CM5908/5907 Plug-n-Play Bluetooth upgrade board

[gath]

Wow! That's all I can say. This will give older stereos modern functionality and keep the old school looks. Would you be able to do this for a cd43?

[jaysterling]

Pre-assembled makes the most sense, I assume with pre-assembled you'd be going SMT route and as compact as possible?

I work with SMT all day, so whichever route you go, I would like to be able to order an unpopulated board.

Alpine makes this radio right? I wonder if the signaling is common with their other BMW radios, like the C33. I have one laying around from my E36.

Right, pre-assembled being SMT design, kit being through hole.

At this point, I actually don't think a kit would really make sense though. For one, the BT chip is going to be SMT no matter what. Second, there will be a PIC microcontroller that needs to be flashed with my firmware using a programmer (~$45 of hardware). Then the BT module needs to be configured to setup the IO functions and device behavior using a different programmer (another $20 of HW). Given all that, just not seeing the kit being worth supporting.

There is definitely some sharing of internals across the units. I bought a cheap CM5907 on ebay on a hunch that the cassette assembly would be the same as the 5908, and it is. Then I've heard that the C33 and CM5903L share the same deck as well.

Wow! That's all I can say. This will give older stereos modern functionality and keep the old school looks. Would you be able to do this for a cd43?

Sure. The concept could be applied to practically any old head unit that plays some obsolete medium.

[earthwormjim]

Right, pre-assembled being SMT design, kit being through hole.

At this point, I actually don't think a kit would really make sense though. For one, the BT chip is going to be SMT no matter what. Second, there will be a PIC microcontroller that needs to be flashed with my firmware using a programmer (~$45 of hardware). Then the BT module needs to be configured to setup the IO functions and device behavior using a different programmer (another $20 of HW). Given all that, just not seeing the kit being worth supporting.

There is definitely some sharing of internals across the units. I bought a cheap CM5907 on ebay on a hunch that the cassette assembly would be the same as the 5908, and it is. Then I've heard that the C33 and CM5903L share the same deck as well.



Sure. The concept could be applied to practically any old head unit that plays some obsolete medium.

That's interesting about the C33 sharing the same deck, I'll open mine up and see.

You can order preflashed PICs by the way from microchips webstore. I have a RealICE at work though, so that's not an issue for me.

What BT module are you using? They do make modules (BT chip, balum, radio, antenna on board) with through hole, but they're pretty big.

How is the module configured? UART? Also have you tried sealing the radio with the module inside? Curious how reception is.

Edit: Turns out I have a C43, not a C33, so it's pretty different. Having a hard time finding the pinout of the tape deck connector...

[jaysterling]

That's interesting about the C33 sharing the same deck, I'll open mine up and see.

You can order preflashed PICs by the way from microchips webstore. I have a RealICE at work though, so that's not an issue for me.

What BT module are you using? They do make modules (BT chip, balum, radio, antenna on board) with through hole, but they're pretty big.

How is the module configured? UART? Also have you tried sealing the radio with the module inside? Curious how reception is.

Edit: Turns out I have a C43, not a C33, so it's pretty different. Having a hard time finding the pinout of the tape deck connector...

Thanks for the tip on the pre-flashed PICs, I'll have to look into that.

The BT chip I'm using is the CSR 8645. It's a tiny, dense BGA package so I'm using a little SMT module that houses that chip, antenna, some circuitry, and brings out the important pins. I don't know of any through-hole modules that are designed for audio use cases. It's configured using the SPI interface on the chip along with some CSR software that you need to be a direct customer of CSR to get, unless you were to search some suspiciously-named Chinese websites for a copy. CSR makes an official programmer, but there is this git-hub project that lets you use a common FT232RL chip as the programmer:

https://github.com/lorf/csr-spi-ftdi/blob/master/README.md

that's what I'm using right now. Haven't been able to test reception with it all sealed up yet, although I'm getting close. And that brings me to an update. I made the first rev of this thing and assembled it and started testing it this week! Here's what it looks like:



I threw the name RetDecks on there as the name of this operation. I might change it if I find something I like better, but it works for now. Anyway, mounting-wise it has 3 screw terminal tabs that you screw the original mounting tabs off the cassette deck onto. Then there are a total of 6 connections off the board: the 3 from the cassette deck, 2 for the volume pot signal-stealing, and a 1/8" mic input. In the 5908, you can slide the mic cable in from the left side through a big hole in the chassis. In the 5907, it looks like it might require enlarging a ventilation hole on the top lid, which sucks. You'll see there's the one new white cable added, which completes the circuit with the volume pot board so we can get in the middle of the signal flow for the push-button.



So as usual I made some errors, destroyed a few BT modules, and still don't have it all working, but I'll be working on that this week. Another thing I want to try to resolve is that the mounting tabs that are reused have a slight lip along the bottom that curls around an edge to help locate it and keep it level, but the screw terminals I used are slightly too tall so the lip doesn't curl around the edge and sit flush without some hole enlargement on the tabs. Hopefully I can resolve that, I really don't want to require drilling.

[James Crivellone]

I'd take two pre-assembled, although I do have one question (that perhaps was shown earlier)

Does the radio still work? IE I can toggle between FM, AM, BT?

If so my E30 Touring / E30 Simulator are getting updates

[jaysterling]

I'd take two pre-assembled, although I do have one question (that perhaps was shown earlier)

Does the radio still work? IE I can toggle between FM, AM, BT?

If so my E30 Touring / E30 Simulator are getting updates

Yep. I repurposed the inward push of the volume knob to toggle between BT and radio. The band button is still how you scroll through FM/AM/WB, then click the volume knob to switch to BT and back. Originally, pushing the volume knob started a sort of radio station demo mode, but I figure most people don't care if they lose it.

[James Crivellone]

Yep. I repurposed the inward push of the volume knob to toggle between BT and radio. The band button is still how you scroll through FM/AM/WB, then click the volume knob to switch to BT and back. Originally, pushing the volume knob started a sort of radio station demo mode, but I figure most people don't care if they lose it.

Understood, works for me, I never use that function

[djjerme]

...how is the heat build up. You're adding a lot more components in the unit, and I am just wondering about the excess heat radiated by the active and passive components when it's installed in the dash with everything else around it.

I'm still on board for this when you have it up for either beta or whichever.. Also, have you thought of doing a Kickstarter to get some funds for production rolling in? Get people committed to the initial rollout/beta testing? I'd be down for that.

[cbouchez]

I need to find the cassette player now...

[earthwormjim]

...how is the heat build up. You're adding a lot more components in the unit, and I am just wondering about the excess heat radiated by the active and passive components when it's installed in the dash with everything else around it.

I'm still on board for this when you have it up for either beta or whichever.. Also, have you thought of doing a Kickstarter to get some funds for production rolling in? Get people committed to the initial rollout/beta testing? I'd be down for that.

There is no way his components use more than the tape deck motors. His board at most uses 1/4 watt. He has a little 8 bit processor, and a bluetooth module basically, thats really it.

I've used a similar CSR chip in a bluetooth mesh application, where it is constantly flooding with receive and transmits, it's 25mA at 3.3V, so even with 100% utilization of the radio, still basically nothing power wise.

[gath]

I am very interested and I want to find out what will be needed for it to be compatible with a CD43 since it does not have a tape, and whether there is a possibility for it to show titles and artist names like Grom iPod adapter or Dice.

[jaysterling]

...how is the heat build up. You're adding a lot more components in the unit, and I am just wondering about the excess heat radiated by the active and passive components when it's installed in the dash with everything else around it.

Keep in mind I removed a much larger number of components crammed in there before adding my little board. The whole thing pulls less than 100mA and has plenty of room to breath.

I'm still on board for this when you have it up for either beta or whichever.. Also, have you thought of doing a Kickstarter to get some funds for production rolling in? Get people committed to the initial rollout/beta testing? I'd be down for that.

I might do a kickstarter, that's not a bad idea. I want to have a fully working prototype before taking people's money though. I don't want to be holding on to people's money for a long time.

I am very interested and I want to find out what will be needed for it to be compatible with a CD43 since it does not have a tape, and whether there is a possibility for it to show titles and artist names like Grom iPod adapter or Dice.

This version wouldn't be compatible with anything but the CM5908, 5907, and 5905, since they turn out to use the same cassette deck and pinouts inside. (I actually have not tested anything in a 5907/5905 yet, but the deck is the same, the cables are the same, it's probably the same).

That said, IF this goes well, I've got my eye on the C33 and C43/CD43. But it would be a whole different board and require reverse-engineering the pinouts of the tape/CD deck inside.

[bmwman91]

The CD43 and similar are probably entirely different beasts. I believe that the audio stream in those is digitally transmitted from the CD transport to the main DSP chip on the motherboard (via either PCM or I2S format). Beyond that, the DSP chip is likely to engage in some handshaking and error detection with the CD transport and the control IC on it. Of course, it does not mean that it is impossible...only that it is more challenging. I have a beaten / hacked up CD43 laying around at home that I'd be up for volunteering for experiments at some point.

A much more likely avenue to go with on the CD43 and the like is to spoof the I-BUS bus and make the head unit think that it is connected to a CD changer. Grom's Aux/BT input units do this. If you went the route of installing a daughterboard to intercept faceplate functions and the display, you could do all sorts of stuff with the CD changer input. I decoded the entire faceplate protocol of the CD43 like 5 years ago and it is just a 5 wire master/slave SPI setup (5th wire serves as a heartbeat/arbitration signal IIRC). The display is super easy to control, and most of the buttons talk to the motherboard via SPI. I think that the power and eject lines are the only ones that have dedicated signal lines. Anyway, I bought all of the full internal electrical schematics for it back when I was messing with this.

Sorry to hijack...

[jaysterling]

Yeah, after searching around a bit, I see there is already the BT solution out there for the CD43 from Grom like you mentioned. I also read about a wired input solution by DICE for the C33/C43, but everything I read is people complaining about it not working correctly and I think it's NLA. So it seems it's the C33 and C43 that are left out in the cold for tech, that's probably where I'd concentrate. And if those two share the same deck, and also share it with the 5903L like I've read (can't confirm), then that covers a nice range of years and models of BMW cassette stereos with just 2 versions. Anyway, I'm getting ahead of myself...

[earthwormjim]

Yeah, after searching around a bit, I see there is already the BT solution out there for the CD43 from Grom like you mentioned. I also read about a wired input solution by DICE for the C33/C43, but everything I read is people complaining about it not working correctly and I think it's NLA. So it seems it's the C33 and C43 that are left out in the cold for tech, that's probably where I'd concentrate. And if those two share the same deck, and also share it with the 5903L like I've read (can't confirm), then that covers a nice range of years and models of BMW cassette stereos with just 2 versions. Anyway, I'm getting ahead of myself...

Grom works with the C43, it hijacks the CD changer functionality.

You don't want to use a C33 though, it has much lower output than the C43 and CD43, and has a very lossy low pass filter.