Applikationsnoten

Jennic : How to build a remote control using Jennic

Von: Jennic

1. Introduction

This document describes the concept of using Jennic wireless microcontrollers for remote controls applications. Most common remote adaptations as well as nowadays trends for remote controls have been described. The document contains also fundamental benefits of using Jennic solutions compared to traditional RF according to remote controls technology.



To get a fundamental understanding of IEEE 802.15.4 and Zigbee which are basis for Jennic technology please refer to "JN5121-EK010 - Getting Started".

2. Remotes
2.1 Applications

Remote controllers are used in many everyday situations serving their users specialized functionalities. Remotes are not used only for TV sets or audio systems. Remotes are used also in industry i.e. to allow control the machinery working in dangerous environments, for PCs to allow the users control almost every function of their personal computer, in hospitals and hotels to control television and also air conditioning systems, for changing the track points followed by trams and in many other situations.

2.2 Technology

Traditional remote controls are using infrared technology (IR). Each remote is equipped with light emitting diode (LED) emitting 940 nm wavelength beam of light that reaches the destination device. The simplest one button remote can be used to trigger a function of device using carrier signal however present-day multi function remotes use frequency modulating of carrier for command coding. The most popular standard protocol for infrared communication is RC5 developed by Philips.

2.3 Trends

During past months consumer electronics market has shown increasing interest in changing Infrared (IR) technology for Radio Frequency (RF) communication. It is promoted by a number of benefits of using RF comparing with traditional IR. The most intuitive one is lack of limitation for line of sight operation for the remote, because the control doesn't have to point directly at the destination device. What is more using RF technology we can control equipment in other rooms or behind cupboard doors. The second benefit is bidirectional connection that allows interactive communication with any equipment that is controlled by the user. This new functionality makes sense for using inter alia LCD displays on the remote that can be used to display the status of the controlled device or advanced browsing of menus, allowing, for example, to display the song playlist and choosing the favorite one when playing music in the room not equipped with an audio system but only a set of loudspeakers. That exciting functionality can be used also to display program guide information on the remote without interference with main TV viewing, or control multi room devices consisting, for example, of media server in one room and TV in the second one. Using RF creates also great potential for networking devices together i.e. in home theater systems expanded with intelligent building managing functionality.

3. RF technology

Considering RF wireless communication for remote controllers there is a set of different solutions that can be chosen. The most common are ZigBee, Bluetooth and its low-power extension called Wibree, Wi-Fi and a number of proprietary solutions. Considering Wi-Fi that is developed generally for network connectivity with key applications such as TVs, DVD players or digital cameras, power consumption is a concern compared with Zigbee or Bluetooth. On the other hand, Bluetooth's weakness of secure communication which is based on weak (1) E22 algorithm and E0 cipher, makes it useless for any advanced LCD equipped remotes interoperating with set-top boxes where in most cases transmitted data has to meet strict requirements for protection of content and access. It comes out that only Jennic wireless microcontrollers incorporates low price, very low power consumption, secure networking (AES 128 encryption) with large and small-scale networking stack within one device, integrating 32-bit RISC processor and 2.4 GHz IEEE802.15.4 transceiver. Jennic IEEE802.15.4 guarantees optimal solution with a lowest price with prospect of interoperability (integration with home control networks using ZigBee) and coexistence with other wireless networks like i.e. Wi-Fi. To take a brief comparison between different RF technologies please refer to the table presented below.

       
4. Conception of using Jennic for remote controls

The heart of the remote control will be Jennic JN5139 wireless microcontroller enabling developer to implement IEEE802.15.4 or ZigBee compliant system with minimum time to market and the lowest price. Each Jennic wireless microcontroller is comprehensive System-on-a-Chip (SoC) solution which provides IEEE802.15.4 transceiver and 32-bit RISC microcontroller features. The transceiver of each IC is equipped with MAC accelerator with packet formatting, CRCs, address check, auto-acknowledgements, timers and 128-bit AES security processor. The 32-bit RISC processor sustains 32 MIPs with low power offering additional features with peripherals such as 4 input 12-bit ADC, two 11-bit DACs, temperature sensor, two timer/counters, two UARTs, SPI Port, 2 wire serial interface and GPIOs. The microcontroller is equipped also with 192kB of ROM which stores system code, including protocol stack, 96kB of RAM for system data and optionally boot-loaded program code and 48-byte OTP eFuse storing MAC ID on-chip. The Integrated Peripheral API defines functions that allow simple use of all presented peripherals without need of accessing registers by the software developer. Jennic JN5139 operates with supply voltage equal 2.2V to 3.6V. Very low current consumption (200nA in deep sleep mode, 1.3µA sleep current with active sleep timer and 34mA when transmitting or receiving data) enables Jennic chip to use less than 1/50th power of IR to send packets. There are no special external components requirements for JN5139 module what significantly improve simplicity of any prototype design. The only requirements should be JN5139 chip, Flash memory, Crystal, PCB with printed antenna, keyboard and passives. A low price single ended PCB antenna module reference design (JN-RD-6005) with full schematics and Gerber files is available on Jennic support web portal for free even without need of registration. This reference design is an ideal starting point for any low-cost remote control application as well as functionality extension for vide variety of high-end products. The following schematic presents fully functional circuit of the JN-RD-6005 module which can be easily expanded with keyboard functionality through the use of up to 21 GPIOs.

(1) www.terminodes.org/micsPublicationsDetail.php www.cl.cam.ac.uk/research/dtg/~fw242/publications/2005-WongStaClu-bluetooth.pdf

Copyright
Reproduction of this material without written permission of Scantec GmbH is strictly prohibited.

Disclaimer
Scantec GmbH makes no warranty about the suitability or accuracy of the information contained in this document. All the information presented in this document is only for general information purposes.

Trademarks
ZigBee is a trademark of the ZigBee Alliance.

Quelle
Scantec GmbH - www.scantec.de