SPI MAX7219 demo

File content as of revision 0:bd34a367f642:

/* 06_spi_max7219_led8x8
 *
 * Simple demo to drive a 8x8-as LED matrix by a MAX7219 LED driver IC
 * After initialisation two characters (H and W) are displayed alternatively.
 * The MAX7219 IC is driven by hardware SPI: SPI0 module at PTD1, PTD2, PTD3.
 */

#include "mbed.h"

SPI spi(PTD2, PTD3, PTD1);          // Arduino compatible MOSI, MISO, SCLK
DigitalOut cs(PTD0);                // Chip select

const unsigned char led1[]= {
    0xFF,0x18,0x18,0x18,0x18,0x18,0x18,0xFF
};  //H
const unsigned char led2[]= {
    0x1F,0x60,0x80,0x40,0x40,0x80,0x60,0x1F
};  //W

/// Send two bytes to SPI bus
void SPI_Write2(unsigned char MSB, unsigned char LSB)
{
    cs = 0;                         // Set CS Low
    spi.write(MSB);                 // Send two bytes
    spi.write(LSB);
    cs = 1;                         // Set CS High
}

/// MAX7219 initialisation
void Init_MAX7219(void)
{
    SPI_Write2(0x09, 0x00);         // Decoding off
    SPI_Write2(0x0A, 0x08);         // Brightness to intermediate
    SPI_Write2(0x0B, 0x07);         // Scan limit = 7
    SPI_Write2(0x0C, 0x01);         // Normal operation mode
    SPI_Write2(0x0F, 0x0F);         // Enable display test
    wait_ms(500);                   // 500 ms delay
    SPI_Write2(0x01, 0x00);         // Clear row 0.
    SPI_Write2(0x02, 0x00);         // Clear row 1.
    SPI_Write2(0x03, 0x00);         // Clear row 2.
    SPI_Write2(0x04, 0x00);         // Clear row 3.
    SPI_Write2(0x05, 0x00);         // Clear row 4.
    SPI_Write2(0x06, 0x00);         // Clear row 5.
    SPI_Write2(0x07, 0x00);         // Clear row 6.
    SPI_Write2(0x08, 0x00);         // Clear row 7.
    SPI_Write2(0x0F, 0x00);         // Disable display test
    wait_ms(500);                   // 500 ms delay
}

int main()
{
    cs = 1;                         // CS initially High
    spi.format(8,0);                // 8-bit format, mode 0,0
    spi.frequency(1000000);         // SCLK = 1 MHz
    Init_MAX7219();                 // Initialize the LED controller
    while (1) {
        for(int i=1; i<9; i++)      // Write first character (8 rows)
            SPI_Write2(i,led1[i-1]);
        wait(1);                    // 1 sec delay
        for(int i=1; i<9; i++)      // Write second character
            SPI_Write2(i,led2[i-1]);
        wait(1);                    // 1 sec delay
    }
}