Understanding Datalink 86

[Storck]

Ok, I need some help understanding the datalink 86 protocol!

I will try and update this post with my findings, so it can work as a reference for future hobbyists!

I want to build a device for Home Assistant so I can take control of my Beomaster 6500. I want to be able to automatically turn it on and off when the TV goes on and off, and use my phone or the TV remote to control the volume etc. Nothing fancy. I’ve read about some similar projects here on the forum, but not exactly what I want.

I’ve hooked up a esp32 to a logic level shifter and wrote some software that sends the data I input, so far so good.

I’ve followed the documentation here: https://www.mikrocontroller.net/attachment/33137/datalink.pdf

Start: 3 bits
In the documentation it says “four pulses”, but in the example diagram (2045-4) I only see three, this is also what the datalink sends out when I use the remote.

t1 t1 t5

Format (local/2adresses): 4 bits
This Is a bit of a mystery for me. From the signals I gathered I get 0000 for “short” remote signals, and 0011 for the much longer messages. Is there any documentation about this?

Address (to): 5 bits

I suppose this is the device/source you want to control, so “0 0000” for TV, “0 0001” for Radio etc?

Address (from): 5 bits

I haven’t sent this part, from what I read on other posts this isn’t included in the “short” message system.

Data: 8 bits

The actual message, this is pretty well documented as well:
https://github.com/toresbe/datalink/blob/main/datalink86-captures-new.txt

https://github.com/christianlykke9/Beomote/blob/master/Commands.h

for example I get “1010 1100” when pressing standby. “1000 0000” when pressing the “TV” source button.

Stop: 1bit

T4 + tailing pulse.

With this logic a message like this should work.
Start | Format | Address (to) | Data | Stop

STX | 0000 | 00000 | 1010 1100 | ETX

I can’t get this code to work, even though it’s the same as I’m receiving when I press the remote.
On the other hand some codes work. This code for example works, and changes the radio to channel 2.

STX | 0000 | 00001 | 0000 0010 | ETX

 

The full/long messages

For a lot of button presses on the remote I get the long message type. These seem to consist of 40 bits, much longer than the datalink 86 documentation I linked above.

Example from Toresbe github:

STX 0011 1011 1100 0001 0100 0000 0000 0010 0000 0000  ETX # Power off

How are these codes structured? Format, Address (to), Address (from), Data? How many bits for each?

From right to left the data seems to be 8bits data, 16 bits display settings (?), 5 bits source(Adress(to)). I cant figure out the first 11 bits, I suppose that the four first is the mysterious “Format”. I read somewhere that 0011 is “Local format”.

Start | Format | ????? | Address(to) | data (display) | data (command) | Stop

STX 0011 | 1011 110 | 1 0010 | 0100 0000 0000 0000 | 0000 0000  ETX # CD

STX 0011 | 1011 110 | 0 0001 | 0100 0000 0000 0000 | 0000 0000  ETX # RADIO

Are you supposed to include all the display data when you send commands? Or is this just used to broadcast information to other units about which track your listening to etc?

Does this have anything to do with the different “Beolink options” you can choose in settings? 1 for same room, 2 for TV in another room, 3-4 for different MCL2 units. Or does this only impact the remote?

All input will be much appreciated.

• This topic was modified 12 hours, 47 minutes ago by Storck.

[TK]

Sounds like a great project.  Datalink ’86 is a very extendable protocol for its time, that is intended to handle multi-component 2-way communications.  If all you are looking to accomplish is emulate the function of a Beo4 (sending one-way commands using MCL2 over the Aux port), then you need not worry too much about the various message formats and permutations of MCL2.

A standard Beo4 command is implemented via an MCL2 ‘AAC’ command (Address-To, Address-From, Command) through the MCL network.  This is accomplished by sending a fixed-length command of 22 bits, and looks as follows:

:STX:00:10:ToADR:FrADR:DATA_CMD:ETX:

In this message, the preceding ’00’ is what you will usually send to start message for what you are doing, and the ’10’ tells the listening component the structure of the message.  Namely, that the following message contains a 5-bit destination address, a 5-bit sender address, and an 8-bit single instruction. There are many other message formats and combinations, which allow for messages of different structures and lengths. However, since you are not doing anything overly complicated, you’ll likely only need to use the AAC format of ’10’ and most of your commands will look like this:

:STX:00:10:00001:00001:DATA_CMD:ETX:

This is basically sending an 8-bit command from the “Radio” (00001) to itself “Radio” (00001).  DATA_CMD is a number from 0 to 255, and is a singular function, such as “STANDBY” ( 00001100 ) or “UNMUTE” ( 00011100), for example.   You can use the already published list of commands, which has many of the most commonly-used ones, to have the 6500 do your bidding.

Here are some commands you will likely need:

:STX:00:10:00001:00001:10000011:ETX: -> Set source to A-Aux (Powers on)

:STX:00:10:00001:00001:00011100:ETX: -> UnMute (needed when sending MCL)

:STX:00:10:00001:00001:00001100:ETX: -> Standby

Some of the data you are looking at from your example from Toresbe is Beomaster OUTPUT – i.e. what the Beomaster is updating the other components on the system on. These longer messages contain things like system volume, track number, RDS data, etc.  Once you are ready to start listening for status updates, you can begin to process and act on Beomaster messages as well.  I’ll refrain from posting more about that protocol so as not to confuse you. The entire protocol is very rich, and has many quirks.  Much of the protocol basics are defined in the TJE 1985 document, but the entire protocol syntax has advanced well beyond that point until its final iteration in the mid 90’s.

Feel free to ask any follow-up questions you may have.

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