Short Range Wireless
the desired pattern of interconnect. How can this crude process be improved to churn out fine-featured printed circuit designs cheaply and on an industrial scale? Wouldn’t it be clever if, instead of all that wasteful etching, you took an “additive” approach to lay down – maybe on an inexpensive plastic surface – the finest of copper tracks and other geometric features? You’d start by spraying on a special catalytic ink which precisely defines where copper should be deposited when the plastic sheet is drawn through a special solution. In effect, the copper could be “written” onto the surface on the substrate. That roughly describes how Cambridge-based CIT does it.
CIT has developed a low-cost manufacturing process for the rapid production of a variety of printed circuit products, including RFID tags, medical sensors, touch- screens and novel OLED displays. This process uses special UV curable inks, reagents and either digital inkjet printing or flexographic printing technology to enable the “direct write” of conductive metals onto polymer substrates. Given this unique capability, CSR turned to CIT to manufacture the working prototype of its µEnergy wireless keyboard concept, the ultra-thin touch-surface. The exact physical construction of the CSR touch- surface – less than 0.5-mm thick – remains confidential, suffice to say that it comprises meshes of sub-millimetre wide, multi-micron deep copper patterning sandwiched between layers of thin plastic substrate: Polyethylene Terephthalate, in this case. PET is widely used, for example, to fabricate plastic bottles. Using PET renders the keyboard area flexible, featherweight, durable, and inexpensive – and suitable for use in some harsh environments: industrial, military, and medical. Furthermore, the printed circuit area can be extended beyond the active keyboard to form landing space for surface-mount components: controller IC, Bluetooth Smart chip, passives, connectors, battery, antenna, etc. (As the photograph shows, the prototype accommodates this circuitry on a bolt-on PCB).
Ready for Bluetooth Smart
Formerly known as Bluetooth low energy (BLE), Bluetooth Smart is the re-imagining of the WPAN standard for wireless connectivity requirements that specify always-on operation, modest data rates, lean power consumption, speedy pairing, and easy development.
Bluetooth Smart Ready hosts – smartphones, tablets and laptops – are compatible with both Bluetooth Smart enabled devices and classic Bluetooth enabled peripherals/accessories. So, for example, your Apple iPad Mini 2 – with Bluetooth 4.0 built-in – can happily stream stereo audio to your Bluetooth stereo headphones using A2DP (Advanced Audio Distribution Profile) of Bluetooth, while at the same time wirelessly connecting to CSR’s Bluetooth Smart ultra-thin touch-surface keyboard using the HID over GATT profile. (GATT stands for Generic Attribute). Simple.
www.cieonline.co.uk
Feeling the ethereal force A touch-surface design (touch-screens, track-pads, graphics tablets, etc) can exploit one a number of different electro-physical effects to sense the position of a pointing instrument (finger, stylus, light-beam, etc) on a 2-dimensional plane, be it curved or flat. Aside from exploiting resistive and capacitive behaviours, touch-surfaces can use piezoelectric, ultrasonic, and photoelectric effects to determine the precise location of stimuli, be it contact pressure or non-contact proximity. CIT describes the touch-surface technology used by the ultra-thin keyboard as “capacitive coupling”. This capacitive coupling effect requires that the pointing instrument be conductive. So, for example, a gloved finger cannot be sensed unless the glove material is slightly conductive: a dentist’s latex glove works since it simply adds a thin layer of dielectric; however, a ski-glove is a no-go: that’s why skiers tap their smartphone screens with the tip of their nose.
Control and communication The keyboard controller – in this prototype, one of the chips in the Atmel maXTouch product range – orchestrates a number of complex operations, from continuously scanning the touch-surface keyboard and track-pad area, detecting and computing the multi- touch input, to buffering the stream of characters and
The hipKey smart fob
vectors generated by keystrokes and gestures. This data is passed to the on-board CSR1010 µEnergy chip which radios the Bluetooth Smart receiver incorporated in the host machine. The operating system (OS) in the Bluetooth Smart Ready host then interprets this symbolic data into alphanumeric characters and other actions.
Software development
Bluetooth Smart is a highly sophisticated Wireless Personal Area Network (WPAN) standard. For developers, the Bluetooth SIG has made life as easy as possible by simplifying the scheme of “Profiles” used by Bluetooth 4.0 and focusing them on a variety of popular applications. So the “HID over GATT profile” (HOGP) is specifically purposed for keyboard and mouse devices, whereas the Heart Rate, Blood Pressure, and Blood Glucose profiles are tailored for heath & fitness monitoring.
In common with other providers of Bluetooth Smart
hardware, CSR offers a comprehensive, user-friendly software development kit (SDK) for the CSR µEnergy product family of Bluetooth Smart platforms. The CSR µEnergy SDK provides a complete graphical code development environment to quickly build, debug and test applications such as keyboards and remote controls.
CSR |
www.csr.com Paul Williamson is Director of Low Power Wireless, CSR
Components in Electronics November 2013 11
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