MSP432P401R: Setting up I2C with PCA9685

Part Number: MSP432P401R

Hello,

As a part of my senior design project, I am trying to drive an I2C PWM LED Driver (PCA9685 from NXP Sem, DataSheet attached). To test I understand the I2C protocol, I am just trying to turn on 1 LED channel by writing a value to a control register and reading that value back. PCA9685.pdf

Here is my code. 

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/******************************************************************************
 *  MSP432P4 I2C - EUSCI_B0 I2C Master TX/RX bytes to PCA9685A Slave-Repeated Start
 * 
 *  Description: This demo connects two MSP432's via the I2C bus. This is the
 *  MASTER CODE.The master transmits 2B to the slave, then receives a byte. 
 *  The master transmits two bytes to the slave followed by a
 *  repeated start and a single-byte read from the slave.
 *  This is a common operation for bytes from I2C slave devices such as EEPROMs.
 *  The transaction for the I2C that is written looks as follows:
 *  ________________________________________________________
 *  |  Start    | WData | WData | Start    | RData  |       |
 *  | 0x48 Addr | 0x007 | 0x013 |0x48 Addr |  0x13  | Stop  |
 *  |    W      |       |       |    R     |        |       |
 *  |___________|_______|_______|__________|________|_______|
 *
 *  ACLK = n/a, MCLK = HSMCLK = SMCLK = BRCLK = default DCO = ~3.0MHz
 *
 *                                /|\  /|\
 *                   PCA9685      10k  10k      MSP432P401R
 *                   slave         |    |         master
 *             -----------------   |    |   -----------------
 *            |          P27/SDA|<-|----+->|P6.4/UCB1SDA     |
 *            |                 |  |       |                 |
 *            |                 |  |       |                 |
 *            |          P26/SCL|<-+------>|P6.5/UCB1SCL     |
 *            |                 |          |             P2.7|-- Error
 *            |                 |          |             P2.6|-- Activity
 *
 *****************************************************************************/
/* DriverLib Defines */
#include <ti/devices/msp432p4xx/driverlib/driverlib.h>

/* Standard Defines */
#include <stdint.h>
#include <stdbool.h>
#include <string.h>

/* Slave Address for I2C Slave */
#define SLAVE_ADDRESS       0x48
#define NUM_OF_REC_BYTES    1

/* Variables */
const uint8_t TXData[] = {0x013,0x007};
static uint8_t RXData;

/* I2C Master Configuration Parameter */
const eUSCI_I2C_MasterConfig i2cConfig =
{
        EUSCI_B_I2C_CLOCKSOURCE_SMCLK,          // SMCLK Clock Source
        3000000,                                // SMCLK = 3MHz (default)
        EUSCI_B_I2C_SET_DATA_RATE_100KBPS,      // Desired I2C Clock of 100khz
        0,                                      // No byte counter threshold
        EUSCI_B_I2C_NO_AUTO_STOP                // No Autostop
};

int main(void)
{
    /* Disabling the Watchdog  */
    MAP_WDT_A_holdTimer();

    /* Select Port 6 for I2C - Set Pin 4, 5 to input Primary Module Function,
     *   (UCB0SIMO/UCB0SDA, UCB0SOMI/UCB0SCL).
     */
    MAP_GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P6,
            GPIO_PIN5 + GPIO_PIN4, GPIO_PRIMARY_MODULE_FUNCTION);
    MAP_GPIO_setAsOutputPin(GPIO_PORT_P2, GPIO_PIN7);
    MAP_GPIO_setOutputLowOnPin(GPIO_PORT_P2, GPIO_PIN7);

    MAP_GPIO_setAsOutputPin(GPIO_PORT_P2, GPIO_PIN6);
    MAP_GPIO_setOutputLowOnPin(GPIO_PORT_P2, GPIO_PIN6);

    /* Initializing I2C Master to SMCLK at 100khz with no autostop */
    MAP_I2C_initMaster(EUSCI_B1_BASE, &i2cConfig);

    /* Specify slave address */
    MAP_I2C_setSlaveAddress(EUSCI_B1_BASE, SLAVE_ADDRESS);

    /* Enable I2C Module to start operations */
    MAP_I2C_enableModule(EUSCI_B1_BASE);
    MAP_Interrupt_enableInterrupt(INT_EUSCIB1);

    // enable RX interrupts
    MAP_I2C_enableInterrupt(EUSCI_B1_BASE, EUSCI_B_I2C_RECEIVE_INTERRUPT1);

    while (1)
    {
	    RXData=0;

        /* Making sure the last transaction has been completely sent out */
        while (MAP_I2C_masterIsStopSent(EUSCI_B1_BASE));

        /* Send out EEPROM Mock Read Cmd (2 databytes) */
        MAP_I2C_masterSendMultiByteStart(EUSCI_B1_BASE, TXData[1]);  // Start + 1Byte
        MAP_I2C_masterSendMultiByteNext(EUSCI_B1_BASE, TXData[0]); // Poll for TXINT,Send 1Byte
        /*---------------------------------------------*/
        /* Now we need to initiate the read */
        /* Wait until 2nd Byte has been output to shift register */
        while(!(EUSCI_B1->IFG & EUSCI_B_IFG_TXIFG0));

        // Send the restart condition, read one byte, send the stop condition right away
        EUSCI_B1->CTLW0 &= ~(EUSCI_B_CTLW0_TR);
        EUSCI_B1->CTLW0 |= EUSCI_B_CTLW0_TXSTT;
        while(MAP_I2C_masterIsStartSent(EUSCI_B1_BASE));
        EUSCI_B1->CTLW0 |= EUSCI_B_CTLW0_TXSTP;
        //while(!(EUSCI_B1->IFG & EUSCI_B_IFG_RXIFG0));
        //RXData = EUSCI_B0->RXBUF;

        //---------------------------------
        //MAP_PCM_gotoLPM0InterruptSafe();

        // Slave should send a single 0x13 back
        if(RXData != 0x13){
            // Error- set P2.7 high
            MAP_GPIO_setOutputHighOnPin(GPIO_PORT_P2, GPIO_PIN7);
            while(1);
        }
        __delay_cycles(300000); // ~100ms pause between transmissions
    }
}

/*******************************************************************************
 * eUSCIB0 ISR. The repeated start and transmit/receive operations happen
 * within this ISR.
 *******************************************************************************/
void EUSCIB0_IRQHandler(void)
{
    uint_fast16_t status;

    status = MAP_I2C_getEnabledInterruptStatus(EUSCI_B1_BASE);

    /* Receives bytes into the receive buffer. If we have received all bytes,
     * send a STOP condition */
    if (status & EUSCI_B_I2C_RECEIVE_INTERRUPT1)
    {
        // One-byte Read
        RXData = MAP_I2C_masterReceiveSingle(EUSCI_B1_BASE);
        MAP_GPIO_toggleOutputOnPin(GPIO_PORT_P2, GPIO_PIN6);
    }
}

I am trying to troubleshoot by probing the interface signals with an oscilloscope, but I am unable to confirm my read or write.

Thanks so much.