Description
The ESP-32 WROOM 32 is a development board that is built around the powerful ESP32 system on a chip microcontroller. It is a development platform with programmer, Serial-to-USB module, voltage regulator and several peripherals. The dual core board has bluetooth and Wifi modules to fullfil various IOT and home automations tasks. Additionally, it comes with USB-to-UART interface, so that you can easily program it using Arduino IDE or other development environment.
If you’re familiar with the ESP8266, the ESP32 (and all boards based on it) is its sucessor. The ESP32 is loaded with lots of new features. The most relevant: it combines WiFi and Bluetooth wireless capabilities and it’s dual core for more complex tasks that demand multitasking.
Image: Function block diagram for Espressif’s ESP32
Features of the ESP32 include the following:
Processors:
CPU: Xtensa dual-core (or single-core) 32-bit LX6 microprocessor, operating at 160 or 240 MHz and performing at up to 600 DMIPS
Ultra low power (ULP) co-processor
Memory: 520 KiB SRAM
Wireless connectivity:
Wi-Fi: 802.11 b/g/n
Bluetooth: v4.2 BR/EDR and BLE
Peripheral interfaces:
12-bit SAR ADC up to 18 channels
2 × 8-bit DACs
10 × touch sensors (capacitive sensing GPIOs)
Temperature sensor
4 × SPI
2 × I²S interfaces
2 × I²C interfaces
3 × UART
SD/SDIO/CE-ATA/MMC/eMMC host controller
SDIO/SPI slave controller
Ethernet MAC interface with dedicated DMA and IEEE 1588 Precision Time Protocol support
CAN bus 2.0
Infrared remote controller (TX/RX, up to 8 channels)
Motor PWM
LED PWM (up to 16 channels)
Hall effect sensor
Ultra low power analog pre-amplifier
Security:
IEEE 802.11 standard security features all supported, including WFA, WPA/WPA2 and WAPI
Secure boot
Flash encryption
1024-bit OTP, up to 768-bit for customers
Cryptographic hardware acceleration: AES, SHA-2, RSA, elliptic curve cryptography (ECC), random number generator (RNG)
Power management:
Internal low-dropout regulator
Individual power domain for RTC
5uA deep sleep current
Wake up from GPIO interrupt, timer, ADC measurements, capacitive touch sensor interrupt
The ESP32 can be programmed in different programming environments. You can use:
Arduino IDE (Recommended)
Espressif IDF (IoT Development Framework)
Micropython
JavaScript
LUA
Image: ESP32-WROOM32-Board Pinout
Processor
The predecessor of ESP32, the ESP8266 has a builtin processor. However due to multitasking involved in updating the WiFi stack, most of the applications use a separate micro-controller for data processing, interfacing sensors and digital Input Output. With the ESP32 you may not want to use an additional micro-controller. ESP32 has Xtensa® Dual-Core 32-bit LX6 microprocessors, which runs up to 600 DMIPS. The ESP32 will run on breakout boards and modules from 160Mhz upto 240MHz . That is very good speed for anything that requires a microcontroller with connectivity options.
The two cores are named Protocol CPU (PRO_CPU) and Application CPU (APP_CPU). That basically means the PRO_CPU processor handles the WiFi, Bluetooth and other internal peripherals like SPI, I2C, ADC etc. The APP_CPU is left out for the application code. This differentiation is done in the Espressif Internet Development Framework (ESP-IDF). ESP-IDF is the official software development framework for the chip. Arduino and other implementations for the development will be based on ESP-IDF.
ESP-IDF uses freeRTOS for switching between the processors and data exchange between them. We have done numerous tutorials on freeRTOS and with all the bare-metal programming tutorials for ESP32 we will try and cover this aspect in detail. Although the feature set is great at the price at which the chip is being sold, the complexity is enormous. For the chip to get widely adopted, it will require huge efforts from Espressif as well as the community.
Internal Memory
The processors have closely tied internal memory for the following usage:
- 448 KBytes ROM for booting and core functions.
- 520 KBytes on-chip SRAM for data and instruction.
- 8 KBytes SRAM in RTC, which is called RTC SLOW Memory and can be accessed by the co-processor
- during the Deep-sleep mode.
- 8 KBytes 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.
- 1 Kbit of EFUSE, 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
External Flash and SRAM
Most of the modules like ESP32 Wroom use external Flash-W25Q32 (4M Bytes!) for storing the application code. The chip supports 4 x 16 MBytes of external QSPI flash and SRAM with hardware encryption based on AES.
ESP32 accesses the external QSPI flash and SRAM through high-speed caches.
- Up to 16 MBytes of external flash are memory-mapped onto the CPU code space, supporting 8, 16 and 32-bit access. Code execution is supported.
- Up to 8 MBytes of external SRAM are memory-mapped onto the CPU data space, supporting 8, 16 and 32-bit access. Data-read is supported on the flash and SRAM. Data-write is supported on the SRAM.
The WiFi
ESP32 implements TCP/IP, full 802.11 b/g/n/e/i WLAN MAC protocol, and Wi-Fi Direct specification. This means ESP 32 can speak to most of the WiFi Routers out there when used in station(client) mode. Also it is able to create an Access point with full 802.11 b/g/n/e/i.
ESP32 also supports the Wi-Fi Direct . Wifi-Direct is good option for peer-to-peer connection without the need of a access point. The Wifi-Direct is easier to setup and the data transfer speeds are much better than bluetooth. This could potential be used to configure ESP32 based projects from a phone/tablet that supports WiFi direct. There is no code example in the ESP-IDF SDK at the time of the writing. The ESP-IDF WiFi implementation has following features in the development:
- Infrastructure BSS Station mode / P2P mode / softAP mode support
- P2P Discovery, P2P Group Owner, P2P Group Client and P2P Power Management
- WPA/WPA2-Enterprise and WPS driver
- Additional 802.11i security features such as pre-authentication and TSN
- Open interface for various upper layer authentication schemes over EAP such as TLS, PEAP, LEAP, SIM, AKA or customer specific
- Clock/power gating combined with 802.11-compliant power management dynamically adapted to current connection condition providing minimal power consumption
- Adaptive rate fallback algorithm sets the optimal transmission rate and transmit power based on actual Signal Noise Ratio (SNR) and packet loss information
- Automatic re-transmission and response on MAC to avoid packet discarding on slow host environment
Bluetooth Classic and Bluetooth Low Energy(BLE)
ESP32 not just supports the latest BLE Bluetooth 4.2, it also supports classic bluetooth. It basically means it can speak to old and new bluetooth phones/tables. This could one of the best features especially, if you’re designing a device that needs to work with existing as well as new phones/tablets in the market. The ESP32 Bluetooth Radio and Baseband supports the following features:
- Class-1, class-2 and class-3 transmit output powers and over 30 dB dynamic control range
- π/4 DQPSK and 8 DPSK modulation
- High performance in NZIF receiver sensitivity with over 98 dB dynamic range
- Class-1 operation without external PA
- Internal SRAM allows full speed data transfer, mixed voice and data, and full piconet operation
- Logic for forward error correction, header error control, access code correlation, CRC, demodulation, encryption bit stream generation, whitening and transmit pulse shaping
- ACL, SCO, eSCO and AFH
- A-law, µ-law and CVSD digital audio CODEC in PCM interface
- SBC audio CODEC
- Power management for low power applications
- SMP with 128-bit AE
Classic Bluetooth Link Controller Features
- Device Discovery (inquiry and inquiry scan)
- Connection establishment (page and page scan)
- Multi connections
- Asynchronous data reception and transmission
- Synchronous links (SCO/eSCO)
- Master/Slave Switch
- Adaptive Frequency Hopping and Channel assessment
- Broadcast encryption
- Authentication and encryption
- Secure Simple Pairing
- Multi-point and scatternet management
- Sniff mode
- Connectionless Slave Broadcast (transmitter and receiver)
- Enhanced power control
- Ping
Bluetooth Low Energy Link Controller Features
- Advertising
- Scanning
- Multiple connections
- Asynchronous data reception and transmission
- Adaptive Frequency Hopping and Channel assessment
- Connection parameter update
- Date Length Extension
- Link Layer Encryption
- LE Ping
