Electronics · Embedded Systems

ESP32

Reference entry · last updated 20260914

ESP32 is a 2.4 GHz Wi-Fi and Bluetooth system-on-chip (SoC) from Espressif Systems. The silicon is not a complete product: a module adds flash and an antenna, and a development board adds USB, a 3.3 V regulator, and pin headers.[1][3]

1. First principles and definitions

A microcontroller is a computer on one die: CPU, RAM, ROM, timers, and I/O. A radio SoC adds a wireless PHY and MAC on the same die. ESP32 is the second kind. It integrates 802.11 b/g/n Wi-Fi, Bluetooth BR/EDR, Bluetooth LE, an Xtensa CPU, SRAM, and peripherals, plus RF blocks (antenna switch, balun, power amplifier, LNA, filters).[1][4]

Firmware lives in flash and runs on the chip. Espressif's official path is to compile an application with ESP-IDF and flash it over a serial adapter. That is not a general-purpose operating system with a userland and a disk.[2]

Digital I/O is 3.3 V class. The datasheet's typical supply is 3.3 V, with 3.6 V as the recommended maximum on the 3.3 V domains. A USB 5 V rail on a development board feeds a regulator. It is not a GPIO voltage.[1][3] See volts and Ohm's law.

2. Chip, module, and board

Three packaged products share the name:

SoC. The ESP32 silicon (for example ESP32-D0WD-V3). It needs external flash (unless the variant has in-package flash), a crystal, power, and an antenna network.[1]
Module. A certified RF module such as ESP32-WROOM-32E (flash, PCB or IPEX antenna) or ESP32-WROVER (flash plus PSRAM). The module is the usual unit a board designer places.[12]
Development board. Espressif's ESP32-DevKitC V4 mounts a module, a USB-to-UART bridge, EN and Boot buttons, a 3.3 V regulator, and dual pin headers for a breadboard.[3]

ESP-IDF's ESP32 getting-started page links official boards including ESP32-DevKitC, ESP32-DevKitM-1, ESP32-Ethernet-Kit, ESP32-PICO-KIT-1, ESP32-PICO-DevKitM-2, and ESP32-LCDKit. Third-party boards reuse the same SoC and module parts with different USB chips and antenna layouts.[2]

3. Original ESP32 specifications

Espressif released ESP32 in 2016, after the Wi-Fi-only ESP8266 (2014).[5][6] The series datasheet (v5.3) describes a 40 nm combo chip with these headline numbers:

Item	Value (ESP32 series)
CPU	Xtensa 32-bit LX6, one or two cores, up to 240 MHz
On-chip memory	448 KB ROM, 520 KB SRAM, 16 KB RTC SRAM
Wi-Fi	802.11 b/g/n, 2.4 GHz, up to 150 Mbps (802.11n)
Bluetooth	v4.2 BR/EDR and Bluetooth LE
GPIO	34 programmable pins (some input-only; some reserved for in-package flash/PSRAM)
Analog	12-bit SAR ADC (up to 18 channels), two 8-bit DACs, 10 touch sensors
Digital I/O examples	SPI, I2C, I2S, UART, SDIO, LED PWM, motor PWM, RMT, TWAI (CAN 2.0), Ethernet MAC
Supply (typical)	3.3 V (recommended max 3.6 V on the 3.3 V domains)
Operating temperature	-40 °C to 125 °C; -40 °C to 85 °C for some in-package flash/PSRAM parts

Sources: Espressif ESP32 Series Datasheet v5.3.[1]

The chip can run standalone or as a slave radio for a host MCU over SPI, SDIO, I2C, or UART.[4] Several early package variants are marked NRND or EOL; ESP32-D0WD-V3 remains in the current datasheet set.[1]

4. Later ESP32-named SoCs

Espressif reused the ESP32 name for later SoCs that are not drop-in replacements. CPU ISA, Bluetooth generation, and extra radios change by series.

Series	CPU (vendor description)	Radio notes	Launch year (Espressif)
ESP32	Xtensa LX6, dual or single, 240 MHz typical	2.4 GHz Wi-Fi + Bluetooth 4.2 BR/EDR and LE	2016
ESP32-S2	Xtensa LX7, single core, 240 MHz	2.4 GHz Wi-Fi; no Bluetooth in the ESP-IDF comparison	2020
ESP32-C3	RISC-V, single core, 160 MHz	2.4 GHz Wi-Fi + Bluetooth 5 LE	2020
ESP32-S3	Xtensa LX7, dual core, 240 MHz	2.4 GHz Wi-Fi + Bluetooth 5 LE; 512 KB SRAM	2020
ESP32-C6	RISC-V HP core up to 160 MHz plus an LP core	2.4 GHz Wi-Fi 6, Bluetooth 5 LE, IEEE 802.15.4 (Thread/Zigbee)	2022 product page

ESP32, ESP32-S2, and ESP32-C3 rows follow Espressif's ESP-IDF v4.3 chip-series comparison. ESP32-S3 follows Espressif's 31 December 2020 announcement. ESP32-C6 follows Espressif's product page.[5][6][7][8]

A board labeled "ESP32" may be any of these. Firmware, pin maps, and radio APIs must match the variant.

5. Programming stacks

ESP-IDF. Espressif's official IoT Development Framework. C/C++ toolchain, FreeRTOS-based runtime, Wi-Fi and Bluetooth stacks, and idf.py to build and flash.[2]
Arduino-ESP32. Arduino APIs on top of ESP-IDF. Espressif's Arduino core 3.3.11 documents itself as based on ESP-IDF 5.5.[9]
MicroPython. A Python interpreter ported to ESP32, ESP32-C3, ESP32-C6, ESP32-S2, and ESP32-S3, with a serial REPL.[10]
ESPHome. YAML firmware for Home Assistant. The esp32 platform takes a variant that must match the silicon, including esp32, esp32s2, esp32s3, esp32c3, and esp32c6.[11]

All four flash firmware onto the chip. They differ in language and in how much of ESP-IDF they expose.

6. Voltage, pins, and power

Recommended digital supply is 3.3 V typical. Absolute maximum on those pins is 3.6 V. Some in-package flash/PSRAM parts need at least 3.0 V; parts without in-package memory may go down to 2.3 V.[1]

Not every GPIO is general-purpose. Espressif marks some pins input-only (no output, no on-chip pull resistors), some as strapping pins that set boot mode, and some as reserved for in-package flash or PSRAM. On DevKitC, GPIO0 is the Boot button; pulling it low at reset enters download mode.[1][3][11]

Radio current is large compared with sleep current. At 3.3 V and 25 °C, Espressif measures typical 240 mA transmit for 802.11b at +19.5 dBm, 95-100 mA Wi-Fi receive, and 10 µA in Deep-sleep (RTC memory can stay powered).[1] Average power depends on duty cycle, not on the peak TX number alone.

The on-chip radio is 2.4 GHz. ESP32 modules ship with a PCB antenna or an IPEX connector for an external antenna.[12]