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Position information over 180 deg instead of 360

Question asked by inaresh on May 8, 2014
Latest reply on May 21, 2014 by ShaneO

I'm trying to read position information over SPI using EVAL-AD2S1210EDZ. In this process I'm using microchip dsPIC33FJ32MC204 for SPI communication.

 

Eval Board Config: Res0:1; Res1:0 (16 bit) and A0:0; A1:0 to give position information all the time. Communication mode: Serial

 

There are two cases I tried.

 

Case 1: Framed SPI mode, the mode in which Clock Pulse will be continuously sent regardless of the data transmission. The position information is coming correct varying from 0 - 65535.

 

Problem: Problem with this case is the position variation from 0 to 65535 is happening over 90° instead of 360°. Could some one point out where the error is?

 

Case 2: Normal SPI mode, the mode in which Clock Pulse is transmitted only when the data is required. Here the position information varies from 32767 to 65535. 0-32767 is completely missing. Why is this so?

 

If the attached waveforms are observed, Case 1 though giving reliably right information is taking about 19 Clock Pulses. And in case 2, it is 16 pulses. Is there some thing I'm missing? Please highlight.

 

Update1: I'm using 4x resolver, which actually outputs Sin4θ and Cos4θ. So it gives 4 NM pulses for one complete mechanical rotation; meaning it should give 4 cycles of 0-65535. But I see 16 cycles as such.


Thanks

Naresh

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