AD7794 does not work during use

problem:

The AD7794 is used for temperature measurement. The external connection is a six-way temperature platinum resistance. The data sampling of six channels is performed in a single sampling mode (six times are sampled once per second). But ad7794 will die at some point. This moment may be 5000s or more after power-on, there is no certain time point. When setting the SPI bus, the SCK clock used is 5khz. If the sck clock is 500khz, this dead situation will occur about ten minutes or up to half an hour. If the AD7794 dies, it must be powered down and restarted to return to normal. I would like to ask, what is the problem caused by this phenomenon? I looked at our evaluation board. I don't have the 1M ohm pull-up resistor on the SPI bus. I use the signal output directly from the FPGA.

In addition, we have a continuous conversion, continuous acquisition mode, I am not quite sure, if I want to collect six channels of data, what is the significance of continuous conversion? If I collect continuously, how can I tell which channel the data corresponds to? Thanks a lot, online.

Reply:

"Dead" may be the SPI bus out of step.

For example, if you send a 16-bit instruction, but because of the interference, the ADC may think that SCLK has jumped 17 times. As a result, the subsequent instructions and data are all misplaced.

You can try to send more than 32 consecutive 1s to the ADC from the SPI. This is a soft reset.

Continuous conversion means that after you have configured the ADC, the ADC automatically starts the next conversion after each conversion.

Corresponding to this is a single conversion, stopping after each conversion to enter a low power state

The AD7794 does not support automatic polling of individual channels. That function is available in the AD719x series and the AD717x. Generally, the data+status is opened, and the channel number is seen from the status following the data.

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