uartspi.c

SPI communications for ATmega128/ATmega2560 (native SPI and UART in SPI-mode).

#include "uartspi.h"

void uartspi_init()
{
      UBRR2 = 0;
      DDRH  |= ((1<<DDH2) | (1<<DDH3)); //pin PH2 = XCK, PH3 = nCS
      PORTH |= (1<<PH2);
      PORTH &= ~(1<<PH3);
      UCSR2C = (1<<UMSEL21) | (1<<UMSEL20) | (1<<UCPHA2) | (1<<UCPOL2);
      UCSR2B = (1<<RXEN2) | (1<<TXEN2);
      UBRR2 = 10;

      for (unsigned char i = 0; i < 4; ++i)
            uartspi_send_byte(0xFF);

      PORTH |= (1<<PH3);
}


unsigned char uartspi_send_byte(unsigned char data)
{
unsigned char incoming;

      PORTH &= ~(1<<PH3);

      while ( !(UCSR2A & (1<<UDRE2)) );
      UDR2 = data;
      while ( !(UCSR2A & (1<<RXC2)) );
      incoming = UDR2;

      PORTH |=  (1<<PH3);

      return incoming;
}