Arduino Serial Input to Stop and Start - arduino

Question

I am trying to wait for user input to start a program operation and then when the user sends a stop command, the loop stops running. I have been unable to get the Serial port to keep reading an input while the loop is running.
So I want the user to Press 1 and then it'll go into the loop and will display the data from the interrupt. But I want it to keep monitoring the Serial Input so when I type in 2, I will get out of the loop and stop printing to the Serial Port.
The serial port isn't registering my second input.
I left out some of the code, but the important stuff should be there.
int userStart = 0; // Holder for user input to start program
int userStop = 0; // Holder for user input to stop program
void setup() {
Serial.begin(115200);
pinMode(motorEncoderA, INPUT);
digitalWrite(motorEncoderA, HIGH); // Pull up resistor
pinMode(motorEncoderB, INPUT);
digitalWrite(motorEncoderB,HIGH); // Pull up resistor
// Interrupt on change of Pin A
attachInterrupt(digitalPinToInterrupt(2), encoderFunc, CHANGE);
Serial.print("Press 1 to start the Process & 2 to Stop");
}
void loop() {
if (Serial.available() > 0)
{
userStart = Serial.read();
if (userStart = 1) {
Serial.print('\n');
while(userStop != 2) {
unsigned long timee = millis();
// Only update if the shaft has moved
if (encoderPositionLast != rotationCounter) {
Serial.print("Time: ");
Serial.print(timee);
Serial.print(" Count: ");
Serial.print (rotationCounter);
Serial.print('\n');
encoderPositionLast = rotationCounter;
Serial.print(userStart);
}
if (Serial.available() > 0) {
userStop = Serial.read();
Serial.print(userStop);
}
}
}
}

Answer 1

Well, I think your problem is that userStart and userStop should not be 1 and 2, but '1' and '2'.
That said, there are some things in your code I dislike.
First of all why is everybody using int as the base type for all numeric variables? If one single byte is enough, use it. On 32bit machines int and byte are almost the same, but on 8bit ones working with ints wastes space and time.
Secondly, I highly discourage you to block the loop function, otherwise you won-t be able to do anything else. Instead, use a variable to track wheter you are running or not, update it with the serial interface, and then execute the code if you are running.
This code should do it. And IMHO it is much better than blocking the loop:
bool running = false;
void setup()
{
...
running = false;
}
void loop()
{
if (Serial.available() > 0)
{
switch(Serial.read())
{
case '1':
running = true;
Serial.print('\n');
break;
case '2':
running = false;
Serial.print("stopped");
break;
}
}
if (running)
{
unsigned long timee = millis();
// Only update if the shaft has moved
if (encoderPositionLast != rotationCounter) {
Serial.print("Time: ");
Serial.print(timee);
Serial.print(" Count: ");
Serial.print (rotationCounter);
Serial.print('\n');
encoderPositionLast = rotationCounter;
Serial.print("running");
}
}
}