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modified SetSampleTime() to allow PID::Compute() synch to external timing source #111

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modified SetSampleTime() to allow PID::Compute() synch to external timing source #111

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9e7662e
modified SetSampleTime() to set the internal SampleTime variable to z…
paynterf May 15, 2021
a30df92
Updated README.txt to include information about synching PID engine t…
paynterf May 15, 2021
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8 changes: 7 additions & 1 deletion PID_v1.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -130,6 +130,8 @@ void PID::SetTunings(double Kp, double Ki, double Kd){

/* SetSampleTime(...) *********************************************************
* sets the period, in Milliseconds, at which the calculation is performed
* 15 May 2021 gfp - a value of zero will force Compute() to generate a new output every time it is called
* but avoids the 'divide-by-zero' problem
******************************************************************************/
void PID::SetSampleTime(int NewSampleTime)
{
Expand All @@ -139,7 +141,11 @@ void PID::SetSampleTime(int NewSampleTime)
/ (double)SampleTime;
ki *= ratio;
kd /= ratio;
SampleTime = (unsigned long)NewSampleTime;
//SampleTime = (unsigned long)NewSampleTime;
}
else if (NewSampleTime == 0)
{
SampleTime = (unsigned long)NewSampleTime;
}
}

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4 changes: 4 additions & 0 deletions README.txt
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Expand Up @@ -9,3 +9,7 @@
http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/

- For function documentation see: http://playground.arduino.cc/Code/PIDLibrary

- To synchronize PID::Compute with an external timing source such as a TIMER ISR,
call SetSampleTime() with an argument of zero. This will force Compute to generate a
new output value each time it is called.