# 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 and pin45 connect to breadboard's positive and negative line which are red and blue. Pin19 and pin20 are i2c2_SCL and i2c2_SDA which will be connected to LED matrix's c pin and d pin. Don't forget the two 4.3KΩ pull-up resistors.

The wire connection picture:

## Software Design

After I went through the sample code. I found several points very important and you need to understand:

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

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 will be on, all the others will be off on that line. 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--;
}

usleep(3000000);
```

The source code can be download from my github at: Mini-project 2 by Xia Li.