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Adafruit: 8x8 Red LED Matrix Panel

Revision as of 00:05, 18 October 2012 by Lix (Talk | contribs)

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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.

Software Design

After I went through the sample code. I found several points very important and you need to understand: 1. i2cbus is 3; 2. i2c address is 0x70; 3. oscillator daddress is 0x21; 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}