Input Ranges

What if we want to achieve different behavior on our outputs using different ranges of analog input? We will learn how to do that now, using a new kind of logic structure called a switch case and a new function called map().

Open the analog-range sketch.

Inside the loop, we see this:

int range = map(piezo_val, piezo_max, piezo_min, 0, 3);

This command uses the map() function to take piezo_val and break it into four pieces (called 0,1, and 2… the counting starts at 0). The largest piece starts at piezo_max and the smallest piece ends at piezo_min. Each time through the loop, map() takes the value of the input, converts it to a numbered piece of the full range, and stores the result in the variable range.

Just below map(), we see the switch-case function. The function argument and first case is shown here:

switch (range) {
case 0:    // light knock, turn on green LED
    Serial.print(piezo_val);
    Serial.print(" ");
    Serial.println("light knock");
    digitalWrite(greenled_pin, 1);
    break;
...
}

The line switch (range) indicates that we want to use the variable range for each case. So, we have case 0, case 1, case 2, and case 3.

Within each case, we print the value of piezo_val, a note about what this physically corresponds to, and control our LEDs accordingly. Then, the line break; tells the Arduino to leave the switch-case and go back into the loop.

Try making the third case

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