Position feedback with DRV8825?

Is there any possibility to get a position feedback out of the driver?
What i mean is the following: i have a mechanical end-position which stops the further rotation of my stepper motor. is it possible to get a feedback of the driver, when the motor doesn’t change its step-position? i know that there is a nHome-Signal pin on the driver chip. but what does it exactly show? lets say i drive my mother in 1/8 step mode and there comes a step signal from my uController, i would say the nHome would switch every 8 step-signals to “home”. but what happens, if only the signal comes from the controller, but the motor itself stands still? does the driver recognize this, or do i need an additional encoder to determine a blocked stepper motor?

You need a shaft encoder or a limit switch.

The “nHome” output is active only on phase 1 of the full step state table, and is active only every 32 steps in 1/8 step mode.

It is very difficult, if not impossible, to determine from the winding current whether the motor has actually taken a step, especially in microstepping mode.

ok, i see. that is exactly what i did until now. i thought, i could get rid of the encoder:-(
but what about your new #2970 driver? if i understood it correctly, thats exactly what this driver does - measuring the EMF of coils?
how difficult would it be setting up a measuring system for lost steps? is there a inbuilt function for comparing incoming step signals and real coil movements or do i have to do this with the uController? i only have a arduino mega2560, so i think there is a limit doing this via software…

[quote]how difficult would it be setting up a measuring system for lost steps[/quote] Excellent question! Here is what the AMIS-30543 data sheet has to say about its capabilities:

[quote]The chip provides a so−called “speed and load angle” output. This allows the creation of stall detection algorithms and control loops based on load−angle to adjust torque and speed.[/quote]In fact, the pin just outputs the back EMF generated during zero-current periods. So, the skipped-step algorithm is up to you.

What would you think about using the Arduino Encoder-Library for dealing with the Back-EMF output of the Amis Driver?