Start/Stop a function using pushbutton - button

Question

I am trying to display the readings of LDR on my 0.96" Adafruit OLED. I have succeeded with obtaining that results.
Now I want to start the display of the reading only when I push the button and stop it once I push it again. This should go on a loop.
I tried to draft a code for that:
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
int sensorPin = A0; // select the input pin for ldr
int sensorValue = 0;
boolean state = false;
int buttonpin;
#define OLED_RESET 4 // not used / nicht genutzt bei diesem Display
Adafruit_SSD1306 display(OLED_RESET);
char inChar;
String string;
void setup() {
pinMode(13, OUTPUT);
buttonpin = 2; //whatever pin your button is plugged into
pinMode(buttonpin, INPUT_PULLUP);
// initialize with the I2C addr 0x3C / mit I2C-Adresse 0x3c initialisieren
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
Serial.begin(9600);
display.display();
delay(2000);
display.clearDisplay();
display.setTextColor(INVERSE);
}
void loop()
{
while (state == false)
{
if (digitalRead(buttonpin) == HIGH)
{
display.clearDisplay();
sensorValue = analogRead(sensorPin);
Serial.println(sensorValue);
display.setCursor(30,0);
display.setTextSize(1);
display.print("LDR Reading:");
display.setCursor(30,10);
display.setTextSize(2);
display.print(sensorValue);
delay(500);
display.display();
state = false;
}
}
}
But the screen starts displaying the results only when I keep the push button pressed continuously and when I release the button , the program halts with the last reading displayed on the screen.
I need the results as follows:
1st press: starts displaying readings
2nd press: screen should be blank. (display.clearDisplay() does that job)
I am unfamiliar with the usage of switch case in Arduino.

Answer 1

Thie is to elaborate on #shaunussain's answer.
Here is an exampole of a toggle:
Create a boolean variable : bool toggle = false; The variable state is at false at the beginning. Thus, the screen will start blank.
Then do something like this. This is just a logic.
If the button is pressed
if( buttonPressed() ) {
Change toggle's state. So if it was ON / true, it will change to OFF / false.
toggle = !toggle;
Now, we wait until the button has been released, otherwise the code might go a little crazy! And then we close the brackets.
while ( buttonPressed() );
}
Then in your loop, you will have a switch case. We start by innitializing the switch case.
switch( toggle ) {
Then we set up a case for when the toggle is on ON / true. 1 is true, 0 is false.
case 1 :
Then we write the code body.
displayTextOnScreen();
Then we exit the switch case because toggle matched with our case.
break;
Then, if we toggle isn't true or it is something else (because there was a glitch in the code), we will have a default case.
default:
In the default, we want the screen to be off, so if it isn't suppose to be on, or if there is a bug, it will be off. Then we will close the switch case and exit it because default is the last possible case in a switch case.
display.clearDisplay();
}

Answer 2

Thank you so much, it helped me a lot. The code is working fine. Updated code :
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
int sensorPin = A0; // select the input pin for ldr
int sensorValue = 0;
bool toggle = false;
int buttonpin;
#define OLED_RESET 4 // not used / nicht genutzt bei diesem Display
Adafruit_SSD1306 display(OLED_RESET);
char inChar;
String string;
void setup() {
pinMode(13, OUTPUT);
buttonpin = 2;
pinMode(buttonpin, INPUT_PULLUP);
// initialize with the I2C addr 0x3C / mit I2C-Adresse 0x3c initialisieren
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
Serial.begin(9600);
display.display();
delay(2000);
display.clearDisplay();
display.setTextColor(INVERSE);
}
void loop()
{
if (digitalRead(buttonpin) == HIGH)
{
toggle = !toggle;
while(digitalRead(buttonpin) == HIGH);
}
switch( toggle )
{
case 1:
display.clearDisplay();
sensorValue = analogRead(sensorPin);
Serial.println(sensorValue);
display.setCursor(30,0);
display.setTextSize(1);
display.print("LDR Reading:");
display.setCursor(30,10);
display.setTextSize(2);
display.print(sensorValue);
delay(500);
break;
case 0:
display.clearDisplay();
break;
}
display.display();
}

Answer 3

Keep a Boolean to track the toggle state and a Boolean to keep the state of the button from the previous loop. If the button goes from low to high between loop iterations then update the toggle Boolean,
toggle = !togggle
Base your condition for the display state then on the toggle instead of directly on the button.