ESP32 is a low-cost, low-power system on a chip (SoC) series microcontroller with WiFi & dual-mode Bluetooth capabilities ^[1]. ESP32 SoC is highly integrated with built-in antenna switches, power amplifier, low-noise receive amplifier, filters, and power management modules. Inside all family of ESP32 there is a single-core or dual-core Tensilica Xtensa LX6 microprocessor with a clock rate of up to 240 MHz. ESP32 is designed for mobile, wearable electronics, and Internet-of-Things (IoT) applications. It features all the state-of-the-art characteristics of low-power chips, including fine-grained clock gating, multiple power modes, and dynamic power scaling. For now the ESP32 family includes the following chips in mass production:

• ESP32-D0WD-V3 (Figure 1) ,
  
• ESP32-U4WDH (Figure 2),
  
• ESP32-PICO-D4 – SiP (system in package) (Figure 3) – additionally contains crystal oscillator, 4MiB flash memory, filter capacitors and RF matching links,
  
• ESP32-PICO-V3 – SiP (system in package ) – new core (ECO V3)
• ESP32-PICO-V3-02 – SiP (Figure 4 – package size is slightly thicker - 7 × 7 × 1.11 (mm), chip integrates 8 MiB flash and 2 MiB PSRAM with different pin layout.
  

and older chips, not for new designs:

• ESP32-D0WDQ6 (Figure 5),
  
• ESP32-D0WDQ6-V3,
  
• ESP32-D0WD (Figure 6),
  
• ESP32-S0WD (Figure 8),
  

Functional block diagramm of ESP32 chip is shown in the (Figure 9). Main common features of the ESP32 are: ^{[2, 3]}.

Processors

• Main processor: Tensilica Xtensa 32-bit LX6 microprocessor.
  • Cores: 2 or 1 (depending on variation). (All chips in the ESP32 series are dual-core except for ESP32-S0WD, which is single-core.)
  • Internal 8 Mhz oscillator with calibration.
  • External 2 MHz to 60 MHz crystal oscillator (40 MHz only for WiFi/BT functionality).
  • External 32 kHz crystal oscillator for RTC with calibration.
  • Clock frequency: up to 240 MHz.
  • Performance: up to 600 DMIPS.
• Ultra low power co-processor: allows you to do ADC conversions, I2C connecting, computation, and level thresholds while in a deep sleep.

Wireless connectivity

• WiFi: 802.11 b/g/n/e/i (802.11n @ 2.4 GHz up to 150 Mbit/s) with simultaneous Infrastructure BSS Station mode/SoftApp mode/Promiscuous mode.
• Bluetooth: v4.2 BR/EDR and Bluetooth Low Energy (BLE) with multi-connections Bt and BLE and simultaneous advertising and scanning capability.

Memory: Internal memory

• ROM: 448 KiB (for booting and core functions).
• SRAM: 520 KiB (for data and instruction).
• RTC fast SRAM: 8 KiB (for data storage and main CPU during RTC Boot from the deep-sleep mode).
• RTC slow SRAM: 8 KiB (for co-processor accessing during deep-sleep mode).
• eFuse: 1 Kibit (of which 256 bits are used for the system (MAC address and chip configuration) and the remaining 768 bits are reserved for customer applications, including Flash-Encryption and Chip-ID).
• Embedded flash (flash connected internally via IO16, IO17, SD_CMD, SD_CLK, SD_DATA_0 and SD_DATA_1 on ESP32-D2WD and ESP32-PICO-D4):
  • 0 MiB (ESP32-D0WDQ6, ESP32-D0WD, and ESP32-S0WD chips),
  • 2 MiB (ESP32-D2WD chip).

External Flash & SRAM

• ESP32 supports up to four 16 MiB external QSPI flashes and SRAMs with hardware encryption based on AES to protect developers' programs and data. ESP32 can access the external QSPI flash and SRAM through high-speed caches.
• Up to 16 MiB of external flash are memory-mapped onto the CPU code space, supporting 8-bit, 16-bit and 32-bit access. Code execution is supported.
• Up to 8 MiB of external flash/SRAM memory is mapped onto the CPU data space, supporting 8-bit, 16-bit and 32-bit access. Data-read is supported on the flash and SRAM. Data-write is supported on the SRAM.

ESP32 chips with embedded flash do not support the address mapping between external flash and peripherals.

Peripheral Input/Output

• Rich peripheral interface with DMA that includes capacitive touch (10× touch sensors).
• 12-bit ADCs (analog-to-digital converter) up to 18 channels.
• 2 × 8 bit DACs (digital-to-analog converter).
• 2 × I²C (Inter-Integrated Circuit.
• 3x UART (universal asynchronous receiver/transmitter).
• CAN 2.0 (Controller Area Network).
• 4 × SPI (Serial Peripheral Interface).
• 2 × I²S (Integrated Inter-IC Sound).
• RMII (Reduced Media-Independent Interface).
• Motor PWM (pulse width modulation).
• LED PWM up to 16 channels.
• Hall sensor.
• Internal temperature sensor.

Security

• Secure boot.
• Flash encryption.
• IEEE 802.11 standard security features all supported, including WFA, WPA/WPA2 and WAPI.
• 1024-bit OTP, up to 768-bit for customers.
• Cryptographic hardware acceleration:
  • AES,
  • SHA-2,
  • RSA,
  • elliptic curve cryptography (ECC),
  • random number generator (RNG).

The company also produces ready-made modules using the aforementioned processors^[4]. These modules combines ESP32 microcontroller and additional components mounted on PCB with EM shield:(Table 1).

The ESP32-PICO-D4^[5] is a System-in-Package (SiP) module that is based on ESP32. ESP32-PICO-D4 integrates all peripheral components, including a crystal oscillator, flash, filter capacitors and RF matching links in one single package. The module has a size as small as 7.0 mm × 7.0 mm × 0.94 mm, thus requiring minimal PCB area. Main characteristics that distinguish it from the ESP32 family are:

• Integrated crystal oscillator, filter capacitors and RF matching circuit,
  
• Internal built-in memory 4 MiB SPI flash,
  
• chip size 7.0 mm × 7.0 mm × 0.94 mm.
  

The ESP32-PICO-V3^[6] is a System-in-Package (SiP) module that is based on ESP32 but with a new ECO V3 wafer. The module has a size as small as 7.0 mm × 7.0 mm × 1.11 mm. Distinguishing features from the ESP32-PICO-D4 chips are:

• New silicone wafer ECO V3,
  
• 16 KiB SRAM in RTC,
  
• chip size 7.0 mm × 7.0 mm × 1,11 mm.
  

The ESP32-PICO-V3-02^[7] is based on ESP32-PICO-V3 with additional SPi flash and SPI PSRAM. Distinguishing features from the ESP32-PICO-V3 chips are:

• Internal built-in SPI flash memory 8 MiB,
  
• Internal built-in SPI PSRAM memory 2 MiB,
  
• additional GPIO pin - GPIO20,
  
• For chip security purpose, flash pins DI, DO, /HOLD, /WP and PSRAM pins SI/SIO0, SO/SIO1, SIO2, SIO3 are not led out.

The company also produces ready-made modules using the ESP32-PICO SOCs ^{[8, 9]}. These modules combines ESP32 microcontroller and additional components mounted on PCB with EM shield (Table 2)“

To accelerate the design of circuits, developers can use specially prepared sets with ESP32 which are ready to use. The original Espressif best known small development boards are:

• ESP32-DevkitC (Figure 17);
• ESP32-PICO-KIT-V4 (Figure 18),
• ESP32-PICO-KIT-1 with ESP32-PICO-V3 (Figure 19),
• ESP32-PICO-DevKitM-2 with ESP32-PICO-Mini-02 (Figure 20),

Each ESP32 is equipped with standard 38/40-pis male connector containing universal GPIO ports, VCC 3.3/5 V, GND, CLK, I2C/SPI buses pins which developers can use to connect their external sensors, switches and other controlled devices to the ESP32 board and then program their behaviour within the code loaded to the board.

• ESP32-DevkitC v2 pins (Figure 21).

• ESP32-PICO D4 pins (Figure 22).

• ESP32 Wemos Pro pins (Figure 23).