ESP32 SIM800C GSM/GPRS Module

Code Examples

Below you can find code examples of SIM800C GSM/GPRS Module with ESP32 in several frameworks:

• Arduino IDE
• ESP-IDF
• ESPHome
• PlatformIO
• MicroPython

If you encounter issues while using the SIM800C GSM/GPRS Module, check the Common Issues Troubleshooting Guide.

ESP32 SIM800C Arduino IDE Code Example

Example in Arduino IDE

Fill in your main Arduino IDE sketch file with the following code to use the SIM800C GSM/GPRS Module:

#include <SoftwareSerial.h>

SoftwareSerial sim800c(10, 11); // RX, TX

void setup() {
    Serial.begin(9600);
    sim800c.begin(9600);

    // Power on the module
    pinMode(9, OUTPUT);
    digitalWrite(9, LOW);
    delay(1000); // PWRKEY needs to be low for at least 1 second
    digitalWrite(9, HIGH);
    delay(5000); // Wait for the module to initialize

    // Test AT communication
    sim800c.println("AT");
    delay(1000);
    while (sim800c.available()) {
        Serial.write(sim800c.read());
    }
}

void loop() {
    // Send an SMS
    sim800c.println("AT+CMGF=1"); // Set SMS to text mode
    delay(1000);
    sim800c.println("AT+CMGS=\"+1234567890\""); // Replace with recipient's number
    delay(1000);
    sim800c.print("Hello from SIM800C");
    delay(1000);
    sim800c.write(26); // CTRL+Z to send SMS
    delay(5000);
}

This Arduino sketch interfaces with the SIM800C module using the SoftwareSerial library. The module is powered on by toggling the PWRKEY pin. An AT command is sent to verify communication. In the loop, the sketch sends an SMS by setting the module to SMS text mode, specifying the recipient's number, and sending the message, finalized with CTRL+Z (ASCII 26) to initiate transmission.

Connect your ESP32 to your computer via a USB cable, Ensure the correct Board and Port are selected under Tools, Click the "Upload" button in the Arduino IDE to compile and upload the code to your ESP32.

ESP32 SIM800C ESP-IDF Code Example

Example in Espressif IoT Framework (ESP-IDF)

If you're using ESP-IDF to work with the SIM800C GSM/GPRS Module, here's how you can set it up and read data from the sensor. Fill in this code in the main ESP-IDF file:

#include <stdio.h>
#include "driver/uart.h"
#include "driver/gpio.h"
#include "freertos/task.h"

#define TX_PIN 17
#define RX_PIN 16
#define PWRKEY_PIN 4
#define UART_PORT UART_NUM_1

void init_uart() {
    uart_config_t uart_config = {
        .baud_rate = 9600,
        .data_bits = UART_DATA_8_BITS,
        .parity = UART_PARITY_DISABLE,
        .stop_bits = UART_STOP_BITS_1,
        .flow_ctrl = UART_HW_FLOWCTRL_DISABLE
    };

    uart_param_config(UART_PORT, &uart_config);
    uart_set_pin(UART_PORT, TX_PIN, RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE);
    uart_driver_install(UART_PORT, 1024, 0, 0, NULL, 0);
}

void power_on_sim800c() {
    gpio_set_direction(PWRKEY_PIN, GPIO_MODE_OUTPUT);
    gpio_set_level(PWRKEY_PIN, 0);
    vTaskDelay(1000 / portTICK_PERIOD_MS); // Hold PWRKEY low for 1 second
    gpio_set_level(PWRKEY_PIN, 1);
    vTaskDelay(5000 / portTICK_PERIOD_MS); // Wait for the module to initialize
}

void app_main(void) {
    init_uart();
    power_on_sim800c();

    char *test_cmd = "AT\r\n";
    uart_write_bytes(UART_PORT, test_cmd, strlen(test_cmd));

    while (true) {
        char data[128];
        int len = uart_read_bytes(UART_PORT, data, sizeof(data), 100 / portTICK_PERIOD_MS);
        if (len > 0) {
            data[len] = '\0';
            printf("Response: %s\n", data);
        }
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

This ESP-IDF example initializes UART communication with the SIM800C module and powers it on using the PWRKEY pin (GPIO4). The UART interface is configured with GPIO17 as TX and GPIO16 as RX. An AT command is sent to test communication, and responses from the module are printed to the console. The function `power_on_sim800c()` toggles the PWRKEY pin to activate the module.

Update the I2C pins (I2C_MASTER_SDA_IO and I2C_MASTER_SCL_IO) to match your ESP32 hardware setup, Use idf.py build to compile the project, Use idf.py flash to upload the code to your ESP32.

ESP32 SIM800C ESPHome Code Example

Example in ESPHome (Home Assistant)

Fill in this configuration in your ESPHome YAML configuration file (example.yml) to integrate the SIM800C GSM/GPRS Module

uart:
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 9600

switch:
  - platform: gpio
    name: "SIM800C Power"
    pin:
      number: GPIO4
      inverted: true

switch:
  - platform: template
    name: "Send AT Command"
    turn_on_action:
      - uart.write: "AT\r\n"

sensor:
  - platform: custom
    lambda: |-
      return {nullptr};
    sensors:
      - name: "SIM800C Response"

This ESPHome configuration sets up UART communication with the SIM800C using GPIO17 (TX) and GPIO16 (RX) at 9600 baud. A GPIO-based switch is used to control the PWRKEY pin (GPIO4) for powering the module on or off. A template switch allows sending the AT command, and a custom sensor can be implemented to process responses from the module.

Upload this code to your ESP32 using the ESPHome dashboard or the esphome run command.

ESP32 SIM800C PlatformIO Code Example

Example in PlatformIO Framework

For PlatformIO, make sure to configure the platformio.ini file with the appropriate environment and libraries, and then proceed with the code.

Configure platformio.ini

First, your platformio.ini should look like below. You might need to include some libraries as shown. Make sure to change the board to your ESP32:

[env:sim800c]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200

ESP32 SIM800C PlatformIO Example Code

Write this code in your PlatformIO project under the src/main.cpp file to use the SIM800C GSM/GPRS Module:

#include <HardwareSerial.h>
#include <Arduino.h>

HardwareSerial sim800c(1);
#define PWRKEY 4

void power_on_sim800c() {
    pinMode(PWRKEY, OUTPUT);
    digitalWrite(PWRKEY, LOW);
    delay(1000); // Hold PWRKEY low for 1 second
    digitalWrite(PWRKEY, HIGH);
    delay(5000); // Wait for initialization
}

void setup() {
    Serial.begin(115200);
    sim800c.begin(9600, SERIAL_8N1, 16, 17); // RX, TX
    power_on_sim800c();

    // Test AT command
    sim800c.println("AT");
    delay(1000);
    while (sim800c.available()) {
        Serial.write(sim800c.read());
    }
}

void loop() {
    sim800c.println("AT+CMGF=1"); // Set SMS to text mode
    delay(1000);
    sim800c.println("AT+CMGS=\"+1234567890\""); // Replace with recipient's number
    delay(1000);
    sim800c.print("Hello from PlatformIO");
    delay(1000);
    sim800c.write(26); // CTRL+Z to send SMS
    delay(5000);
}

This PlatformIO code interfaces with the SIM800C module using HardwareSerial on an ESP32. The `power_on_sim800c` function toggles the PWRKEY pin (GPIO4) to activate the module. The AT command is sent to test communication, and SMS functionality is implemented in the loop. GPIO16 (RX) and GPIO17 (TX) are configured as serial pins.

Upload the code to your ESP32 using the PlatformIO "Upload" button in your IDE or the pio run --target upload command.

ESP32 SIM800C MicroPython Code Example

Example in Micro Python Framework

Fill in this script in your MicroPython main.py file (main.py) to integrate the SIM800C GSM/GPRS Module with your ESP32.

from machine import UART, Pin
import time

# Initialize UART
uart = UART(2, baudrate=9600, tx=17, rx=16)
pwrkey = Pin(4, Pin.OUT)

def power_on_sim800c():
    pwrkey.value(0)
    time.sleep(1)  # Hold PWRKEY low for 1 second
    pwrkey.value(1)
    time.sleep(5)  # Wait for module to initialize

def send_at(command):
    uart.write(command + '\r\n')
    time.sleep(1)
    while uart.any():
        print(uart.read().decode('utf-8'), end='')

# Power on the module
power_on_sim800c()

# Test communication
send_at('AT')

# Send SMS
send_at('AT+CMGF=1')  # Set SMS to text mode
send_at('AT+CMGS="+1234567890"')  # Replace with recipient's number
uart.write("Hello from MicroPython" + chr(26))

This MicroPython code communicates with the SIM800C module over UART. The `power_on_sim800c` function activates the module using the PWRKEY pin (GPIO4). The `send_at` function sends AT commands and prints the responses. The script initializes the module, tests communication, and sends an SMS with a specified message.

Upload this code to your ESP32 using a MicroPython-compatible IDE, such as Thonny, uPyCraft, or tools like ampy.