interface ad7478 ADC to atmega128

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I need to interface ad7478 ADC to atmega128. I am going to filter a 500kHz signal.So I need atleast 1MSPS adc. I go through the data sheet, but didn't got an idea how to interface it with atmega128a. I need help....

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The AD7478 has an "SPI" interface.

The M128 has an "SPI" interface.

Connect them together and your hardware connections are done.

Two additional thoughts:

If you are sampling at 1 MS/Sec you are going to be collecting a lot of data very quickly. You can very quickly fill the memory available.

This means that either you trigger on when you want to start data collection and then collect a short burst of data, or you pick a micro with LOTs of memory, or you feed the data out to a PC at the same rate you are collecting the incoming data.

Second thought: Although >= 1MS/Sec meets Shannon-Nyquist criterion, minimally meeting such criterion is often insufficient for real world data processing purposes. (It meets theoretical processing requirements, not real world processing requirements.)

In practice, for many applications, significantly higher sampling is beneficial.

Lastly:
You might do well to simulate your system on a PC, where it is easy to generate a sample data set and process it to see the output before tightly specifying the hardware requirements.

JC