NXP uses smartphone audio jack to connect to IoT sensors - Embedded.com

NXP uses smartphone audio jack to connect to IoT sensors

In 2010, students and staff at the University of Michigan came up with a way to use the audio jack on almost any smartphone, mobile phone, MP3 player/recorder and some audio book readers operate as a data port.

Called Project HiJack, it triggered wide spread use by do it yourselfers as a way to add another channel of data when all the other communications ports on their devices were busy.

Their idea was smple: hijack power and bandwidth from a mobile phone’s audio interface to create a cubic-inch peripheral sensor ecosystem. If that was possible a whole range of possibilities would open up that allowed use of the smartphone as not only an additional way to link to the Internet,but to also act as a hub for collecting and crunching sensor data, supervising communication with all the wireless devices in its associated network and presenting all this to the user.

Their original HiJack platform energy unit can supply 7.4 mW to a load with 47% power conversion efficiency, using components totaling a mere $2.34. Beyond mobile phones their ideas moved more in the direction of wireless sensor, machine to machine and internet of things applications using the audio jack as the link to various sensorboards to detect various signals such as carbon monoxide and ozone.

Since then the idea has slowly taken off, especially now in the era of consumer IoTs and wearable devices where all the comm channels possible are needed for simultanous operations. The project won the support and bulding blocks donated by a variety of companies: Energy Micro  (now part of Silicon Labs), Google, Nokia, Microsoft, and Texas Instruments. But the earliest commercial use of HiJack that I remeber seeing was in 2012, with its use by ChargeAnywhere, as a dataport to allow its device to turn a mobile or smartphone into a credit card reader.

NXP joins the audio jack connection
Now NXP Semiconductor has taken notice of its potential in a side variety of consumer IoT applications where the smartphone is being thought of as the central hub to collect readings from sensors, control switches, data collected by external meters. For these kinds of things tying up the phone's high-bandwidth USB/Lightning port is unnecessary.

It has just introduced its Quick-Jack Solution, an all in one kit that includes the QuickJack schematics, a small board along with a free example app for popular smartphone OSs, and design documentation.

The board (see above ) contains everything that a would-be IoT developer would need: the company's LPC812 microcontroller to handle decoding/encoding of the Manchester algorithm (enabling use of the left audio channel for data transport) and communication with external peripherals, free source code for the LPC812 and access to the company's LPCXpresso tools

The board's expansion header allows connection fo a rrange of sensors (such as temperature, humidity, wind, heart rate, accelerometer, etc.), switches (lights, power, etc.), HMI devices (such as keyboards, game controllers, etc.) or other devices that collect or log data from a variety of sources.

It also incorporates an energy harvesting circuit utilizes the right audio channel to draw power from the smart device to power the Quick-Jack board and attached sensor(s). Also included is an onboard joystick to run a demo UI implementation, with results displayed by by a mobile App on the connected smartphone or tablet. The supplied example App for Android phones and iPhone displays joystick position and temperature, and can turn devices on the Quick-Jack board on and off.

In conjunction with the launch, NXP plans to host a competition to which designers can submit ideas on what application they would create if they had a Quick-Jack board. They are then part of a free drawing to win one of five boards they can then use to implement their ideas. The contest is now open and entries will be accepted until June 20, 2014.

Klutz that I am, I am tempted to download the kit and get started on some ideas I have, how about you? If you do try it out let me know how and what you are doing, here or in the form of later blogs or design articles for the site.

Embedded.com Site Editor Bernard Cole is also editor of the twice-a-week Embedded.com newsletters as well as a partner in the TechRite Associates editorial services consultancy. He welcomes your feedback. Send an email to , or call 928-525-9087.

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