Analog smoothing of multiple inputs

Using Arduino Programming Questions
21

It gets better with age :confused: No it doesn't.

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22

Hi All

So I've been testing my code for a couple of days. And I still can't get to grips with the sampling side of things.

const int NINPUTS = 4;

const byte inputPin[NINPUTS] = { A0, A4, A3, A5 };

int reading[NINPUTS];
float smoothedReading[NINPUTS];

void takeReadings() {
  for(int i = 0; i<NINPUTS; i++) {
    reading[i] = analogRead(inputPin[i]);
    smoothedReading[i] = smoothedReading[i] * .75 + reading[i] * .25;
  }
}

As I understand it.

smoothedReading[i] = smoothedReading[i] * .75 + reading[i] * .25;

Is the sampling side of things.

My problem is that as a non programmer I don't understand it at all. But I wish to learn.

If someone can please explain to me what is happening, I would have a greater understanding of what to adjust, and what effect it has on the outcome.

Regards

Fred

23

You tell us what 'you' think is going on with each line of code:

const int NINPUTS = 4;
const byte inputPin[NINPUTS] = { A0, A4, A3, A5 };
int reading[NINPUTS];
float smoothedReading[NINPUTS];
void takeReadings() {
for(int i = 0; i<NINPUTS; i++) {
  reading[i ] = analogRead(inputPin[i ]);
  smoothedReading[i ] = smoothedReading[i ] * .75 + reading[i ] * .25;
}
}

Moderator edit: [code] ... [/code] tags added. (Nick Gammon)

24 
Declare NINPUTS as a constant integer with a value of 4
Declare input[NINPUTS] with the values of the A0, A4, A3,A5  and the values are a constant byte
Declare reading[NINPUTS] as an integer
Declare smoothedReading[NINPUTS] as a float
Declare the function void takeReadings()
I don't know. Spomething to do with counting the readings I guess
I don't know. Making reading[i] = analogRead(inputPin[i]). But why would you do that
I don't know. Making smoothReading[i] = smoothReading[i] and some confusing equation.

So here's what I don't understand, what is [i]? And how do we know how many readings we are taking per input.

That should be good for a giggle. But I'm not a programmer, and I still struggle with the correct terms.

Regards

Fred

Moderator edit: [code] ... [/code] tags added. (Nick Gammon)

25

It's math. You're taking 25% of the current reading, and adding 75% of the previous reading. If it were 50/50 it would be a standard average. Get it? Then rinse and repeat. The result becomes the previous reading for the next round.