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    DIY Bluetooth Retrofit CM5908

    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:
    Click image for larger version  Name:	e30_bluetooth_diagram_1.png Views:	5 Size:	200.8 KB ID:	9955924

    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..)
    Click image for larger version  Name:	e30_bluetooth_diagram_2.png Views:	5 Size:	187.4 KB ID:	9955925

    Here are some build pictures with annotations:


    Click image for larger version  Name:	combined_build_images_2.jpg Views:	73 Size:	76.0 KB ID:	9955931

    And the final product (3d printed bracket available here: https://www.tinkercad.com/things/63HjVIQ4z0e )
    Click image for larger version  Name:	IMG_1142.jpg Views:	0 Size:	94.6 KB ID:	9955930


    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
    Last edited by bbowman; 10-28-2020, 07:02 AM.

    #2
    "Very nice!"
    -Borat
    sigpic

    Comment


      #3
      Wow this is super clean! I ended up gutting my radio and sticking a bluetooth amp in it.

      Comment


        #4
        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

        Comment


          #5
          Oh man, you all are motivating me to see if I can get bluetooth installed into my Clarion
          Click image for larger version

Name:	FZ102E,21.jpg
Views:	662
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ID:	9958684

          Comment


            #6


            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?

            Comment


              #7
              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.

              Comment


                #8
                Originally posted by tyeler18 View Post
                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
                Hey tyeler18 and bbowman.

                I am about to undertake this project. I have my working deck and I just received the Drok bluetooth module. The switching circuit is on the way still. I have a few clarification questions,

                1. Does the radio function work normally?
                2. The bi-stable latching circuit, that just allows you to control the volume with the knob and or power up the Drok module?
                3. How do you connect to the Drok System once its been installed? Do you just press the Mode button and it recognizes it as a cassette ?
                4. Do either of guys have a resource on removing the cassette from the radio itself?

                thank you.

                Daniel

                Comment


                  #9
                  Originally posted by dfraid View Post

                  Hey tyeler18 and bbowman.

                  I am about to undertake this project. I have my working deck and I just received the Drok bluetooth module. The switching circuit is on the way still. I have a few clarification questions,

                  1. Does the radio function work normally?
                  2. The bi-stable latching circuit, that just allows you to control the volume with the knob and or power up the Drok module?
                  3. How do you connect to the Drok System once its been installed? Do you just press the Mode button and it recognizes it as a cassette ?
                  4. Do either of guys have a resource on removing the cassette from the radio itself?

                  thank you.

                  Daniel
                  Radio functions normally-
                  I'm not using the latching circuit, I have an external switch that powers the drok on. With it powered on it enables bluetooth and you connect to it like a normal bluetooth device. It auto connects on power up anytime after that. I don't have a resource for removing the cassette drive but once you get the radio apart it's obvious and easy to do.

                  Comment


                    #10
                    Originally posted by tyeler18 View Post

                    Radio functions normally-
                    I'm not using the latching circuit, I have an external switch that powers the drok on. With it powered on it enables bluetooth and you connect to it like a normal bluetooth device. It auto connects on power up anytime after that. I don't have a resource for removing the cassette drive but once you get the radio apart it's obvious and easy to do.
                    Thanks for the clarification tyeler18. Do you think it would be possible to use the latching circuit proposed by bbowman with the Drok? Do you have a photo of your external switch - Just curious what it looks like and how it's mounted. Where you drawing power from?
                    Last edited by dfraid; 11-24-2021, 06:35 PM.

                    Comment


                      #11
                      Originally posted by dfraid View Post

                      Thanks for the clarification tyeler18. Do you think it would be possible to use the latching circuit proposed by bbowman with the Drok? Do you have a photo of your external switch - Just curious what it looks like and how it's mounted. Where you drawing power from?
                      Yes the latching relay should work fine. I don't have a picture but its a toggle switch mounted on a dummy button above the radio. It draws power from the radio ignition wire.

                      Comment


                        #12
                        Originally posted by dfraid View Post

                        Thanks for the clarification tyeler18. Do you think it would be possible to use the latching circuit proposed by bbowman with the Drok? Do you have a photo of your external switch - Just curious what it looks like and how it's mounted. Where you drawing power from?
                        Hey so the latching circuit I think works great. feels very OEM to just push the volume knob and have it switch over to bluetooth. Unfortunately the latch I used looks like it's hard to get at least in North America. Any latching circuit should work. There seem to be plenty available from China if you don't mind waiting a long time. This is essentially the same one I used: https://www.ebay.com/itm/30397982088...EAAOSwNWBcjMSO. If you search something like "bistable latch" or "bistable flip-flop" on eBay/Amazon you will get a bunch of boards that all more-or-less do the same thing. If you have any questions i'm happy to help

                        Comment


                          #13
                          Originally posted by bbowman View Post

                          Hey so the latching circuit I think works great. feels very OEM to just push the volume knob and have it switch over to bluetooth. Unfortunately the latch I used looks like it's hard to get at least in North America. Any latching circuit should work. There seem to be plenty available from China if you don't mind waiting a long time. This is essentially the same one I used: https://www.ebay.com/itm/30397982088...EAAOSwNWBcjMSO. If you search something like "bistable latch" or "bistable flip-flop" on eBay/Amazon you will get a bunch of boards that all more-or-less do the same thing. If you have any questions i'm happy to help

                          Thank you bbowman !
                          I actually got one from icstation- just arrived.

                          https://www.icstation.com/mobile/sin...02-p-9309.html
                          It just has a single voltage and single toggle pin as opposed to the one you used with two of each / 6 pins. So hopefully that simplifies the wiring further.

                          I am just trying to get my hands on FPC connector to plug into the cassette ribbon cable. I can’t really tell how you got access to the ground pin but it looks like you shaved that particular pin(#14) on your diagram and soldered to it?

                          The ribbon cable looks like its 18 pins and has a 1.25mm pitch.

                          tyeler18 what pins did you use to connect the power and ground on the Drok? The holes look pretty large.

                          I will document my process and upload it as a hybrid solution between both of your suggestions
                          Last edited by dfraid; 12-04-2021, 06:39 PM.

                          Comment


                            #14
                            Originally posted by dfraid View Post


                            Thank you bbowman !
                            I actually got one from icstation- just arrived.

                            https://www.icstation.com/mobile/sin...02-p-9309.html
                            It just has a single voltage and single toggle pin as opposed to the one you used with two of each / 6 pins. So hopefully that simplifies the wiring further.

                            I am just trying to get my hands on FPC connector to plug into the cassette ribbon cable. I can’t really tell how you got access to the ground pin but it looks like you shaved that particular pin(#14) on your diagram and soldered to it?

                            The ribbon cable looks like its 18 pins and has a 1.25mm pitch.

                            tyeler18 what pins did you use to connect the power and ground on the Drok? The holes look pretty large.

                            I will document my process and upload it as a hybrid solution between both of your suggestions
                            Awesome yeah that latch board looks perfect.

                            And yeah if you can source the proper ribbon cable connector that would make the install super clean. I did the quick-n-dirty approach of just soldering a wire to the pad of the ribbon cable. No need to shave the pad or anything it takes solder fine just the way it is. The only catch is you need to use a VERY thin gauge wire. If you use a thick wire, it will put too much force on the solder pad when your moving all the parts around and it will start pulling the trace away from the cable. After I finished I also wrapped the connector in kapton tape to further help prevent strain on the solder joint, and also insulate the other pins on the cable.

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