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DRV2625: using drv2625 in RTP

jack bi
Intellectual 290 points
Part Number: DRV2625
Other Parts Discussed in Thread: DRV2604, DRV2624

dear TI expert,

      there is following description in drv2625.pdf datasheet ,section 8.3.4.2 Real-Time Playback (RTP) Interface


Because of the similarity between RTP mode and legacy PWM modes, any API (application-programming
interface) designed for use with a PWM generator in the host processor can write the data values over the I2C
rather than writing the data values to the host timer. This ability frees a timer in the host while retaining
compatibility with the original software.
using in RTP mode ,i think that an array with amplitude-time pairs  should be used like {{0x12,12},{0x34 ,20}} ,in this case both 0x12 and 0x34 is amplitude value, 12 and 20 is duration time for each amplitude respectively,right? after sending amplitude value(0x12,0x34) throuth i2c bus ,i think the duration time(12,20) still should be implement by timer in host processor in most cases. but the datasheet says it can free a timer.so i am confused. please kindly detail it

many thanks

  • 0
    TI__Guru* 84915 points

    Hi, Jack,

    I think the description that you mentioned about the amplitude-time pairs are actually part of other function (they are used in RAM mode, but this function is only supported by the DRV2604 and DRV2624).

    The RTP mode is completely configured via I2C. You just need to write the correct value that corresponds from 0% to 100% of the duty cycle. The output will be adjusted in real time. There's no need to configure the amplitude-time pairs in this case, only the duty cycle is adjusted.

    I hope this is clear. Please let me know if you have additional questions. We will be glad to help you.

    Best regards,

    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 290 points

    dear luis,

        sorry ,i am still confused, i am sure following description is from drv2625 datasheet.

    8.3.4.2 Real-Time Playback (RTP) Interface
    The real-time playback mode is a simple, single 8-bit register interface that holds an amplitude value. When realtime
    playback is enabled, the RTP_INPUT parameter, which represents an amplitude value, is sent directly to the
    playback engine. Once triggered, the value is played until the user sends a stop trigger or removes the device
    from RTP mode. The RTP mode is a digital streaming mode where the user enters a register value over the I2C.
    Because of the similarity between RTP mode and legacy PWM modes, any API (application-programming
    interface) designed for use with a PWM generator in the host processor can write the data values over the I2C
    rather than writing the data values to the host timer. This ability frees a timer in the host while retaining
    compatibility with the original software.

    from this description ,to use RTP mode ,amplitude is sent by i2c but not the value that corresponds from 0% to 100% of the duty cycle

    also from this datasheet page 18 ,section 8.3.16.2 , there is figure to clarify this. so which is correct? for RTP mode ,how can i use, what value should i send through i2c (amplitude or duty cycle?)

    in a word , how can i use RTP to achieve expected waveform, can you detail it ? i will be very grateful

    many thanks

  • 0 in reply to jack bi
    TI__Guru* 84915 points

    Hi, Jack,

    I would recommend to take a look at the picture below for more details.

    The value that the will be stored in address 0x0E corresponds to a percentage of the RATED_VOLTAGE. So, the RTP will be adjusted depending of the RATED_VOLTAGE and the value of address 0x0E.

    Please let me know if you have additional questions or comments on this.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 290 points

    Dear luis,

         i understand now. many thanks. by the way where you get the figure attached(input - output match)? i can't find in my drv2625.pdf  datasheet  (SLOS879B –APRIL 2014–REVISED SEPTEMBER 2016)

  • 0 in reply to jack bi
    TI__Guru* 84915 points

    Hi, Jack,

    This picture was taken and modified from the DRV2604.

    https://www.ti.com/lit/ds/symlink/drv2604l.pdf#page=24

    We will include this picture in the next DRV2625 datasheet revision.

    Best regards,
    Luis Fernando Rodríguez S.

  • 0 in reply to Luis Fernando Rodriguez S.
    Intellectual 290 points

    dear Luis，

          thanks for your kind explanation. for drv2625 to drive motor, my customer only take similar product from other manufactures and it can produce haptic feedback , for example ,it vibrates when button is pressed. my customer told me that this is the haptic effect that they want. in this case , can you suggest me how i can start my work? or what should i ask customer to provide to me in order to implement this function. if possible ,will you please detail it for me . it will be very grateful.

  • 0 in reply to jack bi
    TI__Guru** 108795 points

    Hi Jack,

    There are different ways to do something like what you describe. The data sheet and appnotes provides descriptions of its operation modes and  how the device is configured.

    One option would be to use TRIG pin to start a waveform. The TRIG signal can be sent from your host processor when a button is pressed.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators