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Question 1: Is there any workaround to use torque control instead of speed control. The SPEED_LOOP_DIS can be set, but then torque references need to be set with i2c which is problematic since you can't use i2c when a motor is spinning. Is there a way that the SPEED pin can be used to generate torque setpoints
Question 2: We learned that even though FG is an optional open drain output, if there is not pullup then no i2c communications work. Is there any workaround to this?
Hey Joe,
Thank you for your question. We will take a look at this and aim to provide feedback before the end of next week.
Best,
Akshay
Hi Joe,
Q1: There is no work around for using torque control instead of speed control for the MCF8316A due to it's i2c issue. I recommend taking a look at the MCF8315A, which is rated up to 4A peak current, this device's i2c can function when the motor is spinning allowing for torque control.
Q2: There is no work around for FG pin, the FG pin requires a pull-up resistor to 1.8V - 5V.
Regards,
Joshua
Thanks. I have the MCF8315A populated now. I can get the speed commands to work with:
SPEED_LOOP_DIS = 0, SPEED_MODE = 2, OVERRIDE = 1, DIGITAL_SPEED_CTRL = speed
I am trying current control mode with the following but it does not work:
SPEED_LOOP_DIS = 1, FORCE_IQ_REF_SPEED_LOOP_DIS = current
Are there any other settings I need to update? Does the speed pin setting matter?
Hi Joe,
I will need some time to look into this. I will aim to get back to you by Friday at the latest.
Regards,
Joshua
Hi Joe,
When setting up and using torque control please follow these steps:
Regards,
Joshua
Hi Joe,
The MCF8316A offers active breaking which can be used to generate negative torque, please see section 7.3.16 of the datasheet for more information.
Regards,
Joshua
So only in speed control mode then? How could setting a positive current setpoint generate braking without a speed control loop? So my question is: in current control mode can you only command positive currents without braking? Thanks.
Hi Joe,
Let me look into this, I will get back to you by next Wednesday at the latest.
Regards,
Joshua
Hi Joe,
I am still looking into this, I will aim to get back to you by Friday.
Regards,
Joshua
Hi Joe,
The MCF8315A does have the ability to generate a negative currents. You can set a negative current if you manually set the current in the FORCE_IQ_REF_SPEED_LOOP_DIS register. To be able to set the Iq_ref current using the FORCE_IQ_REF_SPEED_LOOP_DIS register you must follow these steps:
Regards,
Joshua
This is still not working for me. Do I need to start the motor in another mode first?
ok, seems like you need to wait after sending the first setpoint. If you update the setpoints while it is starting then it stops.