DIY Bluetooth mod for OEM E36 radio

[johann3s]

Introduction

Most of you probably know that there are a lot of bluetooth available for BMW stereo's from brands like Yatour and GROM. The problem is that these are only available for stereo's newer than around 1996, when the radio has the IBus protocol. I also wanted to have an OEM look in my car as well as bluetooth. The problem is that the head units that support this for the E36 are (because of that probably) quite expensive and easily more than 300 euros. At that point I got an idea, why not make this myself for an older and therefore cheaper radio.

There are ways to do this by opening up the radio and soldering some wires to replace for instance the tape deck. But what I wanted to do was something different, and exactly like the commercial modules, only use the CD changer port, so that there is no need to open the radio and the bluetooth functionality will be plug and play. The additional benefit of this is that it could give me the option to use the buttons on the radio for playing/pausing the music, and changing track.

So I did, and I bought the following components:



Philips PH7850 aka BMW Business RDS and its CD Changer:





Tinkering


All right! After some time playing around with my messy test setup I came to some results. The radio is playing my music in CD mode, even though I disconnected the CD changer plug! I have some limited possibilities to change text on the display of the head unit and I can listen to the buttons (see the computer screen)

jMGUrZul.jpg lauzDifl.jpg







Result

Zw7MJQ2l.jpg Uda2NQGl.jpg

The prototype shown here is currently installed in my car, and gives me the possibility to play bluetooth music on my stock head unit. I also have the possibility to play/pause and change tracks. Pretty sweet .

The next step will be to design a custom PCB to integrate these functions in a somewhat nicer design. More on that later!

[e30luv318i]

Great work ! I’d be interested in one! I always wondered why no one made an aux for the round plug cd changers

[Singing6]

Because the audio is much better from the post 96 head units.


Sent from my iPhone using Tapatalk

[franco90]

nice

[dudu850]

Interested !!! Please, let us know if you have some advance about this.

Best

[johann3s]

Interested !!! Please, let us know if you have some advance about this.

Best

Thanks for all the feedback . It has already been silent for a while, but that does not mean there has not been progress. Especially with these PCB's and electronics parts I have to wait for parts and shipment before I can continue.

Like I mentioned in my first post I was working on a custom PCB to do these functions, and so far I have partially succeeded in this.

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As you can see the build of the PCB has been succesful. I also have been able to use the first prototype to test that the head unit still enters CD-mode, and I have also been able to play music over the speakers. This means that the design seems to be ok. Somewhere at that point I made a short circuit by accident destroying my first prototype.

I have not been able to get my second and third prototype to work. The main reason for this is the chip on the left side. That one is just too small to be 'hand soldered' reliably. Furthermore, it has no exposed pins, so once it is in place I have no way to validate that everything is connected correctly to the chip.

At that point I decided to change my design to a different component so that I do not need to rely on the small chip anymore, and I can more reliably produce the next version. Currently I am still waiting for the parts for this updated version. See the two designs side by side below.

MYSyPFW.jpg 9xw9LOH.jpg

[dudu850]

Thanks for the update. Please, keep us posted.

[johann3s]

Small update: I made the second version of the PCB with the larger component as described in my last update.

So far I have tested Bluetooth audio and CD Changer hack functionalities and everything seems to work great! The only issue that I still have is that the board is getting too hot when I apply 14V. So far I had done all my testing at 12V, but this means that in the vehicle there would be an issue. I will make some changes to the power supply side of the board in version 3 and after that everything should be finished hopefully .

IMG_20191124_174836873.jpg

[dudu850]

Small update: I made the second version of the PCB with the larger component as described in my last update.

So far I have tested Bluetooth audio and CD Changer hack functionalities and everything seems to work great! The only issue that I still have is that the board is getting too hot when I apply 14V. So far I had done all my testing at 12V, but this means that in the vehicle there would be an issue. I will make some changes to the power supply side of the board in version 3 and after that everything should be finished hopefully .

IMG_20191124_174836873.jpg

Hoping to see the final product. Would a Zener Diode work ?

[keliuss]

Any update on this? Also interested.

Keliuss

[johann3s]

Thanks for your interest. The coming months will be quite busy for work, so I am afraid I can't finish this until March, but I will keep this thread updated! In the meantime I have put some more detailed project logs online here:

E36 Bluetooth

[keliuss]

Thanks for the link. Your project blog is pretty interesting, but definitely outside my sphere of knowledge lol. I have it bookmarked and await the next update
My PH7850 is in my project car so not in daily use. I'm in no rush to implement an Aux/BT solution so will watch this space. I had considered buying a cd changer myself and trying to implement some sort of "silent cd" workaround by tapping into the units L/R outputs, which of course is a whole lot less elegant than your solution.

Merry Christmas

Keliuss

[runnr548]

Wow! We are waiting for an update. This is very interesting and difficult work.

[MarcoZandrini]

How about a DC to DC converter. Check www.mouser.com.

[johann3s]

Finally after a long silence I have been able to continue this project to implement Bluetooth audio on my old BMW. An updated version of the PCB has arrived which fixes the issues in the previous design. Now that we have a final hardware version, there are a few minor tasks remaining on the software side, but then the project should be finished .

Read more


third.jpg

[keliuss]

Finally after a long silence I have been able to continue this project to implement Bluetooth audio on my old BMW. An updated version of the PCB has arrived which fixes the issues in the previous design. Now that we have a final hardware version, there are a few minor tasks remaining on the software side, but then the project should be finished .

Read more


third.jpg

Great to see some more progress with this and an interesting read on your blog. I hope you will be able to offer something for sale soon. Keep us posted

Keliuss

[keliuss]

For anyone following this, Johann has updated his blog https://maakbaas.com/bluetooth-cd-changer-emulator/

A setback due to alternator whine, so a complete redesign. An interesting read.

Keliuss

[wabazuza]

Following this thread , looking forward to see the final result soon (and drop some cash too) and I'm looking to replace my FM transmitter on my CD43 with a proper bluetooth solution.

[keliuss]

Johann has updated his blog and is offering a product for sale. You can use the link I posted above.

Keliuss

[johann3s]

@Keliuss: Thanks for keeping this thread updated .

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And indeed, I finally have a product that I am happy with! It has been working great in my car over the past few weeks, and since the adapter generated quite some interest, I decided to offer it online.

For those of you who are interested, click here for the shop where you can buy the adapter including a small case and the correct cable.

[johann3s]

Just as an update to this thread: this week I got the adapter working for the KE-91ZBM as well. This might be interesting to you guys, since I believe this is a more popular head unit in the US market as compared to the radio units that are offered in Europe.

Check it out!

https://maakbaas.com/shop/bmw-bluetooth-adapter/