it will look like this when done -
/*
LED Matrix - Display scrolling text
Version: 1.0
Author: electricteardown (http://insidegadgets.wordpress.com)
Created: 6/11/2010
Last Modified: 6/11/2010
*/
//Pin connected to ST_CP of 74HC595
int latchPin = 8;
//Pin connected to SH_CP of 74HC595
int clockPin = 12;
//Pin connected to DS of 74HC595
int dataPin = 11;
int counter = 0;
int movement = 0;
int LEDs[8][17] = {
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
};
int letterH[8][8] = {
{0, 1, 0, 0, 0, 0, 1, 0},
{0, 1, 0, 0, 0, 0, 1, 0},
{0, 1, 0, 0, 0, 0, 1, 0},
{0, 1, 1, 1, 1, 1, 1, 0},
{0, 1, 1, 1, 1, 1, 1, 0},
{0, 1, 0, 0, 0, 0, 1, 0},
{0, 1, 0, 0, 0, 0, 1, 0},
{0, 1, 0, 0, 0, 0, 1, 0}
};
int letterI[8][8] = {
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
{0, 0, 0, 1, 1, 0, 0, 0},
};
void setup() {
//set pins to output because they are addressed in the main loop
pinMode(latchPin, OUTPUT);
pinMode(clockPin, OUTPUT);
pinMode(dataPin, OUTPUT);
}
void loop() {
if (movement == 0) {
int x;
int y;
for (x = 0; x < 8; x++) {
for (y = 0; y < 8; y++) {
LEDs[x][y+8] = letterH[x][y];
}
}
}
if (movement == 8) {
int x;
int y;
for (x = 0; x < 8; x++) {
for (y = 0; y < 8; y++) {
LEDs[x][y+8] = letterI[x][y];
}
}
}
if (counter % 25 == 0) {
movement++;
int x;
int y;
for (x = 0; x < 8; x++) {
for (y = 0; y < 16; y++) {
LEDs[x][y] = LEDs[x][y+1];
}
}
}
if (movement >= 16) {
counter = 0;
movement = 0;
}
lightLED();
counter++;
}
void lightLED() {
byte columnbitsToSend = 0;
byte rowbitsToSend = 0;
int x = 0;
int y = 0;
for (x = 0; x < 8; x++) {
columnbitsToSend = 0;
rowbitsToSend = 0;
for (y = 0; y < 8; y ++) {
if (LEDs[x][y] == 1) {
bitWrite(rowbitsToSend, y, HIGH);
}
}
digitalWrite(latchPin, LOW);
bitWrite(columnbitsToSend, x, HIGH);
shiftOut(dataPin, clockPin, MSBFIRST, columnbitsToSend);
shiftOut(dataPin, clockPin, MSBFIRST, rowbitsToSend);
digitalWrite(latchPin, HIGH);
delay(2);
}
}
Why the LEDs array is 17?
Because of this little bit of code -
for (x = 0; x < 8; x++) {
for (y = 0; y < 16; y++) {
LEDs[x][y] = LEDs[x][y+1];
}
Because in this code it looks like he was using 16 elements, but the y+1 (that he never writes to, probably should be filled with zeros) makes the 17th element. elements 0-15 make for 16 elements. element 16 is the 17th element. (don't you just love C...) When you have that little quirk mastered you will be a level 1 C programmer.
