Update

- the faster IP mode tests now work for PTC type heaters
- various other fixes
- updated examples
- updated documentation

Author: Dlloydev

examples/MAX31856_PTC_SSR/Get_All_Tunings/Get_All_Tunings.ino

@@ -1,5 +1,7 @@
 /*****************************************************************************
-  sTune Get All Tunings Example (MAX31856, PTC Heater and SSR)
+  sTune Get All Tunings Example (MAX31856, PTC Heater / SSR / Software PWM)
+  This runs a fast inflection point test to determine tuning parameters.
+  Open serial printer to view test progress and results.
   Reference: https://github.com/Dlloydev/sTune/wiki/Examples_MAX31856_PTC_SSR
   ****************************************************************************/
 #include <Adafruit_MAX31856.h>
@@ -12,13 +14,13 @@ const uint8_t drdyPin = 5;
 
 // user settings
 uint32_t settleTimeSec = 10;
-uint32_t testTimeSec = 500;
+uint32_t testTimeSec = 500;  // sample interval = testTimeSec / samples
 const uint16_t samples = 500;
-const float inputSpan = 220;
+const float inputSpan = 200;
 const float outputSpan = 1000;
 float outputStart = 0;
 float outputStep = 50;
-float tempLimit = 100;
+float tempLimit = 150;
 
 // variables
 float Input, Output;
@@ -30,7 +32,6 @@ void setup() {
   pinMode(drdyPin, INPUT);
   pinMode(relayPin, OUTPUT);
   Serial.begin(115200);
-  while (!Serial) delay(10);
   delay(3000);
   Output = 0;
   if (!maxthermo.begin()) {

examples/MAX31856_PTC_SSR/QuickPID_Basic/QuickPID_Basic.ino

@@ -0,0 +1,54 @@
+/***************************************************************************
+  QuickPID Basic Example (MAX31856, PTC Heater / SSR / Software PWM)
+  Update your user settings and tuning parameters, then run and view results
+  using serial plotter.
+  Reference: https://github.com/Dlloydev/sTune/wiki/Examples_MAX31856_PTC_SSR
+  ***************************************************************************/
+#include <Adafruit_MAX31856.h>
+#include <sTune.h>
+#include <QuickPID.h>
+
+// pins
+const uint8_t inputPin = 0;
+const uint8_t relayPin = 3;
+const uint8_t drdyPin = 5;
+
+uint32_t testTimeSec = 1;  // runPid interval = testTimeSec / samples
+const uint16_t samples = 1;
+const float outputSpan = 1000; // window size
+float tempLimit = 150;
+
+// variables
+float Input, Output, Setpoint = 80, Kp = 2.00, Ki = 0.02, Kd = 0.06;
+
+Adafruit_MAX31856 maxthermo = Adafruit_MAX31856(10); //SPI
+sTune tuner = sTune(); // for softPWM and tempLimit
+QuickPID myPID(&Input, &Output, &Setpoint);
+
+void setup() {
+  pinMode(relayPin, OUTPUT);
+  Serial.begin(115200);
+  delay(3000);
+  if (!maxthermo.begin()) {
+    Serial.println("Could not initialize thermocouple.");
+    while (1) delay(10);
+  }
+  maxthermo.setThermocoupleType(MAX31856_TCTYPE_K);
+  maxthermo.setConversionMode(MAX31856_CONTINUOUS);
+  tuner.Configure(0, 0, 0, 0, testTimeSec, 0, samples);
+  tuner.SetEmergencyStop(tempLimit);
+  myPID.SetOutputLimits(0, outputSpan * 0.1);
+  myPID.SetSampleTimeUs((outputSpan - 1) * 1000);
+  myPID.SetMode(myPID.Control::automatic); // the PID is turned on
+  myPID.SetProportionalMode(myPID.pMode::pOnMeas);
+  myPID.SetAntiWindupMode(myPID.iAwMode::iAwClamp);
+  myPID.SetTunings(Kp, Ki, Kd); // set PID gains
+}
+
+void loop() {
+  float optimumOutput = tuner.softPwm(relayPin, Input, Output, Setpoint, outputSpan, 0); // ssr mode
+  if (myPID.Compute()) {
+    if (!digitalRead(drdyPin)) Input = maxthermo.readThermocoupleTemperature();
+    tuner.plotter(Input, optimumOutput, Setpoint, 0.5f, 3); // output scale 0.5, plot every 3rd sample
+  }
+}

examples/MAX31856_PTC_SSR/sTune_PID_v1/sTune_PID_v1.ino

@@ -1,12 +1,10 @@
 /****************************************************************************
-  sTune PID_v1 Example
-  This sketch does on-the-fly tunning and PID SSR control of a
-  PTC heater. Tunning parameters are quickly determined and
-  applied during the temperature ramp-up to setpoint. Open
-  the serial plotter to view the graphical results.
+  sTune PID_v1 Example (MAX31856, PTC Heater / SSR / Software PWM)
+  This sketch does on-the-fly tuning and PID control. Tuning parameters are
+  quickly determined and applied during temperature ramp-up to setpoint.
+  View results using serial plotter.
   Reference: https://github.com/Dlloydev/sTune/wiki/Examples_MAX31856_PTC_SSR
   ****************************************************************************/
-
 #include <Adafruit_MAX31856.h>
 #include <sTune.h>
 #include <PID_v1.h>
@@ -18,18 +16,18 @@ const uint8_t drdyPin = 5;
 
 // user settings
 uint32_t settleTimeSec = 10;
-uint32_t testTimeSec = 500;
+uint32_t testTimeSec = 500;  // runPid interval = testTimeSec / samples
 const uint16_t samples = 500;
 const float inputSpan = 200;
 const float outputSpan = 1000;
 float outputStart = 0;
-float outputStep = 30;
-float tempLimit = 75;
+float outputStep = 50;
+float tempLimit = 150;
 uint8_t debounce = 1;
 
 // variables
-double input, output, setpoint = 50, kp, ki, kd; // PID_v1
-float Input, Output, Setpoint = 50, Kp, Ki, Kd; // sTune
+double input, output, setpoint = 80, kp, ki, kd; // PID_v1
+float Input, Output, Setpoint = 80, Kp, Ki, Kd; // sTune
 
 Adafruit_MAX31856 maxthermo = Adafruit_MAX31856(10); //SPI
 sTune tuner = sTune(&Input, &Output, tuner.ZN_PID, tuner.directIP, tuner.printOFF);
@@ -39,7 +37,6 @@ void setup() {
   pinMode(drdyPin, INPUT);
   pinMode(relayPin, OUTPUT);
   Serial.begin(115200);
-  while (!Serial) delay(10);
   delay(3000);
   if (!maxthermo.begin()) {
     Serial.println("Could not initialize thermocouple.");
@@ -57,18 +54,17 @@ void loop() {
   switch (tuner.Run()) {
     case tuner.sample: // active once per sample during test
       if (!digitalRead(drdyPin)) Input = maxthermo.readThermocoupleTemperature();
-      tuner.plotter(Input, Output, Setpoint, 1, 3);
+      tuner.plotter(Input, Output, Setpoint, 0.5f, 3); // output scale 0.5, plot every 3rd sample
       break;
 
     case tuner.tunings: // active just once when sTune is done
       tuner.GetAutoTunings(&Kp, &Ki, &Kd); // sketch variables updated by sTune
       myPID.SetOutputLimits(0, outputSpan * 0.1);
-      myPID.SetSampleTime(outputSpan * 0.4);
-      debounce = 0; // switch to SSR optimum cycle mode
+      myPID.SetSampleTime(outputSpan - 1);
+      debounce = 0; // ssr mode
       setpoint = Setpoint, output = outputStep, kp = Kp, ki = Ki, kd = Kd;
+      Output = outputStep;
       myPID.SetMode(AUTOMATIC); // the PID is turned on
-      output = outputStep;
-      Output = output;
       myPID.SetTunings(kp, ki, kd); // update PID with the new tunings
       break;
 
@@ -77,7 +73,7 @@ void loop() {
       input = Input;
       myPID.Compute();
       Output = output;
-      tuner.plotter(Input, optimumOutput, Setpoint, 1, 3);
+      tuner.plotter(Input, optimumOutput, Setpoint, 0.5f, 3);
       break;
   }
 }

examples/MAX31856_PTC_SSR/sTune_QuickPID/sTune_QuickPID.ino

@@ -1,12 +1,10 @@
 /***************************************************************************
-  sTune QuickPID Example
-  This sketch does on-the-fly tunning and PID SSR control of a
-  PTC heater. Tunning parameters are quickly determined and
-  applied during the temperature ramp-up to setpoint. Open
-  the serial plotter to view the graphical results.
+  sTune QuickPID Example (MAX31856, PTC Heater / SSR / Software PWM)
+  This sketch does on-the-fly tuning and PID control. Tuning parameters are
+  quickly determined and applied during temperature ramp-up to setpoint.
+  View results using serial plotter.
   Reference: https://github.com/Dlloydev/sTune/wiki/Examples_MAX31856_PTC_SSR
   ***************************************************************************/
-
 #include <Adafruit_MAX31856.h>
 #include <sTune.h>
 #include <QuickPID.h>
@@ -18,17 +16,17 @@ const uint8_t drdyPin = 5;
 
 // user settings
 uint32_t settleTimeSec = 10;
-uint32_t testTimeSec = 500;
+uint32_t testTimeSec = 500;  // runPid interval = testTimeSec / samples
 const uint16_t samples = 500;
 const float inputSpan = 200;
 const float outputSpan = 1000;
 float outputStart = 0;
-float outputStep = 30;
-float tempLimit = 75;
+float outputStep = 50;
+float tempLimit = 150;
 uint8_t debounce = 1;
 
 // variables
-float Input, Output, Setpoint = 50, Kp, Ki, Kd;
+float Input, Output, Setpoint = 80, Kp, Ki, Kd;
 
 Adafruit_MAX31856 maxthermo = Adafruit_MAX31856(10); //SPI
 sTune tuner = sTune(&Input, &Output, tuner.ZN_PID, tuner.directIP, tuner.printOFF);
@@ -40,6 +38,7 @@ void setup() {
   Serial.begin(115200);
   while (!Serial) delay(10);
   delay(3000);
+  Output = 0;
   if (!maxthermo.begin()) {
     Serial.println("Could not initialize thermocouple.");
     while (1) delay(10);
@@ -56,14 +55,15 @@ void loop() {
   switch (tuner.Run()) {
     case tuner.sample: // active once per sample during test
       if (!digitalRead(drdyPin)) Input = maxthermo.readThermocoupleTemperature();
-      tuner.plotter(Input, Output, Setpoint, 1, 3);
+      tuner.plotter(Input, Output, Setpoint, 0.5f, 3); // output scale 0.5, plot every 3rd sample
       break;
 
     case tuner.tunings: // active just once when sTune is done
       tuner.GetAutoTunings(&Kp, &Ki, &Kd); // sketch variables updated by sTune
       myPID.SetOutputLimits(0, outputSpan * 0.1);
-      myPID.SetSampleTimeUs(outputSpan * 1000 * 0.4);
-      debounce = 0; // switch to SSR optimum cycle mode
+      myPID.SetSampleTimeUs((outputSpan - 1) * 1000);
+      debounce = 0; // ssr mode
+      Output = outputStep;
       myPID.SetMode(myPID.Control::automatic); // the PID is turned on
       myPID.SetProportionalMode(myPID.pMode::pOnMeas);
       myPID.SetAntiWindupMode(myPID.iAwMode::iAwClamp);
@@ -73,7 +73,7 @@ void loop() {
     case tuner.runPid: // active once per sample after tunings
       if (!digitalRead(drdyPin)) Input = maxthermo.readThermocoupleTemperature();
       myPID.Compute();
-      tuner.plotter(Input, optimumOutput, Setpoint, 1, 3);
+      tuner.plotter(Input, optimumOutput, Setpoint, 0.5f, 3);
       break;
   }
 }