DRV2605: Clearing the GO bit

Hello y'all,

we are developing consumer electronics that include a ERM motor, which buzzes periodically with a defined time interval (like a metronome). The motor is controlled with the DRV2605L in internal trigger mode over I2C, playing haptic effects from the ROM libraries.

I encountered a bug in our firmware: When the interval is considerably small, only every second iteration the motor buzz will be triggered. I suspect that this is happening because at the time I trigger a new haptic effect, the old effect is still being played. Instead of cancelling and playing back the new effect, the DRV2605 ignores the I2C commands to trigger a new effect.

After some investigation and reading the datasheet again I found that I have to clear the GO bit to cancel the current haptic effect and then trigger the new one. However, when I write a 0x00 to address 0x0C (the GO bit address), nothing happens, and the GO bit stays asserted. I tried continuously writing the value in a while loop, and it sometimes takes longer or less long until the command is actually written.

I am wondering what I am missing?

All the best,

Julian

Here's the I2C commands I am sending to play a haptic effect.

    // Assert EN
    DRV_EN_Write(1);
    
    // De-Assert STANDBY if was asserted / Set MODE to ACTIVE=0x00
    IICwriteByte(DRV2605_ADDR, ADDR_MODE, MODE_ACTIVE);
    
    // set library (optional)
    IICwriteByte( DRV2605_ADDR, ADDR_LIBRARY,		library );
    
    // write waveform ID to 0x04 register (or write mltiple as a sequence from 0x04 to 0x0B)
    IICwriteByte( DRV2605_ADDR, ADDR_WAV_SEQ1,		effect );
    IICwriteByte( DRV2605_ADDR, ADDR_WAV_SEQ2,	        0x00 );
    
    // clear the GO BIT if was asserted
    goBit = I2C_ReadOneByte( DRV2605_ADDR, ADDR_GO ) & 0x01;
    printf("playEffect GO\tBEFORE : %d\t", goBit);

    if (goBit == GO) {

        while (goBit != STOP) {
             IICwriteByte( DRV2605_ADDR, ADDR_GO,       STOP );
             goBit = I2C_ReadOneByte( DRV2605_ADDR, ADDR_GO ) & 0x01;
             printf("GO is %d\r\n", goBit);
        }

    }

    // Set GO bit
    IICwriteByte( DRV2605_ADDR, ADDR_GO,			GO );