Becker Unilink

This project is dedicated to support the Unilink changer bus on Becker car radios.

Becker has implemented some downgraded version of Unilink protocol in there radios. The hardware layer is the same like the one from Sony, but the software layer is different.
Good news is, that you can use my interface without changes to hardware (you need just another connector, at least at European radios) and you have to download a code with Becker support.

Since the Becker Unilink protocol is more different than I thought, I decided to make a seperate code for Becker units.The following features are supported by Becker units in CD changer mode (AFAIK):

– CD changers only (an MD ID is recognized as changer, but not supported by display)
– CD names in Custom File style with 8 characters/name
– Disc and track number, track and disc time
– Random play on actual disc
– Track repeat
– Fast forward and rewind
– Track scan, 12 seconds/track

While playing around with my unit, I found out that MD changer mode is also supported, with MD disc and title name. So the code while support also MD changer mode.

I have got a Becker Monza 7882 European model. There is no original Unilink connector. Just two big DIN-ISO connectors and an Mini-ISO connector field. The CDC will be connected via Mini-ISO. (Mini-ISO connectors are easy to get)

Here is the Becker Monza 7882 unit pinout:
Becker Monza pinout

signal input (speed dependent volume control)
1 Speaker
rear right +
2 Speaker
rear right –
mute / audio enable
3 Speaker
front right +
4 Speaker
front right –
automatic antenna / amplifier
5 Speaker
front left +
6 Speaker
front left –
7 Speaker
rear left +
Ground 8 Speaker
rear left –
1 Line-out
rear left
7 Unilink
2 Line-out
rear right
8 Steady
3 Gound
line audio
9 Gound
4 Line-out
front left
10 Unilink
5 Line-out
front right
11 Unilink
6 Line-out
12 Unilink
13 Line-in
phone audio
14 Ground
phone audio
15 RS232
out – ST10 Firmware upgrade
16 RS232
in – ST10 Firmware upgrade
17 Steady
18 Ground
CD/Aux audio
19 CD/Aux
line-in left
20 CD/Aux
line-in right
Becker Mexico 2330 Logs
Becker Mexico 2330 Logs
11.2 KB
Becker Monza 7882 Logs
Becker Monza 7882 Logs
8.8 KB
Becker Unilink Firmware
Becker Unilink Firmware
Version: 1.02
94.2 KB
Becker Unilink for Mexico 2330
Becker Unilink for Mexico 2330
Version: 1.02
102.3 KB
Version: 1.2
876.4 KB
Unilink Logger
Unilink Logger
Version: 1.04
30.2 KB

25 thoughts on “Becker Unilink

  1. Great writeup! Do you have a good source for mini iso connectors? I have found some sources but they are so expensive and I´d like to buy of bunch of them.

    • Sorry, don´t know a source for plain connectors. Just bought some adaptor harness from old ISO to mini-ISO and cut off the old ISO standard connectors.

    • Tried all files, they download fine for me. Also first time I got note about such problem.

      May you post the ULR of the page you will be redirected?

  2. Hi, I have a feeling I found exactly what I need although I just understand about 2,8 % of what is written here. I have a Becker Mexico 2330 radio and I want it to recognize and play my external source as it was a CD changer. Can you help me? What do I need to get and – if possible – where do I get it?

    • You are right, the interface will enable the CD changer input.

      You need the interface electronic based on the schematic I provided. First source would be of course making one yourself.

  3. Hi, I have a Becker Mexico Pro (MD) 4937, which I use with both a Becker Silverstone 10CD CDC, and also a Sony MDX-62. Both of these units work fine with the radio.

    What I want to do is connect both to the radio at the same time, this could be done with a Sony radio using a source selector (e.g. a Sony XA-C30).

    Do you know if the Becker Unilink system can support multiple changers?

    Thank you for any help.

  4. Hi there. I know you worked on this a long time ago, but I’m building an Android interface to my Alfa 166 head unit – which appears to be a Becker unit. I’m using a Microchip PIC16 MCU (cause I’m used to them) and an FT232R for comms with the Android device.

    I will get the Unilink comms working next but could do with the list of commands that you are aware of so I can exploit the head unit’s interface as much as possible. You have a link above to the Commands you’ve determined, but the link is dead. Do you still have that page?

    Thanks for publishing your work on this!



  5. Hi, I would like to ask what happened to forums page? I am looking for Alfa Unilink Protocol and some other forums ( points to forum on this site. But it cannot be found anywhere. Could you provide me with some information on this topic? Or do you have the forum thread backed up somewhere? Thanks for your help.

  6. Does anyone have any information about when did Becker start to use this protocol? I´m trying to figure out if it was used in the Mercedes´ Mexico 2000 (BE14xx) or the equivalent BMW Bavaria C Professional (BE1801) radios. The 10 CD-Changer compatible with those was Becker Silverstone 980, afaik. Unfortunately I don´t have the changer to check how they´re communicating.

  7. I would like to build an interface to enable a Becker Mexico 2330 to work with a Sony MD changer.

    I understand the a Sony CD changer will work with the above model, and I also know that a Sony MD changer is supported on the next generation Becker models (Mexico 4627, Traffic Pro 4720), but on these models a Sony CD changer is not supported.

    Have you ever done this?

  8. Hello!

    About the RS232 interface. Do you know how to use the Remote Protocol? I think the Baud is 9600. But I don´t know what i have to send to the Radio to control the Volume for example. Does anyone knows it?


  9. I have a Becker Traffic Pro (Harmon Kardon) 4773 that works with a Becker (Porsche) BE2660 CD player. The label says: Brand/Typ: CDC-3. Is CDC-3 the Becker Unilink?

  10. Dear Michael

    First congratullations for this great engineering job researching unilink protocol, just one question, I want to build the AVR Interface, isi it possible to get in Gerber files GBR instead of PDF?
    Thanks in advance
    Best Regards

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