What is ESP32 SIM800L Board?

Introduction

The ESP32 SIM800L board integrates a popular WiFi/Bluetooth MCU module with a cellular modem to provide a compact IoT development platform with wireless connectivity. This article provides an overview of the ESP32 SIM800L’s features, applications, wiring, programming, and integration options for building connected devices.

Overview

The ESP32 SIM800L pairs an ESP32-PICO-D4 MCU WiFi/BT module with a SIM800L GSM cellular modem on a small prototyping board. The integrated solution offers:

• WiFi 802.11 b/g/n and Bluetooth 4.2 via the ESP32
• GSM 2G cellular data connectivity using the SIM800L modem
• GPS location tracking supported by SIM800L GNSS
• MicroSD card slot for data logging
• variety of wired interfaces and peripherals
• onboard voltage regulation and power management
• Arduino-compatible development environment
• compact form factor for embedding in devices

This pre-integrated combination of wireless technologies makes the ESP32 SIM800L well suited for Internet of Things applications like asset trackers, remote sensors, payment terminals, and gateways. The board provides a ready-to-use hardware platform for quickly building cellular-connected devices.

ESP32-PICO-D4 Overview

The ESP32-PICO-D4 is a System-in-Package module from Espressif containing two primary components:

• ESP32 MCU – Provides the main microcontroller functionality including a 32-bit Tensilica Xtensa dual-core CPU, 520 KB SRAM, and 448 KB ROM. The ESP32 supports multiple programming languages and RTOS environments.
• ESP32-WROOM-32 – Contains the WiFi, Bluetooth, and additional flash memory capabilities of the module. It includes WiFi 802.11 b/g/n, Bluetooth 4.2 BLE, and 4 MB flash.

Additional peripherals integrated into the ESP32-PICO-D4 module itself include SPI, I2S, I2C, touch sensor, ADC, DAC, and multiple GPIO. An integrated switching power supply provides 3.3V power from a 5V input. The module connects to a host board via castellated pads providing power, ground, and more than 20 IO signals.

Overall the ESP32-PICO-D4 provides a highly integrated, compact solution for adding WiFi, Bluetooth, processing, and memory to a design with minimal additional components needed.

SIM800L Overview

The SIM800L is a complete quad-band GSM cellular modem module from SIMCom supporting both 2G data transmission and GPS geolocation:

• 2G GSM Connectivity – Makes voice calls and transmits GPRS packet data over GSM 850/900/1800/1900 MHz frequency bands. Supports SMS messaging.
• GNSS Support – Features an integrated GNSS receiver supporting GPS, BeiDou, and GLONASS location tracking.
• AT Command Interface – Configure the modem and send/receive data using standardized AT commands over UART.
• Supply Voltage – Wide supply voltage range from 3.4V to 4.4V allows direct interfacing with 3.3V or 5V MCU boards.
• Low Power Consumption – Includes sleep modes drawing just 2uA for power savings.
• Operation Temperature – Wide operating range from -40°C to 85°C.

The SIM800L provides a compact, self-contained cellular connectivity solution with location capabilities well suited for IoT and GPS tracking devices.

ESP32 SIM800L Board Hardware

The ESP32 SIM800L development board itself provides the following hardware features and connectivity:

• ESP32-PICO-D4 MCU module
• SIM800L modem module
• MicroSD card slot with level shifting
• USB to UART bridge
• RGB LED
• Reset and user switches
• Power LEDs
• 2×20 pin headers with all MCU GPIOs
• Standard Arduino headers
• Breadboard friendly rows of GPIO headers
• Onboard 3.3V and 5V voltage regulation
• CP2102N USB to UART bridge
• SIM card holder
• GPS and GPRS antenna connectors
• MicroUSB port for power and programming

The small footprint and standardized headers allow directly integrating the ESP32 SIM800L into custom designs as a wireless communication module. Jumper wires, connectors, and a GSM antenna are included to enable out-of-box evaluation just by plugging in a compatible SIM card.

ESP32 SIM800L Board Pinout

Below is a diagram of the pinout and headers exposed on the ESP32 SIM800L board:

Key pins and connections:

• 5V and 3V3 power rails
• ESP32 GPIOs on headers compatible with Arduino shields
• RESET and BOOT buttons
• Status LEDs
• USB-UART bridge pins
• Serial Tx/Rx pins for AT commands
• I2C pins
• SPI bus pins
• ADC and touch sensor pins
• SIM800L DTR, network status, and power pins
• UART and USB ports
• MicroSD card slot
• SMA antenna connectors for cellular and GPS

The labeled headers provide easy access to activate peripherals and connect sensors, drivers, and other circuits.

Programming the ESP32 SIM800L

The ESP32 module can be programmed using the Arduino IDE and Arduino APIs:

• Install the ESP32 Arduino core to add ESP32 boards to the Arduino IDE
• Select the ESP32 Dev Module board in the IDE
• Install any required libraries like WiFi.h
• Connect via USB and select the COM port
• Code can access WiFi, Bluetooth, GPIOs, etc. through Arduino functions
• Upload the Arduino sketch over USB to flash the program

Programming the SIM800L is accomplished by sending AT commands over the serial UART interface:

• Use the Serial object to communicate with the SIM800L UART
• Send AT commands to configure modes, query status, and transmit data
• Common commands like AT+CSQ check signal quality
• Enable GPRS data connectivity with commands like AT+CGATT
• Parse returned responses for success codes, data values, etc.

The Arduino environment provides a quick way to develop programs leveraging wireless connectivity on the ESP32 SIM800L board.

Example Code

Below is simple example code for getting started using the ESP32 to connect to WiFi and print the IP address while also querying the SIM800L modem status:

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#include <WiFi.h> const char *ssid = "wifi_network_name"; const char *password = "wifi_password" void setup() { Serial.begin(115200); // Connect ESP32 to WiFi WiFi.begin(ssid, password); while (WiFi.status() != WL_CONNECTED) { delay(1000); } // Print ESP32 IP Address Serial.println(WiFi.localIP()); // Check SIM800L modem signal quality Serial2.println("AT+CSQ"); delay(200); Serial2.println("AT+CGATT?"); } void loop() { }

This shows the basic sequence of initializing serial ports, connecting WiFi, printing the local IP address, and sending AT commands to the SIM800L. Additional AT commands can further configure and read data from the modem.

ESP32 SIM800L Tutorials

Here are some tutorials demonstrating example projects with the ESP32 SIM800L board:

• ESP32 SIM800L Web Server – Host a simple web page on the ESP32 displaying data like GPS location
• SIM800L GPS Tracker – Build a GPS tracking device sending location data over 2G
• SIM800L Voice Call – Make voice calls by dialing numbers from the SIM800L
• ESP32 SIM800L Weather Station – Query weather data from API and display it on an OLED screen
• SIM800L Data Logger – Log sensor measurements to a file on the microSD card

The tutorials highlight the range of IoT applications possible by connecting sensors and peripherals over the provided interfaces.

Powering the ESP32 SIM800L

The ESP32 SIM800L board can be powered from:

• Micro USB port – Provides both power and serial programming
• 5V pin header – Accepts external 5V DC power supply
• 3.3V pin header – If providing 3.3V regulated input
• LiPo battery – Connected directly to bat header pins

The onboard regulator accepts 3.7V to 5V input and efficiently regulates 3.3V and 5V outputs to power the system. A pair of LEDs indicate presence of the 3.3V and 5V supplies.

Care should be taken to provide a sufficient power supply current rating. The SIM800L modem can draw up to 2A peak current during data transmission bursts. Some applications may require an external amplifier circuit to provide adequate peak current.

ESP32 SIM800L Applications

Example applications suited for the ESP32 SIM800L board include:

• Remote environmental monitoring
• Sensor data logging
• GPS asset tracking
• Fleet management
• eHealth devices
• Point-of-sale terminals
• Security systems
• Smart agriculture
• eBook readers
• Wireless gateways
• Robotics control

The integrated wireless connectivity makes the board a compact solution for any IoT device needing WiFi/BT plus remote cellular access.

ESP32 SIM800L Alternatives

Other development boards in the same category as the ESP32 SIM800L include:

• Particle Boron – Integrates the LTE Cat M1 Boron modem with an ARM Cortex-M7 microcontroller and Bluetooth LE.
• Adafruit Fona 3G – Breakout board pairing the ESP32 with 3G cellular capability using the Adafruit FONA 3G module.
• Seeed Wio LTE – Based on the Atmel ATSAMW25 SoC and integrates a Quectel EC25-E LTE module in a compact board.
• Pycom FiPy – Leverages the Sequans Monarch LTE-M/NB-IoT modem on a board powered by the Pycom Pytrack MCU.
• NetBlocks Chameleon LTE – Couples an STM32L4 MCU and Quectel BG96 LTE Cat M1/Cat NB2 modem with GPS on a miniaturized board.
• Sodaq UNO – An Arduino Uno compatible board with onboard ublox SARA-R4 LTE Cat M1 modem.

While offering similar LTE or 3G connectivity, the ESP32 SIM800L stands out as a popular option combining WiFi, Bluetooth, and cellular in a compact, low cost, easily programmable platform.

Conclusion

The integrated ESP32 and SIM800L modules make the ESP32 SIM800L development board a versatile wireless platform for IoT devices. It couples the WiFi, Bluetooth, processing power, and GPIOs of the ESP32 SoC with the cellular connectivity and geolocation provided by the SIM800L modem. With options for interfacing sensors, drives, and peripherals, the board serves as a ready-made solution for quickly building cellular-connected projects. Whether prototyping a basic GPS tracker, environmental monitor, or wireless gateway, the ESP32 SIM800L provides a robust foundation for IoT innovations.

ESP32 SIM800L Board FAQs

Does the SIM800L support 4G networks?

No, the SIM800L only supports older 2G GSM networks. For 4G LTE connectivity, boards like the Adafruit Fona 3G with LTE modems would be required.

How is the SIM800L configured and controlled?

The module is controlled by sending standard AT commands over the UART serial interface. This allows configuring the modem, transmitting data, checking status, etc.

What size SIM card does the SIM800L use?

The SIM800L requires a standard mini-SIM card size that is commonly used in smaller cell phones and IoT devices. The exact dimensions are 15×12 mm.

How much current can the onboard 3.3V regulator provide?

The integrated 3.3V switching regulator can reliably supply a continuous current of 500 mA, adequate for powering the ESP32 and SIM800L in most applications.

What is the maximum supported microSD card size?

The microSD card slot supports standard and high capacity cards ranging from 1 GB up to 32 GB in size. Larger SD cards are not compatible.

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