ADC library, settings sampling window and conversion time in real time units

DrM

Well-known member
Hi,

For this question, I am interested in the ADC settings in the ADC library, for both the T3 and T4.

The ADC library provides settings for the sampling window in units of ADCK. Conversion time is specified there only as "SLOW" to "FAST" and "VERY FAST".

The documentation says ADCK depends on ADC_F_BUS, but I have not seen where it tells us about ADC_F_BUS or how ADCK depends on it.

Second, for the T4, there are settings for the series resistor embedded in the analog input. How are these selected in the library?

The sampling window can be a critical setting. This is the time within which he voltage on the sampling capacitor needs to be within 1 LSB of the voltage applied to the input pin. So that depends on the selection of that series resistance, and the external resistor or source impedance connected to the analog input pin.

So sampling time and series resistance can be super important to know, when you are designing something to use the analog inputs.

The processor reference manual has more about this, of course. But it is quite opaque, really, and fishing the settings out of the library source code seems like quite a task as well. It would be helpful to have more specific information in the document for the library.

Is there a more complete and more detailed table of these values posted anywhere?

Thank you
 
That is pretty much the same information. It is missing the same details, and it does not come to a bottom line. What is ADCK, before we select one of the free running clocks? What do the settings slow, fast, very fast, etc, correspond to? For the T4, what are the values of RADIN for each setting?

it is a very nice job of implementing the ADC functionality, but for leaving out this small set of details, we do not know to select the settings or what is required of the external circuit to produce realistic readings.
 
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