ESP32-WROOM-32D & ESP32-WROOM-32U Datasheet

1 Overview

ESP32-WROOM-32D and ESP32-WROOM-32U are powerful, generic Wi-Fi+BT+BLE MCU modules that target a wide variety of applications, ranging from low-power sensor networks to the most demanding tasks, such as voice encoding, music streaming and MP3 decoding.

ESP32-WROOM-32U is different from ESP32-WROOM-32D in that ESP32-WROOM-32U integrates a U.FL connector. For detailed information of the U.FL connector please see Chapter 10. Note that the information in this data sheet is applicable to both modules. Any differences between them will be clearly specified in the course of this document. Table 1 lists the difference between ESP32-WROOM-32D and ESP32-WROOM-32U.

At the core of the two modules is the ESP32-D0WD chip that belongs to the ESP32 series* of chips. The chip embedded is designed to be scalable and adaptive. There are two CPU cores that can be individually controlled, and the CPU clock frequency is adjustable from 80 MHz to 240 MHz. The chip also has a low-power co-processor that can be used instead of the CPU to save power while performing tasks that do not require much computing power, such as monitoring of peripherals. ESP32 integrates a rich set of peripherals, ranging from capacitive touch sensors, Hall sensors, SD card interface, Ethernet, high-speed SPI, UART, I2S and I2C.

Note: * For details on the part numbers of the ESP32 family of chips, please refer to the document ESP32 Datasheet.

The integration of Bluetooth®, Bluetooth LE and Wi-Fi ensures that a wide range of applications can be targeted, and that the module is all-around: using Wi-Fi allows a large physical range and direct connection to the Internet through a Wi-Fi router, while using Bluetooth allows the user to conveniently connect to the phone or broadcast low energy beacons for its detection. The sleep current of the ESP32 chip is less than 5 µA, making it suitable for battery powered and wearable electronics applications. The module supports a data rate of up to 150 Mbps, and 20 dBm output power at the antenna to ensure the widest physical range. As such the module does offer industry-leading specifications and the best performance for electronic integration, range, power consumption, and connectivity.

The operating system chosen for ESP32 is freeRTOS with LwIP; TLS 1.2 with hardware acceleration is built in as well. Secure (encrypted) over the air (OTA) upgrade is also supported, so that users can upgrade their products even after their release, at minimum cost and effort.

Table 2 provides the specifications of ESP32-WROOM-32D and ESP32-WROOM-32U.

Notice:

1. ESP32-WROOM-32D and ESP32-WROOM-32U with 8 MB flash or 16 MB flash are available for custom order.
2. ESP32-WROOM-32D and ESP32-WROOM-32U with high temperature range (-40 °C ~ +105 °C) option are available for custom order. 4 MB SPI flash is supported on the high temperature range version.
3. For detailed ordering information, please see ESP Product Selector.

2 Pin Definitions

2.1 Pin Layout

Note: Figure 1: ESP32-WROOM-32D Pin Layout (Top View)

The pin layout of ESP32-WROOM-32U is the same as that of ESP32-WROOM-32D, except that ESP32-WROOM-32U has no keepout zone.

2.2 Pin Description

The ESP32-WROOM-32D and ESP32-WROOM-32U have 38 pins. See pin definitions in Table 3.

Notice: * Pins SCK/CLK, SDO/SD0, SDI/SD1, SHD/SD2, SWP/SD3 and SCS/CMD, namely, GPIO6 to GPIO11 are connected to the integrated SPI flash integrated on the module and are not recommended for other uses.

2.3 Strapping Pins

ESP32 has five strapping pins, which can be seen in Chapter 6 Schematics:

• MTDI
• GPIO0
• GPIO2
• MTDO
• GPIO5

Software can read the values of these five bits from register "GPIO_STRAPPING”.

During the chip's system reset release (power-on-reset, RTC watchdog reset and brownout reset), the latches of the strapping pins sample the voltage level as strapping bits of "0" or "1", and hold these bits until the chip is powered down or shut down. The strapping bits configure the device's boot mode, the operating voltage of VDD_SDIO and other initial system settings.

Each strapping pin is connected to its internal pull-up/pull-down during the chip reset. Consequently, if a strapping pin is unconnected or the connected external circuit is high-impedance, the internal weak pull-up/pull-down will determine the default input level of the strapping pins.

To change the strapping bit values, users can apply the external pull-down/pull-up resistances, or use the host MCU's GPIOs to control the voltage level of these pins when powering on ESP32.

After reset release, the strapping pins work as normal-function pins. Refer to Table 4 for a detailed boot-mode configuration by strapping pins.

Note:

• Firmware can configure register bits to change the settings of "Voltage of Internal LDO (VDD_SDIO)" and "Timing of SDIO Slave" after booting.
• Both ESP32-WROOM-32D and ESP32-WROOM-32U integrate a 3.3 V SPI flash, so the pin MTDI cannot be set to 1 when the modules are powered up.

3 Functional Description

This chapter describes the modules and functions integrated in ESP32-WROOM-32D and ESP32-WROOM-32U.

3.1 CPU and Internal Memory

ESP32-D0WD contains a dual-core Xtensa® 32-bit LX6 MCU. The internal memory includes:

• 448 KB of ROM for booting and core functions.
• 520 KB of on-chip SRAM for data and instructions.
• 8 KB of SRAM in RTC, which is called RTC FAST Memory and can be used for data storage; it is accessed by the main CPU during RTC Boot from the Deep-sleep mode.
• 8 KB of SRAM in RTC, which is called RTC SLOW Memory and can be accessed by the co-processor during the Deep-sleep mode.
• 1 Kbit of eFuse: 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.

3.2 External Flash and SRAM

ESP32 supports multiple external QSPI flash and SRAM chips. More details can be found in Chapter SPI in the ESP32 Technical Reference Manual. ESP32 also supports hardware encryption/decryption based on AES to protect developers' programs and data in flash.

ESP32 can access the external QSPI flash and SRAM through high-speed caches.

• The external flash can be mapped into CPU instruction memory space and read-only memory space simultaneously.
  • When external flash is mapped into CPU instruction memory space, up to 11 MB + 248 KB can be mapped at a time. Note that if more than 3 MB + 248 KB are mapped, cache performance will be reduced due to speculative reads by the CPU.
  • When external flash is mapped into read-only data memory space, up to 4 MB can be mapped at a time. 8-bit, 16-bit and 32-bit reads are supported.
• External SRAM can be mapped into CPU data memory space. Up to 4 MB can be mapped at a time. 8-bit, 16-bit and 32-bit reads and writes are supported.

Both ESP32-WROOM-32D and ESP32-WROOM-32U integrate a 4 MB of external SPI flash. The integrated SPI flash is connected to GPIO6, GPIO7, GPIO8, GPIO9, GPIO10 and GPIO11. These six pins cannot be used as regular GPIOs.

3.3 Crystal Oscillators

The module uses a 40-MHz crystal oscillator.

3.4 RTC and Low-Power Management

With the use of advanced power-management technologies, ESP32 can switch between different power modes. For details on ESP32's power consumption in different power modes, please refer to section "RTC and Low-Power Management” in ESP32 Datasheet.

4 Peripherals and Sensors

Please refer to Section Peripherals and Sensors in ESP32 Datasheet.

Note: External connections can be made to any GPIO except for GPIOs in the range 6-11. These six GPIOs are connected to the module's integrated SPI flash. For details, please see Section 6 Schematics.

5 Electrical Characteristics

5.1 Absolute Maximum Ratings

Stresses beyond the absolute maximum ratings listed in Table 5 below may cause permanent damage to the device. These are stress ratings only, and do not refer to the functional operation of the device that should follow the recommended operating conditions.

Notes:

1. The module worked properly after a 24-hour test in ambient temperature at 25 °C, and the IOs in three domains (VDD3P3_RTC, VDD3P3_CPU, VDD_SDIO) output high logic level to ground. Please note that pins occupied by flash and/or PSRAM in the VDD_SDIO power domain were excluded from the test.
2. Please see Appendix IO_MUX of ESP32 Datasheet for IO's power domain.

5.2 Recommended Operating Conditions

5.3 DC Characteristics (3.3 V, 25 °C)

Notes:

1. Please see Appendix IO_MUX of ESP32 Datasheet for IO's power domain. VDD is the I/O voltage for a particular power domain of pins.
2. For VDD3P3_CPU and VDD3P3_RTC power domain, per-pin current sourced in the same domain is gradually reduced from around 40 mA to around 29 mA, V_OH>=2.64 V, as the number of current-source pins increases.
3. Pins occupied by flash and/or PSRAM in the VDD_SDIO power domain were excluded from the test.

5.4 Wi-Fi Radio

Notes:

1. Device should operate in the frequency range allocated by regional regulatory authorities. Target operating frequency range is configurable by software.
2. For the modules that use IPEX antennas, the output impedance is 50 Ω. For other modules without IPEX antennas, users do not need to concern about the output impedance.
3. Target TX power is configurable based on device or certification requirements.

5.5 BLE Radio

5.5.1 Receiver

5.5.2 Transmitter

5.6 Reflow Profile

A graph shows the temperature profile for reflow soldering. The zones are Ramp-up, Preheating, Reflow, and Cooling. Specific temperatures and times are indicated for each zone.

• Ramp-up zone: Temp.: 25~150 °C, Time: 60 ~ 90 s, Ramp-up rate: 1~3°C/s
• Preheating zone: Temp.: 150~200 °C, Time: 60 ~ 120 s
• Reflow zone: Temp.: >217 °C, Time: 60 ~ 90 s; Peak Temp.: 235 ~ 250 °C, Time: 30 ~ 70 s
• Cooling zone: Peak Temp. ~ 180 °C, Ramp-down rate: -1 ~ -5 °C/s
• Solder: Sn-Ag-Cu (SAC305) lead-free solder alloy

Note: Solder the module in a single reflow.

6 Schematics

Figure 3: ESP32-WROOM-32D Schematics

Figure 4: ESP32-WROOM-32U Schematics

7 Peripheral Schematics

Figure 5: ESP32-WROOM-32D & ESP32-WROOM-32U Peripheral Schematics

Note:

• Soldering Pad 39 to the Ground is not necessary for a satisfactory thermal performance. If users do want to solder it, they need to ensure that the correct quantity of soldering paste is applied.
• To ensure the power supply to the ESP32 chip during power-up, it is advised to add an RC delay circuit at the EN pin. The recommended setting for the RC delay circuit is usually R = 10 kΩ and C = 1 µF. However, specific parameters should be adjusted based on the power-up timing of the module and the power-up and reset sequence timing of the chip. For ESP32's power-up and reset sequence timing diagram, please refer to Section Power Scheme in ESP32 Datasheet.

8 Physical Dimensions

Figure 6: Physical Dimensions of ESP32-WROOM-32D

Figure 7: Physical Dimensions of ESP32-WROOM-32U

9 Recommended PCB Land Pattern

Figure 8: Recommended PCB Land Pattern of ESP32-WROOM-32D

Figure 9: Recommended PCB Land Pattern of ESP32-WROOM-32U

10 U.FL Connector Dimensions

Figure 10: ESP32-WROOM-32U U.FL Dimensions

11 Learning Resources

11.1 Must-Read Documents

The following link provides documents related to ESP32.

• ESP32 Datasheet: This document provides an introduction to the specifications of the ESP32 hardware, including overview, pin definitions, functional description, peripheral interface, electrical characteristics, etc.
• ESP32 ECO V3 User Guide: This document describes differences between V3 and previous ESP32 silicon wafer revisions.
• ECO and Workarounds for Bugs in ESP32: This document details hardware errata and workarounds in the ESP32.
• ESP-IDF Programming Guide: It hosts extensive documentation for ESP-IDF ranging from hardware guides to API reference.
• ESP32 Technical Reference Manual: The manual provides detailed information on how to use the ESP32 memory and peripherals.
• ESP32 Hardware Resources: The zip files include the schematics, PCB layout, Gerber and BOM list of ESP32 modules and development boards.
• ESP32 Hardware Design Guidelines: The guidelines outline recommended design practices when developing standalone or add-on systems based on the ESP32 series of products, including the ESP32 chip, the ESP32 modules and development boards.
• ESP32 AT Instruction Set and Examples: This document introduces the ESP32 AT commands, explains how to use them, and provides examples of several common AT commands.
• ESP Product Selector

11.2 Must-Have Resources

Here are the ESP32-related must-have resources.

• ESP32 BBS: This is an Engineer-to-Engineer (E2E) Community for ESP32 where you can post questions, share knowledge, explore ideas, and help solve problems with fellow engineers.
• ESP32 GitHub: ESP32 development projects are freely distributed under Espressif's MIT license on GitHub. It is established to help developers get started with ESP32 and foster innovation and the growth of general knowledge about the hardware and software surrounding ESP32 devices.
• ESP32 Tools: This is a webpage where users can download ESP32 Flash Download Tools and the zip file "ESP32 Certification and Test".
• ESP-IDF: This webpage links users to the official IoT development framework for ESP32.
• ESP32 Resources: This webpage provides the links to all available ESP32 documents, SDK and tools.

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