MSP430FR2355: I2C communication

HI Yibo,

Do you have an oscilloscope or logic probe to capture the I2C signals?

Hi Dennis,

As attached.

Thanks Yibo,

Ok, looking at the waveforms, I see that the MSP has acknowledged or ACK'd (SDA low on 9th clock pulse) the USB2ANY.  This tells me the MSP430 is responding correctly to the data being sent from the USB ANY. 

Not sure in this case why there is a timeout.  Let me dig up a USB2ANY and give it a try.

Thanks Dennis, by the way, after the address 0x48 and the register 0x00, the data according to the USB2ANY should be 0x02, but according to the waveform, it is 0x01? It also confuses me..

Hi Yibo,

No, the waveform is correct.  See annotated diagram below. You can see the slave has /NACK (acknowledges) after each byte received.

Hi Dennis,

USB2ANY: USB2ANY Interface Adapter - Amplifiers forum - Amplifiers - TI E2E support forums

Through the above forum, I modified the program, which added some code(enable RX interrupt and read RXBUF data). And the write timeout problem seems to be fixed.

The new question is.. when I read the data, the value is not what I wrote into the register.

Following is my modified code and the result from USB2ANY,

#include <msp430.h>
#include <stdint.h>
#include <stdlib.h>
#include <driverlib.h>

volatile unsigned char TXData;
volatile unsigned char RXData;


#define REGISTER_0_ADDRESS 0x00 // Replace with your chosen address
#define REGISTER_1_ADDRESS 0x01 // Replace with another address

// Define variables to store received values
double A = 0.0;
double B = 0.0;
int i;

uint8_t receivedbyte;


int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;

    // Configure GPIO
    P1SEL0 |= BIT2 | BIT3;
    P1SEL1 &= ~(BIT2 | BIT3);

    // Disable the GPIO power-o9n default high-impedance mode to activate
    // previously configured port settings
    PM5CTL0 &= ~LOCKLPM5;


    // Configure USCI_B2 for I2C mode
    UCB0CTLW0 = UCSWRST;                    // Software reset enabled
    UCB0CTLW0 |= UCMODE_3 | UCSYNC;         // I2C mode, sync mode
    UCB0I2COA0 = 0x48 | UCOAEN;             // own address is 0x48 + enable
    UCB0CTLW0 &= ~UCSWRST;                  // clear reset register
    UCB0IE |= UCRXIE0 | UCTXIE0 | UCSTPIE;            // transmit,stop interrupt enable

    __bis_SR_register(LPM0_bits | GIE);     // Enter LPM0 w/ interrupts
    __no_operation();

    while (1) {
        PMM_unlockLPM5();
        // Toggle P1.0 output

        if(A==5){ //green
            P1OUT &= ~BIT0;                         // Clear P1.0 output latch for a defined power-on state
            P1DIR |= BIT0;                          // Set P1.0 to output direction
            P1OUT |= BIT0;
        }
        if(B==7){ //red
            P6OUT &= ~BIT6;                         // Clear P1.0 output latch for a defined power-on state
            P6DIR |= BIT6;                          // Set P1.0 to output direction
            P6OUT |= BIT6;
        }
        for(i=10000; i>0; i--);
        // Your application logic here
        // Process the received value (e.g., update LEDs, perform actions, etc.)
    }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector = EUSCI_B0_VECTOR
__interrupt void USCI_B0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(EUSCI_B0_VECTOR))) USCI_B0_ISR (void)
#else
#error Compiler not supported!
#endif
{
    switch(__even_in_range(UCB0IV, USCI_I2C_UCBIT9IFG))
    {
        case USCI_NONE:          break;     // Vector 0: No interrupts
        case USCI_I2C_UCALIFG:   break;     // Vector 2: ALIFG
        case USCI_I2C_UCNACKIFG: break;     // Vector 4: NACKIFG
        case USCI_I2C_UCSTTIFG:  break;     // Vector 6: STTIFG
        case USCI_I2C_UCSTPIFG:             // Vector 8: STPIFG
            TXData = 0;
            UCB0IFG &= ~UCSTPIFG;           // Clear stop condition int flag
            break;
        case USCI_I2C_UCRXIFG3:  break;     // Vector 10: RXIFG3
        case USCI_I2C_UCTXIFG3:  break;     // Vector 12: TXIFG3
        case USCI_I2C_UCRXIFG2:  break;     // Vector 14: RXIFG2
        case USCI_I2C_UCTXIFG2:  break;     // Vector 16: TXIFG2
        case USCI_I2C_UCRXIFG1:  break;     // Vector 18: RXIFG1
        case USCI_I2C_UCTXIFG1:  break;     // Vector 20: TXIFG1
        case USCI_I2C_UCRXIFG0:
            RXData = UCB0RXBUF;
            if (RXData == REGISTER_0_ADDRESS) {
                // Combine the received byte into A
                uint64_t temp_A = *(uint64_t*)&A;
                temp_A = (temp_A << 8) | receivedbyte;
                A = *(double*)&temp_A;
//                receiving_A = 0; // Switch to receiving B next
            }
            else if (RXData == REGISTER_1_ADDRESS) {
                            // Combine the received byte into B
                            uint64_t temp_B = *(uint64_t*)&B;
                            temp_B = (temp_B << 8) | receivedbyte;
                            B = *(double*)&temp_B;
            //                receiving_A = 1; // Switch back to receiving A
            }
            break;     // Vector 22: RXIFG0
        case USCI_I2C_UCTXIFG0:             // Vector 24: TXIFG0
            UCB0TXBUF = TXData++;
            break;
        case USCI_I2C_UCBCNTIFG: break;     // Vector 26: BCNTIFG
        case USCI_I2C_UCCLTOIFG: break;     // Vector 28: clock low timeout
        case USCI_I2C_UCBIT9IFG: break;     // Vector 30: 9th bit
        default: break;
    }
}

Thanks for your help in advance.