DRV2604L: In closed loop mode, constant PWM drive is interrupted every 50 - 70 ms

Ryan

Prodigy 80 points

Part Number: DRV2604L
Other Parts Discussed in Thread: DRV2605L

The attached screenshot shows the waveform of a PWM pulse lasting one second. (Pink is OUT+ and blue is OUT-)

This pulse is a constant PWM duty, but you can see that it is being interrupted by a number of drive signals from OUT-

This makes the motor sensation very jittery, not smooth. Why would it be doing this? How to fix it to be smooth?

(I know it could be switched to open-loop, but this loses features of the device such as braking.)

over 3 years ago

0 Carson Allen over 3 years ago

TI__Genius 13610 points

Hello,

Are you using this on an LRA or ERM? and what mode do you have it set for currently in register 0x1A?

Best Regards,

Carson

0 Ryan over 3 years ago in reply to Carson Allen

Prodigy 80 points

Yes, this is an ERM, and calibration was successful.

After calibration register 0x1A is equal to 0x34

0 Carson Allen over 3 years ago in reply to Ryan

TI__Genius 13610 points

could you provide full register dump if possible?

0 Ryan over 3 years ago in reply to Carson Allen

Prodigy 80 points

Yep. Below are the registers in order from address 0x00 to 0x22

(0xC0, 0x05, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x19, 0xFF, 0x19, 0xFF, 0x94, 0xBC, 0x2A, 0x56, 0x34, 0x93, 0xF5, 0x80, 0x20, 0x80, 0x33, 0xAD, 0x3F)

The only ones I have written to are the MODE (0x01) and 0x16 through 0x1A for motor settings and calibration.

0 Carson Allen over 3 years ago in reply to Ryan

TI__Genius 13610 points

Hello,

Ill take a look at this and get back to you in 24 hours

Best Regards,

Carson

0 Carson Allen over 3 years ago in reply to Carson Allen

TI__Genius 13610 points

So you said you are using PWM but you have mode set for RTP?

Did you switch?

0 Ryan over 3 years ago in reply to Carson Allen

Prodigy 80 points

Sorry for the confusion. We are definitely using RTP.

(In the original post I was describing the waveform of the output from the driver as PWM.)

0 Carson Allen over 3 years ago in reply to Ryan

TI__Genius 13610 points

So you are playing at a constant RTP value?

0 Ryan over 3 years ago in reply to Carson Allen

Prodigy 80 points

Yes, exactly. One constant RTP value, which is originating from a single command (i.e. the command is not sent repeatedly).

0 Carson Allen over 3 years ago in reply to Ryan

TI__Genius 13610 points

Hello,

I am not sure why this is happening. Have you tried with multiple devices?

And can i assume this does not happen in open-loop?

The only functionality lost in open-loop is that auto-brake which can just be replicated in open loop by going to a negative voltage for a certain amount of time.

Best Regards,

Carson

0 Ryan over 3 years ago in reply to Carson Allen

Prodigy 80 points

I have tested with a different microcontroller attached to a DRV2605L as well and it produces the same behaviour.

In open-loop it does not happen, that mode is perfectly smooth.

How is the negative voltage applied when using Open Loop Mode? And is there a way to retrieve the time period for this from the calibration routine?

0 Carson Allen over 3 years ago in reply to Ryan

TI__Genius 13610 points

Hello,

In open loop depending on the RTP format chosen you will control voltage value using this diagram where midpoint is transition from positive to negative.

You can run in closed loop in RTP then stop it and catch the breaking section with a oscilloscope and replicate that.

Best Regards,

Carson

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DRV2604L: In closed loop mode, constant PWM drive is interrupted every 50 - 70 ms