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AS5048 SPI Communication trouble

Question asked by Thomas Carrington on Apr 18, 2017
Latest reply on Apr 21, 2017 by Andres Cao

Hi All,

 

Have just moved over to the STM32 (have the Nucleo-F103RB!) device from 8bit devices, and am finding the STM32 device to be pretty cool

Currently working on a personal project, to build a robotic arm and have decided to use the AS5048A (SPI interface) as a way to measure the angular position of each joint. I've configured the STM32 to use the SPI1 interface configured with CPHA = 1, and CPOL = 0; so the clock is idle low, and the trailing edge is used to capture data, which aligns with the AS5048A datasheet. It is also setup to only send 8bits at a time, I am aware that the device requires 16bits, so I've set up the transmit to take this into account, 2 bytes are transmitted between slave selections.

 

When I read from the device, it seems to work.....sometimes, most of the time, I get weird data that doesn't make sense:

I am unable to clear the error flag with each package (even when reading from the "Clear Error Flag" register; when reading data from the "Clear Error Flag" register I get 0xC000 or 0xC001, the last one makes the least amount of sense as the data should be EVEN parity (note I have read this register multiple times, and still get this).

Even with a magnet over the chip, I seem to get sporadic data, telling me that the angle is 0/1, even when rotating the magnet in multiple directions (the magnet I have used is the one provided in the AS5048A Development board)

 

So, I'm a little lost as to what I've not done wrong, I've attached a copy of my code to interface to the device to this post.

The function within called "AS5048_CompleteRead" has been able to get some good data, but as I have stated above,  it works very intermittently, and the angles I get are not consistent; one minute it says it's at angle 150deg, move it around a bit and then return, and I get a completely different number

 

Any help that can be provided will be most appreciated.

 

Regards,

  Thomas

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