write_to_dacs.c

//MOSI:
#define DATAOUT 11
//MISO: (not used, but part of builtin SPI)
#define DATAIN 12
#define SPICLOCK  13
#define SLAVESELECT 10
#define LDAC 8

void setup() {
 byte clr;
 pinMode(LDAC, OUTPUT);
 pinMode(DATAOUT, OUTPUT); 
 pinMode(DATAIN, INPUT);
 pinMode(SPICLOCK,OUTPUT);
 pinMode(SLAVESELECT,OUTPUT);
 digitalWrite(SLAVESELECT,HIGH); //disable device

 SPCR = (1<<SPE)|(1<<MSTR); // SPI-Control = SPi-Enable, MaSTeR
 clr=SPSR;                  // read reg twice 
 clr=SPDR;
 delay(10);
}

void write_values(uint16_t samplex, uint16_t sampley)
{
 uint8_t dacSPI0 = 0;
 uint8_t dacSPI1 = 0; 
 dacSPI0 = (samplex >> 8) & 0x00FF;  // data bits 15-12.
 dacSPI0 |=  dacSPI0 |= B00110000;; 
 dacSPI1 = samplex & 0x00FF; // data
 digitalWrite(SLAVESELECT,LOW);
 SPDR = dacSPI0;                    // Start the transmission
 while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
 {
 };
 SPDR = dacSPI1;
 while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
 {
 };
 digitalWrite(LDAC, LOW);
 digitalWrite(LDAC, HIGH);

 digitalWrite(SLAVESELECT,HIGH);
 dacSPI0 = 0;
 dacSPI1 = 0;
 dacSPI0 = (sampley >> 8) & 0x00FF;  // data bits 15-12.
 dacSPI0 |= B10110000;
 dacSPI1 = sampley & 0x00FF; // data
 digitalWrite(SLAVESELECT,LOW);
 SPDR = dacSPI0;                    // Start the transmission
 while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
 {
 };
 SPDR = dacSPI1;
 while (!(SPSR & (1<<SPIF)))     // Wait the end of the transmission
 {
 };
 digitalWrite(SLAVESELECT,HIGH);
}

void loop(){
//... 
}