DRV8889-Q1: DRV8889-Q1

Hello Lakshmi,

You can read more about Open Load Detection here:  https://www.ti.com/lit/an/slvae49c/slvae49c.pdf

A few things to check:

• Per the datasheet, "If the motor is held at a position corresponding to 0°, 90°, 180° or 270° electrical angles, for more than the open
  load detection time, open load fault will be flagged, as one of the coil current is zero".  Rotate the motor slightly and see if the same result occurs. 
• Is your SPI circuit set up as recommended in 7.5.1.4 SPI for Multiple Slave Devices in Daisy Chain Configuration ? 
• What happens if you do the steps in the opposite order - perform the test on stepper2 with the debugger first, then upload firmware and power-cycle? 

I am a little unclear as to what isn't working in your second test - is it not correctly observing an open-load fault in stepper 2?  Or is it detecting an open-load fault when there shouldn't be a fault?   

Regards, 

Jacob

Hi Jacob,

Thank you for the reply.

• Is your SPI circuit set up as recommended in 7.5.1.4 SPI for Multiple Slave Devices in Daisy Chain Configuration ? ----NO, we are connecting the devices in Parallel Configuration.
• I am a little unclear as to what isn't working in your second test - is it not correctly observing an open-load fault in stepper 2?  Or is it detecting an open-load fault when there shouldn't be a fault?  ----- the stepper2 is detecting the fault which is not expected- it should not detect any fault.

We are performing this Open Load test only on stepper-1.

Regards,

Lakshmi Teja

Thanks Lakshmi, 

Parallel Configuration should work fine, that shouldn't be the issue.  

Can you describe or post a drawing/picture of the Open Load Test setup and procedure that you are doing?  Showing where each motor is connected, what you're disconnecting to make an open load, any extra pull up/downs, etc. 

Please post an oscilloscope picture as well, ideally showing the step signal, current, and nFault signal.  It would also be useful for us to see the register settings like the fault status and diagnostics.  

Regards,

Jacob

Hi Jacob,

Thank you.

Please find the below drawing of how we are doing the Open Load for the stepper1, we are not using any external pull-up/downs.

also find the capture from the Oscilloscope-this information is related to stepper2.

Regards,

Lakshmi Teja

Thanks,

It looks like that's a scope shot of the SPI communication, could you post a picture of the motor step signal, phase current, and fault signal so we can see what the motor driver should be sensing at the time of the fault? 

Regards,

Jacob

Lakshmi,

On case #2, if you issue a clear fault command for stepper driver #2, does the fault go away or come back as open load again?

Regards,

Ryan

Hi Ryan,

We are performing test only on steper1 by making it as open load, we are not performing any open load test on 2nd stepper.

Now, at Normal voltage both the steppers were working fine, But if we reduce the voltage <7.5V  we are observing the status register readings of both the steppers(1 & 2) as below---- SReg0=0x81, sreg1=0x00, SReg2=0x03  could you please suggest what may be the reason?

Regards,

Lakshmi Teja

Lakshmi,

Yes, I fully understand you are only removing the motor from stepper #1, but getting an error only on stepper #2.  

From the register readback, device is signaling an "open load".  

Unfortunately, you did not answer my question above which would help in the debug, so please allow me to ask again with more detail from my side.

When you get the error on driver 2, can you please try and issue a CLR_FLT and read the status registers again?  Please see detail below on how to do that.  

Regards,

Ryan