Sending Data from BME280 to Graphite using ESP32
Electronics
Lastmod: 2024-09-21
Published: 2021-02-08

This is a record of obtaining temperature, humidity, and pressure with the BME280 and sending it directly to Graphite via ESP32’s Wi-Fi connection. There will be no explanation of Graphite or Grafana.

Items Used

Item NamePurchase
ESP-32SAliExpress
Amazon
楽天
BME280AliExpress
Amazon
楽天

Connection Diagram

The BME280 and ESP-32S are connected via I2C. The GPIO21 of ESP-32S serves as SDA, and GPIO22 serves as SCL.

ESP-32SBME280
3.3VVIN
GNDGND
GPIO21SDA
GPIO22SCL

Content

  • Connect to Wi-Fi
  • Query NTP server to get the time
  • Create a timer interrupt to send data every second

Code

#include <Arduino.h>
#include <WiFi.h>
#include <Wire.h>
#include <Adafruit_BME280.h>
#include <Ticker.h>
#include <WiFiUdp.h>
#include <time.h>

// Wi-Fi
const char SSID[] = "";
const char PASSWORD[] = "";

// NTP Server
const char NTP_SERVER[] = "ntp.nict.jp";

// Graphite
IPAddress graphite(192,168,0,10);

// Ticker
Ticker ticker;
bool flagTicker = false;

// BME280 Sensor
Adafruit_BME280 bme;

void setTicker() {
    flagTicker = true;
}

// UDP
WiFiUDP udp;

void setup() {
  Serial.begin(115200);
  while (!Serial);

  if (!bme.begin(0x76)) {
    Serial.println("BME280 sensor error!");
    while (1);
  }

  // Wi-Fi connection
  WiFi.begin(SSID, PASSWORD);
  Serial.print("WiFi connecting");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(100);
  }

  IPAddress ipaddr, gateway;
  ipaddr = WiFi.localIP();
  gateway = WiFi.gatewayIP();
  Serial.println("WiFi Connected.");
  Serial.print("IPAddr:");
  Serial.println(ipaddr);
  Serial.print("Gateway:");
  Serial.println(gateway);

  // NTP
  configTime(9 * 3600L, 0, NTP_SERVER); 

  // ms
  struct timeval tv;
  int ms = 0;
  while(1) {
     if (gettimeofday(&tv, NULL) != 0) {
       Serial.println("error gettimeofday.");
     }else{
      ms = tv.tv_usec / 1000LL;
    }
    if(ms == 0) {
        ticker.attach_ms(1000, setTicker);
        Serial.println("set ticker");
        break;
    }
  }
}

void send() {
    time_t now;
    time(&now); 
    udp.beginPacket(graphite, 2003);
    udp.println("sec.esp32.temperature " + String(bme.readTemperature()) + " " + now);
    udp.println("sec.esp32.humidity " + String(bme.readHumidity()) + " " + now);
    udp.println("sec.esp32.pressure " + String(bme.readPressure() / 100) + " " + now);
    udp.endPacket();
}

void loop() {
  if(flagTicker) {
      send();
      flagTicker = false;
  }
}

Libraries Used

Visualizing with Grafana

I was able to obtain sensor data from the BME280 using the ESP32, accumulate it in Graphite (go-carbon) via Wi-Fi, and visualize it with Grafana.

Data is added every second, allowing for quite real-time data acquisition. Since power consumption was also kept below 0.5W, it seems convenient for collecting data at home.