ESP32 SIM800A GSM/GPRS Module
Overview
The SIM800A is a versatile GSM/GPRS module that provides dual-band connectivity for voice, SMS, and data applications. Its compact design and low power requirements make it suitable for a wide range of communication projects.
About SIM800A GSM/GPRS Module
The SIM800A is a compact GSM/GPRS module designed for voice, SMS, and data transmission over dual-band (900/1800MHz) networks. With its small size and low power consumption, it is an excellent choice for wearables, IoT devices, and industrial automation.
⚡ Key Features
- Dual-Band GSM (900/1800MHz) – Ensures reliable connectivity in supported regions.
- Versatile Communication – Supports voice calls, SMS, and GPRS data transfer.
- Multiple Interfaces – Includes UART and USB for seamless integration.
- Compact & Low Power – Ideal for battery-powered and space-constrained applications.
🔗 Still deciding on a SIM module? Check the ESP32 SIM Modules Comparison Table for a breakdown of LTE, 3G, and GPRS options. 🚀
Where to Buy
Starting from
5.27$ per unit
Prices are subject to change. We earn from qualifying purchases as an Amazon Associate.
Technical Specifications
Pinout Configuration
The VCC pin is used to supply power to the sensor, and it typically requires 3.3V or 5V (refer to the datasheet for specific voltage requirements). The GND pin is the ground connection and must be connected to the ground of your ESP32.
The SIM800A pinout includes:
- VBAT: Power supply input (3.4V to 4.4V).
- GND: Ground connection.
- UART_TXD: UART Transmit Data (connects to microcontroller RX).
- UART_RXD: UART Receive Data (connects to microcontroller TX).
- PWRKEY: Power on/off control (active low).
- NETLIGHT: Network status indication.
- STATUS: Module operating status indication.
- SIM_VDD: SIM card power supply.
- SIM_DATA: SIM card data I/O.
- SIM_CLK: SIM card clock.
- SIM_RST: SIM card reset.
Wiring with ESP32
- Connect
VBATto a stable power supply within the range of 3.4V to 4.4V. - Connect
GNDto the ground of the microcontroller. - Connect
UART_TXDto the RX pin of the microcontroller andUART_RXDto the TX pin. - Connect
PWRKEYto a GPIO pin on the microcontroller; to power on the module, pull this pin low for at least 1 second. - Optionally, connect
NETLIGHTandSTATUSpins to LEDs for network and status indications. - For SIM card connections, connect
SIM_VDD,SIM_DATA,SIM_CLK, andSIM_RSTto the corresponding pins on the SIM card holder.
Troubleshooting Guide
Common Issues
❌ Module Fails to Power On
Issue: The SIM800A module does not power up or respond to commands.
Possible causes include insufficient power supply, incorrect wiring, or faulty hardware.
Solution: Ensure the module is connected to a stable power source within the recommended voltage range of 3.4V to 4.4V. Verify that all connections are secure and correctly configured. If the problem persists, consider testing the module with a different power source or replacing it.
📱 SIM Card Not Recognized
Issue: The module fails to detect or register the SIM card.
Possible causes include improper SIM card insertion, unsupported SIM card type, or SIM card lock.
Solution: Ensure the SIM card is properly inserted into the module's SIM card slot and is compatible with the GSM network. Verify that the SIM card is active and unlocked. If necessary, test the SIM card in another device to confirm its functionality.
⚠️ Poor Network Signal or Connectivity Issues
Issue: The module experiences weak signal strength or fails to maintain a stable network connection.
Possible causes include improper antenna connection, environmental interference, or network coverage limitations.
Solution: Ensure the GSM antenna is securely connected to the module and positioned for optimal signal reception. Avoid placing the module near sources of electromagnetic interference. Check the network coverage in your area to ensure adequate signal strength.
💬 AT Commands Not Responding
Issue: The module does not respond to AT commands sent from the microcontroller or computer.
Possible causes include incorrect baud rate settings, faulty serial connections, or improper command syntax.
Solution: Verify that the baud rate of the module matches that of the microcontroller or computer; the default baud rate is 9600 bps. Check that the TX and RX lines are correctly connected and that there are no loose connections. Ensure that AT commands are correctly formatted and terminated with a carriage return.
🔥 Module Overheating
Issue: The SIM800A module becomes excessively hot during operation.
Possible causes include overvoltage, excessive current draw, or continuous high-power transmission.
Solution: Confirm that the power supply voltage is within the recommended range (3.4V to 4.4V). Monitor the current consumption to ensure it does not exceed the module's specifications. If the module is transmitting continuously, consider implementing power-saving modes or reducing the transmission frequency to prevent overheating.
Debugging Tips
🔍 Serial Monitor
Use the Serial Monitor to check for error messages and verify the sensor's output. Add debug prints in your code to track the sensor's state.
⚡ Voltage Checks
Use a multimeter to verify voltage levels and check for continuity in your connections. Ensure the power supply is stable and within the sensor's requirements.
Additional Resources
Code Examples
Arduino Example
#include <SoftwareSerial.h>
SoftwareSerial sim800a(10, 11); // RX, TX
void setup() {
Serial.begin(9600);
sim800a.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
sim800a.println("AT");
delay(1000);
while (sim800a.available()) {
Serial.write(sim800a.read());
}
}
void loop() {
// Send an SMS
sim800a.println("AT+CMGF=1"); // Set SMS to text mode
delay(1000);
sim800a.println("AT+CMGS="+1234567890""); // Replace with recipient's number
delay(1000);
sim800a.print("Hello from SIM800A");
delay(1000);
sim800a.write(26); // CTRL+Z to send SMS
delay(5000);
}ESP-IDF Example
#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_sim800a() {
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_sim800a();
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);
}
}power_on_sim800a() function toggles the PWRKEY pin to activate the module.ESPHome Example
uart:
tx_pin: GPIO17
rx_pin: GPIO16
baud_rate: 9600
switch:
- platform: gpio
name: "SIM800A 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: "SIM800A Response"PlatformIO Example
platformio.ini
[env:sim800a]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200PlatformIO Example Code
#include <HardwareSerial.h>
#include <Arduino.h>
HardwareSerial sim800a(1);
#define PWRKEY 4
void power_on_sim800a() {
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);
sim800a.begin(9600, SERIAL_8N1, 16, 17); // RX, TX
power_on_sim800a();
// Test AT command
sim800a.println("AT");
delay(1000);
while (sim800a.available()) {
Serial.write(sim800a.read());
}
}
void loop() {
sim800a.println("AT+CMGF=1"); // Set SMS to text mode
delay(1000);
sim800a.println("AT+CMGS="+1234567890""); // Replace with recipient's number
delay(1000);
sim800a.print("Hello from PlatformIO");
delay(1000);
sim800a.write(26); // CTRL+Z to send SMS
delay(5000);
}power_on_sim800a 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.MicroPython Example
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_sim800a():
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_sim800a()
# 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))power_on_sim800a 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.Conclusion
The ESP32 SIM800A GSM/GPRS Module is a powerful SIM sensor that offers excellent performance and reliability. With support for multiple development platforms including Arduino, ESP-IDF, ESPHome, PlatformIO, and MicroPython, it's a versatile choice for your IoT projects.
For optimal performance, ensure proper wiring and follow the recommended configuration for your chosen development platform.
Always verify power supply requirements and pin connections before powering up your project to avoid potential damage.
