MSP430f2274 SPI interfacing with DAC8830.

FINAL WORKING SOLUTION!

So finally I managed to solve the problems also thanks to the 2 replies.

For if someone is ever interested, and has the same problem I have. I am going to writte the code that I used with all the helpfull comments.

Thank you very much again for your help.

Let me say that this thing works as perfectly.

#include "msp430x22x4.h"

void main(void) {
 
unsigned char byte0, byte1, i;

WDTCTL = WDTPW + WDTHOLD;             // Stop watchdog timer, always put it after the declaration of variables
UCB0CTL1 = UCSWRST;
P1DIR |= 0x40;        //Set port1 pin6 as an output 01000000 (TI FORUM:its a pin that sets an led)
P1OUT = 0x40;        //Activate that PIN as an output
P3SEL |= 0x0A;        //We activate P3.1 and P3.3 (pin10 and 12) for USCI mode
P4DIR |= 0x2A;         //we activate as outputs P4.1, P4.3 and P4.5 (pins: 16, 18 and 20) (TI FORUM:final objective is to control DAC's)
P4OUT &= 0x00;        //Make sure that everything is low
P4OUT |= 0x28;        //we set high P4.3 and P4.5, so data only goes to P4.1. Remember that data loads on low (Because there is where i have hooked up my test DAC)
UCB0CTL0 |= UCCKPL + UCMSB + UCMST + UCSYNC;  // 3-pin, 8-bit SPI master
UCB0CTL1 |= UCSSEL_2;                     // SMCLK
UCB0BR0 |= 0x02;                            //baudrate/2
UCB0BR1 = 0;                              //

UCB0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**

byte0 = 0xA3;        //Set some random number to see if it works
byte1 = 0x8F;        //Set some random number to see if it works

P4OUT &= ~0x02;        //Make sure that it's low, probably not needed in this code
while ((IFG2 & UCB0TXIFG) == 0);
      UCB0TXBUF = byte0;             // Send clocks to the DAC, this shifts 1st byte
                          // Wait until all 8 bits have been received.
while ((IFG2 & UCB0TXIFG) == 0);
      UCB0TXBUF = byte1 ;             // Send clocks to the DAC, this shifts 2nd byte
                          // Wait until all 8 bits have been received.
while ((IFG2 & UCB0TXIFG) == 0);    //wait until it is done too put CS on high
i=1;        //To waist some time after so CS is not going up to fast (problem detected with an osciloscope
P4OUT |= 0x02;

}

//Right now with byte0 and byte1 we would get 0.6389*Vref. The way that this works is that first it shifts
//the byte0 and MSB first, then it shifts in the byte1 and MSB first. So that means that what the DAC will read
//is: first byte0 and then byte1 resulting A38F. In decimal that would be A38F = 41871. So the Vout should be
//Vout=Vref*41871/65536.
//To clarify, for Vref*0.5 type byte0=0x80 and byte1=0x00. That would give 1000 0000 0000 0000.

Hi

        I have going to interface the MSP430f5438 with digital potentiometer MCP41010 by SPI communication.For that i have write the code as below.My spi  had some problem because of that i am not able to write the value in the data registers.If anyone had any solution for me then please send me.

void spi_init(void)
{
   
  //unsigned char spi_cmd,spi_data;
  WDTCTL = WDTPW+WDTHOLD;                   // Stop watchdog timer

  P10OUT |= 0x01;                            //Chip select
  P10DIR |= 0x01;                            // Set P10-1 to output direction
  P10SEL |= 0xA;                            // P10.1,3 option select for the si and clk

  UCB3CTL1 |= UCSWRST;                      // **Put state machine in reset**
  UCB3CTL0 |= UCMST+UCSYNC+UCMSB;    // 3-pin, 8-bit SPI master
                                            // Clock polarity high, MSB
  UCB3CTL1 |= UCSSEL_2;                     // SMCLK
  UCB3BR0 = 0x02;                           // /2
  UCB3BR1 = 0;                              //
  //UCA3MCTL = 0;                             // No modulation
  UCB3CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
 // UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt

  P10OUT &= ~0x01;                           // Now with SPI signals initialized,
  P10OUT |= 0x01;                            // reset slave


}

void spi_write(unsigned char data)
{
   while (!(UCB3IFG&UCTXIFG));               // USCI_A0 TX buffer ready?
  UCB3TXBUF = data;    

}

void main (void)

{

spi_init();

P10OUT&=~0x01;

spi_write(17);      //command set for the digital pot IC

spi_write(120);   //values given to the data register

P10OUT |=0x01;

}

Hi,

My first recommendation is to get a picture of your SPI data transfer word using an oscilloscope. Here we can check the clock phasing and polarity as well as verify you are writing to the DAC what you think you are.

Regards,

Tony Calabria

Hi,

          I have check  on CRO but it don't show clock pulses on pin no 10.3. Is their any problem with the code?

Hi,

I haven't checked your data sheet to see the number of bytes you can output, pin connections and I have not checked the POT neither but I suggest this:

In your function:

void spi_write(unsigned char data)
{
   while (!(UCB3IFG&UCTXIFG));               // USCI_A0 TX buffer ready?
  UCB3TXBUF = data;    

}

Try this instead:

void spi_write(unsigned char data)
{
 int i=0;

while (!(UCB3IFG&UCTXIFG));

  UCB3TXBUF = data;    

while (!(UCB3IFG&UCTXIFG));        //waits for the data to have transfered completly

i = 0;                      //waits a little instant more

}

One thing more, shouldnt it be UCB3TXIFG?

I supose that you are transfering 16 bit and that your MCU is 8bit SPI I/O right?

You also want to make sure that before setting your SPI interface you have this command:

UCB3CTL1 |= UCSWRST; //Make sure that the SPI interface is off while setting it.

That should work, tell us if it worked :)