Why interrupt is stopping program instead of jumping back? - c

Question

i'm working on arduino and i have made two modes in loop(),mode1 in while loop and mode second in while loop they have conditions to be met, i switch between them using button that interrupts routine that is currently executed,changes flags to force program to change to second mode and for some reason instead of breaking out of current while loop (since conditoins are not met anymore )to change to the other it just doesnt respond
or changes from automatic->stops responding
#define modeSwitch 2
boolean manual;
boolean automatic;
String sOld;
boolean flagPrint = false;
volatile int modeSwitchValue;
String receivedData = "";
String invitation = "Welcome to Morse Code Encoder!\nPlease choose a mode: Write 'automatic' for an automatic mode or 'manual' or manual code.\n";
void setup() {
pinMode(modeSwitch, INPUT);
attachInterrupt(0, changeMode, RISING);
manual = false;
automatic = false;
volatile int modeSwitchValue = 5;
Serial.begin(9600);
Serial.println(invitation);
}
void loop() {
if (Serial.available() > 0) {
receivedData = Serial.readStringUntil('\n');
if (receivedData == "manual" ) {
manual = true;
automatic = false;
modeSwitchValue = 0;
}
if ( receivedData == "automatic") {
automatic = true;
manual = false;
modeSwitchValue = 1;
}
while ((manual == true) && (modeSwitchValue == 0) ) {
String s = "Manual mode:";
while (checkPrint(s) == true) {
Serial.println(s);
}
automatic = false;
}
while ((automatic == true) && (modeSwitchValue == 1)) {
String s = "Automatic mode:";
while (checkPrint(s) == true) {
Serial.println(s);
}
manual = false;
}
}
}
void changeMode() {
if ( modeSwitchValue == 0) {
modeSwitchValue = 1;
automatic = true;
manual = false;
}
if ( modeSwitchValue == 1) {
modeSwitchValue = 0;
manual = true;
automatic = false;
}
}
I deleted checkPrint() function cause it only ensures msgs are printed once so its not essential to show here i think
I thought that while executing automatic code, i press button and it interrupts,changing mode variable then goes back to same place in program where the interrupt occured. then software notices that while loop condition of automatic mode is not fulfilled anymore so it breaks out to loop() and finds while loop of manual mode to be executed since the conditions are met. am i thinking wrong? or have i missed something?

Answer 1

If you really want to attach an ISR to the RISING edge of a button signal, you should ignore multiple triggers. Minimum 2 msec, but why not ignore everything that's unrealistic (e.g. 100 msec)
As you just toggle two states, I'd propose a boolean variable istate.
volatile bool istate; // the state maintained in the ISR changeMode
void changeMode() {
static unsigned long lastime;
if (millis() - lastime > 100) {
lastime = millis();
istate = ! istate;
}
}
All other redundant stuff (automatic, manual) can be built from that volatile ISR variable in the main code, if necessary.
In my unterstanding, the name buttonState is just wrong. And the variable unnecessary.
Do you know the data type enum?
enum {MANUAL, AUTO} mode;
if (istate) mode = AUTO;
else mode = MANUAL;
might be nice for your purpose.

Answer 2

You are mixing up assignment "=" and comparison "==" in your changeMode() function. Here is a corrected version of the function.
void changeMode() {
if ( buttonState == HIGH) {
modeSwitchValue = 1;
automatic = true;
manual = false;
buttonState = LOW;
}
if (buttonState == LOW) {
modeSwitchValue = 0;
manual = true;
automatic = false;
buttonState = HIGH;
}
}
You should also realize that mechanical buttons can have contact bounce. Since you are using an interrupt to detect changes in the button state you might get erratic behavior. Usually, it is better to poll the button state and apply a de-bounce time delay on the order of 20ms.
You also have not shared how the button is wired. Since you are detecting a rising edge, I assume that the button is wired to pull the pin high when pressed. If you are using a single-pole single-though button, you will need a pull down resistor to ground, otherwise the interrupt pin will float.
You can avoid the required pull-up or pull down resistor, by connecting a simple button between the input pin and ground. Then change your initialization code to
pinMode(pin, INPUT_PULLUP)
You will then want to trigger interrupt on the falling edge.
I hope this helps.