Home > Cherry uses Nordic’s 2.4 GHz transceivers for MARLIN Wireless Laser MultiMedia Desktop

Cherry uses Nordic’s 2.4 GHz transceivers for MARLIN Wireless Laser MultiMedia Desktop

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article image Semiconductor 2.4 GHz transceivers

Cherry’s ultra-slim MARLIN wireless multimedia keyboard and mouse employ Nordic ultra-low power nRF2402 transmitters, communicating with USB dongle using Nordic nRF2401A transceiver. Keyboard battery life is an impressive 12 months, range is 10 m plus, and mouse features rechargeable batteries chargeable via USB cable so device can still be used.

Nordic Semiconductor ASA announced that Germany computer peripherals giant Cherry GmbH has selected the ultra-low power nRF2402 transmitter and nRF2401A transceiver for use in its MARLIN wireless laser multimedia desktop keyboard and mouse, the flagship product of Cherry’s eVolution range of PC peripherals.

The nRF2401A and nRF2402 both operate in the global 2.4 GHz ISM band and endow the MARLIN with a maximum range of at least 10 m and a reliable, robust RF link even in the presence of obstructions such as desks, people and furniture. Moreover, the wireless keyboard and mouse are immune to interference from other MARLIN multimedia desktops, Wireless LANs, Bluetooth and other 2.4 GHz technologies transmitting in close proximity.

The MARLIN is designed with simplicity in mind to mimic the ease-of-use of a wired keyboard by providing a robust wired connection, infrequent battery replacement, transmission security and plug-and-play operation. There is no user set-up or adjustment required.

In addition, the MARLIN wireless laser multimedia desktop features flat, ergonomic, highly functional yet simple wireless keyboards on the market with silent, soft-touch keys and 10 HotKeys. The laser mouse operates on any flat surface and includes seven programmable individual function keys plus an illuminated scroll-wheel that provides battery charge status information.

The MARLIN’s impressive interference immunity is assured by Cherry’s proprietary channel-hopping algorithm that guarantees transmissions are always made on interference-free channels. In addition, robust communication is reinforced by automatic pairing of transmitter and USB dongle receiver via a unique 32-bit identifier. Each transmitter periodically sends the mouse or keyboard data across a factory-determined selection of channels from a possible 64-channel set. Encrypted data transfer is used to protect all wirelessly transmitted keystrokes.

Nordic’s ultra-low power transmitters and transceivers combined with low duty cycle operation ensure battery lifetimes of 12 months from the keyboard’s two AAA 1.5 V batteries (depending on usage patterns). The mouse features sealed-in AA Rechargeable Alkaline Manganese dioxide (RAM) batteries that never need replacement and are charged via a USB cable while the mouse is in normal use.

According to Cherry, Nordic’s technical support and highly experienced engineering team helped it overcome issues such as signal reflection and distortion, a particular challenge in a crowded office environment.

By partnering with Nordic, Cherry was able to design the MARLIN so that it can plugged in by the user and will work perfectly with no need for user adjustments. In addition, Nordic’s product roadmap means Cherry knows that it will be able to design winning wireless product for years to come.

According to Nordic Semiconductor, while Cherry has considered Bluetooth in the past it was able to demonstrate Nordic’s superiority for simple, low duty cycle applications like several computer HIDs [Human Interface Devices] such as wireless mice and. Nordic’s ultra-low power transceivers extend battery life in HID applications to many months or even years, compared with Bluetooth’s typical monthly battery replacement rate in this type of application

About Bluetooth power consumption

Bluetooth’s strength, the ability to easily form and manage an ad-hoc piconet of up to eight devices (one master and seven slaves), also turns out to be a weakness in point-to-point battery-powered applications.

The master determines the 1600 frequencies to be used each second across the nominal 2.4-GHz band. In operation, the master sends a 160-bit packet every 675 µS (1600 packets/s, or a net data rate of 256 kbit/s) to maintain the link, whether the target device is in use or not.

This synchronisation scheme was developed to avoid the inevitable clashes that would occur in a piconet if the master were to randomly transmit to the slaves. Although the IEEE802.15 standard does provide for missed or corrupted packets to be resent, this reduces the data transfer rate and further increases power consumption.

While synchronisation is a distinct advantage for maintaining data transmission when several devices are communicating over a single piconet, it is a drawback in point-to-point applications. The simplicity of these applications does not demand synchronisation, yet this feature is mandatory because it is a part of the Bluetooth standard. As a result, unnecessary synchronisation packets reduce bandwidth, and the transmitter consumes more power because of the increased duty cycle.

Furthermore, Bluetooth’s packet structure is uneconomical. The packet structure comprises 68 or 72-bit access code plus 56-bit header and 32-bit data payload, requiring 160-bits, with an overhead of 128-bits and an efficiency of 20 percent. This relative inefficiency is a by-product of ensuring interoperability with a wide range of devices.

About the nRF2401A

The nRF2401A is a high sensitivity (-93 dBm), true GFSK single chip transceiver with a maximum date rate of 1 Mbit/s. The nRF2401A consists of a fully integrated frequency synthesiser, a power amplifier, a crystal oscillator and a modulator. Output power and frequency channels are easily programmable by use of a 3-wire serial interface. Current consumption is low, only 10.5 mA at an output power (TX) of -5 dBm and 18 mA in receive (RX) mode. Built-in Power Down modes make significant power savings easily realisable.

The nRF2401A requires just two external components and no external SAW filter, so is well suited to compact applications. The nRF2401A can communicate across 125 channels and switch between each in under 200 µs. This transceiver is designed specifically to block interference in crowded 2.4GHz environments and utilises a unique ShockBurst feature in both receive and transmit modes to greatly simply protocol and software design, minimise power consumption and relax MCU requirements.

The nRF2401A comes in a small 24-pin QFN24 5 x 5-mm package, offers a 0 to 1 Mbit/s data rate, multi-channel operation and supports frequency hopping across up to 125 channels with a channel switching time of less than 200 µs. This includes data slicing and clock recovery of data plus address and CRC computations.

The nRF2401A also features DuoCeiver technology for simultaneous dual receiver topologies and a ShockBurst mode for ultra low-power operation and relaxed MCU performance. Power supply range is 1.9 to 3.6 V, supply current is just 10.5 mA peak (TX) at -5 dBm output power and 18 mA peak (RX) in receive mode. Operating temperature range is -40 to +85 ºC.

Prime applications include wireless mouse, keyboards and joysticks, keyless entry, wireless data communication, alarm and security systems, home automation, surveillance, automotive, telemetry, intelligent sports equipment (e.g. wrist watches and associated sensors), industrial sensors and toys.

About the nRF2402

The nRF2402 2.4GHz RF transmitter complements the nRF2401A to offer designers and equipment vendors a cost effective and simple way to build unidirectional wireless communications into their product or application. The nRF2402 includes all inductors and filters pre-integrated into a single chip. The only external components needed to make a complete RF system are a crystal and single resistor.

Current consumption is around 10mA in transmit mode -5dBm. The total solution fits into a compact 4 x 4-mm package. Prime applications include the transmitter, only parts of wireless game controllers, PC peripherals, wireless headsets, sports and leisure equipment, toys, RFID, remote control and interactive equipment.

All configuration of the nRF2402 transmitter is done via a standard serial interface and the nRF2402 can replace IR and typical 27 MHz wireless comms in several applications. Like its nRF2401A cousin, the nRF2402 also features Nordic Semiconductor’s ShockBurstTM technology that uses an onboard FIFO (First-In-First-Out) arrangement to buffer data and transmit in highly power efficient, short bursts.

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