2 x MCP4921 digital to analog converter / DAC

Forum 2005-2010 (read only) Hardware Interfacing
1

Thought I should share this.

I am using two DAC to supply the X and Y voltage on an old
"Houston Instrument Omnigraphic 2000 XY Recorder Plotter".

The plotter's X and Y input range is 0 - 5v.
This code simply lets the plotter pen move to it's extremes and back.

The MCP4921 communicates with the Arduino via Serial Peripheral Interface (SPI).

Code here:
http://maybevideodoes.de/howto/DAC/SPI_MCP4921.pde

2

Do you know how can I send saved serial data from arduino to MCP4921??

how to set it??
just like this

void setup(){
  //Timer2 setup  This is the audio rate timer, fires an interrupt at 15625 Hz sampling rate
  TIMSK2 = 1<<OCIE2A;  // interrupt enable audio timer
  OCR2A = 127;
  TCCR2A = 2;               // CTC mode, counts up to 127 then resets
  TCCR2B = 0<<CS22 | 1<<CS21 | 0<<CS20;   // different for atmega8 (no 'B' i think)
  SPCR = 0x50;   // set up SPI port
  SPSR = 0x01;
  DDRB |= 0x2E;       // PB output for DAC CS, and SPI port
  PORTB |= (1<<1);   // CS high

  sei();           /
3

here is the SPI code i used:

#define DATAOUT 11//MOSI
//#define DATAIN 12//MISO - not used, but part of builtin SPI
#define SPICLOCK  13//sck
#define SLAVESELECT0 10//ss



void SPI_setup(){

  pinMode(9, OUTPUT); //+5V for SHDN on mcp4922 mini board
  digitalWrite(9,HIGH);

  byte clr;
  pinMode(DATAOUT, OUTPUT);
//  pinMode(DATAIN, INPUT);
  pinMode(SPICLOCK,OUTPUT);
  pinMode(SLAVESELECT0,OUTPUT);
  digitalWrite(SLAVESELECT0,HIGH); //disable device
  //  pinMode(SLAVESELECT1,OUTPUT);
  //  digitalWrite(SLAVESELECT1,HIGH); //disable device

  SPCR = (1<<SPE)|(1<<MSTR);
  clr=SPSR;
  clr=SPDR;
  delay(10); 
}




void write_valueX(int sample)
{
  // splits int sample in to two bytes 
  byte dacSPI0 = 0; 
  byte dacSPI1 = 0;
  dacSPI0 = (sample >> 8) & 0x00FF; //byte0 = takes bit 15 - 12
  dacSPI0 |= (1 << 7);        // A/B: DACa or DACb - Forces 7th bit  of    x to be 1. all other bits left alone.
  dacSPI0 |= 0x10;
  dacSPI1 = sample & 0x00FF; //byte1 = takes bit 11 - 0
  digitalWrite(SLAVESELECT0,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(SLAVESELECT0,HIGH);
  delay(5);
}

void write_valueY(int sample)
{
  // splits int sample in to two bytes 
  byte dacSPI0 = 0; 
  byte dacSPI1 = 0;
  dacSPI0 = (sample >> 8) & 0x00FF; //byte0 = takes bit 15 - 12
  dacSPI0 |= 0x10;
  dacSPI1 = sample & 0x00FF; //byte1 = takes bit 11 - 0
  digitalWrite(SLAVESELECT0,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(SLAVESELECT0,HIGH);
  delay(5);
}
4

i dont know how to declare cs and sck.