diff --git a/ampel-firmware/co2_sensor.cpp b/ampel-firmware/co2_sensor.cpp
index 5dff6765fb7c4a6b19d9dc631af15c3474d9840b..b573c4b49d2bc03d08cfafad6d78ef6277ae439a 100644
--- a/ampel-firmware/co2_sensor.cpp
+++ b/ampel-firmware/co2_sensor.cpp
@@ -15,6 +15,7 @@ namespace config {
const float temperature_offset = -3.0; // [K] Temperature measured by sensor is usually at least 3K too high.
#endif
bool auto_calibrate_sensor = AUTO_CALIBRATE_SENSOR; // [true / false]
+ const bool debug_sensor_states = false; // If true, log state transitions over serial console
}
namespace sensor {
@@ -24,12 +25,39 @@ namespace sensor {
float humidity = 0;
char timestamp[23];
int16_t stable_measurements = 0;
- uint32_t waiting_color = color::blue;
- bool should_calibrate = false;
+
+ /**
+ * Define sensor states
+ * INITIAL -> initial state
+ * BOOTUP -> state after initializing the sensor, i.e. after scd.begin()
+ * READY -> sensor does output valid information (> 0 ppm) and no other condition takes place
+ * NEEDS_CALIBRATION -> sensor measurements are too low (< 250 ppm)
+ * PREPARE_CALIBRATION -> forced calibration was initiated, waiting for stable measurements
+ * CALIBRATION -> the sensor does calibrate itself
+ */
+ enum state {
+ INITIAL,
+ BOOTUP,
+ READY,
+ NEEDS_CALIBRATION,
+ PREPARE_CALIBRATION_UNSTABLE,
+ PREPARE_CALIBRATION_STABLE,
+ CALIBRATION
+ };
+ const char *state_names[] = {
+ "INITIAL",
+ "BOOTUP",
+ "READY",
+ "NEEDS_CALIBRATION",
+ "PREPARE_CALIBRATION_UNSTABLE",
+ "PREPARE_CALIBRATION_STABLE",
+ "CALIBRATION" };
+ state current_state = INITIAL;
+ void switchState(state);
void initialize() {
#if defined(ESP8266)
- Wire.begin(12, 14); // ESP8266 - D6, D5;
+ Wire.begin(12, 14); // ESP8266 - D6, D5;
#endif
#if defined(ESP32)
Wire.begin(21, 22); // ESP32
@@ -49,6 +77,8 @@ namespace sensor {
ESP.restart();
}
+ switchState(BOOTUP);
+
// SCD30 has its own timer.
//NOTE: The timer seems to be inaccurate, though, possibly depending on voltage. Should it be offset?
Serial.println();
@@ -91,19 +121,21 @@ namespace sensor {
previous_measurement_at = now;
}
- void countStableMeasurements() {
+ bool countStableMeasurements() {
+ // Returns true, if a sufficient number of stable measurements has been observed.
static int16_t previous_co2 = 0;
if (co2 > (previous_co2 - config::max_deviation_during_calibration)
&& co2 < (previous_co2 + config::max_deviation_during_calibration)) {
stable_measurements++;
Serial.print(F("Number of stable measurements : "));
Serial.println(stable_measurements);
- waiting_color = color::green;
+ switchState(PREPARE_CALIBRATION_STABLE);
} else {
stable_measurements = 0;
- waiting_color = color::red;
+ switchState(PREPARE_CALIBRATION_UNSTABLE);
}
previous_co2 = co2;
+ return (stable_measurements == config::enough_stable_measurements);
}
void startCalibrationProcess() {
@@ -115,10 +147,11 @@ namespace sensor {
scd30.setMeasurementInterval(2); // [s] The change will only take effect after next measurement.
Serial.println(F("Waiting until the measurements are stable for at least 2 minutes."));
Serial.println(F("It could take a very long time."));
- should_calibrate = true;
+ switchState(PREPARE_CALIBRATION_UNSTABLE);
}
void calibrateAndRestart() {
+ switchState(CALIBRATION);
Serial.print(F("Calibrating SCD30 now..."));
scd30.setAltitudeCompensation(config::altitude_above_sea_level);
scd30.setForcedRecalibrationFactor(config::co2_calibration_level);
@@ -137,12 +170,41 @@ namespace sensor {
Serial.println(humidity, 1);
}
- void displayCO2OnLedRing() {
- if (co2 < 250) {
- // Sensor should be calibrated.
- led_effects::showWaitingLED(color::magenta);
+ void switchState(state new_state) {
+ if (new_state == current_state) {
return;
}
+ if (config::debug_sensor_states) {
+ Serial.print(F("Changing sensor state: "));
+ Serial.print(state_names[current_state]);
+ Serial.print(" -> ");
+ Serial.println(state_names[new_state]);
+ }
+ current_state = new_state;
+ }
+
+ void switchStateForCurrentPPM() {
+ if (co2 == 0) {
+ // NOTE: Data is available, but it's sometimes erroneous: the sensor outputs
+ // zero ppm but non-zero temperature and non-zero humidity.
+ Serial.println(F("Invalid sensor data - CO2 concentration supposedly 0 ppm"));
+ switchState(BOOTUP);
+ } else if ((current_state == PREPARE_CALIBRATION_UNSTABLE) || (current_state == PREPARE_CALIBRATION_STABLE)) {
+ // Check for pre-calibration states first, because we do not want to
+ // leave them before calibration is done.
+ bool ready_for_calibration = countStableMeasurements();
+ if (ready_for_calibration) {
+ calibrateAndRestart();
+ }
+ } else if (co2 < 250) {
+ // Sensor should be calibrated.
+ switchState(NEEDS_CALIBRATION);
+ } else {
+ switchState(READY);
+ }
+ }
+
+ void displayCO2OnLedRing() {
/**
* Display data, even if it's "old" (with breathing).
* A short delay is required in order to let background tasks run on the ESP8266.
@@ -157,6 +219,30 @@ namespace sensor {
}
}
+ void showState() {
+ switch (current_state) {
+ case BOOTUP:
+ led_effects::showWaitingLED(color::blue);
+ break;
+ case READY:
+ displayCO2OnLedRing();
+ break;
+ case NEEDS_CALIBRATION:
+ led_effects::showWaitingLED(color::magenta);
+ break;
+ case PREPARE_CALIBRATION_UNSTABLE:
+ led_effects::showWaitingLED(color::red);
+ break;
+ case PREPARE_CALIBRATION_STABLE:
+ led_effects::showWaitingLED(color::green);
+ break;
+ case CALIBRATION: // Nothing to do, will restart soon.
+ break;
+ default:
+ Serial.println(F("Encountered unknown sensor state")); // This should not happen.
+ }
+ }
+
/** Gets fresh data if available, checks calibration status, displays CO2 levels.
* Returns true if fresh data is available, for further processing (e.g. MQTT, CSV or LoRa)
*/
@@ -169,34 +255,15 @@ namespace sensor {
co2 = scd30.getCO2();
temperature = scd30.getTemperature();
humidity = scd30.getHumidity();
- }
- //NOTE: Data is available, but it's sometimes erroneous: the sensor outputs zero ppm but non-zero temperature and non-zero humidity.
- if (co2 <= 0) {
- // No measurement yet. Waiting.
- led_effects::showWaitingLED(color::blue);
- return false;
- }
+ switchStateForCurrentPPM();
- /**
- * Fresh data. Log it and send it if needed.
- */
- if (freshData) {
- if (should_calibrate) {
- countStableMeasurements();
- }
+ // Log every time fresh data is available.
logToSerial();
}
- if (should_calibrate) {
- if (stable_measurements == config::enough_stable_measurements) {
- calibrateAndRestart();
- }
- led_effects::showWaitingLED(waiting_color);
- return false;
- }
+ showState();
- displayCO2OnLedRing();
return freshData;
}
@@ -207,6 +274,7 @@ namespace sensor {
Serial.print(F("DEBUG. Setting CO2 to "));
co2 = fakeCo2;
Serial.println(co2);
+ switchStateForCurrentPPM();
}
void setAutoCalibration(int32_t autoCalibration) {