#define SCK 7   // SPI clock
#define SDO 5   // SPI Data output (RFM12B side)
#define SDI 6   // SPI Data input (RFM12B side)
#define CS  4   // SPI SS (chip select)
#define NIRQ 2  // (PORTD)

#define HI(x) PORTB |= (1<<(x))
#define LO(x) PORTB &= ~(1<<(x))
#define WAIT_NIRQ_LOW() while(PIND&(1<<NIRQ))

#define LED 6
#define LED_OFF() PORTD &= ~(1<<LED)
#define LED_ON() PORTD |= (1<<LED)

#define BAUDRATE 25 // 19200 at 8MHz

#include <avr/io.h>

void rsInit(unsigned char baud) {
  UBRRL = baud;
  UCSRC = (1<<UCSZ0) | (1<<UCSZ1);  // 8N1
  UCSRB = (1<<RXEN) | (1<<TXEN);   
}

void rsSend(unsigned char data) {
  while( !(UCSRA & (1<<UDRE)));
  UDR = data;
}

unsigned char rsRecv() {
  while( !(UCSRA & (1<<RXC)));
  return UDR;
}

void portInit() {
  HI(CS);
  HI(SDI);
  LO(SCK);
  DDRB = (1<<CS) | (1<<SDI) | (1<<SCK);
  DDRD = (1<<LED); 
}

unsigned int writeCmd(unsigned int cmd) {
  unsigned char i;
  unsigned int recv;
  recv = 0;
  LO(SCK);
  LO(CS);
  for(i=0; i<16; i++) {
    if(cmd&0x8000) HI(SDI); else LO(SDI);
    HI(SCK);
    recv<<=1;
    if( PINB&(1<<SDO) ) {
      recv|=0x0001;
    }
    LO(SCK);
    cmd<<=1;
  }
  HI(CS);
  return recv;
}

void rfInit() {
  writeCmd(0x80E7); //EL,EF,868band,12.0pF
  writeCmd(0x8239); //!er,!ebb,ET,ES,EX,!eb,!ew,DC
  writeCmd(0xA640); //frequency select
  writeCmd(0xC647); //4.8kbps
  writeCmd(0x94A0); //VDI,FAST,134kHz,0dBm,-103dBm
  writeCmd(0xC2AC); //AL,!ml,DIG,DQD4
  writeCmd(0xCA81); //FIFO8,SYNC,!ff,DR
  writeCmd(0xCED4); //SYNC=2DD4�G
  writeCmd(0xC483); //@PWR,NO RSTRIC,!st,!fi,OE,EN
  writeCmd(0x9850); //!mp,90kHz,MAX OUT
  writeCmd(0xCC17); //OB1�COB0, LPX,�Iddy�CDDIT�CBW0
  writeCmd(0xE000); //NOT USE
  writeCmd(0xC800); //NOT USE
  writeCmd(0xC040); //1.66MHz,2.2V
}

void rfSend(unsigned char data){
  while(WAIT_NIRQ_LOW());
  writeCmd(0xB800 + data);
}

int main() {
  volatile unsigned int i,j;
  asm("cli");
  for(i=0;i<1000;i++)for(j=0;j<123;j++);
  portInit();
  /* rsInit(BAUDRATE); */
  rfInit();
  while(1){
    LED_ON();
    writeCmd(0x0000);
    rfSend(0xAA); // PREAMBLE
    rfSend(0xAA);
    rfSend(0xAA);
    rfSend(0x2D); // SYNC
    rfSend(0xD4);
    for(i=0; i<16; i++) {
      rfSend(0x30+i);
    }
    rfSend(0xAA); // DUMMY BYTES
    rfSend(0xAA);
    rfSend(0xAA);
    LED_OFF();
    for(i=0; i<10000; i++)
      for(j=0; j<123; j++);
  }
}