DRV8889-Q1: Micro stepping from GUI

Vinu Gopalakrishnan

Part Number: DRV8889-Q1

Hi,

I was evaluating DRV8889-Q1 EVM with 17hs19-2004s1 stepper motor. Everything is working fine except for the following -

1. STEP_SIZE

It seems the motor is always executing the same step length, irrespective of full or 1/2 or 1/4 etc.. step sizes set in GUI.

360 degree move

I am seeing a 360 degree rotation for all the step sizes. Should the total angle covered by motor reduce when step size decrease ?

Am i missing something here ? Please help.

2. FAULT CLEAR

The fault clear is not working in GUI. Always i have to asleep & awake the motor_driver toggle switch. Any thoughts on this?

regards,
Vinu

over 4 years ago

0 Wang5577 over 4 years ago

TI__Guru 56650 points

Vinu,

After set a different micro-stepping, we can go to "register map page" to read all register values to see if the new setting is finished or not.

DRV8889-Q1EVM SPI bus is very busy to read torque-count register value to show the chart in GUI. So, the new micro-stepping setting may not be sent out immediately before read back.

Similar situation, clear fault command may also not be sent out immediately. We may need to wait for couple seconds.

Regards,

Wang

0 Vinu Gopalakrishnan over 4 years ago in reply to Wang5577

Prodigy 58 points

Wang,

I tried to read back the registers, but didnt notice any change in step value.
If the value had changed, then the angle covered of a 1/2 step move would be half of a full step move, correct?
I am always seeing the same angular displacement of the rotor for all step sizes.

Any thoughts?

0 Ryan Kehr over 4 years ago in reply to Vinu Gopalakrishnan

TI__Guru 55605 points

Vinu,

Are you able to manual write/read to the registers on the register page? Seems like maybe a connection issue. Does GUI show a connection on the bottom left of page?

You are correct. If you change from full-step to 1/2 step and issue the same number of steps, you should get 1/2 the rotation you achieved in full step mode.

Regards,

Ryan

0 Vinu Gopalakrishnan over 4 years ago in reply to Ryan Kehr

Prodigy 58 points

Ryan,

Seems like a connection issue. Now micro steps are working.

Thanks!

0 Don Dapkus over 4 years ago in reply to Vinu Gopalakrishnan

TI__Guru**** 189401 points

Hi, Vinu,

Thanks for letting us know this solved your issue. If you have any other questions, please let us know!

Best regards,

Don

0 Vinu Gopalakrishnan over 4 years ago in reply to Ryan Kehr

Prodigy 58 points

This might be a motor related question.. but please help if you can..

What is the relation between step size and starting speed ?
The motor i am using has its torque curve defined for half steps. Its starting speed is around 500PPS, where each pulse is a half pulse.
I would like to know the starting speed when the step sizes are 1/4, 1/8 steps etc..

Any idea guys ?

+1 Ryan Kehr over 4 years ago in reply to Vinu Gopalakrishnan

TI__Guru 55605 points

Vinu,

As you go to higher levels of micro-stepping, you would just increase the starting speed proportionally. So, moving from 1/2 step at 500PPS, to 1/4 step...should be 1000pps for the same starting speed.

Let us know if that doesn't work out for you.

Regards,

Ryan

0 Vinu Gopalakrishnan over 4 years ago in reply to Ryan Kehr

Prodigy 58 points

Thanks Ryan. Now it makes sense. Appreciate the timely support you guys provided.

Thanks,

Vinu

0 Vinu Gopalakrishnan over 4 years ago in reply to Wang5577

Prodigy 58 points

Yes, there is a delay (2-3 sec) for the settings to be written into the driver.

Thanks Wang.

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DRV8889-Q1: Micro stepping from GUI