Add temperature hysteresis

Do not refresh display if value not changed

bme280.ino

@@ -1,12 +1,23 @@
 #include "Seeed_BME280.h"
 
 BME280 sensor;
+float highTemp = 0.0, lowTemp = 0.0;
+const float blindZone = 0.03;
 
 void initBME280() {
   sensor.init();
 }
 
 void readTemperature() {
-  // TODO: add hysteresis
-  temperature = sensor.getTemperature();
+  float newTemperature = sensor.getTemperature();
+
+  if (newTemperature > highTemp) {
+    temperature = newTemperature;
+    highTemp = newTemperature;
+    lowTemp = highTemp - blindZone;
+  } else if (newTemperature < lowTemp) {
+    temperature = newTemperature;
+    lowTemp = newTemperature;
+    highTemp = lowTemp + blindZone;
+  };
 }

metronom.ino

@@ -32,6 +32,7 @@ void setup() {
   TaskTimer.attachInterruptInterval_MS(20, TasksHandler);
   TasksISRs.setInterval(PERIOD_MS, runMetronome);
   TasksISRs.setInterval(PERIOD_MS, readTemperature);
+  // TODO: move display from ISR to loop()
   TasksISRs.setInterval(200, updateTube);
 }
 

tube.ino

@@ -1,22 +1,30 @@
 #include "grove_alphanumeric_display.h"
 
 Seeed_Digital_Tube tube;
+char tubeText[5] = "";
 
 void initTube() {
   // Wire initialized by BME280 sensor
   tube.setTubeType(TYPE_4, TYPE_4_DEFAULT_I2C_ADDR);
   tube.setBrightness(15);
   tube.setBlinkRate(BLINK_OFF);
-  tube.setPoint(true,true);  
 }
 
 void updateTube() {
-  char tube_str[5];
+  char newText[5];
+  bool highPoint = false, lowPoint = false;
 
-  if (countdown <= 0)
-    sprintf(tube_str, "%4u", (unsigned int) (temperature * 100.0));
-  else
-    sprintf(tube_str, "%4u", countdown);
-
-  tube.displayString(tube_str);
+  if (countdown <= 0) {
+    sprintf(newText, "%4u", (unsigned int) (temperature * 100.0));
+    lowPoint = true;
+  } else {
+    sprintf(newText, "%4u", countdown);
+  }
+
+  if (strcmp(tubeText, newText)) {
+    strcpy(tubeText, newText);
+    tube.displayString(tubeText);
+    tube.setPoint(highPoint, lowPoint);
+    tube.display();
+  }
 }