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I've been having some issues diagnosing the relationship between writing to the registers through SPI commands and stepping the motors. That is, it seems like when I write SPI_STEP=1 (and STEP=1) to register CTRL3, pins AOUT1, AOUT2 and BOUT1, BOUT2 produce a PWM when I expected just a single-step.

So my question is, are the outputs to the DRV8889 chip pulses despite the inputs being a single write command (which I have as 0x50 for CTRL3 register)?

asked Oct 18, 2019 at 2:47
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1 Answer 1

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I would say yes, at first it seemed weird to me, but there is an internal regulator that regulates the current that goes through the motor windings.

A hint from the Datasheet page 17

Hint from datasheet

answered Oct 18, 2019 at 6:32
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  • \$\begingroup\$ Oooh okay I was suspicious about this part being the culprit... I’m not sure how to go about calculating how long the pulses are for and thus determining the duty cycle. Any ideas? \$\endgroup\$ Commented Oct 19, 2019 at 4:32
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    \$\begingroup\$ Oscilloscope is my best idea. \$\endgroup\$ Commented Oct 19, 2019 at 7:52

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