eusci_b_spi_ex1_3WireMaster.c

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/*******************************************************************************
 * MSP430i2xx EUSCI_B SPI - 3 Wire Incrementing Data Master
 *
 * Description: In this example, the device is configured as a SPI master using
 * ACLK as the clock source. The SPI communication is setup to run at 16kHz.
 * The initial data is written to the TX Buffer, once the data is sent out the
 * device gets an RX interrupt that contains the data it recieved from the
 * slave. The slave and master data values should stay in sync and if there is
 * a problem in communication the LED will turn on. The device stays in LPM0
 * and sends the data in the ISR. To properly demo this example connect to
 * slave version of this example and start the slave device first.
 *
 *                MSP430i2041
 *             ------------------
 *         /|\|                  |
 *          | |              P1.4|--->LED
 *          --|RST               |
 *            |     P1.7/UCB0SIMO|--->Data Out
 *            |                  |
 *            |     P1.6/UCB0MISO|<---Data In
 *            |                  |
 *            |      P1.5/UCB0CLK|--->Serial Clock
 *
 * Author: Zack Lalanne
 ******************************************************************************/
#include "driverlib.h"
 
uint8_t TXData = 0;
uint8_t RXData = 0;
 
int main(void)
{
    EUSCI_B_SPI_initMasterParam spiMasterConfig =
    {
        EUSCI_B_SPI_CLOCKSOURCE_ACLK,              // ACLK Clock Source
        32000,                                     // ACLK = 32kHz
        16000,                                     // SPICLK = 16kHz
        EUSCI_B_SPI_MSB_FIRST,                     // MSB First
        EUSCI_B_SPI_PHASE_DATA_CHANGED_ONFIRST_CAPTURED_ON_NEXT,    // Phase
        EUSCI_B_SPI_CLOCKPOLARITY_INACTIVITY_HIGH, // High polarity
        EUSCI_B_SPI_3PIN                           // 3Wire SPI Mode
    };
 
    WDT_hold(WDT_BASE);
 
    // Setting P1.5, P1.6 and P1.7 as SPI pins.
    GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P1,
            GPIO_PIN5 | GPIO_PIN6 | GPIO_PIN7,
            GPIO_PRIMARY_MODULE_FUNCTION);
 
    // Setting P1.4 as LED Pin
    GPIO_setOutputLowOnPin(GPIO_PORT_P1, GPIO_PIN4);
    GPIO_setAsOutputPin(GPIO_PORT_P1, GPIO_PIN4);
 
    // Setting the DCO to use the internal resistor. DCO will be at 16.384MHz
    // ACLK is at 32kHz
    CS_setupDCO(CS_INTERNAL_RESISTOR);
 
    // Configure and enable the SPI peripheral
    EUSCI_B_SPI_initMaster(EUSCI_B0_BASE, &spiMasterConfig);
    EUSCI_B_SPI_enable(EUSCI_B0_BASE);
 
    // Put the first byte in the transfer buffer
    EUSCI_B_SPI_transmitData(EUSCI_B0_BASE, TXData);
 
    EUSCI_B_SPI_enableInterrupt(EUSCI_B0_BASE, EUSCI_B_SPI_RECEIVE_INTERRUPT);
 
    // Go into LPM0 with interrupts enabled
    __bis_SR_register(LPM0_bits | GIE);
}
 
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCI_B0_VECTOR
__interrupt
#elif defined(__GNUC__)
__attribute__((interrupt(USCI_B0_VECTOR)))
#endif
void USCI_B0_ISR(void)
{
    switch(__even_in_range(UCB0IV, USCI_SPI_UCTXIFG))
    {
        case USCI_NONE: break;
        case USCI_SPI_UCRXIFG:
                        // Read what slave sent. Should be same as transferred. If there
                        // is a mismatch turn on the LED
                        RXData = EUSCI_B_SPI_receiveData(EUSCI_B0_BASE);
                        if(RXData != TXData)
                        {
                            GPIO_setOutputHighOnPin(GPIO_PORT_P1, GPIO_PIN4);
                            while(1);
                        }
                        EUSCI_B_SPI_transmitData(EUSCI_B0_BASE, ++TXData);
                        break;
        case USCI_SPI_UCTXIFG:
                        break;
        default: break;
    }
}