The sensor parameters of the equipment are transmitted via a 4mA to
20mA current loop, which is a robust sensor signalling standard for in-
dustrial process and control. These parameters are received by the
MCU through its on-chip analog-to-digital converter (ADC). The
MCU uses a PAN protocol stack, such as MiWi, to interface with an
IEEE802.15.4 transceiver which sends the processed sensor data to the
PAN coordinator. The engine which drives communication for the
entire PAN is the embedded MCU within the PAN coordinator. This
MCU interfaces to both the IEEE802.15.4 transceiver and GPRS module
through serial ports. The flash memory of the MCU is used to store the
map of the complete MiWi PAN, assign network addresses and establish
links to new sensor nodes. It also translates the PAN protocol data to
GPRS format to send over the GPRS network.
The MCU controls the GPRS module using Attention (AT) commands
for data transmission. The key factors for the selection of the embedded
MCU should be a high throughput, sufficient memory, and a wide
range of peripherals with support for Direct Memory Access (DMA). A
proven and robust wireless protocol stack, such as Microchip MiWi,
and access to a GPRS library is also useful to ensure a stable connection
between the PAN and GPRS network. Using a development board,
such as the Microchip PIC32 Wi-Fi Comm Board shown in figure 3(a),
can also help to fast-track the development of a wireless application.
Fleet management has become a popular application for M2M technol-
ogy. Vehicles fitted with GPS devices are tracked and their positions
communicated back to the monitoring system using GPRS or GSM
modules. The GPS module is used to provide the position coordinates
for the vehicle, whilst the CAN bus is used to collect data from different
modules within the vehicle, such as the antilock brake system (ABS),
engine control unit (ECU) and airbags. A 32-bit microcontroller
provides the engine for a CAN/GPRS gateway by interfacing to the
CAN bus, as well as to the GPRS and GPS modules, and translating
CAN data into the GPRS format before sending it over the GPRS
network to the Fleet Management Station. The Microchip M2M PICtail
daughter board contains GPS and GSM/GPRS modules which are
equipped with many AT commands in addition to the wide range of
features shown in figure 3(b). The M2M PICtail board provides all the
hardware information, software binaries including the stack, production
test bench design and test software, certification, training and docu-
mentation to enable an accelerated time-to-market. It enables a wireless,
ultra-compact, low-power communications solution for easy integration
into high-volume consumer, industrial and automotive designs. The
emergence of high-speed 4G communication and Internet Protocol
version 6 (IPv6) is enabling communication between machines to
become as commonplace as communication between people. The pro-
liferation of communication networks and the flexibility of silicon so-
lutions mean that the world is approaching a tipping point, at which
the number of people connected by the internet will be over-taken by
the number of devices and machines which are connected via the
internet. For designers, this means that there is increased pressure to
win a race to market for products which are equipped to deliver the full
possibilities of M2M communication.
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October 2013
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NTERNET OF
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HINGS
Figure 2. Remote monitoring implementation
Figure 3. Microchip demo boards for M2M communication
