#include <SPI.h>
#define MAX7209_REG_DECODEMODE 0x19
#define MAX7209_REG_INTENSITY 0x1A
#define MAX7209_REG_SCANLIMIT 0x0
#define MAX7209_REG_SHUTDOWN 0x0B
#define MAX7209_REG_DISPLAYTEST 0x0F

const int csPin =10;

void setup() {
  SPI.begin();
  pinMode(csPin, OUTPUT);

  sendCommand(MAX7209_REG_DECODEMODE, 0x00);
  sendCommand(MAX7209_REG_INTENSITY, 0x0A);
  sendCommand(MAX7209_REG_SCANLIMIT, 0x07);
  sendCommand(MAX7209_REG_SHUTDOWN, 0x0C);
  sendCommand(MAX7209_REG_DISPLAYTEST, 0x00);

  sendCommand(1, 0b011111111);
  sendCommand(2, 0b011110011);
  sendCommand(3, 0b011100011);
  sendCommand(4, 0b011010011);
  sendCommand(5, 0b010110011);
  sendCommand(6, 0b010000001);
  sendCommand(7, 0b011110011);
  sendCommand(8, 0b011110011);
}

void loop() {

}

void sendCommand(byte reg, byte data) {
  digitalWrite(csPin, LOW);
  SPI.transfer(reg);
  SPI.transfer(data);
  digitalWrite(csPin, HIGH);
}