Midi Foot Board - Nov 2003

Nov 2003 - Download midifoot.asm (MPASM)

A friend gave me this broken foot board controller for an Ibanez guitar amplifier. The amplifier had a whole range of on board effects. This unit had some proprietary interface to the amp. Rather then throw it away I gutted the insides and turned it in to a more versatile MIDI controller for my DigiTech Studio Quad effects unit.

It was built on two proto boards, one for MCU and the other IO.

The IO board (seen below) consisted of three 8 segment displays, driven by serial in/out shift registers (74HC595.pdf). Bits were banged into the first, the others being synchronously clocked.

The chip on the left is an 8bit SAR ADC from Microchip (ADC0831.pdf), The idea was that I could plug in a pentometer (shown above up and left "Controller Input", turning it caused the MCU to send control change messages on a predefined channel. Very handy, allowed me to change parameters of effects, like delay time, pitch shift frequency, etc.

The MCU board (left) consisted of a PIC16F84A running at 8MHz. And was kind of the heart of the whole project. I found code by Ross Bencina for sending midi data out (by bit banging), so used that as a frame work.

The basic operation of the board went like this. The first 4 buttons (appropriately de-bounced) select a program. The last two buttons select the bank. I think it was 128 programs total, so that's 32 banks. Pressing both Bank buttons put effects unit into bypass mode.

It worked really well, and I used it live for a while. Until I was in a band that was not so effect heavy.

permanent link to this page : http://mrdavec.com/electronics/midi-foot-board