Timespan between two events

I receive a message from serial port that is passed to a variable once every few seconds. The message is generated by a microprocessor and it is basically a simple string containing "1/r" which represent one complete turn of a motor (every time a microswitch is pressed, the micro prints "1/r) on the serial port). In order to show in a text box the revolution per minute of such motor, based on the time interval between the update of the variable, I would like to implement a timespan method. I should therefore obtain the time elapsed between the start and the end of a turn and return the result for further actions to the original method.

This is what I have done so far but does not work:

public void CalcolaRPM (string giriRicevuti, out double RPM)

{

Stopwatch stopWatch = new Stopwatch();

stopWatch.Start();

{

if (giriRicevuti == "1/r")

{

stopWatch.Stop();

}

double elapsedT = stopWatch.ElapsedMilliseconds;

stopWatch.Restart();

RPM = elapsedT;

giriRicevuti = "";

}

The result I get is 0.0, how can I get the time in milliseconds between updates of the variable "giriRicevuti"?

1 Reply

Know the answer? Post it — somebody with the same question will find it here.

Vulpes13y ago
Not sure whether I'm understanding it properly, but try this:

private Stopwatch stopWatch = new Stopwatch();

public void CalcolaRPM (string giriRicevuti, out double RPM)
{
if (stopWatch.IsRunning && giriRicevuti == "1/r")
{
stopWatch.Stop();
RPM = stopWatch.ElapsedMilliseconds;
giriRicevuti = "";
stopWatch = new StopWatch(); // start again from scratch
stopWatch.Start();
}
else if (!stopWatch.IsRunning)
{
RPM = 0.0;
stopWatch.Start(); // first time the method is called so start the stopwatch
}
else // it's running but the string is still empty
{
RMP = 0.0; // or may be something else should be returned here
}
}