How to attach attachment in mail using sim800

The Sim800 is a popular GSM module used in many IoT projects, including sending SMS and MMS messages. To attach an attachment to an MMS message using the Sim800, you'll need to follow these steps:

Prerequisites:

Make sure you have a valid SIM card with a data plan that supports MMS.
Ensure that your Sim800 module is properly configured and connected to a power source.
You'll need to use a programming language like C, Python, or Arduino to communicate with the Sim800 module.

Step 1: Prepare the attachment

Convert your attachment (e.g., an image, audio file, or document) to a format that can be sent via MMS, such as JPEG, PNG, or MP3.
Resize the attachment to a reasonable size (e.g., 100KB or less) to avoid issues with sending large files.

Step 2: Set up the MMS message

Use your programming language to send an AT command to the Sim800 module to set up the MMS message:
```
AT+CMGF=1 // Set the message format to MMS
AT+CMMS="recipient_number" // Set the recipient's phone number
```
Replace recipient_number with the actual phone number of the recipient.

Step 3: Attach the file

Use the AT command AT+CMXT to attach the file to the MMS message:
```
AT+CMXT="attachment_name", "attachment_type", "attachment_data" // Attach the file
```
Replace attachment_name with the name of the attachment (e.g., "image.jpg"), attachment_type with the MIME type of the attachment (e.g., "image/jpeg"), and attachment_data with the actual binary data of the attachment.

For example:

AT+CMXT="image.jpg", "image/jpeg", "ffd8...ff" // Attach a JPEG image

Note that the attachment_data part should be a binary string representing the attachment file.

Step 4: Send the MMS message

Use the AT command AT+CMSS to send the MMS message:
```
AT+CMSS=1 // Send the MMS message
```
The Sim800 module will then send the MMS message with the attached file to the recipient's phone.

Example code in C:

#include <stdio.h>
#include <string.h>

int main() {
    // Set up the MMS message
    printf("AT+CMGF=1\r\n");
    printf("AT+CMMS=\"+1234567890\"\r\n");

    // Attach the file
    FILE *file = fopen("image.jpg", "rb");
    fseek(file, 0, SEEK_END);
    long file_size = ftell(file);
    fseek(file, 0, SEEK_SET);
    char *attachment_data = malloc(file_size);
    fread(attachment_data, 1, file_size, file);
    fclose(file);

    printf("AT+CMXT=\"image.jpg\", \"image/jpeg\", %s\r\n", attachment_data);

    // Send the MMS message
    printf("AT+CMSS=1\r\n");

    return 0;
}

This code assumes you have a file named image.jpg in the same directory as the program. You'll need to modify the code to suit your specific requirements.

Remember to check the Sim800 module's documentation and the specific AT commands supported by your module for any variations or additional requirements.

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How to attach attachment in mail using sim800