A quick course in Binary

project #23: displaying an image on an led matrix

In this project we’ll display the image on the matrix shown in Figure 6-23.

Figure 6-23: Layout for our POV display example
We can define each row as a binary number and place these numbers in an array:
byte smile[] = {B00000000, B00000110,
B01000110,
B00000000,
B00011000,
B00000000,
B11000011,
B01111110};
Notice how the 1s in the array resemble the lit LEDs in the layout in Figure 6-23. Our use of binary numbers makes developing an image very easy. By experimenting with MSBFIRST and LSBFIRST in the shiftOut() functions, you can flip each row around, as shown next. We use a for loop at  to display each row in turn:
// Project 23 - Displaying an Image on an LED Matrix
#define DATA 6 // connect to pin 14 on the 74HC595
#define LATCH 8 // connect to pin 12 on the 74HC595 #define CLOCK 10 // connect to pin 11 on the 74HC595
byte smile[] = {B00000000, B00000110, B01000110, B00000000, B00011000,
B00000000, B11000011, B01111110}; int binary[] = {1, 2, 4, 8, 16, 32, 64, 128};
void setup()
{
pinMode(LATCH, OUTPUT); pinMode(CLOCK, OUTPUT); pinMode(DATA, OUTPUT); }
void loop()
{ int i;
 for ( i = 0 ; i < 8 ; i++ )
{
digitalWrite(LATCH, LOW);
shiftOut(DATA, CLOCK, MSBFIRST, ~smile[a]); // columns shiftOut(DATA, CLOCK, LSBFIRST, binary[a]); // rows
digitalWrite(LATCH, HIGH);
delay(1);
}
}
The result is a winking smiley face, as shown in Figure 6-24.

Figure 6-24: Result of Project 23

project #24: Animating an led matrix

Using some bitwise arithmetic, we can scroll the image we created in Project 23 off the display in either direction. For example, to have the face move to the right until its gone, we display the image, then shift each bit in the row over by one using >>, and then display the image again.