DIY Bluetooth Retrofit CM5908

[bbowman]

Yeah it looks like the board I used is not on Amazon anymore. Here is an alternative from ebay: https://www.ebay.com/itm/Bistable-fl...N/383925888555

Note that as described in the write-up this is only necessary if you have a momentary switch you are trying to convert into a latching on/off signal. I'm not sure if this is the case in your Pioneer radio. You could also just add a plain old SPST switch to turn on/off the bluetooth module.

Also - i'm pretty sure there are places you can recover your CM5908 code from (maybe this one? https://www.radio-code.co.uk/bmw-radio-codes.html i've never used it so could be fake). So if you did want the OEM glory of the CM5908 I think there are some solutions for the code issue.

[captain confused]

This is awesome and great timing. I am doing this same thing to the Pioneer Ke-83zbm since i dont have the code to my CM5908. I even have the same BT receiver you all bought from amazon. Im glad what i was thinking works after all!

The link to the volume knob switch doesnt work anymore. does anyone know what the item is?

[eternal24k]

Oh man, you all are motivating me to see if I can get bluetooth installed into my Clarion

[tyeler18]

Once again thanks BBowman for the write up. I wanted to add to this for anyone wanting to simplify a little bit. I installed this module in my radio using this writeup and so far its been working flawlessly. It's wired through a switch which I can confirm works perfect based on his diagram, rather than the volume knob. It doesn't require a signal converter or latching relay this way which made it very easy. It has a 3P audio hookup on the board with a pigtail. The power and ground are both friction lock similar to old home stereo systems, but they hold very well. Sound quality is great with it too. It has preouts for an amp or you can use a USB charger to power it, also has expansion modules on amazon to run 50x2 amps and a few other modules you can daisy chain in easily if you wanted

link to the module I used: https://www.amazon.com/Bluetooth-DRO.../dp/B07P94Z9XR

Untitled by Tyeler Andersen, on Flickr

Untitled by Tyeler Andersen, on Flickr

[ZeKahr]

Wow this is super clean! I ended up gutting my radio and sticking a bluetooth amp in it.

[Mike36]

"Very nice!"
-Borat

[bbowman]

My cassette deck belt finally broke on my Alpine CM5908 radio in my 91 vert, so I figured it was time to upgrade. I really love the look of the OEM radio, and I didn't really want to have to replace it. I considered just replacing the belt in the cassette player, but I was tired of using those janky casette-to-3.5mm adapters. So I decided I wanted to try to retrofit Bluetooth into my CM5908 radio. I found some options online, but didn't find any that fit my desired use case. I was after something that was (1) simple, (2) cheap, (3) DIY, (4) retained radio receiver functionality, (5) reversible if I ever wanted to go back to the cassette deck. This is what I came up with.

The design is very simple. I just took out the cassette deck, and did the bare minimum in order to get the Bluetooth module to function in-place of the cassette deck. This means there is no extra integration with the radio display/buttons. The only thing you can do from the radio itself is enter/leave cassette mode (aka Bluetooth mode). In order to do this from the radio itself, I disabled the original volume-knob push-button functionality (I'm not even sure what it did originally), and I used that as the way to turn on/off the Bluetooth mode of the radio. I figured some people may not want to do this, so I also designed a simpler version which uses a simple external SPST switch to enter/leave Bluetooth mode.

Here are the main required parts. Note that for most of these, there are many options that will do the job.



Bluetooth receiver:
These are the ones I bought. They work great. https://www.amazon.com/gp/product/B07W4PJ469

12V to 5V converter:
I harvested mine from an old car USB adapter. Other options would be: https://www.amazon.com/HiLetgo-LM259.../dp/B00LTSC564 or https://www.amazon.com/PoiLee-10pcs-.../dp/B07FS73T9C

Update: another user on here tyeler18 just built one of these using a combined bluetooth receiver+ voltage regulator board. If i were going to do it again I would just buy one of these for $12. This board will take place of the previous two parts (bluetooth receiver + 12v to 5v converter) https://www.amazon.com/gp/product/B07P94Z9XR

Switching circuit:
If you want to use the volume knob push button, you need a way to convert the momentary pulse into a bi-stable latching circuit. You could build this yourself, or just buy one of these like I did: https://www.amazon.com/gp/product/B08593HHDG
If instead you want to mount an external switch, pretty much any switch will do.

So, all in all, we're talking maybe $20 in parts...less if you decide to use up some of those spare parts you have been hoarding for years.

I built my circuit on a piece of perf board, 3d printed a bracket (available at https://www.tinkercad.com/things/63HjVIQ4z0e) that shared the mounting holes with original cassette deck, and used header pins as a way to plug into the existing plugs in the radio. The only soldering on the radio itself was soldering a wire to the volume potentiometer board, and soldering a small wire to the cassette ribbon cable. Both of these mods could be easily un-done to revert to original.

I'll let the pictures do the rest of the talking.

Here is the design based on using the volume knob:


And here is the design without the latching circuit and volume knob integration (disclaimer: I didn't actually build this one...so it may not work.. but it should..)


Here are some build pictures with annotations:




And the final product (3d printed bracket available here: https://www.tinkercad.com/things/63HjVIQ4z0e )



Well I hope this helps someone who is also trying to retrofit Bluetooth on the cheap, but still keep most of their radio functionality.

-bbowman