In this blog we will focus on how to make and code a 4x4 LED matrix using a shift register(SN7HC595N).
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| Arduino Uno | Shift Register | |
|---|---|---|
| 5v | - | SCLR,VCC |
| D11 | - | SCLK |
| D12 | - | RCLK |
| D10 | - | Pin 14 (SER) |
Shift register chip transforms bits that are inserted in series trough the data pin into 8 parallel bits,So if you want to send lets say 10010000 you start with the least significant bit (0) so you set SER to LOW (D10 on the Arduino). Next, you set SCK (D11 on the Arduino) to HIGH and then to LOW, to “save” the value.
byte character[8]={0x00, 0x00, 0x00, 0x00, 0xFf, 0xfF, 0xFf, 0xFf};//for row
uint8_t colPins[4]={2, 3, 4, 5};//specify's column pin,directly connected to arduino
#define SER_PIN 10
#define SCK_PIN 11
#define RCK_PIN 12
void setup() {
// Turn everything to low
for(int i=0; i<8; i++) {
pinMode(colPins[i],OUTPUT);
}
pinMode(SER_PIN, OUTPUT);
pinMode(SCK_PIN, OUTPUT);
pinMode(RCK_PIN, OUTPUT);
Serial.begin(9600);
}
void write595(byte data) {
digitalWrite(RCK_PIN, LOW);
shiftOut(SER_PIN, SCK_PIN, LSBFIRST, data);
digitalWrite(RCK_PIN, HIGH);
}
void loop() {
// iterate each row
int rowbits = 0x08;//for registering the value
for(int row=0; row<4; row++) {
for(int k=0; k<4; k++)
digitalWrite(colPins[k],HIGH); // Cleanup cols
write595(rowbits); // prepare to write the row
for(int col=0; col<4; col++)
digitalWrite(colPins[col]/*operating column pins*/, character[row+4] & 1 << col ? LOW : HIGH);
delay(1000);
write595(0);
rowbits >>= 1;
}
}