test/spi.c

   1 #include <avr/io.h>
   2 #include "spi.h"
   3
   4 #define SPIDONTCARE (0x00)
   5
   6 /* init as SPI-Master */
   7 void spi_init(void) {
   8         // SCK, MOSI as outputs
   9         SPIDDR |= (1<<SPISCK)|(1<<SPISS)|(1<<SPIMOSI);
  10         // MISO as input
  11         SPIDDR &= ~(1<<SPIMISO);
  12
  13         // fck/128 = 16Mhz/128 = 125kHz
  14         // INIT interface, Master, set clock rate fck/128
  15         SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0)|(1<<SPR1);
  16 }
  17
  18 uint8_t spi_readwrite(uint8_t data) {
  19         // set data to send into SPI data register
  20         SPDR = data;
  21         // Wait for transmission complete
  22         while(!(SPSR & (1<<SPIF)));
  23         // return data read from SPI
  24         return SPDR;
  25 }
  26
  27 void spi_write(uint8_t data) {
  28         // set data to send into SPI data register
  29         SPDR = data;
  30         // Wait for transmission complete
  31         while(!(SPSR & (1<<SPIF)));
  32 }
  33
  34 uint8_t spi_read(void) {
  35         return spi_readwrite(SPIDONTCARE);
  36 }
  37