# Difference between revisions of "Adafruit: 8x8 Red LED Matrix Panel"

## Overview

My mini project 2 is using an Adafriut 8*8 red LED matrix to show 2 animations. First animation is to composite a diamond and then fade out. The second animation is to drop down a horizontal bar to the bottom of the LED matrix until all the lines are being filled. When the two animations were done, the LED matrix will flash 5 times and shut down.

The code that being used in this project is modified from the sample code provided by Dr. Mark A. Yoder. The new version of the code that contained my animation has been commited to my github which you can find at here: Mini-project 2 by Xia Li.

## Wire Connection

The wire connection part is not very complex. As you can see in the picture pin3 VDD3.3v ----> breadboard's positive(red line)

pin45 GND ----> breadboard's negative(blue line)

pin19 i2c2_SCL ----> LED matrix's c pin

pin20 i2c2_SDA ----> LED matrix's d pin.

Don't forget the two 4.3KΩ pull-up resistors.

LED matrix's + - pin ----> breadboard's positive and negative

The wire connection picture:

## Software Design

### Important facts

After I went through the sample code. I found several points which are very important. You may need to understand before you move on:

1. i2cbus is 3

4. display on daddress is 0x81

5. Full brightness is 0xE7

6. array smile_bmp[], frown_bmp[], and neutral_bmp[] are save the hex-decimal value for each line on LED matrix

### Theory

The theory is when you convert the hex-decimal value of each line to binary value, you will get a 8 bit binary number for each line. Each bit will stand for each led point on the corresponding line. 0 for off, 1 for on.

For example: 0x18 = 1 * 16 + 8 = 24(decimal) = 0 0 0 1 1 0 0 0(binary)

This value means the 4th and 5th led position of that line will be on, all the other leds will be off. After you understand this, you can program your pattern or animation.

I create 4 patterns for diamond animation:

pic1_bmp[]={0x18, 0x3C, 0x7E, 0xFF, 0xFF, 0x7E, 0x3C, 0x18}

pic2_bmp[]={0x18, 0x3C, 0x7E, 0xE7, 0xE7, 0x7E, 0x3C, 0x18}

pic3_bmp[]={0x18, 0x3C, 0x66, 0xC3, 0xC3, 0x66, 0x3C, 0x18}

pic4_bmp[]={0x18, 0x24, 0x42, 0x81, 0x81, 0x42, 0x24, 0x18}

The horizontal bar only need 1 pattern:

line_bmp[]={0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}

Below is the major part of the code:

static __u16 smile_bmp[]={0x3C, 0x42, 0x95, 0xA1, 0xA1, 0x95, 0x42, 0x3C};
static __u16 test_bmp[]={0x3C, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
static __u16 frown_bmp[]={0x3C, 0x42, 0xA5, 0x91, 0x91, 0xA5, 0x42, 0x3C};
static __u16 neutral_bmp[]={0x3C, 0x42, 0x95, 0x91, 0x91, 0x95, 0x42, 0x3C};
static __u16 pic1_bmp[]={0x18, 0x3C, 0x7E, 0xFF, 0xFF, 0x7E, 0x3C, 0x18};
static __u16 pic2_bmp[]={0x18, 0x3C, 0x7E, 0xE7, 0xE7, 0x7E, 0x3C, 0x18};
static __u16 pic3_bmp[]={0x18, 0x3C, 0x66, 0xC3, 0xC3, 0x66, 0x3C, 0x18};
static __u16 pic4_bmp[]={0x18, 0x24, 0x42, 0x81, 0x81, 0x42, 0x24, 0x18};

static __u16 line_bmp[]={0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

// Demo 1 is showing...
printf("Demo 1 is showing...\n");
while(counter <= 1)
{
for(i=0; i<8; i++){
block[i] = (pic1_bmp[i]&0xfe) >> 1 |
(pic1_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
for(i=0; i<8; i++){
block[i] = (pic2_bmp[i]&0xfe) >> 1 |
(pic2_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
for(i=0; i<8; i++){
block[i] = (pic3_bmp[i]&0xfe) >> 1 |
(pic3_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
for(i=0; i<8; i++){
block[i] = (pic4_bmp[i]&0xfe) >> 1 |
(pic4_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
for(i=0; i<8; i++){
block[i] = (pic3_bmp[i]&0xfe) >> 1 |
(pic3_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
for(i=0; i<8; i++){
block[i] = (pic2_bmp[i]&0xfe) >> 1 |
(pic2_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
for(i=0; i<8; i++){
block[i] = (pic1_bmp[i]&0xfe) >> 1 |
(pic1_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);

counter += 1;
}
// Demo 2 is showing...
printf("Demo 2 is showing...\n");
while(q>=0){
j=0;
while(j<=q){
for(i=0; i<8; i++){
block[i] = (line_bmp[i]&0xfe) >> 1 |
(line_bmp[i]&0x01) << 7;
}
(__u8 *)block);

usleep(500000);
if(j<q){
tmp = line_bmp[j];
line_bmp[j] = line_bmp[j+1];
line_bmp[j+1] = tmp;
}
if(j==q){
line_bmp[0] = 0xFF;
}
j++;
}
q--;
}