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Sigma-Delta ADC interface with BF through SPI

Question asked by Kenny.S on Jul 1, 2011
Latest reply on Jul 11, 2011 by WassimB

Hi guys,

 

I'm now using BF533 to read samples from AD7171(sigma-delta, 16bit, 125Hz output data rate, SPI compatible) through SPI. The serial digital interface of AD7171 consists of two signals: SCLK and DOUT, no /CS. A 24-bit word is placed on the DOUT pin when sufficient SCLK pulses are supplied, this 24-bit word consistes of a 16-bit conversion result followed by eight state bits. As you know, the SPI "word" can only be configured as either 8bit or 16bit, so following are my questions:

1. How should I threat this 24-bit word from ADC using SPI?

2. How can I get pure conversion result?

3. Does it make sense to set SPI word as 8bit and extract conversion result in every three interrupts?

4. Is there any example code for BF reading data from ADC through SPI?

 

Thanking you in advance for any advise!

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