#include <avr/io.h>
#include <avr/wdt.h>
#include <avr/interrupt.h>

#define SET(sfr, bit)    ({ __asm__ __volatile__ ("sbi  %0, %1"::"I" _SFR_IO_ADDR(sfr),"n" (bit)); })
#define CLEAR(sfr, bit)  ({ __asm__ __volatile__ ("cbi  %0, %1"::"I" _SFR_IO_ADDR(sfr),"n" (bit)); })

#define SCK 5   // SPI clock
#define SDO 4   // SPI Data output (RFM12B side)
#define SDI 3   // SPI Data input (RFM12B side)

#define SS 2

#define nSEL_INIT        SET(DDRD,5)
#define nSEL_HI          SET(PORTD,5)
#define nSEL_LOW         CLEAR(PORTD,5)


void portInit(void) 
{
  nSEL_HI;
  nSEL_INIT;
  SET(PORTB,SS);  // Slave Select immer high halten, damit SPI im Master-Mode bleibt
  SET(PORTB,SDI);
  CLEAR(PORTB,SCK);
  DDRB = (1<<SDI) | (1<<SCK) | (1<<SS);  
}

unsigned int writeCmd(unsigned int cmd) 
{
    // the 2 loops below each spin 4 usec with a 2 MHz SPI clock
    unsigned int reply;
	
	reply = 0;
    nSEL_LOW;      // SPI_SS Low
    SPDR = cmd >> 8;
    while (!(SPSR & _BV(SPIF)))
        ;
    reply = SPDR << 8;
    SPDR = cmd;
    while (!(SPSR & _BV(SPIF)))
        ;
    reply |= SPDR;
    nSEL_HI;     // SPI_SS High
    return reply;
}

void rfInit(void) 
{
	writeCmd(0xC000);			// AVR CLK: 1MHz
	writeCmd(0x80D7);			// Enable FIFO
	writeCmd(0xC2AB);			// Data Filter: internal
	writeCmd(0xCA81);			// Set FIFO mode
	writeCmd(0xE000);			// disable wakeuptimer
	writeCmd(0xC800);			// disable low duty cycle
	writeCmd(0xC4F7);			// AFC settings: autotuning: -10kHz...+7,5kHz
	writeCmd(0xA620);           // freq select
	writeCmd(0x9400|((4&7)<<5)|((1&3)<<3)|(4&7));
	writeCmd(0xC600|((344828UL/19200)-1));	// R=344828/Baud-1
	writeCmd(0x9800|(0&7)|((6&15)<<4));
}

void send_RS232(unsigned int data)
{
	unsigned char i;
	unsigned int  nibble;
	
	for(i=0; i<4; i++)
	{
	    nibble = data & 0xF000;
		nibble = nibble>>12;
		while ( !( UCSRA & (1<<UDRE)) )   // Wait for empty transmit buffer 
			;
		if(nibble>9) { UDR = 65+nibble-10; } else { UDR = 0x30+nibble; }
		data = data<<4;
	}
	while ( !( UCSRA & (1<<UDRE)) )  // Wait for empty transmit buffer 
		;
	UDR = 0x20;	
}

unsigned char rfRecv(void) 
{
    unsigned int data;

    do
    {
        data = writeCmd(0x0000);
		//send_RS232(data);
	    if (data&0x0100)
	    {
	      	send_RS232(data);
	    }
    } 
    while((data&0x8000)==0);
	data = writeCmd(0xB000);
	send_RS232(data);
    return (data&0x00FF);
}

int main(void) 
{
    unsigned char data, i;
    volatile unsigned int k,j;

    wdt_disable();
    cli();
    portInit();
	/*--------------------- Initialize USART --------------------------*/
	UBRRH = (unsigned char) (12>>8);                               // Set the baudrate to 4800 bps using 1MHz system clock => 12    
	UBRRL = (unsigned char) 12;
	UCSRB = ( ( 1 << RXCIE ) | ( 1 << RXEN ) | ( 1 << TXEN ) );    // Enable UART receiver and transmitter
	UCSRC = (1<<URSEL)|(1<<UCSZ1)|(1<<UCSZ0);                      // Set frame format: 8 data 1stop
	/*-----------------------------------------------------------------*/

    SPCR = _BV(SPE) | _BV(MSTR);         // Init SPI -> clk/4 is ok for the RF12's SPI 

    for(k=0;k<1000;k++)for(j=0;j<123;j++);
  
    rfInit();

    while(1) 
    {
        writeCmd(0x82C8);			// RX on
	    writeCmd(0xCA81);			// set FIFO mode
	    writeCmd(0xCA83);			// enable FIFO
        for (i=0; i<10; i++) 
	    {
            data = rfRecv();
        }
        writeCmd(0x8208);			// RX off 
    }
    return 0;
}