IEEE Consumer Electronics Magazine - April 2017 - 59

with a preprogrammed attention commands (AT) set and can be
easily interfaced with various microcontrollers. It has 1 MB of
flash memory, works on the 802.11 b/g/n protocol, and supports
Wi-Fi Direct (P2P) and soft-access point. It comes with an integrated transmission-control protocol/Internet protocol stack and a
self-calibrated radio-frequency antenna, which allows it to operate under almost all conditions. However, this module lacks 3-V
to 5-V logic-level shifting.
The second module is the SparkFun Blynk Board [3],
which is an ESP8266-based board with nine general-purpose
input/output (GPIO) pins supporting serial-peripheral interface (SPI) and inter-IC (I2C) communication protocols. It has
an onboard lithium-polymer (Li-Po) battery connector and
charging port. It also comes with onboard Future Technology
Devices International for reprogramming, red-green-blue
light-emitting diode (RGB LED), analog-to-digital converter
(ADC), and temperature and humidity sensor. It can automatically connect to Blynk Cloud and can be controlled with the
Blynk app, which is available for both the iOS and Android
operating systems. This module is a bit more costly than the
first one. Many people have used these modules for fascinating projects such as Home Automation in the Cloud with the
ESP8266 [4] and a solar-powered file server [5].
A new ESP-series module-the ESP32 [6], [7]-is set to
arrive on the market. It will feature upgraded Wi-Fi that will support HT40 speed (150 Mb/s), Bluetooth Low Energy, a dualcore processor 2x Tensilica L108 clocked at 160 MHz, and
peripherals such as capacitive touch, ADCs, digital-to-analog
converters (DACs), I2C, universal asynchronous receiver/transmitter (UART), SPI, and pulsewidth modulation (PWM).

Hobbyists have developed interesting projects [9] powered
by Arduino Yun, such as a cat camera, a bathroom occupancy
detector, an Internet-enabled football trophy, and many more.
Arduino also offers the Genuino MKR1000 [10] with the
capability of a SAMD21 Cortex-M0+ 32-b low-power ARM
MCU and WINC1500 low-power 2.4-GHz IEEE 802.11
b/g/n Wi-Fi. It also includes a Li-Po charging circuit. It
comes with Cryptochip for secure communication. Its I/O
pins can withstand only 3.3 V, which necessitates the use of a
logic-level shifter for 5-V devices.
Arduino is in the process of launching its much-acclaimed
Arduino TRE board [11], which is based on the 1-GHz Sitara
AM335x processor, suitable for computationally complex
applications and algorithms, high-speed communications,
telemetry hubs that gather data wirelessly from sensor nodes,
and many other IoT-based applications.

RASPBERRY Pi
Raspberry Pi 2 is a single-board computer that comes with a
quad-core ARM7 800 MHz, a Videocore IV 250 MHz as a
graphics processing unit, 1 GB of random access memory
(RAM), 40 GPIO pins, four USB 2.0 ports, one Ethernet port,
one HDMI connector, and one micro-SD card slot [12].

ARDUiNO
Arduino offers a vast range of open-source boards capable of
performing tasks from blinking an LED to publishing material online to handling heavy networking tasks. This is made
possible through the Arduino software integrated development environment (IDE), based on processing.
Arduino has a broad range of boards, from simple 8-b
microcontroller boards to products for wearables, IoT items,
three-dimensional (3-D) printing, and much more. There is a
large community of students, hobbyists, and researchers doing
projects on Arduino boards and providing many tutorials, and
support is available online. For supporting IoT applications,
the company offers the Arduino Yun (Figure 3), with onboard
Wi-Fi (IEEE 802.11 b/g/n) and Ethernet (IEEE 802.3
10/100Mb/s) [8]. It has an ATmega32u4 with a clock speed of
16 Mhz and an Atheros AR9331 (MIPS @ 400 MHz), which
backs a Linux distribution called OpenWrt-Yun. The board has
a micro-SD card slot, a USB-A port, seven PWM pins, 12 analog inputs, and a micro-USB connection.
The GPIO pins of the Atheros AR9331 are not accessible,
as these are tied to the ATmega32u4. SPI is available only on
the in-circuit serial programming (ICSP) header, which is
supported by the SPI library. Hence, any shield that uses SPI
and does not have a six-pin ICSP connector will not work
with Arduino Yun.

FIGURE 2. An ESP8266 Wi-Fi module. (Photo courtesy of SparkFun.)

FIGURE 3. An Arduino Yun board. (Photo courtesy of Arduino.)

APRIL 2017

IEEE ConsumEr ElECtronICs magazInE

Table of Contents for the Digital Edition of IEEE Consumer Electronics Magazine - April 2017