MSP430FR5949 Clock Speed

Hi Hari, 

I don't see any issues in the code you posted that could be causing the issue. How are you communicating with the DAC? Could this possibly be a communication issue that was thrown off by changing the clock speed?

Would you mind posting the rest of your code using Syntax highlighter?

Best regards, 
Caleb Overbay

Hi Caleb,

I'm communicating with the DAC through SPI and I can see the output wave when I scope it however I can't output it at higher frequencies. Here is the code that I am using. I was unable to copy and paste the syntax highlighter code it wouldn't insert the code with the colors for some reason. Thank you for your help!

#include <msp430.h>

volatile unsigned char TXDATA;

int sawtooth[150] = {0x2,0x3,0x5,0x7,0x9,0xa,0xc,0xe,0xf,0x11,0x13,0x14,0x16,0x18,0x1a,
0x1b,0x1d,0x1f,0x20,0x22,0x24,0x25,0x27,0x29,0x2b,0x2c,0x2e,0x30,0x31,0x33,
0x35,0x36,0x38,0x3a,0x3c,0x3d,0x3f,0x41,0x42,0x44,0x46,0x47,0x49,0x4b,0x4d,
0x4e,0x50,0x52,0x53,0x55,0x57,0x58,0x5a,0x5c,0x5e,0x5f,0x61,0x63,0x64,0x66,
0x68,0x69,0x6b,0x6d,0x6f,0x70,0x72,0x74,0x75,0x77,0x79,0x7a,0x7c,0x7e,0x80,
0x81,0x83,0x85,0x86,0x88,0x8a,0x8b,0x8d,0x8f,0x91,0x92,0x94,0x96,0x97,0x99,
0x9b,0x9c,0x9e,0xa0,0xa2,0xa3,0xa5,0xa7,0xa8,0xaa,0xac,0xad,0xaf,0xb1,0xb3,
0xb4,0xb6,0xb8,0xb9,0xbb,0xbd,0xbe,0xc0,0xc2,0xc4,0xc5,0xc7,0xc9,0xca,0xcc,
0xce,0xcf,0xd1,0xd3,0xd5,0xd6,0xd8,0xda,0xdb,0xdd,0xdf,0xe0,0xe2,0xe4,0xe5,
0xe7,0xe9,0xeb,0xec,0xee,0xf0,0xf1,0xf3,0xf5,0xf6,0xf8,0xfa,0xfc,0xfd,0xff};


int sin[10] = {0x80,0xca,0xf9,0xf9,0xca,0x80,0x35,0x6,
0x6,0x35,0x80};

void SPI_DATA(unsigned int a);
void SPI_TRANSFER(char TXDATA);
int i = 0;


int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop watchdog timer

// Configure one FRAM waitstate as required by the device datasheet for MCLK
// operation beyond 8MHz _before_ configuring the clock system.
//FRCTL0 = FRCTLPW | NWAITS_1;

// Clock System Setup
//CSCTL0_H = CSKEY >> 8; // Unlock CS registers
//CSCTL1 = DCOFSEL_0; // Set DCO to 16MHz
//CSCTL2 = SELS__DCOCLK;
//CSCTL3 = DIVS__1; // Set all dividers
//CSCTL0_H = 0; // Lock CS registers // Clock System Setup

// Configure GPIO
P2OUT |= BIT7;
P2DIR |= BIT4 | BIT5 | BIT7; //P2.7 = dac cs
P2SEL1 |= BIT4 | BIT5 | BIT6; //A1 CLK, SIMO, SOMI




//PJSEL0 |= BIT4 | BIT5; // For XT1

// Disable the GPIO power-on default high-impedance mode to activate
// previously configured port settings
PM5CTL0 &= ~LOCKLPM5;

// Configure USCI_A0 for SPI operation
UCA1CTLW0 = UCSWRST; // **Put state machine in reset**
UCA1CTLW0 |= UCMST | UCSYNC | UCMSB | UCCKPH; // 3-pin, 8-bit SPI master
// Clock polarity high, MSB
UCA1CTLW0 |= UCSSEL__SMCLK; // ACLK
UCA1BR0 = 0x00; // /2
UCA1BR1 = 0; //
UCA1MCTLW = 0; // No modulation
UCA1CTLW0 &= ~UCSWRST; // **Initialize USCI state machine**
//UCA0IE |= UCRXIE; // Enable USCI_A0 RX interrupt
//TXData = 0x1; // Holds TX data

while(1)
{
//UCA0IE |= UCTXIE;
//__bis_SR_register(LPM0_bits | GIE); // CPU off, enable interrupts

for(i = 0; i < 10; i++){
//__delay_cycles(30); // Delay before next transmission

SPI_DATA(sin[i]); // Increment transmit data

}
}
}

void SPI_DATA(unsigned int a){

unsigned int temp = a;
unsigned int DAC = 0;

temp = temp << 2; //shift 2 bits for DCs
temp |= 0xF000; //control bits output A and B
DAC = temp;
TXDATA = DAC >> 8; //send MSB
P2OUT &= ~BIT7; //set CS low 0111 1111
SPI_TRANSFER(TXDATA);
TXDATA = DAC; //send LSB
SPI_TRANSFER(TXDATA);
P2OUT |= BIT7; //set cs high

}

void SPI_TRANSFER(char TXDATA){
while(!(UCA1IFG & UCTXIFG));
UCA1TXBUF = TXDATA; // Transmit characters
while(UCA1STATW & UCBUSY);
//return UCA1RXBUF;
}

Hi Hari,

Is there are reason you're not using interrupts  and the STE(CS) to do the SPI transfers? I think you could gain some speed by making things interrupt based first. There are examples for how to do this in the TI Resource Explorer in CCS.

Also,  you're using the SMCLK as the source for your SPI communication with no divider. This means that when you change the speed of the DCO, the SPI communication speed changes as well and 16MHz may be too high of a communication speed for your DAC and/or the MSP. This previous E2E post gives a good description of how to calculate the max SPI speed: SPI Unreliable at Speed on MSP430G2553.

I would start with changing things to be interrupt based and go from there. 

Best regards, 

Caleb Overbay

Hi Hari,

Have you made any progress on this issue that you'd like to share?

Best regards,
Caleb Overbay