git.defcon.no Git - AVRduinoSPI-example/blob - master/master.ino

   1 // Simple SPI MASTER example
   2 // Counts number of presses on a button connected to D2 (PD2),
   3 // and sends the count and the count+100 over SPI.
   4 // Uses a mix of Arduino and plain AVR code,
   5 // but does not use the Arduino SPI library.
   6
   7 long int count=1;
   8
   9 void setup()
  10 {
  11   Serial.begin(115200);
  12   Serial.println("Hello from MASTER")
  13
  14   // Declare pushbutton as input using the Arduino-way ;)
  15   pinMode(2, INPUT);
  16
  17   // Set SCK, MOSI and SS as OUTPUTS using the AVR-way ;)
  18   DDRB |= (1<<PB5)|(1<<PB3)|(1<<PB2);
  19   // Enable SPI, MASTER mode, Fosc/64
  20   SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1);
  21
  22   // Make sure SS is pulled HIGH
  23   spi_ss_end();
  24
  25 }
  26
  27 void loop()
  28 {
  29   // Loop with no action until button-pressed is
  30   // detected
  31   if (digitalRead(2)==HIGH)
  32   {
  33     // Wait for button to go back to "idle"
  34     while (digitalRead(2)==HIGH) {}
  35
  36     count=count+1;     // Increment count
  37
  38     Serial.print("Count: ");
  39     Serial.println(count, DEC);
  40
  41     spi_ss_start();    // Set /CS (SS) LOW for transmission
  42     spi_rw(count);     // Send current count
  43     spi_rw(count+100); // and a +100 version ;)
  44     spi_ss_end();      // Re-set /CS (SS) HIGH after transmission
  45
  46   }
  47 }
  48
  49 // Using SS as outgoing /CS pin
  50 void spi_ss_start()
  51 {
  52   PORTB &= ~(1<<PB2); // Set SS low using AVR logic ;)
  53 }
  54 void spi_ss_end()
  55 {
  56   PORTB |= (1<<PB2);  // Set SS high using AVR logic ;)
  57 }
  58
  59 uint8_t spi_rw( uint8_t d )
  60 {
  61   SPDR = d;                    // Start the transmission
  62   while (!(SPSR & (1<<SPIF))); // Wait for transmission to complete
  63   return SPDR;                 // Return the resulting register content
  64 }
  65