youngkin

func writeMax7219Byte(b byte) {
    rpio.SpiTransmit(b)
}

youngkin

func writeMax7219(addr byte, value byte) {
    // The csPin (chip select) is set to LOW to direct the MAX7219 to accept data from the MOSI line.
    // Setting it to HIGH at the end of the function directs the MAX7219 to ignore data on the MOSI line.
    csPin.Low()
    writeMax7219Byte(addr)
    writeMax7219Byte(value)
    csPin.High()
}

youngkin

func initMax7219() {
    writeMax7219(0x09, 0x00) // Decode mode register
    writeMax7219(0x0a, 0x03) //  medium brightness
    //    writeMax7219(0x0a,0x0f);// max brightness
    writeMax7219(0x0b, 0x07) // Scan limit register
    writeMax7219(0x0c, 0x01) // Shutdown register
    writeMax7219(0x0f, 0x00) // Display test register, normal mode
    //    writeMax7219(0x0f,0x01);// Display test register, test mode (light all leds)
}

youngkin

    // Initialize SPI on the SPI0 associated GPIO pins
    if err := rpio.SpiBegin(rpio.Spi0); err != nil {
        fmt.Println(err)
        os.Exit(1)
    }

    csPin.Output()
    rpio.SpiChipSelect(uint8(csPin)) // Select CE0 (csPin) as slave
    initMax7219()

youngkin

func main() {
    // stop channel is used to synchronize exiting the
    // program so that the board is reset to the state
    // it was in prior to the program starting.
    stop := make(chan interface{})
    // sigs is the channel used by Go's signals capability
    // to notify the program that a signal has been raised.
    sigs := make(chan os.Signal)

    // signal.Notify() registers the program's interest

youngkin

const csPin = rpio.Pin(uint8(8)) //csPin represents the chip select pin and specifies it is on GPIO pin 8
const NUM_CHARS = 37             // Number of characters that can be displayed
const MATRIX_ROW = 8             // The number of rows of LEDs on the MAX7219

var disp1 = [][]byte{
    {0x3C, 0x42, 0x42, 0x42, 0x42, 0x42, 0x42, 0x3C}, //0
    {0x08, 0x18, 0x28, 0x08, 0x08, 0x08, 0x08, 0x08}, //1
    ...
}

youngkin

void bcm_peri_set_bits(volatile uint32_t* paddr, uint32_t value, uint32_t mask)
{
    uint32_t v = bcm_peri_read(paddr);
    v = (v & ~mask) | (value & mask);
    bcm_peri_write(paddr, v);
}

youngkin

void bcm_spi_setBitOrder(uint8_t order)
{
    bcm_spi_bit_order = order;

}

youngkin

uint8_t bcm_spi_transfer(uint8_t value)
{
    volatile uint32_t* paddr = bcm_spi0 + BCM_SPI0_CS/4;
    volatile uint32_t* fifo = bcm_spi0 + BCM_SPI0_FIFO/4;
    uint32_t ret;

    bcm_peri_set_bits(paddr, BCM_SPI0_CS_CLEAR, BCM_SPI0_CS_CLEAR);

    /* Set TA = 1, data transfer is active */
    bcm_peri_set_bits(paddr, BCM_SPI0_CS_TA, BCM_SPI0_CS_TA);

youngkin

void bcm_spi_setClockDivider(uint16_t divider)
{
    volatile uint32_t* paddr = bcm_spi0 + BCM_SPI0_CLK/4;
    bcm_peri_write(paddr, divider);
}