05.03.2022, 13:11
NXP Introduction to IoT Components
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Though they will generate and process reams of analyzable data, NFC devices are not usually considered IoT devices. (Neither are mobile handsets.)
They are not generally
intended as data gathering nodes. At best, NFC devices may be considered special-purpose IoT processing nodes.
Intended as credit card replacements, the NFC devices embedded in cell phones are increasingly available as dedicated transportation cards, NFC devices are intended to quickly
process financial transactions. You swipe the NFC device at a point-of-sale terminal, and the appropriate fee is automatically subtracted from your bank account or added to your
monthly cell phone bill.
It may be worth understanding how NFC transactions actually work — perhaps purchasing a development kit — to explore their utility for IoT data gathering.
The NFC transceiver
operates as a short-distance RFID tag, enabling users to perform contactless data exchanges, to access digital content, and connect electronic devices simply by bringing RFID
transmitters and receivers in close proximity (e.g., 4 or 5 cm) to each other. The connection is an inductive coupling (magnetic coupling between two flat coils: one in the transmitter,
another in the receiver).
The NFC reader will automatically detect the presence of a transmitter operating at 13.56 MHz. Electrically
stimulated by the NFC reader, the card will respond with a series of RF
data bursts: One to identify the card and its accounts; additional bursts to complete the transaction, and return to a passive (unreadable) sleep state. Current NFC standards
determine not only the contactless operating requirements, but also the data formats and transfer rates.
While currently used
for financial transactions, including ATMs, turnstiles, vending machines and point-of-sale terminals, they can also support raw data exchanges between mobile
phones, PDAs, and personal computers. Household applications for NFC can include home door locks, lighting controls and thermostats. Swipe your card
on the door post of your
dark house, and it could turn on your lights.
Recently introduced versions of the NFC transceiver modules offer more transmit power than previous versions for increased data integrity and user’s ease of use. An ARM Cortex-
M0 enables a fast wake up from sleep. Contactless NFC chips include coil interfaces and I2C metal connections — and sell for as little as $0.30 per chip.
Component Choices by Application (Key Specifications)
IoT components will inevitably bridge the gap from smart cities to smart home monitoring and control. Invariably there are key specifications affecting your choice of components for
IoT sensor nodes. In addition to the three main building blocks — microcontrollers, sensors and communications ports — you’ll need to specify signal-conditioning components, and
power management devices. A summary of relevant devices and key specifications are listed below.
How much intelligence in the sensor node? How much intelligence in the cloud? The answer will dictate whether you use an 8-, 16- or 32-bit processor,
how much memory is
attached, and what clock rate you’ll use to run your IoT node.
Where is the data concentrated and how is it communicated from the remote sensor node? (ZigBee, BTLE, Ethernet)
How much resolution and what kind of sampling rate is required for sensor signal conditioning? Data Converters for jet engines or truck weight stations may require 16- or 18-
bit resolution; machine tools could make good use of 12 bits.
Are the power sources batteries, offline power supplies, or energy harvesters? A key concern is energy transfer efficiency; 95% or more. You don’t want your voltage regulator
tapping your supply voltage.
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