CM5908/5907 Plug-n-Play Bluetooth upgrade board

[jaysterling]

Could you have 2 flex receptacles on the mainboard, one for each radio? That way users would just plug the flex into the appropriate one, and maybe you could put some logic on there to detect which receptacle is in use so that the MCU would know which set of code to run with.

Maybe, but probably not. They want to be in the same place and if I put them one behind the other it might cause rubbing/strain on the flex for whichever receptacle is in back (since that flex has to come up over the first receptacle then bend downwards towards the second). Good point though, I should verify for certain. The audio output and volume knob harnesses are also slightly different between the two, so I'll need to do have both connectors for those, but they're just little wiring harnesses that are easier to reposition.

As far as detecting which is being used, there are a few pins that are driven high always on the flex for 5908 that aren't for 5907, so auto-detection should be possible. After comparing the flex pinouts across both radios, I don't see any HW reason the same receptacle couldn't be used for both, there's just more possibility of installation error.

He's only modifying the input stage of the head unit to add BT music and phone. So no affect on the amp part at all as currebtly implemented

It WILL come in to play if/when you add line level outputs to the OEM unit at some point. The OEM premium amp has speaker level inputs which just aren't as clean. The design is basically obsolete. While it's true you can use speaker level inputs with some aftermarket amps, it defeats the purpose of adding an amp in the first place. If/when line outs get added you can bypass the OEM premium amp and use your favorite after market power and subwoofer amps with the OEM head unit.

BTW I haven't seen it mentioned here but there are 2 other retrofit possibilities. they are admittedly less useful than what he's chosen to implement in the prototype, but they are there:

- most of the newer BT chips support track and caller info display. You could retrofit the OEM LCD panel at some point as well to take advantage of this to display not only track info but caller info too. You can certainly make a strong argument to just use the phone display for these functions instead. After all you're gonna have a separate nav display anyway..

- the 5908 and several other OEM head units have a CD changer connector. What he's done here is much better though, since the same existing button controls work across all input sources including the added BT music and phone inputs.

I do think the control assignments used in the demo vid could be improved slightly, but it's quite usable as prototyped

The CSR BT chip I'm using doesn't have a serial interface available for getting things like phone numbers or song titles, but that would be cool. I've done the LCD-hacking on my raspberry pi-based 5908 project with the intent of doing this kind of stuff, and the LCD portion of that project could be brought into this. At that point, it quits being plug-n-play though.

Let me know what you'd do different with the buttons. There are some assignments that are forced, like input switching has to be on the volume button push since it's the only event I can get no matter what input is selected



So here's my plan: I'm going to rev the board fixing all the issues til now I've found. I am going to switch a larger PIC microcontroller since I'm out of program space on the model I've been using (with a few fixes to still add) and I need more IO if I want to support the 5907. There is a little work in switching to a different MCU, but I need more program storage space anyway, regardless of 5907 support. I'm going to hook all the IO up to the new MCU for 5907 support, but I can work on that as I get to it without holding up the plan for 5908.

[bradnic]

He's only modifying the input stage of the head unit to add BT music and phone. So no affect on the amp part at all as currebtly implemented

It WILL come in to play if/when you add line level outputs to the OEM unit at some point. The OEM premium amp has speaker level inputs which just aren't as clean. The design is basically obsolete. While it's true you can use speaker level inputs with some aftermarket amps, it defeats the purpose of adding an amp in the first place. If/when line outs get added you can bypass the OEM premium amp and use your favorite after market power and subwoofer amps with the OEM head unit.

BTW I haven't seen it mentioned here but there are 2 other retrofit possibilities. they are admittedly less useful than what he's chosen to implement in the prototype, but they are there:

- most of the newer BT chips support track and caller info display. You could retrofit the OEM LCD panel at some point as well to take advantage of this to display not only track info but caller info too. You can certainly make a strong argument to just use the phone display for these functions instead. After all you're gonna have a separate nav display anyway..

- the 5908 and several other OEM head units have a CD changer connector. What he's done here is much better though, since the same existing button controls work across all input sources including the added BT music and phone inputs.

I do think the control assignments used in the demo vid could be improved slightly, but it's quite usable as prototyped

[reelizmpro]

What I was getting at was that some cars have premium sound and some don't. Some cars have had their premium sound amps bypassed. So if this unit is to be used with the factory premium sound amp, then there's more work to be done on those cars. Cars that don't have premium sound would then need to run an amp, correct?

[bradnic]

Doesn't affect the amp stage of your head unit at all actually.. so whatever you run amp wise is fine

[reelizmpro]

Brilliant. Is this to be used with the premium sound amp or does it have an onboard amp?

[tuckerware]

I'd lean towards selling just the 5908 solution intitially since that has been your test bed.

As is common with new product launches, I'm sure you'll learn a few things and you can incorporate any improvements into subsequent variations and manufacturing runs.

Your expected price range certainly seems like a great value so I'd imagine you'll have plenty of takers.

[bmwman91]

Could you have 2 flex receptacles on the mainboard, one for each radio? That way users would just plug the flex into the appropriate one, and maybe you could put some logic on there to detect which receptacle is in use so that the MCU would know which set of code to run with.

[Todd Black 88]

Hah, thanks everyone :) So I went out today to verify everything worked with the CM5907 since I naively claimed it would work, and I realized an issue - it's not quite the same. The physical foot print is the same, but the flex cable actually has 2 fewer traces than for the slider radio. I dug in and found the signaling scheme for the user inputs are actually totally different on the flex for the 5907. It should still be possible to have 1 board that works for both, but it's just work I wasn't expecting. It will also mean that for the 5907, you would have to slide the flex cable to one side in the connector before tightening the latch since it's narrower.

I guess I should ask though: is anyone actually wanting to use this in a CM5907/CM5905? It's a bit more work to install it into one of these and it will unfortunately require enlarging a hole in the top/side for a mic plug and removing the cassette deck requires desoldering a dab of solder on a (easy to access) screw inside.

But to answer a few questions:

Am I planning on selling them?

Yes

When will they be ready?

Hard to say, but this is roughly what still needs to happen:
1. Finish PCB layout for the (hopefully) final version.
2. Have 1 printed, hand assemble (week fab lead time, then assemble)
3. Validate on the bench
4. Install in my car, use it for at least a week, working through anything new I find
5. Rev board if needed and print a few more for a small beta test. (I've had some interest already, anyone else wanting to be a beta tester, esp. if you're local, PM me)
6. Work through any issues from the beta test (probably a few weeks)
7. Meanwhile, begin taking orders and working with whatever Chinese fab/assembly house for the initial production run. Lead time on this can be 4-5 weeks.

Realistically, it's still 2-3 months before people get their hands on them.

How much will they cost?

Another one that's still early to commit to. I know there are services that will add a simple 1/8" aux jack to the faceplate of these radios for $60 and that a half-decent aftermarket head unit costs about $130. I want to be somewhere between the two.

Yes, I will be wanting to put it into a cm5907/5905 myself. That's what my m3 came stock with.

[bradnic]

I'd say walk before you run, but know where you're going. Extending the design to support other radios significantly increases complexity for you, and delays for us.

So by all means confirm the design diffs between the similar alpines, but please don't take too long :-) if you can leverage similarities and build some modularity into your design to accommodate them that's great. Hopefully you can adapt the design over time - but not all up front though and not make us all wait too long..

Why don't we get a survey going on the site? Find out which OEM radios folks are willing to buy a retrofit BT solution for.

[jaysterling]

Hah, thanks everyone :) So I went out today to verify everything worked with the CM5907 since I naively claimed it would work, and I realized an issue - it's not quite the same. The physical foot print is the same, but the flex cable actually has 2 fewer traces than for the slider radio. I dug in and found the signaling scheme for the user inputs are actually totally different on the flex for the 5907. It should still be possible to have 1 board that works for both, but it's just work I wasn't expecting. It will also mean that for the 5907, you would have to slide the flex cable to one side in the connector before tightening the latch since it's narrower.

I guess I should ask though: is anyone actually wanting to use this in a CM5907/CM5905? It's a bit more work to install it into one of these and it will unfortunately require enlarging a hole in the top/side for a mic plug and removing the cassette deck requires desoldering a dab of solder on a (easy to access) screw inside.

But to answer a few questions:

Am I planning on selling them?

Yes

When will they be ready?

Hard to say, but this is roughly what still needs to happen:
1. Finish PCB layout for the (hopefully) final version.
2. Have 1 printed, hand assemble (week fab lead time, then assemble)
3. Validate on the bench
4. Install in my car, use it for at least a week, working through anything new I find
5. Rev board if needed and print a few more for a small beta test. (I've had some interest already, anyone else wanting to be a beta tester, esp. if you're local, PM me)
6. Work through any issues from the beta test (probably a few weeks)
7. Meanwhile, begin taking orders and working with whatever Chinese fab/assembly house for the initial production run. Lead time on this can be 4-5 weeks.

Realistically, it's still 2-3 months before people get their hands on them.

How much will they cost?

Another one that's still early to commit to. I know there are services that will add a simple 1/8" aux jack to the faceplate of these radios for $60 and that a half-decent aftermarket head unit costs about $130. I want to be somewhere between the two.

[bradnic]

Lulz

[tuckerware]

Most days I feel like a fairly intelligent person until I read a thread like this and feel like a moron. I mean, amazing accomplishment but stop showing off already. ;)

So, even though you are kind of being a dick by making us look like comparative neanderthals I really would like to give you money now for this witchcraftery.

Is it ready yet?

How about now?

[Todd Black 88]

Beautifully executed.

I am in for a few I think.

[Boggie1688]

Turns out using a separate power supply and ground path totally fixes the digital noise issue like I hoped.

So it's all working now! I just made a short demo video with everything buttoned up inside and functioning. Still work to go but it's getting close.

Jay, sent you a PM.

[Eric]

I'd like one of these, how much?