When it comes to IoT, the ESP32 is a chip that packs a powerful punch. The ESP32 is a follow-up to the ESP8266. This low-cost system on a chip (SoC) series was created by Espressif Systems. Based on its value for the price, small size, and relatively low power consumption, the ESP32 is well-suited to a number of different IoT applications.

In this article, I’ll break down the ESP32’s technical specifications and describe some of the different modules available.

What is ESP32?

ESP32 is a chip that provides Wi-Fi and (in some models) Bluetooth connectivity for embedded devices – in other words, for IoT devices. While ESP32 is technically just the chip, the modules and development boards that contain this chip are often also referred to as “ESP32” by the manufacturer. 

The original ESP32 chip had a single core Tensilica Xtensa LX6 microprocessor. The processor had a clock rate of over 240 MHz, which made for a relatively high data processing speed. 

More recently, new models were added, including the ESP32-C and -S series, which include both single and dual core variations. These two series also rely on a Risc-V CPU model instead of Xtensa. Risc-V is similar to the ARM architecture, which is well-supported and well-known, but Risc-V is open source and easy to use. Specifically, Risc-V and ARM have good support from GNU compilers, while the Xtensa needed extra support and development to work with the compilers. 

The newer models are available with combined Wi-Fi and Bluetooth connectivity, or just Wi-Fi connectivity. There are several different chip models available, including:

• ESP32-D0WDQ6 (and ESP32D0WD)
• ESP32-D2WD
• ESP32-S0WD
• System in package (SiP) – ESP32-PICO-D4
• ESP32 S series
• ESP32-C series
• ESP32-H series

The ESP32 is most commonly used for mobile devices, wearable tech, and IoT applications, such as Nabto Edge. Moreover, since Mongoose OS introduced an ESP32 IoT Starter Kit, the ESP32 has gained a reputation as the ultimate chip for hobbyists and IoT developers. It’s suitable for commercial IoT, and its capabilities and resources have grown impressively over the past four years.

ESP32 features and specifications

Here’s a high-level summary of the features and specifications of the ESP32:

And here’s a more detailed summary:

• Processors – The ESP32 uses a Tensilica Xtensa 32-bit LX6 microprocessor. This typically relies on a dual core architecture, with the exception of one module, the ESP32-S0WD, which uses a single-core system. The clock frequency reaches up to 240MHz and it performs up to 600 DMIPS (Dhrystone millions of instructions per second). Moreover, its low power consumption allows for analog to digital conversions as well as computation and level thresholds, even while the chip is in deep sleep mode.
• Wireless connectivity – The ESP32 enables connectivity to integrated Wi-Fi through the 802.11 b/g/n/e/i/. Moreover, Bluetooth connectivity is made possible with the v4.2 BR/EDR, and the series also features Bluetooth low energy (BLE). 
• Memory – Internal memory for the ESP32 is as follows. ROM: 448 KB (for booting/core functions), SRAM: 520 KB (for data/instructions), RTC fast SRAM: 8 KB (for data storage/main CPU during boot from sleep mode), RTC slow SRAM: 8 KB (for co-processor access during sleep mode), and eFuse: 1 KiBit (256 bits used for the system (MAC address and chip configuration) and 768 bits reserved for customer applications). Moreover, some of the ESP32 chips, including the ESP32-D2WD and ESP32-PICO-D4, have internally connected flash. See the respective internal flash memory for each chip in the ESP32 Chips section. 
• External flash and SRAM – ESP32 supports up to four 16 MB external QSPI flashes and SRAMs with hardware encryption based on AES to protect developers’ programs and data. It accesses the external QSPI flash and SRAM through high-speed caches.
• Security – The ESP32 supports all IEEE 802.11 standard security features, including WFA, WPA/WPA2 and WAPI. Moreover, ESP32 has a secure boot and flash encryption.

ESP32 functions

ESP32 has many applications when it comes to IoT. Here are just some of the IoT functions the chip is used for:

• Networking: The module’s Wi-Fi antenna and dual core enables embedded devices to connect to routers and transmit data.
• Data processing: Includes processing basic inputs from analog and digital sensors to far more complex calculations with an RTOS or non-OS software development kit (SDK). A non-OS SDK refers to one that is designed to run directly on the chip without a full operating system supporting it. 
• P2P connectivity: Creates direct communication between different ESPs and other devices using IoT P2P connectivity.
• Web server: Provides access to pages written in HTML or development languages.

ESP32 Applications

The ESP32 modules are commonly found in the following IoT devices:

• Smart industrial devices, including programmable logic controllers (PLCs)
• Smart medical devices, including wearable health monitors
• Smart energy devices, including HVAC and thermostats
• Smart security devices, including surveillance cameras and smart locks

Chip versus modules versus development boards

The ESP32 is just the name of the chip. Device manufacturers and developers have three different format choices, and the decision of which one to go with will depend on their individual circumstances:

• ESP32 chip: This is the bare-bones chip that is manufactured by Espressif. It comes unshielded, meaning there’s no protective casing, and it can’t be attached to a module or board without soldering. Therefore, most device manufacturers do not purchase just the chip, as this will add an additional layer of complexity to the production process.
• ESP32 modules: These are surface mountable modules that contain the chip. The modules are essentially small electrical components that can be attached to a circuit board. The benefit here is that you can easily mount these modules onto an MCU board. The chip is also usually shielded and pre-approved by the FCC, which means device manufacturers do not need to worry about adding additional steps to the production process to achieve FCC compliance regarding Wi-Fi shielding.
• ESP32 development boards: These are IoT MCU development boards that have the modules containing the ESP32 chip preinstalled. They are used by hobbyists, device manufacturers and developers to test and prototype IoT devices before entering mass production. There is a wide variety of makes and models of ESP32 development boards, produced by different manufacturers. Here are some important specs to consider when choosing a suitable IoT ESP32 development board:
  • GPIO pins
  • ADC pins
  • Wi-Fi antennas
  • LEDs
  • Shielding*
  • Flash memory

*Many international markets require shielded Wi-Fi devices, as Wi-Fi produces a lot of radio frequency interference (RFI), and shielding minimizes this interference. This should, therefore, be a key consideration for all developers and embedded device manufacturers.

Manufacturers of ESP32 modules and boards

ESP32 Chips

Espressif Systems is the manufacturer of the ESP32 chip. The chip is available in various sizes, including 7 mm x 7 mm, 6 x 6, 5 x 5, and even 4 x 4 QFN packages. Here are the current models available:

ESP32 modules

●      Espressif

There are too many modules to mention all of them here, but here are some of the top modules that use the Espressif Systems ESP32 chip:

●      Ai-Thinker

Current Ai-Thinker ESP32 modules are the following:

Other manufacturers of ESP32 modules include:

• AnalogLamb
• DFRobot
• Pycom
• u-blox

ESP32 development boards/dev kits

●      Espressif

The current Espressif ESP32 development boards include:

●      Ai-Thinker

The AI-Thinker development boards include:

●      Adafruit

The Adafruit ESP32 development boards include:

●      Wemos

The Wemos ESP32 development boards include:

●      Arducam

The current Arducam ESP32 development board is:

What SDKs are used for ESP32s?

A wide range of SDKs are now available. Espressif provides one official SDK for use with either the ESP32, ESP32-2, or the ESP8266. This is the FreeRTOS-based SDK. FreeRTOS is the real-time operating system offered by Amazon, so the SDK is specifically designed for use with that system. 

Aside from the Espressif options, there are plenty of commercial and open-source SDKs on the market, including:

• ESP Arduino Core – C++ based firmware
• ESP-SDK-Tools – Open integrated SDK for ESP8266
• Espruino – Javascript SDK and firmware
• Micropython – Python for embedded devices
• Moddable SDK – Javascript SDK
• Mongoose OS – C or Javascript open-source OS
• NodeMCU – Open-source Lua based firmware, similar to Node.js
• uLisp – Lisp-based framework
• Zerynth – Python framework for IoT

Which is the best ESP32 module or development board for IoT?

As the above comparisons show, there are a lot of options available with ESP32 IoT boards and modules. To help you with your decision making, we’ve summarized some of the most popular below.

Popular ESP32 modules

Popular ESP32 development boards

Final thoughts

No single article can cover all of the ESP32 series features. However, this information should provide a good starting point for you to find the best ESP32 chips, modules, and development boards for your IoT projects. 

Read Our Other Resources

We’ve published a range of other IoT resources for our community, including:

• A remote control end-to-end example on ESP32: The Nabto ESP32 Virtual Thermostat Guide.
• A complete guide to Microcontrollers for IoT to help you choose the right MCU for your IoT project.
• How to Make a Low-Cost ESP32-Based Remote-Accessible Camera using ESP32-CAM or ESP32-EYE Board, which is a full tutorial for how to create an ESP32 camera with Nabto.