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AD7731 via Arduino SPI

Question asked by ghr@ilstu on Sep 28, 2015
Latest reply on Oct 20, 2015 by ghr@ilstu

We're using an Arduino to control an AD7731.  We think the SPI interface is working in that we can 1) trigger a reset by writing four 0xFF bytes and see the RESET pin go low via our logic analyzer and 2) After the reset, we read the Mode register and get back 0x174 as per the data sheet.  Our problem is that when we try to do a continuous conversion read operation, fully differential, AIN1(+) and AIN2(-), 0 - 1.28 V, Mode bytes as follows (MSB first)   00110001  01110100, we can't ever get the RDY pin to go low.  Is there a way to check the operation of the chip so see if conversions are being made and put in the data register at all?  I don't think we fried the chip, but we don't have a way to check.  Also, we are using the AD780 2.5V reference.  We could send you code if that would help.

 

Thanks,

George

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