To accelerate the building of the actual pedalboard, I purchased a used Line 6 Pedal Board from eBay. The price was right and I didn’t care about it working or not. I wanted the metal frame and the switches.
This is a solid chunck of metal!
Looking inside, you can see three printed circuit boards (PCB). The one on the left responds to pedal movement, the on at the bottom right is the switch board and LED holder, and the one at the top is the main board.
The main board is pretty simple. It communicates with Line 6 amplifiers using an rj45 standard Ethernet patch cable. Doing some research and some testing, I can confirm that the pins have these functions (thanks to Mark Lavelle):
The main board is quite simple. The orange ICs are resistor networks and the black ones are 8-bit shift registers and a schmitt trigger inverter. The board receives messages from the external circuit (in the amplifier, for example) and manages the series of LED lights on the device, including the 2 digit numeric display. It also receives signals from the switches and pedals to send to the external circuit. I have no use for the board, as I will use an Arduino to get the switches response and control a much better 2-line display. I will keep all the connection cables though, as they use standard 0.1 inch spacing, perfect for interfacing with the Arduino.
The switches used in this board are linked by a PCB and are not the most solid design available. If I ever have problems with them, I will replace the lot with heavy duty foot switches, with standard soldered wire connections.
The pedals use an interesting mechanism that I have not seen often in similar devices. Instead of a potentiometer activated by the pedal, the Line6 Floor Board uses a plastic film that gradually changes from transparent to black along its length. A transistor on the pedal sub-board lets me believe that a simple amplifier sends the signal to the main board. My measurements confirm a varying voltage on the pedal pins.
The switches all use the same wire for output. Each is associated to a resistor, and measuring the resistance on the output line can indicate which pedal or pedals have been pressed. This is a simple resistor ladder.
The various LEDs are controlled by a kind of 32 bits signal. I will use the Arduino to control the LEDs also. I could use one digital pin per LED from the Arduino or use a multiplexing technology to reduce the number of pins used. I haven’t decided yet (meaning: I don’t know how!).