LED dot matrix graphic display

Independent LED lights can realize running lights, digital tubes can display multiple digits, and dot matrix LEDs have to display some patterns.

When we want to display patterns, we often have to make some small graphics first. The data of these small graphics needs to be converted into our program. At this time, we need modeling software. Here is a simple modeling software that can be downloaded online. Let's learn how to use it. First, take a look at the operation interface, as shown in Figure 7-3.

Figure 7-3 Font extraction software interface

Click "New Shape" with the mouse, change the width and height to 8 respectively according to the dot matrix on our board, and then click OK, as shown in Figure 7-4.

Figure 7-4 Create a new graphic

Click the "Simulation Animation" menu on the left, then click the "Enlarge Grid" option and zoom in to the maximum. Then we can use the mouse to fill in the black dots in our 8*8 dot matrix and draw the graphics, as shown in Figure 7-5.

Figure 7-5 Drawing with font extraction software

After careful design, we drew a heart-shaped figure and filled it up, and finally the desired effect appeared, as shown in Figure 7-6.

Figure 7-6 Heart-shaped graphic

Since the modeling software sets black as 1 and white as 0, but our dot matrix corresponds to 1 when the LED is off and 0 when the LED is on, and what we need is a lit "heart", we need to select the "Black and white reverse image" option in the "Modify image" menu, and then click "Save image" in the "Basic operation" menu to save the image we designed, as shown in Figure 7-7.

Figure 7-7 Save the graph

Saving the file is just for the convenience of reuse or modification. Of course, you can choose not to save it. After completing this step, click "Other Options" in the "Parameter Settings" menu, as shown in Figure 7-8.

Figure 7-8 Option settings

The options here should be set in conjunction with Figure 7-2. You can see that port P0 controls a row, so use "horizontal modulus". If it controls a column, select "vertical modulus". The "byte reverse order" option is selected because the left side of Figure 7-2 is low-order DB0 and the right side is high-order DB7, so it is byte reverse order. You can understand the other two options yourself. After clicking OK, select the "modulus mode" menu. After clicking "C51 format", 8 bytes of data are automatically generated in the "dot matrix generation area". These 8 bytes of data are the "modulus" taken out, as shown in Figure 7-9.

Figure 7-9 Modulo result

Please note that although we use software to take the modulus, we also need to know the principle. In this picture, a black grid represents a binary 1, and a white grid represents a binary 0. The first byte is 0xFF, which is actually the first row of this 8*8 graphic. All black is 0xFF; the second byte is 0x99, with the low bit on the left and the high bit on the right. Please note that black represents 1 and white represents 0, which constitutes the value 0x99. Similarly, you will know how the other data comes from.

Then we will use the program to send these data to the dot matrix in turn to see how the operation effect is.

#include

sbit ADDR0 = P1^0;

sbit ADDR1 = P1^1;

sbit ADDR2 = P1^2;

sbit ADDR3 = P1^3;

sbit ENLED = P1^4;

unsigned char code image[] = { //Character table of the image

    0xFF, 0x99, 0x00, 0x00, 0x00, 0x81, 0xC3, 0xE7

};

void main(){

    EA = 1; // Enable general interrupt

    ENLED = 0; // Enable U4 and select LED matrix

    ADDR3 = 0;

    TMOD = 0x01; //Set T0 to mode 1

    TH0 = 0xFC; //Assign the initial value 0xFC67 to T0, and the timing is 1ms

    TL0 = 0x67;

    ET0 = 1; // Enable T0 interrupt

    TR0 = 1; //Start T0

    while (1);

}

/* Timer 0 interrupt service function */

void InterruptTimer0() interrupt 1{

    static unsigned char i = 0; //dynamic scan index

    TH0 = 0xFC; //Reload initial value

    TL0 = 0x67;

    //The following code completes the dynamic scanning and refreshing of the LED dot matrix

    P0 = 0xFF; //display blanking

    switch (i) {

        case 0: ADDR2=0; ADDR1=0; ADDR0=0; i++; P0=image[0]; break;

        case 1: ADDR2=0; ADDR1=0; ADDR0=1; i++; P0=image[1]; break;

        case 2: ADDR2=0; ADDR1=1; ADDR0=0; i++; P0=image[2]; break;

        case 3: ADDR2=0; ADDR1=1; ADDR0=1; i++; P0=image[3]; break;

        case 4: ADDR2=1; ADDR1=0; ADDR0=0; i++; P0=image[4]; break;

        case 5: ADDR2=1; ADDR1=0; ADDR0=1; i++; P0=image[5]; break;

        case 6: ADDR2=1; ADDR1=1; ADDR0=0; i++; P0=image[6]; break;

        case 7: ADDR2=1; ADDR1=1; ADDR0=1; i=0; P0=image[7]; break;

        default: break;

    }

}

For 8*8 dot matrix, we can display some simple graphics, characters, etc. But most Chinese characters usually use 16*16 dots, and 8*8 dot matrix can only display some Chinese characters with simple strokes. You can try it yourself. The method of using a large screen to display Chinese characters is similar to that of a small screen. All you need to do is expand the number of rows and columns according to the same principle.