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Inkplate 6MOTION - GET & POST requests

Now that Inkplate is connected to the internet, you will likely want to send and receive data on it: sensor readings, messages, or data from your own APIs. This page contains examples on how to send and receive data on Inkplate via the internet:

GET request​

Using client.GET() will enable you to easily download and handle data on Inkplate however you want. Here is an example on how to GET a .txt file and print it on Inkplate:

// This is the file which will be downloaded:
char httpUrl[] = {"https://raw.githubusercontent.com/SolderedElectronics/Inkplate_Motion_Arduino_Library/refs/heads/main/examples/Inkplate6Motion/Advanced/Web_WiFi/Inkplate_6_Motion_WiFi_Simple/exampleFile.txt"};

// Make sure Inkplate is previously connected to WiFi

// Create the WiFi client object for HTTP request
WiFiClient client;
// Since the file will be received in chunks, keeps track of the byte received
uint32_t totalSize = 0;
// Try to open the page
if (client.begin(httpUrl))
{
    // Make GET request on that httpUrl
    if (client.GET())
    {
        // GET was successful! Let's print some info
        inkplate.print("Connected, file size: ");
        inkplate.print(client.size(), DEC);
        inkplate.println("bytes");
        inkplate.partialUpdate(true);
        inkplate.println("");
        inkplate.println("File contents:");

        // Read file contents:
        while (client.available())
        {
            // Use blocking method to get all chunks of the HTTP
            {
                if (client.available() > 0)
                {
                    char myBuffer[2000];
                    int n = client.read(myBuffer, sizeof(myBuffer));
                    totalSize += n;

                    // Print out the chunk.
                    for (int i = 0; i < n; i++)
                    {
                        inkplate.print(myBuffer[i]);
                    }
                }
            }
        }
    }
}
else
{
    inkplate.println("Failed to get the file!");
}
// Show updates on the display
inkplate.partialUpdate(true);

// Really important, end the WiFiClient connection!
// Otherwise any other AT command to the modem will fail!
client.end();
⚠️
It's important to end the client connection with client.end(), otherwise communicating with the ESP32 modem won't work and no further requests can be made.

POST request​

To send data from Inkplate to a web server, you can use the same built-in WiFiClient class. Let's use webhook.site, which is a great resource for testing POST and GET requests. By visiting the site, you get a unique URL which can then be sent a POST request to from Inkplate which will then be visible on the site:

// Add webhook.site URL here, something like
// https://webhook.site/0e92fcdc-test-1234-test-44e5ca8a0b47
char httpUrl[] = {""};

// This function sends a POST request to the set URL
void sendPost()
{
    // Before using this function, make sure Inkplate is connected to the internet

    // Create the WiFi client object for HTTP request
    WiFiClient client;

    // Since the file will be received in chunks, keeps track of the byte received
    uint32_t totalSize = 0;

    // Begin connection to URL
    if (client.begin(httpUrl))
    {
        // We're connected! 
        // Create request body, a simple request with one data field
        char bodyStr[256];
        // Here is where data is added
        // In this case, we will add a random number from -126 to 128
        sprintf(bodyStr, "data=%d", random(-127, 128));
        // See details of the sprintf c++ function to see how to add different types of data here
        // Do the actual POST request
        if (client.POST(bodyStr, strlen(bodyStr)))
        {
            // Read the response
            // This is optional
            while (client.available())
            {
                // Use blocking method to get all chunks of the HTTP reply
                {
                    if (client.available() > 0)
                    {
                        char myBuffer[2000];
                        int n = client.read(myBuffer, sizeof(myBuffer));
                        totalSize += n;

                        // Print out the response chunk on Inkplate
                        for (int i = 0; i < n; i++)
                        {
                            inkplate.print(myBuffer[i]);
                        }
                    }
                }
            }
        }
        // Add new line at the end
        inkplate.println();

        // Refresh the screen
        inkplate.partialUpdate();
    }
    else
    {
        // Error? inform the user
        inkplate.println("Failed to do POST request!");
        inkplate.partialUpdate();
    }
    
    // Really important, end the WiFiClient connection!
    // Otherwise any other AT command to the modem will fail!
    if (!client.end())
    {
        inkplate.println("Client end problem");
    }
}

The randomly generated number will then be visible on webhook.site.

⚠️
It's important to end the client connection with client.end(), otherwise communicating with the ESP32 modem won't work and no further requests can be made.

POST request with JSON​

You don't have to send data as plain form fields. With the ArduinoJson library, Inkplate can post JSON instead:

// Include ArduinoJson library. Get it from here: https://github.com/bblanchon/ArduinoJson
#include <ArduinoJson.h>

// Add webhook.site URL here, something like
// https://webhook.site/0e92fcdc-test-1234-test-44e5ca8a0b47
char httpUrl[] = {""};

// This function sends the POST request but with a JSON body
void sendPostWithJson()
{
    // Create the WiFi client object for HTTP request
    WiFiClient client;

    // Since the file will be received in chunks, keeps track of the byte received
    uint32_t totalSize = 0;

    // Connect to the URL
    if (client.begin(httpUrl))
    {
        // Add a HTTP header (must be added for JSON in this case)
        client.addHeader("Content-Type: application/json");

        // Create body with JSON
        char jsonData[256];
        StaticJsonDocument<200> webhookSiteJSON;
        // Add number data to field1
        webhookSiteJSON["dataField"] = random(-127, 128);
        // Serialize it so that it can be added to the POST request
        serializeJson(webhookSiteJSON, jsonData);

        // Do POST
        if (client.POST(jsonData, strlen(jsonData)))
        {
            while (client.available())
            {
                // Use blocking method to get all chunks of the HTTP reply
                {
                    if (client.available() > 0)
                    {
                        char myBuffer[2000];
                        int n = client.read(myBuffer, sizeof(myBuffer));
                        totalSize += n;

                        // Print out the chunk
                        for (int i = 0; i < n; i++)
                        {
                            inkplate.print(myBuffer[i]);
                        }
                    }
                }
            }
        }
        // Update the display
        inkplate.partialUpdate(true);
    }
    else
    {
        // Error? Inform the user
        inkplate.println("Failed to POST");
        inkplate.partialUpdate(true);
    }

    // Really important, end the WiFiClient connection!
    // Otherwise any other AT command to the modem will fail!
    if (!client.end())
    {
        inkplate.println("Client end problem");
    }
}

Full examples​

Inkplate_6_Motion_WiFi_Simple.ino

Full example on how to connect to WiFi, GET a .txt file and print it out to Inkplate

Inkplate_6_Motion_HTTP_POST.ino

Full example on how to send data to a webserver via HTTP and POST request on Inkplate 6MOTION