I'm a student working with the Arduino UNO There's this question always bugging me for the analog input pins, how many samples does it take per cycle. I know it has 10 bit resolution meaning 0-5v would be 0-1023.I think since Arduino UNO uses ATMEGA 328(8 bit) then maybe 256 samples per cycle, but people say 128 bits per cycle. I'm confused.
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\$\begingroup\$ What do you mean by "cycle"? What do you mean by "bits per cycle"? \$\endgroup\$– Elliot AldersonJul 16, 2020 at 23:03
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2 Answers
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The sample rate is nowhere close, neither in samples nor bits per cycle. The datasheet gives the conversion time for a single sample relative to the ADC clock as:
A normal conversion takes 13 ADC clock cycles. The first conversion after the ADC is switched on (ADEN in ADCSRA is set) takes 25 ADC clock cycles in order to initialize the analog circuitry.
The ADC clock itself is taken from the system clock, with a prescaler ranging from /2 to /128, with the condition that the ADC clock ought to be no higher than 200 kHz. This yields a roughly 15 kSps sampling rate at best.
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The ATMega328 uses a successive approximation ADC, that means, that the ADC has to do multiple comparison until it has a result. Therefore, he need multiple cycles, in the datasheet you can find the time for the conversion, measured in number of cycles.
From the datasheet of the ATMega328, Table 23-1
