DRV8899-Q1: Electrical angle questions

Hi Kawasaki-san,

Thanks for your post.

Yoshikazu Kawasaki said:

1. Is it possible to know the exact electrical angle when the motor is held at a position?

With drivers such as the DRV8899-Q1 there is no feedback on the indexer position. To understand the exact electrical angle it can be derived by the MCU keeping track of the number of steps sent to the driver.

Example: Let's assume a stepper is driven with 1/8 step mode. The current waveform will resemble like shown below. One quadrant of the current sinewave will have 8 steps and one full cycle of sinewave will have 32 steps which would be 360 ° electrical angle. One step (mircostep) would be 360 / 32 = 11.25 ° electrical angle. 

This is the electrical angle difference shown between each row in the below table in the datasheet. It was rounded off to 11 °. But the precise value would be 11.25 °. Keeping track of the number of steps will indirectly allow tracking of the precise electrical angle for a specific STEP position.  

With drivers such as the DRV8462, DRV8462, DRV8452 they provide feedback on current indexer position in registers using which electrical angle can be calculated.

Yoshikazu Kawasaki said:

2. It says "The home state is an electrical angle of 45°", but is it possible to change it to another angle like 135° or 225°?

This is hard coded in the digital indexer of the driver. It cannot be changed. This probably the most common for most stepper drivers with integrated indexer.

Using dual H-bridge drivers without an integrated indexer for example the DRV8845, the customer have to have an external indexer in their MCU. In this case they can define what exactly HOME position is in their system. Thank you.

Regards, Murugavel