Datasheet

VREF = DAC_VALUE ·

eVREF

4095

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UART Mode

4.3 Updating DAC Output for Current Control (VREF)

During evaluation, the user may want to study the operation of the ITRIP regulation scheme. Both

MSP430F2617 MCU DAC channels can be controlled through the provided sliders, shown in Figure 6.

Moving these sliders produces the effect of having the regulated current be directly proportional to the

slider position.

It must be noted, however, that during stepper actuation the DAC channels are solely controlled by the

microstepping application.

Figure 6. Current Regulation Control

The 12-bit DAC channels 0/1 are connected to the DRV882x VREF analog inputs VREF. Changing the

DAC digital value from 0 to 4095 changes the analog voltage at the respective VREF pin from 0 V to 2.5 V

respectively, as modeled by Equation 1.

(1)

Where:

• VREF is the MCU DAC output voltage into the DRV882x device.

• DAC_VALUE is a number from 0 to 4095; in this case, it is specified by the slider position.

• eVREF is the R19 potentiometer output, or external reference voltage into the MCU DAC module.

Note that the GUI software is not aware of the setting for the MSP430 eVREF. Slider position to analog

output voltage transformations are made on the assumption that R19 has been set so that eVREF = 2.5 V.

4.4 Stepper Control

Figure 7 illustrates the stepper control frame of the CPG006 GUI software.

Figure 7. Stepper Control Screen

SLMU002–June 2011 DRV882x Evaluation Modules

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