Charlieplexing 20 LEDs

Charlieplex20LEDs.cpp

// pin defines
#define A 12
#define B 11
#define C 10
#define D 9
#define E 8

#define PIN_COUNT 5

#define PIN_CONFIG 0
#define PIN_STATE 1

#define LED_COUNT 20

/*
 * If you want to save bytes in SRAM, this could be a collection of bytes for each DDRx and PORTx
 * on the AVR chip (up to 8 bits or lines) (8 lines would allow for 56 LEDs)
 */
int matrix[LED_COUNT][2][PIN_COUNT] = {
    /*
     *  Each row in this matrix respresents the pin modes and pin states for a single LED
     */
    //              PIN_CONFIG                          PIN_STATE
    //    A       B       C      D      E         A     B    C    D    E
    { { OUTPUT, OUTPUT, INPUT, INPUT, INPUT }, { HIGH, LOW, LOW, LOW, LOW } }, // AB 0
    { { OUTPUT, OUTPUT, INPUT, INPUT, INPUT }, { LOW, HIGH, LOW, LOW, LOW } }, // BA 1
    { { INPUT, OUTPUT, OUTPUT, INPUT, INPUT }, { LOW, HIGH, LOW, LOW, LOW } }, // BC 2
    { { INPUT, OUTPUT, OUTPUT, INPUT, INPUT }, { LOW, LOW, HIGH, LOW, LOW } }, // CB 3
    { { OUTPUT, INPUT, OUTPUT, INPUT, INPUT }, { LOW, LOW, HIGH, LOW, LOW } }, // CD 4
    { { INPUT, INPUT, OUTPUT, OUTPUT, INPUT }, { LOW, LOW, LOW, HIGH, LOW } }, // DC 5
    { { INPUT, INPUT, INPUT, OUTPUT, OUTPUT }, { LOW, LOW, LOW, HIGH, LOW } }, // DE 6
    { { INPUT, INPUT, INPUT, OUTPUT, OUTPUT }, { LOW, LOW, LOW, LOW, HIGH } }, // ED 7
    { { OUTPUT, INPUT, OUTPUT, INPUT, INPUT }, { HIGH, LOW, LOW, LOW, LOW } }, // AC 8
    { { OUTPUT, INPUT, OUTPUT, INPUT, INPUT }, { LOW, LOW, HIGH, LOW, LOW } }, // CA 9
    { { INPUT, INPUT, OUTPUT, INPUT, OUTPUT }, { LOW, LOW, HIGH, LOW, LOW } }, // CE 10
    { { INPUT, INPUT, OUTPUT, INPUT, OUTPUT }, { LOW, LOW, LOW, LOW, HIGH } },  // EC 11
    { { INPUT, OUTPUT, INPUT, OUTPUT, INPUT }, { LOW, HIGH, LOW, LOW, LOW } },  // BD 12
    { { INPUT, OUTPUT, INPUT, OUTPUT, INPUT }, { LOW, LOW, LOW, HIGH, LOW } },  // DB 13
    { { OUTPUT, INPUT, INPUT, OUTPUT, INPUT }, { HIGH, LOW, LOW, LOW, LOW } },  // AD 14
    { { OUTPUT, INPUT, INPUT, OUTPUT, INPUT }, { LOW, LOW, LOW, HIGH, LOW } },  // DA 15
    { { INPUT, OUTPUT, INPUT, INPUT, OUTPUT }, { LOW, HIGH, LOW, LOW, LOW } },  // BE 16
    { { INPUT, OUTPUT, INPUT, INPUT, OUTPUT }, { LOW, LOW, LOW, LOW, HIGH } },  // EB 17
    { { OUTPUT, INPUT, INPUT, INPUT, OUTPUT }, { HIGH, LOW, LOW, LOW, LOW } },  // AE 18
    { { OUTPUT, INPUT, INPUT, INPUT, OUTPUT }, { LOW, LOW, LOW, LOW, HIGH } }  // EA 19
};

void turnOn( int led ) {
    // set all the pin modes
    pinMode( A, matrix[led][PIN_CONFIG][0] );
    pinMode( B, matrix[led][PIN_CONFIG][1] );
    pinMode( C, matrix[led][PIN_CONFIG][2] );
    pinMode( D, matrix[led][PIN_CONFIG][3] );
    pinMode( E, matrix[led][PIN_CONFIG][4] );
    // set all the pin states
    digitalWrite( A, matrix[led][PIN_STATE][0] );
    digitalWrite( B, matrix[led][PIN_STATE][1] );
    digitalWrite( C, matrix[led][PIN_STATE][2] );
    digitalWrite( D, matrix[led][PIN_STATE][3] );
    digitalWrite( E, matrix[led][PIN_STATE][4] );
}

void setup() {}

void loop() {
    for( int l = 0; l < LED_COUNT; l++ ) {
        turnOn( l );
        delay( 1000 / LED_COUNT );
    }
}

This code is so great and clean. I did notice 2 issues, when driving DC the pin state for D is input and A is output,
{ {OUTPUT , INPUT, OUTPUT, OUTPUT, INPUT }, { LOW, LOW, LOW, HIGH, LOW } }, // DC 5

Also the commas are missing after CE in the matrix.

But again, great code and very easy to understand how it works :)

Hey Jeff! Thanks for pointing out the broken stuff. I added the commas, but it's been so long since I worked on this code that I can't see the issue in the pattern on the line for "DC 5" (nothing stood out just staring at it). I've been away from this code for a few years now.

D and C are the channel 5 pins, and A and D and C are outputs for that channel, which causes problems when run. changing the line to below should fix it.
{ {INPUT, INPUT, OUTPUT, OUTPUT, INPUT }, { LOW, LOW, LOW, HIGH, LOW } }, // DC 5

Ah, yes! Thank you for the correction! Code is updated.