Nordic Semiconductor's Tape And Reeled 2.4 GHz Wireless Modules Offered By RF Digital

Oslo, Norway - Ultra low power (ULP) RF specialist Nordic Semiconductor ASA recently announced its official design partner, Irvine, CA-based RF Digital, has released a fully FCC and CE-compliant 2.4GHz ULP wireless module that is supplied tape and reeled at a US$8 unit cost for volume orders.

The tape and reeled format enables customers (or their subcontractors) to place the module on the PCB using automated placement equipment. Automated assembly, together with the low price and the fact that customers require no further certification prior to releasing products to market, makes the module a compelling solution for production runs from 10 to 100,000 units.

The RFD21733 measures just 15 by 15 by 3mm and is powered by Nordic's brand new, class leading nRF24LE1 2.4GHz ULP transceiver. The nRF24LE1 is a high performance wireless device integrating radio, microcontroller and flash memory (see "About the nRF24LE1" below).

The RFD21733 is supplied with RF Digital's proven Frequency Hopping Spread Spectrum (FHSS) firmware, or alternatively with no pre-loaded firmware (module part number RFD21731). Both modules feature a built in chip antenna which is matched, tuned and radiation pattern optimized. A 32kHz crystal required for precision timing when operating in a low duty cycle ULP mode is also integrated into the RFD21732 module which has no pre-loaded firmware. Full access to the wireless module is provided to three digital in/out lines, program line, reset line, power (+V) and ground (GND) connections.

The RFD21733 is particularly suitable for designers that may be new to wireless as everything on the RF side of the device is in place, tested and proven (see "Why use a module?" below). In this configuration, the module runs at 9600 baud and features N, 8, 1 serial interface firmware allowing it to be connected directly to an RS232 level shifter. In addition, the module features a built in switch follower mode. Pressing a button on the transmitter will cause the corresponding button on the receiver to activate; this button could, for example, be connected to an LED to facilitate range testing or used in end-product applications such as keyless entry door openers or long range RFID applications.

For more experienced designers who want to take advantage of the modules' high bandwidth (up to 2Mbps raw data rate), ultra low power consumption (down to microamps average current) and ability to communicate with up to five other devices in a point-to-multipoint topology, the modules can be programmed using Nordic's nRF24LE1 Development and Evaluation Kit. Because the transceiver used in the modules is an integrated device, there is no requirement for a separate development and evaluation kit to access the microcontroller.

RF Digital is also releasing an adaptor board to interface the modules to the Nordic nRF24LE1 Development and Evaluation Kit, and a miniature evaluation board complete with module, three buttons and three LEDs (enabling range testing) powered by a CR2032 3V coin cell-type battery. (This battery is a typical choice for ULP wireless applications.) Since this miniature evaluation board includes the RFD21733 compliance tested module, it no longer requires any further compliance testing and can even be used as the basis of a marketable product. The miniature evaluation board also has 0.100 spacing SIP header which allows it to easily plug into users' development boards.

Requiring only 15 by 15mm2 board area, the modules are suitable for all but the most space-constrained applications. And at a price of as low as US$8 (in volume) they offer a cost effective alternative to a discrete component RF design for production runs numbering up to hundreds of thousands of pieces per year. Should a manufacturer then want to move to a discrete component design later in the product's life, the module represents an ideal reference design.

"Our philosophy is to make life as simple as possible for engineers wanting to implement a wireless link," explains RF Digital President Armen Kazanchian. "With these new modules an engineer can have a link up and running within minutes. And there is no need for any compliance testing as the module already conforms.

"Moreover, these modules are based on the leading 2.4GHz transceiver in its class, so the performance is the best money can buy at this price point. In fact, these modules significantly outperform competitive products costing three or four times as much. And at only 15 by 15mm the modules do not compromise compact designs," says Kazanchian.

"The cost difference between the fully compliant, tested and proven module complete with protocol code and the discrete components required to produce an equivalent design is only around US$3 (in volume) thanks to the advances in technology and manufacturing processes. With compliance testing alone costing thousands of dollars, the module makes great economic sense for all but the largest production runs," Kazanchian concludes.

"RF Digital has excelled in the provision of wireless modules for companies lacking RF engineering experience but needing a proven wireless solution and fast-time-to-market, and this latest product, based on our nRF24LE1, is no exception," says Geir Langeland, Director of Sales & Marketing, Nordic Semiconductor. "And because the functionality of the transceiver used in the module can be modified by employing Nordic's Development and Evaluation Kit, more experienced designers can port their own code to further differentiate their products from the competition."

Why use a wireless module?
An RF module is a good solution for designers looking to add wireless connectivity to a product without committing to an arduous design cycle. By using a module, designers without specialist RF knowledge can build an Ultra Low Power (ULP) ISM-band wireless link into a product or application within hours.

Because all the RF development work has been done, a module only requires a digital In/Out, power (+V) and ground (GND) connection. The module is impedance matched, includes antenna and is tested for range and robustness of communication. In many cases, the module is also tested to the US' FCC and Europe's ETSI regulations. Moreover, by using a module, engineers don't need to get involved with the RF side when developing, for example, a proof of concept.

A module is designed to work in almost any operating environment or product design with the exception of a sealed metal enclosure (which is opaque to RF).

There is one downside: a module takes up more board real estate and have a taller profile than employing the equivalent transceiver (and supporting peripheral components). But at only 15 by 15 by 3mm a module is suitable for all but the most space constrained designs. But even if the module is still too big, and the final design does require discrete components, a module is still worth considering for prototyping because of the time saved during development.

A module also costs slightly more than the equivalent discrete components. However, to make a like-for-like comparison, the savings made in expensive design hours must be factored in. And this is without accounting for the several thousands dollars saved because the module already has FCC compliance approval.

By using an RF module, it's possible to test RF performance at the prototype stage rather than waiting for a production PCB. And when the production PCB arrives, there is rarely a need for a layout revision. With a module, the designer can be confident that all unknown RF variables are stable and independent of the target application. In addition, the RF section of their product is modular and therefore simple to debug. Contrast this with a design that uses discrete RF components: even the most experienced RF engineer doesn't know if such a layout will pass compliance testing until it has gone through the lab. And more often than not, the PCB and layout will require a second and third revision to pass compliance testing.

In addition, the designer faces initial RF engineering costs, the expense of RF test equipment to debug in engineering and production, and further RF engineering costs to address radiation patterns, range limitations and interactions between digital and RF parts of the design (which only become apparent once a complete RF layout is tested). While the competition is designing, prototyping and waiting on compliance test results, an RF module-based product could already be selling in the marketplace.

If volumes then increase and the additional cost of the module becomes significant, it can be replaced with the less expensive discrete components. Because RF Digital's modules are based on Nordic Semiconductors reference designs, the designer can simply adopt the relevant reference design in the space vacated by the module.

SOURCE: Nordic Semiconductor ASA