Wireless Electronics


What’s new in remote control technology?


Infrared (IR) communications technology has been used to link consumer equipment such as a remote control with a television since the late 1970s. Over the years manufacturers have developed a multitude of digital communication protocols most commonly based on Amplitude Shift Keying (ASK) modulation. The introduction of new protocols differentiated communication schemes, improved robustness, and optimised data transmission capability. As IR communication protocols matured, companies developed competing IC solutions tailored to fit OEM remote controls, universal remotes, and computer based hardware. However, specialised hardware solutions for mobile devices are conspicuously missing from this list… until now. Sean Donnelly, applications engineer (US), ams AG, explains


F


lash forward to the era of mobile devices; the technology of IR communications has virtually remained unchanged. However, in living rooms around the world, an increasing number of television watchers are sidelining OEM remotes in favour of smartphones equipped with “IR Blasters”. A multitude of companies have remote control apps that do much more than just change the television channel, such as suggesting programming to users, signaling users when favourite shows are about to start, automatically changing the channel, and presenting individualised advertising content. Sadly, these intriguing features will not continue to be available because manufacturers simply can’t afford the monetary cost or the printed circuit board space using traditional IC solutions. Manufacturers are only willing to offer IR Blaster features if the IC costs less, is smaller, requires less power, drops into the hardware architecture, and integrates seamlessly with the system software. Now,


ams has developed new hardware technology called IRBeam, a tailor made solution to integrate IR communication in mobile device applications.


Despite being ill-suited, an FPGA with 4kB RAM along with discrete MOSFET driver and 940nm LED is the current solution of choice in smartphones. Operating as a FIFO, pattern data originating from the Application Processor (AP) is buffered, mixed with a carrier frequency, and output to an external IR LED circuit. IR communication using FPGAs are a well proven technology but many manufacturers are designing them out of mobile devices. Current FPGA technology has a mixture of advantages and disadvantages in mobile applications. Since the FPGA is re-configurable, HDL code can be quickly written and debugged reducing time to market. Furthermore, FPGA manufacturers offer reference designs to assist OEMs in development. Package size can be as small as ≥7 mm2,


Figure 2: 12-bit SIRC pulse stream


however larger footprints are more common. Disadvantages include high monetary cost and high static power consumption ( ≥75uA). Additionally, OEMs would have to design and maintain an additional HDL codebase. For decades small 8/16-bit


Figure 1: Basic building blocks of a CIR pattern www.cieonline.co.uk


microprocessors have been used in handheld remote control devices and have significant advantages in mobile device applications. They are relatively inexpensive, and perform well. Code optimisation and sleep/wake feature reduces power consumption which increases battery life. A non-volatile memory may be employed to store many protocols to suit a large number of equipment manufacturers. Additionally, both the processor firmware and the non- volatile memory may be reprogrammed to further improve user experience. However, a microprocessor is not an ideal choice for mobile devices. Typically, microprocessor based solutions are large at >15 mm2 and require additional codebase and could be expensive. Furthermore, mobile devices already incorporate at least one processor, the AP, which is capable of IR pattern generation. Interestingly, many mobile device manufacturers employ a two processor scheme. The AP typically has 1 to 2 GB of RAM, 1 to 2 GHz clock, and multiple cores run an OS, user applications. The second processor, called a hub, is a small 8/16-bit low power device that is used to process data from peripherals such as a proximity detector, Ambient Light Sensor (ALS), accelerometer, or barcode emulation. This scheme is used to conserve battery power while offloading sensor specific tasks from the AP. Current hub technology is typically capable to generate IR remote control patterns; however, mobile device manufacturers don’t utilise the hub for this purpose. The hub has a rudimentary operating system that services “always-on” devices and sensors. Therein lies the problem; remote control requires all of the processing power during a transmission. In addition, from a software point of view, remote control transmission algorithm is not


compatible with current hub technology employing an OS with a scheduler. New IR pattern generation technology


from ams is designed to avoid problems when traditional solutions are paired with cutting edge mobile devices. The two most difficult challenges to overcome are physical size and cost of the remote control pattern generator. Additional PCB space eliminated adding IR remote control functionality to an essential existing IC. Smartphones use an optical sensor module to detect ear-to- phone proximity and ambient light, ALS. The addition of IR remote to an IR optical device is a natural fit, and does not increase package size (10mm2 or less). Optical devices are typically mounted atop the phone with a flexible PCB along with other components such as earphone jack, indicator LEDs, and the forward-facing IR LED. Connection from the pattern generator to the IR LED driver is simple and may even help to reduce the size or number of attendant system components. As the component count falls, and the level of integration rises, the monetary cost is reduced to pennies.


Power is conserved in two ways:


removal of a stand-alone IC eliminates current consumption when the remote control pattern generator is idle. The sleep or idle current consumed by the remote control enabled optical device remains at the same level as similar optical devices without the remote control option. Additionally the duty cycle of the carrier frequency is adjustable and can be set as low at 25 per cent. This is useful because peak current consumption occurs during IR transmission as the LED is modulated. IR remote control has been and continues to be the most popular communication solution for consumer equipment. While the development of new protocols has slowed, innovation of new inexpensive and robust transmission solutions is still alive and well. Integration of pattern generation functionality into small, IR based optical devices marks the latest milestone in IR remote control enabled mobile devices.


www.ams.com Components in Electronics July/August 2017 21


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