Arduino MIDI out example

A friend asked me to put together an Arduino with MIDI output example. Since i already had 16 pots and 2 multiplexers breadboarded, i decided to decode the 16 pots to MIDI control numbers 20 - 35 on channel 1. Fixed control numbers and channel are used for the sake of simplicity. They could be easily user-definable by means of a 4-way DIP switch for the channel number and a pot or something for the control number offset.

Find below a schematic, commented sketch and example patch. This has been tested and found working - one should be able to simply copy and paste the sketch and breadboard a circuit quite quickly. The 4051's can be bought at Jaycar, for example for $1.30. Or cheaper still from Futurlec, if you have a few things to buy and a couple of weeks to wait ($0.66 for CD4051).

Sketch:
[expand / collapse code]

/*
16 pots to MIDI CC
by Sebastian Tomczak
9 June 2007
Adelaide, Australia
*/

// command bytes
byte status_byte = 176; // control change on channel 1
byte cc_number = 0; // value for control number

// init transfer and operation values
byte data_send = 0; // stores outgoing byte for spi bus

// init looping and working values
int workPort = 0; // working value for outgoing port
int workAn = 0; // working value for analog input

// setup begins here
void setup() {
Serial.begin(31250); // open serial port
pinMode(2,OUTPUT);
pinMode(3,OUTPUT);
pinMode(4,OUTPUT);
}

// main program begins here
void loop() {

for(int i = 0; i <= 15; i ++) // loop the following code 8 times
{
cc_number = 20 + i; // set control number to between 20 and 25 depending on loop iteration
workPort = (i / 2) * 4; // get pot 1 to 8 ignoring bits 0 and 1 of a 5 bit value
PORTD = workPort; // set pins 2, 3 and 4 to value between 0 (00000) and 7 (11100)
workAn = i % 2; // and read in either analog input 0 or 1 depending on the loop
data_send = analogRead(workAn) / 8; //read analog pin into variable... with 10 bit -> 7 bit
Serial.print(status_byte); // send status byte
Serial.print(cc_number); // send CC number
Serial.print(data_send); // send data value
// loop back...
}
// loop back...
}

Schematic:

Note that the Arduino analog and digital pins are offset by +1 ie. schematic diagram pin 1 = physical board pin marked pin 0 and so on. Click on the image below to see the pinouts of the MIDI DIN 5 connector. The solder side of a female socket is shown.

Example Max Patch: