RS485 and MIDI Signals

Hello community!

I am currently trying to let my Footswitch (with an RJ45 cable, and RS485 protocol) communicate bidirectionally with my guitar amplifier (which has MIDI IN and MIDI OUT jacks).

Therefore, I want to interprete and translate the RS485 signal to MIDI and back, using an Arduino UNO.

Since I'm studying mechanical engineering I don't know much about this topic, so I would really appreciate any kind of help you could offer me (concerning the problem of translating RS485 to MIDI and back).

What would be the best way to translate the signals? How do I start coding the solution? Finally, How would I know which RS485 expression belongs to which function of the footswitch?

Thank your time,
Greets from Germany

RS485 is not a protocol but an electrical specification for a serial interface to transmit/receive a differential signal.
On the other hand, MIDI is a protocol and I believe the Arduino MIDI library uses serial ports anyway, so you should be able to use RS485 in exchange or for the serial port(s).

Thanks for your reply!

So I found out that the protocol, which the footswitch uses is similar to MIDI NRPN. How would the translation between this protocol and MIDI work?

Please post links to your footswitch, and this protocol you found. It's all vague so far.

footswitch: Line 6 Shortboard MK II

amplifier (MIDI): Kemper Profiling Amplifier

I'm not sure about the protocol of the line 6, the only information I have is that it is similar to MIDI NRPN but proprietary.

Concerning the cabels, I do have a connection plan (i dont know how to call it in english) of the RJ-45 cable (8 wires: RXN, TXN; RXP, TXP, GND, GND, PWR, PWR) which connects the footswitch to the arduino. The arduino is then bidirectionally connected to the amplifier using MIDI cables.

Felix19:
Thanks for your reply!

So I found out that the protocol, which the footswitch uses is similar to MIDI NRPN. How would the translation between this protocol and MIDI work?

That's a protocol. Nothing to do with RS485 or the normal way MIDI is wired up (using optical isolators).

Felix19:
Concerning the cabels, I do have a connection plan (i dont know how to call it in english) of the RJ-45 cable (8 wires: RXN, TXN; RXP, TXP, GND, GND, PWR, PWR) which connects the footswitch to the arduino. The arduino is then bidirectionally connected to the amplifier using MIDI cables.

Sounds like a "schematic" or "circuit". Please post this.

Is anything working yet? There still isn't much detail in what you said. RS485 can be used for serial comms, and MIDI uses serial comms, so we are on the right track.

My preliminary guess would be that you would take the RS485 signals and process them with a suitable interface chip (eg. as described here ).

Then to convert the serial data into MIDI use something like this.

Thank you for your reply Mr. Gammon!

No, nothing is working yet. I first want to figure out how to connect the cables on the board and how to code the solution before I try it out.

It's not a circuit. I contacted Line 6 to send me the connections of the wires in the RJ-45 cable, so all I know is which of the 8 wires sends, receives, and which is connected to ground or power.

I know the information is vague, I have to figure out more myself, but I can tell you the functions of the board: It basically sends commands to the amplifier to switch bank, switch effects on/off, turn the tuner on/off etc.
The Footswitch on the other hand needs the information to turn on/off LED's and to display the current amp model/effect.

I saw a youtuber doing EXACTLY what I want to do, but he doesnt give much information about his project, here is the link:

On his board, I see two micro chips, which matches your guess to use an interface chip and an optocoupler.

I hope you can help me out finishing this project.

Felix

I can't "finish" your project when all the hardware is at your house (and no, don't mail it to me) and there is practically no technical information.

I would try to follow up their forum if I were you:

Someone seems to have made boards like what we saw in the video:

Also see this thread: http://forum.fractalaudio.com/other-midi-controllers/65923-axeline-line-6-fbv-converter.html

Someone seems to have made progress but information is light.

Something like this might get you started at the RS485 end: MAX485 module RS-485 TTL to RS485 MAX485CSA Converter Module For Arduino

Thanks for this info!! Exactly the stuff I need.
I have a broken down FBV longboard and I was wondering if I could build this on into a controller for the Line6 POD device, but then with custom software (running on a arduino off course).
I can build the (midi) devices myself, and needed the sequential data analysis to build the code.

It will be my first arduino project, but not the first midi hardware I have built.

Hi,

I have a Line 6 FBV shortboard MK1 that I would like to use as a MIDI controller for Möbius soft-looper. Did your projects (Felix19/howcome) result in any working solution that you can share ?

/Lars

I picked up one of these ... could it be used in this context ?!

You do not need any processor for that, just THE SP485 chip.
This does everything for you.
It converts the MIDI (RS232 TTL) Level to the RS485 symmetric Levels.
Of course the same chip can receiver and/or transmit.
You can send your RS485 MIDI messages over a Standard MIDI cable.
The Transmitter site does not need a power supply.
Just the MIDI OUT PIN 4 Voltage is good enough to supply this chip.
Put it into a MIDI-PLUG, that's it.
The MIDI-Plug has enough space for the entire RS485 Transmitter Hardware.

The MIDI receiving site must be powered, perhaps with a tiny battery CR1220 or you can supply the receiver from the MIDI OUT Jack PIN4 too, if you like