Walfront ESP32 WiFi and Bluetooth Internet of Things Module

Product Information

• Module: ESP32
• Features: WiFi-BT-BLE MCU module

Pin Definitions

Pin Description

Strapping Pins

Functional Description

• CPU and Internal Memory
  The ESP32 module has a dual-core processor and internal memory for system operations.
• External Flash and SRAM
  The ESP32 supports external QSPI flash and SRAM, providing additional storage and encryption capabilities.
• Crystal Oscillators
  The module utilizes a 40-MHz crystal oscillator for timing and synchronization.
• RTC and Low-Power Management
  Advanced power-management technologies enable the ESP32 to optimize power consumption based on usage.

FAQ

• Q: What are the default strapping pins for ESP32?
  A: The default strapping pins for ESP32 are MTDI, GPIO0, GPIO2, MTDO, and GPIO5.
• Q: What is the power supply voltage range for ESP32?
  A: The power supply voltage range for ESP32 is 3.0V to 3.6V.

About This Document
This document provides the specifications for the ESP32 module.

Overview

ESP32 is a powerful, generic WiFi-BT-BLE MCU module that targets 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.

Pin Definitions

Pin Layout

Pin Description
ESP32 has 38 pins. See pin definitions in Table 1.

Table 1: Pin Definitions

Notice:
GPIO6 to GPIO11 are connected to the SPI flash integrated on the module and are not connected out.

Strapping Pins
ESP32 has five strapping pins:

• MTDI
• GPIO0
• GPIO2
• MTDO
• GPIO5

The software can read the values of these five bits from the 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 2 for a detailed boot-mode configuration by strapping pins.

Table 2: 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.
• The internal pull-up resistor (R9) for MTDI is not populated in the module, as the flash and SRAM in ESP32 only support a power voltage of 3.3 V (output by VDD_SDIO)

Functional Description

This chapter describes the modules and functions integrated into ESP32.

CPU and Internal Memory
ESP32 contains two low-power Xtensa® 32-bit LX6 microprocessors. 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.

External Flash and SRAM
ESP32 supports multiple external QSPI flash and SRAM chips. ESP32 also supports hardware encryption/decryption based on AES to pro-tect 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.

ESP32 integrates an 8 MB SPI flash and an 8 MB PSRAM for more memory space.

Crystal Oscillators
The module uses a 40-MHz crystal oscillator.

RTC and Low-Power Management
With the use of advanced power-management technologies, ESP32 can switch between different power modes.

Electrical Characteristics

Absolute Maximum Ratings
Stresses beyond the absolute maximum ratings listed in the table 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.

Table 3: Absolute Maximum Ratings

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 the ground. Please note that pins occupied by flash and/or PSRAM in the VDD_SDIO power domain were excluded from the test.

Recommended Operating Conditions
Table 4: Recommended Operating Conditions

DC Characteristics (3.3 V, 25 °C)
Table 5: DC Characteristics (3.3 V, 25 °C)

Notes: 

1. VDD is the I/O voltage for a particular power domain of pins.
2. For the 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, VOH>=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.

Wi-Fi Radio
Table 6: Wi-Fi Radio Characteristics

1. The device should operate in the frequency range allocated by regional regulatory authorities. The 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 be concerned about the output impedance.
3. Target TX power is configurable based on device or certification requirements.

Bluetooth/BLE

Radio 4.5.1 Receiver
Table 7: Receiver Characteristics – Bluetooth/BLE

Transmitter
Table 8: Transmitter Characteristics – Bluetooth/BLE

Reflow Profile

• Ramp-up zone — Temp.: <150°C Time: 60 ~ 90s Ramp-up rate: 1 ~ 3°C/s
• Preheating zone — Temp.: 150 ~ 200°C Time: 60 ~ 120s Ramp-up rate: 0.3 ~ 0.8°C/s
• Reflow zone — Temp.: >217°C 7LPH60 ~ 90s; Peak Temp.: 235 ~ 250°C (<245°C recommended) Time: 30 ~ 70s
• Cooling zone — Peak Temp. ~ 180°C Ramp-down rate: -1 ~ -5°C/s
• Solder — Sn&Ag&Cu Lead-free solder (SAC305)

OEM Guidance

1. Applicable FCC rules
   This module is granted by Single Modular Approval. It complies with the requirements of FCC part 15C, section 15.247 rules.
2. The specific operational use conditions
   This module can be used in IoT devices. The input voltage to the module is nominally 3.3V-3.6 V DC. The operational ambient temperature of the module is –40 °C ~ 65 °C. Only the embedded PCB antenna is allowed. Any other external antenna is prohibited.
3. Limited module procedures
   N/A
4. Trace antenna design
   N/A
5. RF exposure considerations
   The equipment complies with FCC radiation exposure limits set forth for an uncontrolled environment. This equipment should be installed and operated with a minimum distance of 20cm between the radiator and your body. If the equipment is built into a host as a portable usage, an additional RF exposure evaluation may be required as specified by 2.1093.
6. Antenna
   1. Antenna type: PCB antenna Peak gain: 3.40dBi
   2. Omni antenna with IPEX connector Peak gain2.33dBi
7. Label and compliance information
   An exterior label on OEM’s end product can use wording such as the following: “Contains Transmitter Module FCC ID: 2BFGS-ESP32WROVERE” or “Contains FCC ID: 2BFGS-ESP32WROVERE.”
8. Information on test modes and additional testing requirements
   • The modular transmitter has been fully tested by the module grantee on the required number of channels, modulation types, and modes, it should not be necessary for the host installer to re-test all the available transmitter modes or settings. It is recommended that the host product manufacturer, installing the modular transmitter, perform some investigative measurements to confirm that the resulting composite system does not exceed the spurious emissions limits or band edge limits (e.g., where a different antenna may be causing additional emissions).
   • The testing should check for emissions that may occur due to the intermixing of emissions with the other transmitters, digital circuitry, or due to the physical properties of the host product (enclosure). This investigation is especially important when integrating multiple modular transmitters where the certification is based on testing each of them in a stand-alone configuration. It is important to note that host product manufacturers should not assume that because the modular transmitter is certified they do not have any responsibility for final product compliance.
   • If the investigation indicates a compliance concern the host product manufacturer is obligated to mitigate the issue. Host products using a modular transmitter are subject to all the applicable individual technical rules as well as to the general conditions of operation in Sections 15.5, 15.15, and 15.29 to not cause interference. The operator of the host product will be obligated to stop operating the device until the interference has been corrected.
9. Additional testing, Part 15 Subpart B disclaimer The final host/module combination needs to be evaluated against the FCC Part 15B criteria for unintentional radiators to be properly authorized for operation as a Part 15 digital device.

The host integrator installing this module into their product must ensure that the final composite product complies with the FCC requirements by a technical assessment or evaluation of the FCC rules, including the transmitter operation and should refer to the guidance in KDB 996369. For host products with certified modular transmitters, the frequency range of investigation of the composite system is specified by rule in Sections 15.33(a)(1) through (a)(3), or the range applicable to the digital device, as shown in Section 15.33(b)(1), whichever is the higher frequency range of investigation When testing the host product, all the transmitters must be operating. The transmitters can be enabled by using publicly-available drivers and turned on, so the transmitters are active. In certain conditions, it might be appropriate to use a technology-specific call box (test set) where accessory 50 devices or drivers are not available. When testing for emissions from the unintentional radiator, the transmitter shall be placed in the receive mode or idle mode, if possible. If receive mode only is not possible then, the radio shall be passive (preferred) and/or active scanning. In these cases, this would need to enable activity on the communication BUS (i.e., PCIe, SDIO, USB) to ensure the unintentional radiator circuitry is enabled. Testing laboratories may need to add attenuation or filters depending on the signal strength of any active beacons (if applicable) from the enabled radio(s). See ANSI C63.4, ANSI C63.10 and ANSI C63.26 for further general testing details.

The product under test is set into a link/association with a partnering device, as per the normal intended use of the product. To ease testing, the product under test is set to transmit at a high-duty cycle, such as by sending a file or streaming some media content.

FCC Warning:
Any Changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment. This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) This device must accept any interference received, including interference that may cause undesired operation

Documents / Resources

Walfront ESP32 WiFi and Bluetooth Internet of Things Module [pdf] User Manual ESP32, ESP32 WiFi and Bluetooth Internet of Things Module, WiFi and Bluetooth Internet of Things Module, Bluetooth Internet of Things Module, Internet of Things Module, Things Module, Module

References

• User Manual