Initial SCD4x release

.gitignore

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+.DS_Store
+.pio
+.idea
+.vscode
+CMakeLists.txt
+CMakeListsPrivate.txt
+cmake-build-az-delivery-devkit-v4
+cmake-build-debug
+

README.md

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+# esp32-co2-scd4x
+This project displays the current co2 levels, along with temperature and humidity information, on a HD44780 16x2 display. All of this is powered by an ESP32 devkit and a SCD40/41 photoacoustic NDIR CO2 sensor.
+
+## Wiring
+![Wiring diagram](img/wiring.jpeg)
+
+The main components here are wired up like this:
+- The green, yellow and red LEDs are connected to ground and pins 25, 33 and 32 respectively
+- The HD44780 16x2 display is connected to an I2C daughterboard, which itself is connected to +5V, ground, as well as the I2C bus pins of the ESP32, 22 for clock and 21 for data
+- The SCD40/41 photoacoustic NDIR CO2 sensor is connected to +5V and ground for power and to pins 22 and 21 (ESP32 I2C_bus1; MH-Z19B side pins SCL and SDA respectively)
+- A button to toggle the backlight is connected between pin 23 and ground

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the usual convention is to give header files names that end with `.h'.
+It is most portable to use only letters, digits, dashes, and underscores in
+header file names, and at most one dot.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

include/wifiFix.h

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+#pragma once
+#pragma clang diagnostic push
+#pragma ide diagnostic ignored "OCUnusedGlobalDeclarationInspection"
+
+class WiFiClientFixed : public WiFiClient {
+public:
+	void flush() override;
+};
+
+#pragma clang diagnostic pop

lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into executable file.
+
+The source code of each library should be placed in a an own separate directory
+("lib/your_library_name/[here are source files]").
+
+For example, see a structure of the following two libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional, custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+and a contents of `src/main.c`:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+PlatformIO Library Dependency Finder will find automatically dependent
+libraries scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:az-delivery-devkit-v4]
+platform = espressif32@^6.0.0
+board = az-delivery-devkit-v4
+framework = arduino
+upload_protocol = esptool
+upload_speed = 921600
+monitor_speed = 115200
+monitor_filters = esp32_exception_decoder
+lib_deps = 
+	wifwaf/MH-Z19@^1.5.3
+	adafruit/Adafruit AHTX0@^2.0.1
+	fmalpartida/LiquidCrystal@^1.5.0
+	sparkfun/SparkFun SCD4x Arduino Library@^1.0.4
+	juerd/ESP-WiFiSettings@^3.8.0
+	bblanchon/ArduinoJson@^6.20.0
+

src/main.cpp

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+#include <Arduino.h>
+#include "LiquidCrystal_I2C.h"
+#include "WiFiSettings.h"
+#include "ArduinoJson.h"
+#include <SparkFun_SCD4x_Arduino_Library.h>
+#include <HTTPClient.h>
+#include <SPIFFS.h>
+#include "wifiFix.h"
+
+String weather_lat = "";
+String weather_long = "";
+String weather_apikey = "";
+String weather_final_url = "";
+
+SCD4x scd4x;
+LiquidCrystal_I2C LCD(0x27,2,1,0,4,5,6,7,3,POSITIVE);
+
+WiFiClient* wifi = new WiFiClientFixed();
+HTTPClient* http = new HTTPClient();
+
+#define PIN_LED_GREEN 25
+#define PIN_LED_YELLOW 33
+#define PIN_LED_RED 32
+
+int backlightState = HIGH;
+
+volatile bool interruptFired = false;
+unsigned long lastInterrupt = 0;
+unsigned long lastUpdated = 0;
+unsigned long lastWeatherUpdate = 0;
+
+bool weatherUpdateSuccess = false;
+int lastWeatherPressure = 0;
+int avgAtmosphericPressure = 1013;
+
+unsigned const int updateTimer = 5000;
+unsigned const int interruptTimer = 500;
+
+void led(int red, int green, int yellow)
+{
+	analogWrite(PIN_LED_RED, red);
+	analogWrite(PIN_LED_GREEN, green);
+	analogWrite(PIN_LED_YELLOW, yellow);
+}
+
+void IRAM_ATTR BacklightToggle() {
+	if (!interruptFired)
+		interruptFired = true;
+}
+
+void UpdateWeatherData() {
+	if (lastWeatherUpdate != 0 && millis() - lastWeatherUpdate < 60000) {
+		return;
+	}
+
+	lastWeatherUpdate = millis();
+
+	Serial.print("Attempting to get weather data from ");
+	Serial.println(weather_final_url);
+
+	http->begin(*wifi, weather_final_url);
+	int httpResponseCode = http->GET();
+	if (httpResponseCode == 200) {
+		String payload = http->getString();
+		http->end();
+		Serial.println(payload);
+		StaticJsonDocument<1024> doc;
+		DeserializationError error = deserializeJson(doc, payload.c_str());
+
+		if (error) {
+			weatherUpdateSuccess = false;
+			lastWeatherPressure = avgAtmosphericPressure;
+		}
+
+		float coord_lon = doc["coord"]["lon"]; // 3.45
+		float coord_lat = doc["coord"]["lat"]; // 1.23
+
+		JsonObject weather_0 = doc["weather"][0];
+		int weather_0_id = weather_0["id"]; // 804
+		const char* weather_0_main = weather_0["main"]; // "Clouds"
+		const char* weather_0_description = weather_0["description"]; // "overcast clouds"
+		const char* weather_0_icon = weather_0["icon"]; // "04d"
+
+		const char* base = doc["base"]; // "stations"
+
+		JsonObject main = doc["main"];
+		float main_temp = main["temp"]; // 301.92
+		float main_feels_like = main["feels_like"]; // 306.28
+		float main_temp_min = main["temp_min"]; // 301.92
+		float main_temp_max = main["temp_max"]; // 301.92
+		int main_pressure = main["pressure"]; // 1012
+		int main_humidity = main["humidity"]; // 75
+		int main_sea_level = main["sea_level"]; // 1012
+		int main_grnd_level = main["grnd_level"]; // 1012
+
+		int visibility = doc["visibility"]; // 10000
+
+		JsonObject wind = doc["wind"];
+		float wind_speed = wind["speed"]; // 4.71
+		int wind_deg = wind["deg"]; // 219
+		float wind_gust = wind["gust"]; // 4.52
+
+		int clouds_all = doc["clouds"]["all"]; // 100
+
+		long dt = doc["dt"]; // 1684079803
+
+		long sys_sunrise = doc["sys"]["sunrise"]; // 1684042647
+		long sys_sunset = doc["sys"]["sunset"]; // 1684086466
+
+		int timezone = doc["timezone"]; // 0
+		int id = doc["id"]; // 0
+		const char* name = doc["name"]; // nullptr
+		int cod = doc["cod"]; // 200
+
+		lastWeatherPressure = main_pressure;
+		weatherUpdateSuccess = true;
+
+		Serial.println(String("Got pressure: ") + lastWeatherPressure);
+	}
+	else {
+		http->end();
+
+		lastWeatherPressure = avgAtmosphericPressure;
+		weatherUpdateSuccess = false;
+		Serial.println(String("Failed getting pressure (Error code: ") + httpResponseCode + String("), using avg atmospheric pressure: ") + lastWeatherPressure);
+	}
+}
+
+void UpdateSensorCompensation(){
+	if (weatherUpdateSuccess) {
+		scd4x.setAmbientPressure(lastWeatherPressure * 100); // It wants the data in Pascal!
+	}
+}
+
+void setup()
+{
+	Serial.begin(115200);
+
+	LCD.begin(16, 2);
+	LCD.clear();
+	LCD.setBacklight(backlightState);
+	LCD.print("WiFi init...");
+
+	SPIFFS.begin(true);
+	WiFiSettings.hostname = "co2-scd4x-";
+
+	weather_apikey = WiFiSettings.string("OpenWeatherMap API key", "hskjdfghjkdfhgyuw");
+	weather_lat = WiFiSettings.string("Location: latitude", "1.23");
+	weather_long = WiFiSettings.string("Location: longitude", "3.45");
+	weather_final_url = "http://api.openweathermap.org/data/2.5/weather?lat=" + weather_lat + "&lon=" + weather_long + "&appid=" + weather_apikey;
+
+	WiFiSettings.connect();
+
+	scd4x.enableDebugging();
+
+	if (!scd4x.begin(Wire)) {
+		Serial.println("Could not find SCD4x? Check wiring");
+		LCD.clear();
+		LCD.print("SCD4x not found");
+		LCD.setCursor(0, 1);
+		LCD.print("Check wiring");
+		while (true);
+	}
+
+	scd4x.stopPeriodicMeasurement();
+
+	LCD.setCursor(0, 0);
+	LCD.print("SCD4x SELF TEST ");
+
+	if (!scd4x.performSelfTest()) {
+		Serial.println("SCD4x self test failed");
+		LCD.setCursor(0, 1);
+		LCD.print("FAIL");
+		while (true);
+	}
+
+	scd4x.setAutomaticSelfCalibrationEnabled(true);
+
+	LCD.setCursor(0, 1);
+	LCD.print("PASS");
+	delay(1000);
+
+	Serial.println("SCD4x init:");
+	char mySerial[16];
+	scd4x.getSerialNumber(mySerial);
+	Serial.print("Serial no: ");
+	Serial.println(mySerial);
+
+	LCD.setCursor(6, 0);
+	LCD.print("SERIAL #  ");
+	LCD.setCursor(0, 1);
+	LCD.print(mySerial);
+	delay(1000);
+
+	Serial.print("Altitude: ");
+	Serial.println(scd4x.getSensorAltitude());
+	Serial.print("Self-cal enabled: ");
+	Serial.println(scd4x.getAutomaticSelfCalibrationEnabled() ? "Yes" : "No");
+	Serial.print("Temperature Offset: ");
+	Serial.println(scd4x.getTemperatureOffset());
+
+	UpdateWeatherData();
+	UpdateSensorCompensation();
+
+	scd4x.startPeriodicMeasurement();
+
+	pinMode(23, INPUT_PULLUP);
+	attachInterrupt(23, BacklightToggle, FALLING);
+	LCD.clear();
+}
+
+void loop() {
+	if (interruptFired) {
+		if (millis() - lastInterrupt > interruptTimer || lastInterrupt == 0) {
+			backlightState = !backlightState;
+			Serial.printf("Setting backlight to %i \n", backlightState);
+			LCD.setBacklight(backlightState);
+			lastInterrupt = millis();
+		}
+
+		interruptFired = false;
+	}
+
+	if (millis() - lastUpdated > updateTimer || lastUpdated == 0) {
+		lastUpdated = millis();
+	} else {
+		return;
+	}
+
+	UpdateWeatherData();
+	UpdateSensorCompensation();
+
+	int co2 = scd4x.getCO2();
+	float temp = scd4x.getTemperature();
+	float rh = scd4x.getHumidity();
+
+	LCD.setCursor(0, 0);
+	LCD.print(temp, 1);
+	LCD.print(" C   ");
+	LCD.setCursor(9, 0);
+	LCD.print(rh, 1);
+	LCD.print("%rH");
+	LCD.setCursor(0, 1);
+	LCD.print(co2);
+	LCD.print("ppm   ");
+	LCD.setCursor(9, 1);
+	LCD.print(lastWeatherPressure);
+	LCD.print("hPa");
+
+	Serial.print(co2);
+	Serial.print(" ppm, ");
+	Serial.print(temp);
+	Serial.print(" ºC, ");
+	Serial.print(rh);
+	Serial.println(" %rH");
+
+	if (co2 < 1000)
+		led(0, 1, 0);
+	else if (co2 < 1500)
+		led(0, 0, 5);
+	else
+		led(5, 0, 0);
+}

src/wifiFix.cpp

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+#include <WiFi.h>
+#include <lwip/sockets.h>
+#include "wifiFix.h"
+
+#define WIFI_CLIENT_FLUSH_BUFFER_SIZE    (1024)
+
+void WiFiClientFixed::flush() {
+	int res;
+	size_t a = available();
+	if (!a) {
+		return;//nothing to flush
+	}
+	auto* buf = (uint8_t *) malloc(WIFI_CLIENT_FLUSH_BUFFER_SIZE);
+	if (!buf) {
+		return;//memory error
+	}
+	while (a) {
+		// override broken WiFiClient flush method, ref https://github.com/espressif/arduino-esp32/issues/6129#issuecomment-1237417915
+		res = read(buf, min(a, (size_t)WIFI_CLIENT_FLUSH_BUFFER_SIZE));
+		if (res < 0) {
+			log_e("fail on fd %d, errno: %d, \"%s\"", fd(), errno, strerror(errno));
+			stop();
+			break;
+		}
+		a -= res;
+	}
+	free(buf);
+}

test/README

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+
+This directory is intended for PlatformIO Unit Testing and project tests.
+
+Unit Testing is a software testing method by which individual units of
+source code, sets of one or more MCU program modules together with associated
+control data, usage procedures, and operating procedures, are tested to
+determine whether they are fit for use. Unit testing finds problems early
+in the development cycle.
+
+More information about PlatformIO Unit Testing:
+- https://docs.platformio.org/page/plus/unit-testing.html