Reverse Engineer DIN 5-pin connector

Question

Summary

I have a digitial guitar amplifier that can be controlled via a footswitch. The footswitch is connected to the amplifier via a DIN 5-pin cable. I want to be able to control the amplifier with another device. Therefore, I want to reverse engineer the communication via the DIN 5-pin connector. How would you approach this?

Some more info:

The amplifier is a Yamaha THR100H. I use it live with different effect pedals like overdrives and delays that come after the guitar and before the amplifier in the effect chain to alter the sound. Also, the amplifier has different build in amplifier types I like to switch to get different sounds. The problem is, that sometimes I have to push up to three buttons to get the setting I need for the next part in a song. This really bothers me.

My idea is to use a switching system such as the BOSS ES-8 with which I can switch different pedals on and off simultaneously. The top notch solution would be if I could also switch the amplifier types on the THR100H with this device. Like that, I would have a "One-button"-solution which would be really awesome.

If the protocol between the THR and the footswitch was MIDI then I could very easily integrate it with the a switching system like the BOSS since these often come with a MIDI interface to integrate with more complex devices. Unfortunately, Yamaha states on its website that although they use the standard MIDI connector (the DIN 5-pin) the protocol is not MIDI.

In this forum post a person named spiral opened up the standard footswitch and discovered that it has its own MCU. In the same thread spiral also states that the footswitch requires power over MIDI.

I really like the idea with the BOSS ES-8 and in general controlling the THR via MIDI. But I have never done something like this before although I am not too far away from the topic. I myself am a software engineer. So, if some of you could get me some starting assistance I could maybe build a device that transforms MIDI commands into the THR commands.

The first questions that comes to mind is what hardware do I require to get the footswitch to work with the THR while being able to sniff the communication? In the forum post above spiral says that he got the footswitch to boot but then it did not send anything. Most probably it needs to see the THR. So, the piece of hardware you put in between must really be invisible for the THR as well as the footswitch.

So, what device would you suggest?

Answer 1

How would you approach this?

I would get an oscilloscope and check to see if there were analog or digital signals. I would then find out what the voltage range of those signals are. I would check to see if the signals were periodic. Then I would push the foot switch and observe the change of the signals.

An easier thing would be to pull apart the foot switch to see if there is a microprocessor or only switches and passive devices, and then reverse engineer a schematic to see what the functionality is.