CCS/MSP430F5529: About the MSP430 SPI communication with a potentiometer

Tool/software: Code Composer Studio

Hi, I am new to the msp430. The one I use is msp430f5529. I tried to communicate with a potentiometer which model is mcp41010.

I modified the SPI example code, but it didn't work. The led that connected in series with the potentiometer did not change its brightness when I change the value of the resistance through SPI.

I use the same circuit communicating with a Raspberry Pi, and it worked. I believe it is the problem with the code. Maybe I did not correctly set up the SPI on MSP430.

The following is my code.

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#include "driverlib.h"

//*****************************************************************************
//! This example shows how SPI master talks to SPI slave using 3-wire mode.
//! Incrementing data is sent by the master starting at 0x01. Received data is
//! expected to be same as the previous transmission.  USCI RX ISR is used to
//! handle communication with the CPU, normally in LPM0. If high, P1.0 indicates
//! valid data reception.  Because all execution after LPM0 is in ISRs,
//! initialization waits for DCO to stabilize against ACLK.
//! ACLK = ~32.768kHz, MCLK = SMCLK = DCO ~ 1048kHz.  BRCLK = SMCLK/2
//!
//! Use with SPI Slave Data Echo code example.  If slave is in debug mode, P1.1
//! slave reset signal conflicts with slave's JTAG; to work around, use IAR's
//! "Release JTAG on Go" on slave device.  If breakpoints are set in
//! slave RX ISR, master must stopped also to avoid overrunning slave
//! RXBUF.
//!
//!                  MSP430F5438A
//!                 -----------------
//!            /|\ |                 |
//!             |  |                 |
//!    Master---+->|RST              |
//!                |                 |
//!                |             P3.1|-> Data Out (UCB0SIMO)
//!                |                 |
//!                |             P3.2|<- Data In (UCB0SOMI)
//!                |                 |
//!                |             P3.3|-> Serial Clock Out (UCB0CLK)
//!
//!
//! This example uses the following peripherals and I/O signals.  You must
//! review these and change as needed for your own board:
//! - SPI peripheral
//! - GPIO Port peripheral (for SPI pins)
//! - UCB0SIMO
//! - UCB0SOMI
//! - UCB0CLK
//!
//! This example uses the following interrupt handlers.  To use this example
//! in your own application you must add these interrupt handlers to your
//! vector table.
//! - USCI_A0_VECTOR
//!
//*****************************************************************************

//*****************************************************************************
//
//Specify desired frequency of SPI communication
//
//*****************************************************************************
#define SPICLK                          500000

uint8_t CommandCode = 0x00;
uint8_t DataCode = 0x00;
uint8_t returnValue = 0x00;

void main (void)
{
    //Stop watchdog timer
    WDT_A_hold(WDT_A_BASE);

    //Set P1.1 for slave reset

    //Set P1.1 for slave reset
    //Set P1.0 to output direction
    GPIO_setAsOutputPin(
        GPIO_PORT_P1,
        GPIO_PIN2
        );

    //P3.5,4,0 option select
    GPIO_setAsPeripheralModuleFunctionOutputPin(
        GPIO_PORT_P3,
        GPIO_PIN0+GPIO_PIN2
        );

    //Initialize Master
    USCI_B_SPI_initMasterParam param = {0};
    param.selectClockSource = USCI_B_SPI_CLOCKSOURCE_SMCLK;
    param.clockSourceFrequency = UCS_getSMCLK();
    param.desiredSpiClock = SPICLK;
    param.msbFirst = USCI_B_SPI_MSB_FIRST;
    param.clockPhase = USCI_B_SPI_PHASE_DATA_CHANGED_ONFIRST_CAPTURED_ON_NEXT;
    param.clockPolarity = USCI_B_SPI_CLOCKPOLARITY_INACTIVITY_HIGH;
    returnValue =  USCI_B_SPI_initMaster(USCI_B0_BASE, &param);

    if (STATUS_FAIL == returnValue){
        return;
    }

    //Enable SPI module
    GPIO_setOutputHighOnPin(
            GPIO_PORT_P1,
            GPIO_PIN2
            );
    USCI_B_SPI_enable(USCI_B0_BASE);

    //Enable Receive interrupt

    //Wait for slave to initialize
    __delay_cycles(100);
    while (1)
    {
        CommandCode = 0x11;
            DataCode=0x0A;
            //USCI_A0 TX buffer ready?

            //Transmit Data to slave
            GPIO_setOutputLowOnPin(
                        GPIO_PORT_P1,
                        GPIO_PIN2
                        );
            USCI_B_SPI_transmitData(USCI_B0_BASE, CommandCode);
            USCI_B_SPI_transmitData(USCI_B0_BASE, DataCode);
            GPIO_setOutputHighOnPin(
                        GPIO_PORT_P1,
                        GPIO_PIN2
                        );
            __delay_cycles(1000);
            CommandCode = 0x20;
            GPIO_setOutputLowOnPin(
                                    GPIO_PORT_P1,
                                    GPIO_PIN2
                                    );
            USCI_B_SPI_transmitData(USCI_B0_BASE, CommandCode);
            GPIO_setOutputHighOnPin(
                                    GPIO_PORT_P1,
                                    GPIO_PIN2
                                    );
            __delay_cycles(1000);
    }
    //Initialize data values

    //CPU off, enable interrupts
    __bis_SR_register(LPM0_bits + GIE);
}

//******************************************************************************
//
//This is the USCI_B0 interrupt vector service routine.
//
//******************************************************************************