Esp-32 Sensor Records

A PlatformIO project which records various metrics, such as:

• Temperature
• Humidity
• Carbon Dioxide
• TVOC
• Ethanol
• Hydrogen

This uses the following physical modules:

• ESP32 for running the binary via USB, the core of the project
• DHT22 for recording Temperature and Humidity (aswell as calculating Absolute Humidity for the SGP30)
• SGP30 for recording Carbon Dioxide, Ethanol, etc

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Regarding authentication

For security purposes, the authentication header (auth.h) has been gitignored and is not being actively committed to this repository. For personal usage, the constants inside this file include:

• INFLUXDB_HOST - A host/resolvent which directly points to the InfluxDB instance, usually started locally
• INFLUXDB_BUCKET - The bucket for readings, in this case it is called Sensor-Readings locally
• INFLUXDB_ORGANISATION - The organisation provided when creating the InfluxDB instance
• INFLUXDB_USER - The username chosen when creating the InfluxDB instance
• INFLUXDB_PASS - The password chosen when creating the InfluxDB instance
• INFLUXDB_TOKEN - The token to authenticate the InfluxDB instance to connect to the Arduino
• WIFI_SSID - The WiFi name, used to connect to the WiFi network
• WIFI_PASSWORD - The password used to connect to the WiFi network provided above

This project uses the variant library, as INO C++ is outdated and there is no official variant type.

This is implemented by creating a vector of pairs of strings and variants, where the type can either be a float or an integer.

std::vector<std::pair<std::string, variant<float, uint16_t>>> measurements = {
  {"Temperature", temperature},
  {"Humidity", humidity},
  {"Carbon Dioxide", sgp.eCO2},
  {"TVOC", sgp.TVOC},
  {"Ethanol", sgp.rawEthanol},
  {"Hydrogen", sgp.rawH2}
};

Afterwards, a Visitor is created, available in the Internal namespace, which adds the field provided when the value is called on it:

struct Visitor 
{
    std::string _measurement;
    Visitor(std::string measurement) : _measurement(measurement) {};

    void operator() (float value)const 
    {
        sensor.addField(_measurement.c_str(), value);
    }

    void operator() (uint16_t value)const 
    {
        sensor.addField(_measurement.c_str(), value);
    }
};

And finally the Visitor is applied to the vector:

for (const auto& pair : measurements) 
{
  auto measurement = pair.first;
  auto value = pair.second;
  apply_visitor(Visitor(measurement), value);
}

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About sending the recordings to InfluxDB:

The module first connects to the InfluxDB instance, using this call inside Internal.h

InfluxDBClient client(INFLUXDB_HOST, INFLUXDB_ORGANISATION, INFLUXDB_BUCKET, INFLUXDB_TOKEN);

Note that all of the constants above are inside of a file called auth.h which is gitignored. More information

During runtime setup, the module validates that it has successfully connected to the database:

client.validateConnection()
    ? Serial.printf("Connected to InfluxDB: %s.\n", client.getServerUrl().c_str())
    : Serial.printf("InfluxDB connection failed: %s.\n", client.getLastErrorMessage().c_str());

When writing, it simply attempts to write to the point defined in the authentication header, and logs if it fails.

if (!client.writePoint(sensor)) Serial.printf("InfluxDB write failed: %s.\n", client.getLastErrorMessage().c_str());

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WiFi connection on this ESP32 is reimplemented, using wrapper methods, following this structure:

• WiFi::setup() Disconnects from the WiFi if already connected, configures the WiFi with INADDR_NONE, and sets the mode to STA (standard)
• WiFi::hostname() Sets the hostname of the network to the Sensor-{MAC_ADDRESS}
• WiFi::debug() Prints to the debug console relevant information about the WiFi, such as MAC Address, IP, SSID, etc
• WiFi::connect() Attempts to connect to the WiFi, calling WiFi.begin() with the private WIFI_SSID and WIFI_PASSWORD, waiting for WiFi.status() to be connected.

In practice (Utilities::authenticateWifi()):

• Call WiFi::setup() to configure the connection
• Call WiFi::hostname() to set the network hostname
• Call WiFi::connect() and review the returned boolean:
  • If the return value is true, then the connection was successful!
  • Otherwise, recursively call the authenticateWifi() function again
• Call WiFi::debug() for relevant information about the connection

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♡ Made by Rosie Copyright © 2023 Rosie (acquitelol)

All rights reserved.
All software is provided for educational purposes only, and should not be used for unlawful or unethical purposes.