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DRV8243-Q1: Using SPI to control the driver

Mathias Bennetsen
Prodigy 50 points
Part Number: DRV8243-Q1

Tool/software:

Hi, 

I want to confirm my understanding of the DRV8243P (SPI (P) = variant). I am using two DRV8243P's each configured as a single full bridge to control two seperate DC brushed motors. To reduce the amount of pins used I want to control them over SPI in a daisy chain configuration. 

As far as I can see, the drivers can be fully controlled over the SPI registers (SPI_IN Register) without needing external HW control signals. Is there any way to control the speed via the SPI registers or would it just toggle between 0 and 100% duty cycle whenever activating the driver? 

If no speed is settable trough the SPI registers, could one use a PWM signal on the EN/IN1 pin in the PH/EN mode and then use the SPI registers to write to and activate the driver? So in essence combining the two control modes? Or are these mutually exclusive, so using SPI to control the driver would disable the EN/IN1 and PH/IN2 inputs?

Alternatively, if I am to control only with SPI, would DRV_OFF be tied HIGH, EN/IN1 and PH/IN2 tied to GND or left floating? 

Br, 

Mathias 

  • +1
    TI__Mastermind 45445 points

    Hi Mathias,

    Thank you for posting in this forum. Yes up to 63 devices can be used in a daisy chain configuration. This should be fine. See attached document, should you need additional guidance with daisy chain configuration.

    Daisy Chain SPI with Motor Drivers.pdf

    Mathias Bennetsen said:
    As far as I can see, the drivers can be fully controlled over the SPI registers (SPI_IN Register) without needing external HW control signals. Is there any way to control the speed via the SPI registers or would it just toggle between 0 and 100% duty cycle whenever activating the driver? 

    SPI_IN register provides an alternate method to provide S_EN_IN1 and S_PH_IN2 inputs to the H-Bridge - using SPI registers. The control logic follows Table 8-4 and 8-5 depending on the H-Bridge mode configured. In essence it would just toggle between 0 and 100% duty cycle like you mentioned.

    Mathias Bennetsen said:
    If no speed is settable trough the SPI registers, could one use a PWM signal on the EN/IN1 pin in the PH/EN mode and then use the SPI registers to write to and activate the driver? So in essence combining the two control modes? Or are these mutually exclusive, so using SPI to control the driver would disable the EN/IN1 and PH/IN2 inputs?

    Please refer to the below highlighted information in the datasheet - snippet below. You could configure to AND logic and provide PWM on the physical pin(s) as desired and control via SPI. 

    Mathias Bennetsen said:
    Alternatively, if I am to control only with SPI, would DRV_OFF be tied HIGH, EN/IN1 and PH/IN2 tied to GND or left floating? 

    For DRV_OFF this would depend on DRVOFF_SEL configuration, see Table 8-9 in the above snippet. If you choose OR logic control then the physical pins status don't matter. The DRVOFF pin has internal pullup and EN/IN1 and PH/IN2 has internal pulldown. So they can be left floating if desired.

    Regards, Murugavel