Electronics

myFloorBoard Electronics

N.B. POD and FloorBoard are Trademark of Line6

The circuit of the controller is very simple. Below you will see a schematic.

It consists of

3 resistors;

3 capacitor;

1 crystal quartz;

1 silicon diode;

1 ST6220 microcontroller;

1 DIN , 5 pole on 180° connector;

1 ST 6220 microcontroller;

5 Temporary switches;

2 Pedal-controlled Potentiometers (PROEL makes one as an example);

At present I don't have designed a printed circuit board for the controller.

I have built my own on a prototype board.

The crystal quartz needed to have a standard 31250 (+/- 1%) bit/s speed for the MIDI messages should have a fundamental frequency of 8.125 MHz. If you, like me, have trouble to find an 8.125MHz crystal quartz try to use a 8MHz crystal: it worked well for me!

This gives a speed of about 30769 bit/s slightly less than 1% of 31250 (~30937 bit/s) MIDI standard.

The values of the potentiometers are only indicative: ST Microlectronics suggest that for having better noise immunity the impedance of the analog voltage sources should be less than 30KOhm.

This is why I used two 27KOhm potentiometers. But the program I wrote, use an average of many readings and I found that even higher values cold be safely used (100KOhm and more).

Using higher resistance potentiometers has the further advantage of require less supply current.

The standard MIDI connector is a 5 pole on 180° DIN.

The ST 6220 is a microcontroller which comes in two versions:

a EPROM one that you may reprogram many times;
a OTP (One Time Programmable) cheaper that you may program only once.

A third version is a ROM Based one that you may ask to produce to STMicroelectronics... if you plan to build in large volume :-).

In any case you have to transfer on your ST6220 with a proper programmer this program (right click to start transfer: unzip it after download).

If you are ready we may proceed with the mechanics.

If you have any question ... mail me