Palm-sized RF remotes in Harman Kardon Go + Play and JBL Radial audio systems maximize battery life, range and features with Nordic 2.4GHz transceivers
Nordic Semiconductor has announced that Harman International has specified nRF24L01 single-chip 2.4GHz transceivers to provide the wireless connectivity between its RF remotes and iPod sound stations.
RF REMOTE: iPOD AUDIO PRODUCTS
Harman International selects proven Nordic Semiconductor nRF24L01 single chip 2.4GHz transceivers for robust, bi-directional wireless connectivity, featuring ultra-low power consumption, through-wall non-line-of-sight RF operation, and 30-ft (10m) operating range, for two of its most popular sound systems for iPod
The Harman Kardon Go + Play is a high-end, portable sound station that uses a pair of two-way 30-watt-RMS speakers each comprising a high-frequency transducer and high-excursion (25mm peak-to-peak travel) woofer. High-end Digital Signal Processors (DSPs) and a computer-optimized 360-degree soundstage deliver class-leading levels of audio detail and dynamics across a full 40Hz to 20kHz frequency-response range.
The JBL Radial entertainment dock delivers a 60-watt-RMS output across the same frequency range via two 15-watt midrange/high-frequency aluminum-domed Odyssey speaker drivers plus a single low-frequency 30-watt neodymium-magnet-based woofer. The JBL Radial entertainment dock is a top seller worldwide and has won critical acclaim for audio reproduction from the consumer press.
Control of both products is designed to be as easy and intuitive for end users as possible. This is why each employs a palm-sized remote based on RF technology instead of traditional infrared, which as a result, allows users to adjust volume, change tracks and fast forward/reverse through songs over a superior 30-ft (10m) “through wall” operating range.
The remote used with the Harman Kardon Go + Play also offers full navigation functionality for iPod, including the ability to browse by song, artist or album, and to select playlists, slideshows and videos. To ensure this remote remains in keeping with the elegance of the Go + Play, it was designed to handle 10 functions using only 6 buttons. To achieve this, the remote features some highly novel and intuitive nested-button features, such as a “page” toggle button whereby the user can switch from simple volume and play/pause control to a “navigation” page that allows for full menu navigation of iPod songs and videos. This is supplemented by a blue or amber LED indicator that tells the user which page he or she is currently on. The two-way operation of the nRF24L01 means the remote and speaker system remain in sync at all times.
Indeed, all this is illustrative of why RF remote controls have several advantages over traditional infrared (IR) designs. When using IR, users have to point the remote directly at the IR receiver on the equipment they wish to control, which means a clear path – unobstructed by people, furniture and walls – is necessary. And IR is typically a one-way command-only communications technology that eliminates any means of menu-based “browsing” of the content stored on the device under control or staying in sync – as occurs with the Harman Kardon Go + Play remote.
RF remote controls, in comparison, use non-directional radio frequencies to communicate. This gives users the hugely convenient ability to control a device (e.g. mute the volume to receive a telephone call) from an adjoining room. This is especially appealing to today's modern lifestyle-conscious consumers.
The ultra-low power (ULP) yet high-performance characteristics of the nRF24L01 2.4GHz transceivers mean that they can typically run on coin cell power sources for periods of up to one year or more (depending on duty cycle), making them ideal for small-form-factor RF wireless connectivity without loss of functionality or operational reliability. One transceiver is used in the remote with a “paired” device in the equipment to be controlled.
In operation, the nRF24L01 employs Gaussian Frequency Shift Keying (GFSK) modulation optimized for ULP wireless applications. When transmitting the nRF24L01's supply current is 11 mA peak (at -0 dBm output power, sufficient for 30-ft/10m range). In receive mode, peak supply current is 12.5 mA. When not transmitting, the nRF24L01 enters an ultra-low power standby mode, consuming just 0.9 ¼A. These extremely low power characteristics ensure excellent battery life even from coin cells. For example, when used in the Harman Kardon Go + Play and JBL Radial remote controls with typical usage of 500 button cycles per day, the batteries last for one year. The nRF24L01 has a raw on-air data rate of up to 2 Mbps, providing plenty of overhead for the data transfer required for menu-browsing updates on a remote control with built-in screen.
The nRF24L01 is supplied with a customized Frequency Agility Protocol (FAP) – that is employed in both the remotes described here – and can be optimized for either low latency (with an average response time of 2.5ms including RF power on and link up time) or low power with a latency of between 30 and 50ms. (Typical IR remote control latency is between 70 and 110ms.) The FAP rapidly hops to a different frequency if communication is interrupted by other 2.4GHz sources, such as Bluetooth wireless technology or Wi-Fi, to ensure a robust communication link.
Nordic Semiconductor can also supply a remote control reference design (the nRD24H1) that comes complete with all the firmware required to develop a fully functional remote control.
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