Becker 1432 Bluetooth Mod - PeachParts Mercedes-Benz Forum

300SD81 · #1 08-07-2014, 03:05 AM

Heres a fun little mod I finally got working, adding bluetooth (and 2 other aux inputs) to the 1432 trunk unit.

The trunk unit uses a TDA7300 audio processor that has 5 inputs, but it only uses 3 of them. Its controlled with a common I2C interface. The upper board in the picture is the bluetooth module, and the lower one a custom one I built with a 3-way audio switch and STM32 microcontroller.

For now, I don't have any way to detect when something connects to the bluetooth, so I just have the MCU wait 2 seconds after power up to let the radio use the I2C bus, then it sends a input-1 command to the TDA7300. The MCU has all 3 inputs of the audio switch connected to it's ADC so I should be able to sense audio and switch inputs in the future. It goes back to FM/AM/Cassette if you press any of those functions on the head unit. Power cycling the radio sets it back to bluetooth for now.

I'm working on v2 with better integration of the bluetooth module and 12v regulator, and trying to come up with a way to switch the inputs from the head unit or adding a wireless remote.

If you try it yourself, make sure the audio signals into the 7300 are capactively coupled, I'm pretty sure you can blow the chip if they aren't.

PS - I got 2 extra PCBs free to anyone feeling up to hand soldering the 3x3mm DFN, It really isn't that hard with a hot air tool.

SuperCow · #2 08-07-2014, 04:12 AM

Lol 300SD81. As we speak, I'm also busy with this project.
Only with a Becker 780. With also has the TDA7300.
I almost have the project completed. I'm using a arduino to send the I2c commands.
But i can change it on the fly, also i drive the LCD and the buttons.

I only have 1 thing left, i have to hook up the bluetooth module. I have bought a custom one, that i can drive through serial with AT commands.

So what new features i have now:
Normal FM/AM and cassette.
When a call is coming in, and your on radio mode, the arduino switched the the last free channel on the TDA7300. You will hear the ringtone then. Then i can use the cassette buttons or RC to accept the call, or hang up. When you hang up, it goes back to radio mode.
You also can stream music from the phone.
I have made a Remote control.

Here is a poor quality youtube i made of the radio (WARNING DUTCH) When it worked.
https://www.youtube.com/watch?v=U_3l8vnvsBk

**Edit**
looking at your picture, i have the same bluetooth module OVC3860

Stretch · #3 08-07-2014, 05:56 AM

Quote:

Originally Posted by SuperCow

...
Here is a poor quality youtube i made of the radio (WARNING DUTCH) When it worked.
https://www.youtube.com/watch?v=U_3l8vnvsBk
...

I'm surprised it survived the horrors of Celine Dion!

ah-kay · #4 08-07-2014, 10:54 AM

I admire your gallant effort to add bluetooth function to the radio. It is within my ability to do it as I am an electronic/software engineer by training. I work with cellular modem and bluetooth protocol all day. But I would not do it as it is not cost effective and a lot of work.

1) I can buy a top end BT capable radio for < $100
2) I can install the new radio without cutting or modifying anything with the existing wiring. It has been done with all my cars. All radio is the same brand.
3) I can re-install the old radio anytime for the purist, if necessary, within minutes.

I thank you for sharing with us. Enjoy your BT radio. It is a challenging and interesting project by all accounts but not my cup of tea.

300SD81 · #5 08-07-2014, 11:43 AM

Quote:

Originally Posted by SuperCow

Lol 300SD81. As we speak, I'm also busy with this project.
Only with a Becker 780. With also has the TDA7300.
I almost have the project completed. I'm using a arduino to send the I2c commands.
But i can change it on the fly, also i drive the LCD and the buttons.

I only have 1 thing left, i have to hook up the bluetooth module. I have bought a custom one, that i can drive through serial with AT commands.

So what new features i have now:
Normal FM/AM and cassette.
When a call is coming in, and your on radio mode, the arduino switched the the last free channel on the TDA7300. You will hear the ringtone then. Then i can use the cassette buttons or RC to accept the call, or hang up. When you hang up, it goes back to radio mode.
You also can stream music from the phone.
I have made a Remote control.

Here is a poor quality youtube i made of the radio (WARNING DUTCH) When it worked.
https://www.youtube.com/watch?v=U_3l8vnvsBk

**Edit**
looking at your picture, i have the same bluetooth module OVC3860

Nice! Mind sharing what the LCD interface protocol is? And are you listening to the I2C to determine what the previous state was before a phone call, or just defaulting to FM?

It looks like my module has a serial port as well, not mentioned on any of the seller's webpages. Going to try and see if I can get connection data from it, but unfortunately I never routed the serial connections on the current version of the board, might see if I can bit bang it from the second I2C that wasn't necessary.

Initially I thought I'd have to cut the signal to the TDA, and relay them through the chip, but it wasn't needed since the radio only signals when you press a button, and doesn't care what happens on the bus when its not in use.

Quote:

Originally Posted by ah-kay

I admire your gallant effort to add bluetooth function to the radio. It is within my ability to do it as I am an electronic/software engineer by training. I work with cellular modem and bluetooth protocol all day. But I would not do it as it is not cost effective and a lot of work.

1) I can buy a top end BT capable radio for < $100
2) I can install the new radio without cutting or modifying anything with the existing wiring. It has been done with all my cars. All radio is the same brand.
3) I can re-install the old radio anytime for the purist, if necessary, within minutes.

I thank you for sharing with us. Enjoy your BT radio. It is a challenging and interesting project by all accounts but not my cup of tea.

It really wasn't that much effort, probably a (drunken) night for the PCB and a few hours probing the signals with a buspirate. I'm considering making a v2a with all the current features, and a v2b with an easy to solder SOP chip, where all you would need to do to mod a radio would be soldering 6 wires onto the side of the DIPs, and be able to return it completely stock by removing them. I'm kind of a purist, but only with appearances, no problems with engine mods or adding modern electronics.

winmutt · #6 08-07-2014, 12:30 PM

Quote:

Originally Posted by ah-kay

1) I can buy a top end BT capable radio for < $100

I find the beckers to be very warm and tubesque in sounds. Don't really get that out of anything modern that I have found. Subscribing for the follow ups!

ah-kay · #7 08-07-2014, 12:32 PM

I think we have something in common within the Diesel Forum, like I2C, bit banging ( it is not rude, it means pulsing ), SOP, DIP etc. I may ask for some help if I need to do any electronic projects.

ah-kay · #8 08-07-2014, 12:41 PM

Quote:

Originally Posted by winmutt

I find the beckers to be very warm and tubesque in sounds. Don't really get that out of anything modern that I have found. Subscribing for the follow ups!

This is a DD but I will offer my $0.02. How you perceive sound is subjective. I find the most important component in any sound system are the speakers, it converts electronic current into sound wave and into your ears. Any amplifier/radio would have very low THD so it does not really matter that much. The acoustic in car is never ideal to begin with and you can never compare the same with a modem luxury car.

I am done with this thread.

300SD81 · #9 08-07-2014, 12:45 PM

Quote:

Originally Posted by ah-kay

I think we have something in common within the Diesel Forum, like I2C, bit banging ( it is not rude, it means pulsing ), SOP, DIP etc. I may ask for some help if I need to do any electronic projects.

Unfortunately haven't been around much lately, my SD needs a new engine, and I'm currently driving a 560. I learned almost everything I know about car repair off the 617, so the M117 is like starting over. Thankfully its been mostly reliable, and has enough power that I'm not tempted to mod it daily, but I'd still like to build a bombed out diesel.

SuperCow · #10 08-07-2014, 12:58 PM

Quote:

Originally Posted by 300SD81

Nice! Mind sharing what the LCD interface protocol is? And are you listening to the I2C to determine what the previous state was before a phone call, or just defaulting to FM?

It looks like my module has a serial port as well, not mentioned on any of the seller's webpages. Going to try and see if I can get connection data from it, but unfortunately I never routed the serial connections on the current version of the board, might see if I can bit bang it from the second I2C that wasn't necessary.

Initially I thought I'd have to cut the signal to the TDA, and relay them through the chip, but it wasn't needed since the radio only signals when you press a button, and doesn't care what happens on the bus when its not in use.

The becker 780 is quite different, and much more difficult.
I also have a Becker 1100 everything is i2c on 1 bus. Very easy to do.
I bought a logic analyzer sniffer for the 780, else no chance to get it to work.

I have a becker 1432 without the amp (useless but didnt know then)
I have made code for it to drive the LCD its i2c (also a VS2010 program to set chars). But it is for the dash unit.
So i don't know how it sends over to the cable.

With the 780, i read out when the LCD is driven by the radio.
That way i can see if its on FM or AM.

The LCD from the 780 is cbus, looks kinda the bus of a shift register chip. (clock, data, chipselect) Problem with it, it shares a I2c bus for the button driver, eeprom and some more stuff (not the tda7300) so the lines are always busy, so i have to time a space when i can send my stuff.

The TDA is on a other bus, also sharing shift chips. Also here the bus is always busy and i have to time my data right to send it out. I have soldered a diode on it so i don't drive the clock on the other chips (kills the radio haha)
----

The reason why i do this? I have a modern bluetooth radio in my car. Its ugly, with the blue lights and graphics on it. Also the FM reception is bad.
So i wanted a Becker from the time period of my car.
That would be a Becker 754, 780 or 830. I got an 780.

I put alot of hours in it now (4 weeks orso), but i enjoy doing it. I learn from it.
And when its done i have the only Becker 780 with fully working Bluetooth and IR remote