when I un-pair BT), my phone starts playing music, even if I was using my iPod as the music source rather than the phone.

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