AnsweredAssumed Answered

AD7147 FIFO's do not function

Question asked by Kristof_Mulier on May 15, 2015
Latest reply on Jul 24, 2015 by Kristof_Mulier

I have been using the AD7147 capacitance sensor to detect objects between two parallel copper plates. I stumbled on the following strange fenomenon:

 

- Reading the conversion data from the chip is no problem. I read the following registers through my SPI link:

     CDC_RESULT_S0

     CDC_RESULT_S1

     ...

     CDC_RESULT_S11

I get useful signals from reading these registers, allowing me to detect proximity.

 

- I have also tried reading the following registers:

     STAGE0_CONV_DATA

     STAGE1_CONV_DATA

     ...

     STAGE11_CONV_DATA

Again, this works perfect. I get the same results.

 

- But when I try to read these registers:

     STAGE0_FF_WORD0

     STAGE0_FF_WORD1

     ...

     STAGE0_FF_AVG

I get only some fixed numbers that do not react on any proximity. I have the same problem when I read the registers from the Slow FIFO.

For some reason, I am not able to use the built-in FIFO's in the AD7147.

I believe my SPI link works fine, because reading the conversion results goes perfect.

 

What could cause the FIFO's in the AD7147 to malfunction?

Outcomes