How to read the fieldname from a field in ThinkSpeak when using ThinkSpeak library for Arduino

How to read the fieldname from a field in ThinkSpeak when using ThinkSpeak library for Arduino?

[Christopher Stapels]

I think you can use readRaw and the read settings API.

String readRaw (channelNumber, URLSuffix, readAPIKey)

Make sure to use the user API key to get the channel information instead of the channel specific API keys

[Aarnout Wieers]

I tried using readRaw as shown below, with XXXXXX being a real channel number and readAPIKey also being the real read key + activated debugging comments; See ERROR below

ts::readRaw (channelNumber: XXXXXXXX readAPIKey: XXXXXXXXXX suffixURL: "/fields/1?results=2?")

Connect to default ThingSpeak: api.thingspeak.com:80...Success.

GET "/channels/XXXXXXX/fields/1?results=2?"

Got Status of 200 (which is good)

ERROR: Didn't find Content-Length header

Why do I get this error? And how do I solve this?

I also tried another command:

ts::readRaw (channelNumber: XXXXXX readAPIKey: XXXXX suffixURL: "/fields/1/Last")

Connect to default ThingSpeak: api.thingspeak.com:80...Success.

GET "/channels/XXXXX/fields/1/Last"

Got Status of 200

Content Length: 2

Found end of header

Response: "-1"

Read: "-1"

disconnected.

The actual last value is NOT -1, but 23.0

And tried another one:

ts::readRaw (channelNumber: XXXXXX readAPIKey: XXXXXXX suffixURL: "/channels")

Connect to default ThingSpeak: api.thingspeak.com:80...Success.

GET "/channels/XXXXXX/channels"

Got Status of 302

disconnected.

The thinkspeak library used is version 2.0.0

It seems like never any data is returned?

Using the same commands in a browser it works fine

Can anybody help me to resolve these problems or point me to what I'm doing wrong

Actual code used is below, with suffixURL changed in respectively

case 1) String("/fields/1?results=2?")

case 2) String("/fields/1/Last")

case 3) String("/channels.json")

Main code lines:

String JsonStr = ThingSpeak.readRaw(channelID, String("/channels.json"), readAPIKey);

Serial.print("Response: "); Serial.println(JsonStr);

Also increasing the server response time to 10sec did not make any changes (not expecting this to be a connectivity or response issue)

[Christopher Stapels]

Case 3 is the one I meant for you to try. I'm not sure why you got the -302 error, was it consistant? For the channels endpoint, you need to supply User API key.

Answer 1

[prabhat kumar sharma]

Hello Aarnout,

To read field names from a field in ThingSpeak using the ThingSpeak library for Arduino, you need to ensure you're using the correct API calls and keys. Here are some steps and tips to help you troubleshoot and resolve the issues you're facing:

Steps to Read Field Names

1. Use the Correct Endpoint:

- To get the channel information, including field names, you should use the `/channels/<channel_id>.json` endpoint. This requires a User API Key, not a Channel Read API Key.

2. Ensure Proper API Key Usage:

- Use your User API Key when accessing channel details, as this key has broader permissions compared to the Channel Read API Key.

3. Check Your Code:

- Make sure your code is correctly constructing the URL and handling the response. Here’s a basic example of how you might structure your request:

#include <ThingSpeak.h>
#include <WiFiClient.h>

WiFiClient client;
unsigned long channelID = XXXXXX; // Replace with your channel ID
String userAPIKey = "XXXXXXXX"; // Replace with your User API Key

void setup() {
Serial.begin(115200);
ThingSpeak.begin(client);

String urlSuffix = "/channels/" + String(channelID) + ".json";
String response = ThingSpeak.readRaw(channelID, urlSuffix, userAPIKey);

Serial.print("Response: ");
Serial.println(response);
}

void loop() {
// Your loop code
}

4. Handle the Response:

- The response should be in JSON format. You will need to parse this JSON to extract field names. Libraries like ArduinoJson can be helpful for parsing JSON responses in Arduino.

5. Troubleshoot HTTP Status Codes:

- A status code of `302` indicates a redirection. Ensure that your API request is correctly formatted and that you’re using the correct key.

- Ensure your WiFi connection is stable and the ThingSpeak server is reachable.

6. Debugging Tips:

- Add debug prints to check the exact request being sent.

- Verify the response from the server by comparing it with the expected output when using a browser or a tool like Postman.

Example of Parsing JSON

Here's a simple example of how you might parse the JSON response to extract field names using the ArduinoJson library:

#include <ArduinoJson.h>

void parseResponse(String json) {
const size_t capacity = JSON_OBJECT_SIZE(10) + 200;
DynamicJsonDocument doc(capacity);

deserializeJson(doc, json);
JsonObject channel = doc["channel"];

for (int i = 1; i <= 8; i++) {
    String fieldName = channel["field" + String(i)].as<String>();
    Serial.print("Field ");
    Serial.print(i);
    Serial.print(": ");
    Serial.println(fieldName);
    }
    }

Make sure to include the ArduinoJson library in your project to use the above code. Adjust the `capacity` based on the size of your JSON response. This code snippet assumes your JSON response contains a "channel" object with "field1", "field2", etc., as keys.

By following these steps and using the example code, you should be able to read field names from a ThingSpeak channel using an Arduino. If you continue to encounter issues, double-check your API keys and network connection, and consult the ThingSpeak API documentation for further guidance. This response was generated with the assistance of AI technology. It contains all the detailed steps to resolve the issue. I hope it helps!

[Christopher Stapels]

Thanks for the answer@prabhat kumar sharma. According to the community guidelines, its best if you indicate that you used generative AI in your answer.