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MSP432P401R: MSP432 I2C Address Byte for the HELLOALL Command

Part Number: MSP432P401R

Hi Team,

Do you know if there is any function(MSP432 works as i2c master) can support ONLY send the slave address BUT without sending any data? Something like below. Thanks.

  • If you set UCTXSTT, but then do not write anything to TXBUF, the ACK clock cycle will not happen.

    The MAX11068 does not do clock stretching, so you could simply bit-bang this command.

  • Here is some updating. Appreciate if someone could share me some comments.

    1. Initial the i2c as the master mode with the function “No Autostop”

    2. the test code “only send slaver address” as below

    3. the result show that the slave address can be sent out. But the msp432 haven’t generated the STOP and the SCL turn low

    Waveform

    Log got from the i2c monitor

    4. attach the normal result got from another i2c master device

    waveform

    log got from the i2c monitor

  • Hello,

        As Clemens indicated, you must write to the TX buffer inorder for the ACK to be sent and the communication to continue.

    I have attached a piece of code that simply writes the stop after the API which loads the TX and the start.

    I do not have a slave device to 'ACK' the signal.  Can you please confirm this on your side?  

    Regards,

    Chris

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    /******************************************************************************
     *  MSP432P4 I2C - EUSCI_B0 I2C Master TX/RX bytes to MSP432P4 Slave-Repeated Start
     *
     *  For use with the i2c_master_rw_repeated_start_singlebyte_slave project
     *
     *  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 continuously 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
     *  external EEPROMs.
     *  The transaction for the I2C that is written looks as follows:
     *  ________________________________________________________
     *  |  Start    | WData | WData | Start    | RData  |       |
     *  | 0x48 Addr | 0x042 | 0x041 |0x48 Addr |  0x52  | Stop  |
     *  |    W      |       |       |    R     |        |       |
     *  |___________|_______|_______|__________|________|_______|
     *
     *  ACLK = n/a, MCLK = HSMCLK = SMCLK = BRCLK = default DCO = ~3.0MHz
     *
     *                                /|\  /|\
     *                MSP432P411      10k  10k      MSP432P411
     *                   slave         |    |         master
     *             -----------------   |    |   -----------------
     *            |     P1.6/UCB0SDA|<-|----+->|P1.6/UCB0SDA     |
     *            |                 |  |       |                 |
     *            |                 |  |       |                 |
     *            |     P1.7/UCB0SCL|<-+------>|P1.7/UCB0SCL     |
     *            |                 |          |             P1.0|-- Error
     *            |                 |          |             P2.1|-- 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[] = {0x41,0x42};
    static uint8_t RXData;
    
    /* I2C Master Configuration Parameter */
    // Baud rate selectable (100KBPS, 400KBPS)
    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 1 for I2C - Set Pin 6, 7 to input Primary Module Function,
         *   (UCB0SIMO/UCB0SDA, UCB0SOMI/UCB0SCL).
         */
        MAP_GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P1,
                GPIO_PIN6 + GPIO_PIN7, GPIO_PRIMARY_MODULE_FUNCTION);
        MAP_GPIO_setAsOutputPin(GPIO_PORT_P1, GPIO_PIN0);
        MAP_GPIO_setOutputLowOnPin(GPIO_PORT_P1, GPIO_PIN0);
    
        MAP_GPIO_setAsOutputPin(GPIO_PORT_P2, GPIO_PIN1);
        MAP_GPIO_setOutputLowOnPin(GPIO_PORT_P2, GPIO_PIN1);
    
        RXData=0;
    
        /* Initializing I2C Master to SMCLK at 100khz with no autostop */
        MAP_I2C_initMaster(EUSCI_B0_BASE, &i2cConfig);
    
        /* Specify slave address */
        MAP_I2C_setSlaveAddress(EUSCI_B0_BASE, SLAVE_ADDRESS);
    
        /* Enable I2C Module to start operations */
        MAP_I2C_enableModule(EUSCI_B0_BASE);
    
        while (1)
        {
    	    RXData=0;
    
            /* Making sure the last transaction has been completely sent out */
            while (MAP_I2C_masterIsStopSent(EUSCI_B0_BASE));
    
            /* Send out EEPROM Mock Read Cmd (2 databytes) */
            MAP_I2C_masterSendMultiByteStart(EUSCI_B0_BASE, TXData[1]);  // Start + 1Byte
    //        MAP_I2C_masterSendMultiByteNext(EUSCI_B0_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_B0->IFG & EUSCI_B_IFG_TXIFG0));
    
            // Send the restart condition, read one byte, send the stop condition right away
    //        EUSCI_B0->CTLW0 &= ~(EUSCI_B_CTLW0_TR);
    //        EUSCI_B0->CTLW0 |= EUSCI_B_CTLW0_TXSTT;
    //        while(MAP_I2C_masterIsStartSent(EUSCI_B0_BASE));
            EUSCI_B0->CTLW0 |= EUSCI_B_CTLW0_TXSTP;
    //        while(!(EUSCI_B0->IFG & EUSCI_B_IFG_RXIFG0));
    //        RXData = EUSCI_B0->RXBUF;
    
            // Slave should send a single 'R' back
    //        if(RXData != 'R'){
    //            // Error- set P1.0 high
    //            MAP_GPIO_setOutputHighOnPin(GPIO_PORT_P1, GPIO_PIN0);
    //            while(1);
    //        }
    		__delay_cycles(300000); // ~100ms pause between transmissions
            MAP_GPIO_toggleOutputOnPin(GPIO_PORT_P2, GPIO_PIN1);
        }
    }
    
    

  • Chris 

    thanks for your reply. after changing the code  "set the bit TXSTT(to send start) and TXSTP(to send stop) in meanwhile " (shows as below screenshot), i can got the result which i want. but i don't know if there is any risk to this coding. appreciate if you could share us some comments.

    test code

    image

    waveform

    image

    data log got from i2c monitor

    image

  • The images did not upload properly. Please retry.
    I do have some concerns that this is not the intended flow of the state-machine in the device and it may possibly hang. In the code I provided it was a simple loop and I did not see any issues, but I did not test completely since I am missing an actual slave and the ACK. If you can protect the 'hello all' command by disabling interrupts that would help ensure consistent operation.

    Regards,
    Chris
  • Let me know if you have additional questions or comments. I will treat this thread as closed.

    Regards,
    Chris

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