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MSP432 I2C write to slave bug

Michael Liesenberg85
Mastermind 7560 points


Hi,

i'm facing an issue on the MSP432 I2C as master writing/reading to a slave register.

The register address from the slave is 16Bit and its size is 8Bit.

I go and start a multi byte transmition. First multibyte start with the MSB bit and multibyte next with LSB.

After that, i switch it to receive the 8Bit value from slave.

To make that happen i had to send the multibyte next twice somehow.

This is my code:

I am not sending a multi byte finish or stop because i want to read the register value afterwards.

So here is what i have measured with the oscilloscope:

The register adddress is 0x02 and its value read is 0x02 and thats correct.

I am not using any interrupt handler to handle the transmited interrupt or received.

Any idea why i have to send the "I2C_masterSendMultiByteNext" twice?

Thanks,

Michael

  • 0
    TI__Guru**** 219737 points
    Hi Michael,

    Linking to your previous post: e2e.ti.com/.../1987365

    A similar command structure is followed on all MSP432 Driver Library I2C examples, with comments as such: "Send start and the first byte of the transmit buffer. We have to send two bytes to clean out whatever is in the buffer from a previous send." Therefore this is considered normal operation, not a workaround.

    Regards,
    Ryan
  • 0 in reply to Ryan Brown1
    Mastermind 7560 points
    Hi Ryan,

    i was wandering because this configuration works:

    MAP_I2C_masterSendMultiByteStart(EUSCI_B3_BASE,(uint8_t)((pointer&0xFF00)>>8));

    while(ui8Status_3 == eUSCI_BUSY_3)
    {
    if(MAP_I2C_getInterruptStatus(EUSCI_B3_BASE, EUSCI_B_I2C_TRANSMIT_INTERRUPT0))
    {
    ui8Status_3 = eUSCI_IDLE_3;
    }
    }

    ui8Status_3 = eUSCI_BUSY_3;

    /* Send the MSB to SENSOR */
    MAP_I2C_masterSendMultiByteNext(EUSCI_B3_BASE,(uint8_t)(pointer & 0x00FF));
    MAP_I2C_masterSendMultiByteFinish(EUSCI_B3_BASE, (uint8_t)(writeByte));

    But here i send a multibyte finish after next, maybe thats way.

    Thank you,

    Michael

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