/*
    12-1-2007
    Cai Maver, caimaver(at)yahoo.com
    ARRRduino+NS73M v0.3

    This code allows an Arduino Diecimila to control an NS73M FM Transmitter Module (Arrr matey!)

    This sets the NS73M (available from Sparkfun, SKU#: WRL-08482) to transmit
    at 2mW with 75us pre-emphasis (the standard for North America) on 97.3 MHz.

    Use this formula to determine the register values for a new transmitting frequency (f):

    (f + 0.304)/0.008192 <-- use only the whole number and convert the result to
				   16-bit binary where the lower byte goes in register 3
				   and the upper byte goes in register 4

				   ex.: for 97.3 MHz, (97.3 + 0.304)/0.008192 = 11914.55...
					  11914 = B0010111010001010 so Reg 3=B10001010 and Reg 4=B00101110

    A future version of this code will allow for on-the-fly frequency changes

    Thanks to Nathan Seidle at Sparkfun and Jim "ZAPNSPARK" G. for sharing their NS73M code!
*/

int CK = 12;  //clock pin
int DA = 11;  //data pin
int LA = 10;  //latch pin



void setup(){
  Serial.begin(9600);  //begin Serial connection for debugging

  pinMode(CK, OUTPUT);
  pinMode(DA, OUTPUT);
  pinMode(LA, OUTPUT);
  digitalWrite(LA, LOW); //unlatch transmitter
  delay(100);		//Wait for VDD to settle


  spi_send(0x0E, B00000101); //Software reset

  spi_send(0x01, B10110100); //Register 1: forced subcarrier, pilot tone on

  spi_send(0x02, B00000011); //Register 2: Unlock detect off, 2mW Tx Power

  spi_send(0x03, B10001010); //Register 3: Set broadcast freq to 97.3, lower byte
  spi_send(0x04, B00101110); //Register 4: Set broadcast freq to 97.3, upper byte

  spi_send(0x08, B00011010); //Register 8: set Osc on band 2

  spi_send(0x00, B10100001); //Register 0: 200mV audio input, 75us pre-emphasis on, crystal off, power on

  spi_send(0x0E, B00000101); //Software reset

  spi_send(0x06, B00011110); //Register 6: charge pumps at 320uA and 80 uA

  Serial.print("Transmitting");  //for debugging


}


void loop(){

}




void spi_send(byte reg, byte data)  //routine to send Register Address and Data as LSB-first SPI
{
    int x;
    int n;
    digitalWrite(LA, LOW);

    for(x = 0 ; x < 4 ; x++)	     //send four-bit register address
    {
	  digitalWrite(CK, LOW);	   //Toggle the SPI clock
	  n = (reg >> x) & 1;		//n is the xth bit of the register byte
	  if (n == 1){
		digitalWrite(DA, HIGH);    //Put high bit on SPI data bus
	  }
	  else {
		digitalWrite(DA, LOW);     //Put low bit on SPI data bus
	  }
	  Serial.print(n);		   //send bit to serial connection for debugging
	  digitalWrite(CK, HIGH);	  //Toggle the SPI clock
    }

    for(x = 0 ; x < 8 ; x++)	     //send eight-bit register data
    {
	  digitalWrite(CK, LOW);	   //Toggle the SPI clock
	  n = (data >> x) & 1;
	  if (n == 1){
		digitalWrite(DA, HIGH);    //Put high bit on SPI data bus
	  }
	  else {
		digitalWrite(DA, LOW);    //Put low bit on SPI data bus
	  }
	  Serial.print(n);		  //send bit to serial connection for debugging
	  digitalWrite(CK, HIGH);	 //Toggle the SPI clock
    }
    delayMicroseconds(1);		 //might not be needed, supposedly unstable command anyway

    digitalWrite(LA, HIGH);	     //Latch this transfer
    delayMicroseconds(4);
    digitalWrite(LA, LOW);

    digitalWrite(CK, LOW);		//This is to keep CK pin at 0V at end of data transfer
    Serial.print("\n");		   // send new-line to serial for debugging

}