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Tiny $7 IoT module packs WiFi, BLE, and sensors, runs FreeRTOS

Sep 6, 2016 — by Eric Brown 22,927 views

[Updated: Sept. 8] — SeeedStudio’s “ESP3212” COM taps Espressif’s IoT-focused ESP32 follow-on to the ESP8266 SoC, which uses a faster Tensilica LX6 MCU and adds BLE and sensors.

Espressif’s highly integrated and highly anticipated ESP32 follow-on to its popular ESP8266 wireless system-on-chip is now shipping. It’s available as part of a tiny SeedStudio ESP3212 computer-on-module, as well on Espressif’s own, slightly larger ESP-WROOM-32 reference design board and more expansive ESP32 Development Board.

The ESP8266 SoC has been somewhat of a Cinderella story in the IoT hacker world over the past two years. It has been especially popular among Arduino developers who have used ESP8266-based modules to add WiFi to Arduino projects without requiring a hybrid Linux-driven design that uses a WiFi module such as the Qualcomm AR9331.


Espressif, a small but fast growing company based in China, was surprised by the hit it had on its hands, and has in the past struggled to support and document the ESP8266 to meet the unexpectedly accelerating demand. Yet, hundreds of maker projects based on ESP8266 modules have emerged, thanks to a thriving open source community that has helped document the SoC and develop the open source toolchain for it.

The ESP8266 has been incorporated into a wide variety of more commercial IoT modules and single-board computers such as Arduino Srl’s Arduino Uno WiFi and Arduino STAR Otto. It’s also found in the new 4Duino-24 from 4D Systems, among other boards.

Espressif ESP32 SoC details

Espressif ESP32

Built with a 40nm TSMC low power process, the ESP32 wireless system-on-chip is not a replacement for the ESP8266, but a higher-end sibling. It similarly supports either standalone operation or use as a slave device, for example as a subsystem incorporated into an Arduino board.

Unlike the ESP8266, the ESP32 provides dual-mode Bluetooth 4.2 with legacy classic and LE (low energy) support. The SoC also offers faster, up to 150Mbps HT40 (40MHz channel width) 2.4GHz WiFi compared to the previous HT20 WiFi.

Espressif ESP32 SoC block diagram (left) and chip pin-out
(click images to enlarge)

The 802.11b/g/n/e/i WiFi is delivered with integrated baseband, stack, and LWIP, as well as onboard PCB and external IPEX antenna connectors. The 802.11i mode offers extra security features, and the 802.11e mode provides multiple queue management for QoS. WPS security and WiFi Direct support are also available.

Many of the improvements in the ESP32 come from the switch to Cadence’s 32-bit Tensilica Xtensa LX6 (PDF), a dual-core MCU announced in Jan. 2015 that advances to an 80MHz to 240MHz clock rate with 600 DMIPS performance. The ESP8266 uses an older, single-core, 80MHz Tensilica Xtensa L106 MCU.

Espressif’s ESP32 SoC is equipped with 520KB RAM (up from 160KB) and 448KB ROM, and supports up to 64MB of external flash (via up to four QSPI 16MB modules), as well as up to 8MB of external SRAM with 8-, 16-, and 32-bit access options. The device also builds in security features including WEP/WPA WiFi protocols, and hardware-accelerated AES, SHA2, RSA-4096 and Elliptical Curve crypto.

New ESP32 features offers a new Ethernet MAC and a wider range of interfaces. These include almost twice the number of GPIO signals with 36, all of which offer PWM/timer I/O support and 5v tolerance.

The GPIO offers new CAN 2.0, 10x capacitive touch interface, and temperature sensor interfaces, and in several cases supplies more signals per interface for other I/O. You now get 3x or 4x SPI and 2x or 3x UARTS, depending on conflicting product page and datasheet specs presented by Espressif.

GPIO is further available in 2x I2C, 2x I2S, 2x 10-bit DAC, and 12-bit, up to 16-channel ADC, compared to the previous 10-bit. Additional GPIO includes SD/eMMC/SDIO host and SDIO/SPI slave interfaces, as well as IR, motor PWM, LED PWM, and an OpenOCD debug interface. There’s also a Hall sensor, an ultra low noise analog amplifier, and a 32KHz oscillator, in addition to other timers and oscillators.

The ESP32 runs on 2.5V to 3.6V voltage, and offers power saving features including dynamic power sharing and a 5 μA or 2.5 μA deep sleep current, depending on the citation. Once again, the SoC supports a wide -40 to 125°C temperature range.

Espressif has thus far created two board designs around its ESP32 SoC, with other designs in the queue. The first “ESP32 Development Board” (shown below) was created primarily for in-house ESP32 debug, testing, and initial software development.

ESP32 Development Board
(click image to enlarge)

The initial board offers exposed pins for the GPIO, as well as a separate bank of UART pins. It provides an 2.2V to 3.6V power supply, a power jack, and several power on/off switches. Other features include a pair of 8-digit toggle switches and an antenna jack. The board’s design is said to support a -40 to 85°C operating temperature range, presumably to enable extended temperature testing and qualification of the ESP32 SoC.

In addition to the ESP32 Development Board, Espressif has also developed the design for a tiny, 25.5 x 18mm “ESP-WROOM-32” reference board (shown below). The ESP-WROOM-32 appears to be aimed at accelerating the proliferation of third-party ESP32-based modules, similar to those currently using Espressif’s ESP8266.

ESP-WROOM-32 schematic diagram and board details
(click images to enlarge)

Schematics for the ESP-WROOM-32 reference design are already available. Additionally, the board is supported by an open-source FreeRTOS SDK, which is designed to run on a Debian or Ubuntu Linux based x86 desktop. Future reference designs are expected to support features such as LCD interfaces, touchpads, and serial-to-USB connections.

SeeedStudio’s ESP32 based ESP3212 module

The SeeedStudio ESP3212 module appears to be one of the first boards to be derived from Espressif’s slightly larger ESP-WROOM-32 reference design. The company is aiming the ESP3212 at low-power IoT sensor hubs, loggers, video streamer attachments, and other home automation and mesh network applications.

SeeedStudio ESP3212 front and rear views
(click images to enlarge)

The 24 x 16 x 3mm ESP3212 module adds an RTC with 16KB SRAM, plus 4MB SPI flash storage via a Winbond W25Q32FV module. The ESP3212 module runs on 3.0V to 3.6V with an average working current of 90mA. The tiny board also includes a built-in 3DBi PCB antenna. The SeeedStudio module supports a wide operating temperature range of -40 to 50°C.

SeeedStudio ESP3212 angled view and module details
(click images to enlarge)

Not surprisingly, the ESP3212 ships with the ESP32’s FreeRTOS SDK firmware, and with open source toolchains based on GCC.

Further information

SeeedStudio’s ESP3212 module, based on the Espressif ESP32 SoC, is available for pre-order at $6.95 apiece in single helpings ranging down to $5.91 apiece for 50-piece orders. Single unit shipments to the U.S. cost $4.79, but volume orders get significant discounts, says Seeed. After quickly shipping out the initial batch, the module will now ship around Oct. 10. More information may be found at Seeed’s ESP3212 product page.

Espressif’s ESP32 SoC is now shipping. More information may be found at this ESP32 product page, this GitHub page, and this unofficial ESP32 resources site. More information about the company’s ESP-WROOM-32, which does not appear to be shipping currently, may be found on the company’s website, here, including in an ESP-WROOM-32 datasheet [PDF].

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10 responses to “Tiny $7 IoT module packs WiFi, BLE, and sensors, runs FreeRTOS”

  1. Lyubomyr says:

    Hello. May I, please, ask for a link where to buy a ESP32 development board?

  2. Hamilton says:

    Module msrp is actually $3.75 just wait for the supply chain to catch up.

  3. Pure Engineering (@PureEngineerLLC) says:

    Group buy for the module here. so far the best price

  4. Shital says:


    Is this just a wifi BLE and sensor addon board or complete development board, i mean if i buy this board for $7 will i be able to proceed learning FreeRTOS?

  5. Philip W (@dude8604) says:

    First ESP3212 breakout board immediately available

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