Allegro A8904 and AVR

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#1
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Does anybody have worked with allegro A8904?
I need to drive a 3 phase hybrid stepper motor
Any suggests, tips, code, advice is very appreciated.
First of all I need to initialize the device (serial data) an to start to move the motor...

Many thanks in advance..
:D

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Have you read the datasheet for the A8904? What exactly are you having difficulty with?

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Yes I did a fast read to data sheet. First of all data sheet don't report an example of to connect the A8904 centertap pin. My motor has only 3 wire...Have you any idea? how to menage centeratap pin ?
I attach a allegro evaluation board scheme...:P

Attachment(s): 

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Quote:
My motor has only 3 wire...Have you any idea? how to menage centeratap pin ?

Hmm, I'm not sure the A8904 is an appropriate device for controlling your motor in that case. What model motor is it?

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The motor in KT42EM1-002 (servo catalog) The centertap seems to be useful for probe the speed control by sensed back-EMF signal from stator phases. Is possible to override this stage?

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That's the problem, I don't think you can. Sensing back-EMF is kind of central to the way that chip works. Besides it is really intended for speed control of brushless motors rather than the position of stepper motors.

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On page 9 of A8904 data sheet there is a figure which illustrate a normal waveform of centertap signal. Do you think is possible to generate the same waveform putting a shunt through gnd_path and sensing the voltage at shunt?
Also on page 14 is write if centertap is not connected A8904 has inside a network of 10K resistors that emulates its behavior... May I trust in this?

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Hadn't noticed that. Its usually best with things like this to experiment. I could not say whether or not it will work just off the top of my head.

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Ok, I'm gone to make a wired prototype for test this devices... Have you a pieces of code for init this devices? Only for reference, for to say ok guy with this code may 3-phase stepper motor should rotate...
Thanks for your interest!

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I don't have any code for that device, sorry.