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Trouble reading AD7799 registers

Question asked by Neddie on Apr 26, 2017
Latest reply on Apr 26, 2017 by JellenieR

Cant read AD7799  

I cant seem to read any of the registers in the 7799.

I send the device a reset. If I hold the CS line low I can see the Dout/Ready pin giving a pulse

every 16mS or so , so I know the chip is running/autoconverting.

If I want to read the ID Register for instance , I send the value 0b01100000 to the Communication register

and then do another "dummy" spi send to read the contents of the ID register , but I always get FF back.

The ID register is 8 bits wide.

Something I'm not sure of is when to enable / disable the CS line. Do I keep it low after the first write the 

the Communication register and the next "read" of the ID register or go :    cs=LOW , write com reg CS=HIGH 

CS=LOW read ID reg CS = HIGH 

I'm using a pic16lf1827 spi peripheral. I've checked with a scope and I'm getting the correct number of clock pulses

etc.

 

Cheers

Neddie

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