Cannot get arduino voltage data to upload to Thingspeak

I am trying to collect battery voltage data from arduino parts and upload it from arduino into my Thingspeak channel. So far, I have troubleshot the hardware/wiring aspect, and that doesn't seem to be the issue.

At this point, I am assuming the issue is with the code or the Thingspeak channel. Since my arduino board (elegoo arduino Uno R3) is hooked up to my computer using a USB cord, I tried using an HTTP GET request in order to send the information to the Thingspeak channel. I am under a time crunch and am unable to access any kind of Wifi or Ethernet shield, so that is why I am using the USB cord. I could be completely wrong in using the HTTP GET request --I am quite the novice here! Here is the code so far:

#include <SoftwareSerial.h>

SoftwareSerial Serial1(2, 3); // RX, TX

// Define variables
float voltage;
unsigned long previousMillis = 0;
const long interval = 60000; // Upload interval (in milliseconds)
String apiKey = "P5LPXSRJT0G4K7VA";
String field = "field1";
String server = "api.thingspeak.com";
String channelID = "2131761";

void setup() {
  Serial.begin(9600);
  Serial1.begin(9600);
}

void loop() {
  // Read voltage from sensor
  voltage = analogRead(A0) * 0.0049; // convert analog reading to voltage (0-5V)
  voltage = voltage * 5.17; // adjust the voltage to reflect the actual voltage
  
  // Print voltage to serial monitor
  Serial.print("Voltage: ");
  Serial.print(voltage);
  Serial.println(" V");

  // Get current timestamp
  unsigned long currentMillis = millis();

  // Check it's time to upload to ThingSpeak
  if (currentMillis - previousMillis >= interval) {
    // Update timestamp
    previousMillis = currentMillis;
    
    // Construct HTTP GET request
    String getRequest = "GET /update?api_key=";
    getRequest += apiKey;
    getRequest += "&";
    getRequest += field;
    getRequest += "=";
    getRequest += String(voltage);
    getRequest += "&";
    getRequest += "field2=Times";
    getRequest += " HTTP/1.1\r\n";
    getRequest += "Host: ";
    getRequest += server;
    getRequest += "\r\n";
    getRequest += "Connection: close\r\n\r\n";
    getRequest += "X-THINGSPEAK-CLIENT: arduino\r\n";
    getRequest += "Content-Type: application/x-www-form-urlencoded\r\n";
    getRequest += "Content-Length: ";
    getRequest += String(voltage);
    getRequest += "\r\n";
    getRequest += "Host: api.thingspeak.com\r\n";
    getRequest += "User-Agent: Arduino/1.0.0\r\n";
    getRequest += "\r\n";
    getRequest += "\r\n";
    getRequest += channelID;

    // Send HTTP GET request to ThingSpeak via serial communication
    Serial1.println(getRequest);

    // Print response from ThingSpeak to serial monitor
    while (Serial1.available()) {
      Serial.write(Serial1.read());
    }
    Serial.println();
  }
  
  delay(1000);
}

Again, I really have no clue what I am doing here, so I am not surprised if what I have is entirely wrong. Any feedback is greatly appreciated!

Answer 1

[Christopher Stapels]

The Uno R3 cannot make HTTP requests without an ethernet or wifi connection. It is not able to send those requests through a USB connection without a corresponding app to send the requests running on the computer that it is conencted to.

Answer 2

[Ser Gio]

As explained by Mr Stapels, Arduino UNO R3 by itsef cannot connect to internet.

I suggest you to use something like a ESP8266 or ESP32 and use ESP.getVcc()

BR.