EE Times Under the Hood - June 23, 2008 - (Page U35)

UTH0623DIGI_pg28_38.qxd 6/11/08 3:01 PM Page 35 D I G I T A L HOME w w w. e e t i m e s . c o m under the hood • w w w. t e c h o n l i n e . c o m a proprietary mesh network, SonosNet, rather than work with existing 802.11based access points. The downside to the mesh is that at least one unit must be wired to the home network (now mitigated with the ZoneBridge). “But this is more than outweighed by the ease of setup, the increased range of the mesh and some other, more-minor changes that increase the robustness of the network,” Schulert said. To make the network more robust, two antennas yield a choice of any of four combinations for devices to talk to one another. Also, SonosNet is a secure network that uses 128-bit AES encryption and runs on 2.45-GHz 802.11b/gbased radios. Rather than a server process on the PC, the team decided to use file sharing to access music. “Having a server would let us leverage the processing power of the PC,” said Schulert. “However, we didn’t like the complexity of setup and requiring that the server always be running.” Finally, the team chose a thick client rather than a Web-based interface that could run in a browser on both Windows PCs and Macs. So, how’d they do it? For all wireless connectivity, the team went with an IEEE 802.11b/g wireless mini-PCI card design from Atheros. The ZP100 design uses Atheros’ AR5213A baseband/media-access control (MAC) and AR2112A transceiver chips. With SonosNet, the user doesn’t have to worry about SSIDs and passwords. Also, the antenna placement is buried within the enclosure, allowing the user to perceive the ZonePlayer as a stereo. The main processing on the ZP100 is shared among key chips. First is the Renesas SH-4 microcontroller running Linux. Linux allowed the engineers to get complete access to all the source code for debug. The Renesas SH-4 was picked because it is low-power; it does floating-point, for efficiently decoding MP3 audio; and it supports mini-PCI interfaces. The other main processor, the Texas Instruments TMS320V5402, resides on the main amplifier board. This 16-bit, fixed-point DSP performs real-time buffering to keep the codec full and also does audio equalization. Supporting the main processors is a Renesas M16 16-bit microcontroller to tie up loose control ends, as well as a Cirrus Logic CS42416-CQZ 192-kHz multichannel digital-to-analog and analog-to-digital codec with on-board phase-locked loop and a minimum 110-dB dynamic range. The codec also provides digital volume control and differential analog outputs. Other support chips include a RealTek RTL8139CL Ethernet MAC, a Kendin KS8995MA Layer 2 Ethernet switch with five 10/100 transceivers, a Lankom SQ-H48W Ethernet transformer module and an Atmel AT27LV512A 512-kbyte one-time-programmable (OTP) boot EPROM. Two EPROM, two ISSI 16-Mbyte x 8 synchronous DRAMs and Samsung NAND (32 Mbytes). Though the ZP80 has only two Ethernet ports, it still uses a Marvell 88E6060 six-port Ethernet switch (vs. the Kendin controller on the ZP100) with an LF-H20P-1 magnetics chip. The controller relies on an Atheros AR2414A mini-PCI card and has 16 Mbytes of Samsung NAND flash. It also has a ball-bearing-based motion sensor and a Sharp quarter-VGA transflective LCD. Again, a Renesas M16 MCU is included, but this time to also manage the control buttons and scroll wheel. Design issues When it came to system design, wireless and electromagnetic-interference issues took center stage, particularly on the ZP100. That system’s memory bus—between the SH-4, the NAND flash and the synchronous DRAM— was designed to operate at 60 MHz. But Wi-Fi interference ensued, and it was discovered that the 40th harmonic of 60 MHz fell smack into the 2.46GHz region, affecting channel 11 of the Wi-Fi network. The designers had to bump up the frequency to 80 MHz, pushing that harmonic safely out to 2.48 GHz. But that wasn’t all. On the ZP100, the casing and support structures within act as a Faraday cage. But the ZP80 has far less metal surrounding it, only a plastic housing. EMI problems led designers to encase the Wi-Fi and digital processing circuitry in metal enclosures. That worked. “Wireless performance has to be designed from the ground up, both in hardware and software,” said Schulert. “Removing interference in our Wi-Fi was much harder than passing FCC [regulations].” Sonos wouldn’t comment on plans for future upgrades, but said it was looking at other ways to move audio throughout the home. Patents surround its core technology and relate to audio performance, audio synchronization and mesh networking. “We also have many applications around our GUI, addressing the ease of use of our product and setup,” Schulert said. “Finally, we have several design applications capturing our unique style.” ■ ‘Removing interference in our Wi-Fi was much harder than passing FCC regulations.’ ISSI IS42S16800B-7T 16-Mbyte x 8 (128-Mbit) synchronous DRAMs store main program code, and 32 Mbytes of Samsung NAND flash store code as well as the index to the stored music archive, which can hold 50,000 titles. The main amplifier section is a Class T design with two STA505 half-bridge FET power amps controlled by a Tripath TC2000 Class T controller with proprietary Digital Power Processing. The TC2000 is a 5-volt CMOS signal processor that amplifies the audio input signal and converts it to a switching pattern fed to the MOSFET drivers. LC filters on the outputs prevent the transfer of noise components to the speakers. Other power devices include two National Semiconductor LMS1587 3-amp fast-response lowdropout regulators. The ZP80 is similar to the ZP100 but without the amplifier. Again, it relies on an Atheros wireless-LAN design, but this time using the more-integrated AR2413A mini-PCI card. It, too, has the Renesas SH-4 and M16 MCUs, TI 5402 DSP, RealTek RTL8139CL Ethernet MAC, Atmel OTP June 23, 2008 | Electronic Engineering Times, TechOnline 35 http://www.techonline.com http://www.eetimes.com

Table of Contents Feed for the Digital Edition of Under the Hood - June 23, 2008

Under the Hood - June 23, 2008 Extreme Design: SuitSat Pushes Desigers' Limits Evolution of the Smart Phone Mature Devices get Rolly Rocking GPS: Garmin Nuvi 750 vs. HP iPaq 310 Inside the Sony OLED TV Multizone Dgital Audio Flip Ultra Camcorder - An Ode to Clean Design Robot Guitar Tunes Itself E-book is a Sight for Sore Eyes Scientific Calculator Boils Down to Two ICs $100 BOM Eludes First OLPC Laptop 45 nm: What Intel Didn't Tell You Next Step in NAND Flash Evolution Surveillance on a Shoestring Hot 3G Phone Owes Debt to Analog SecurID Fob: Single-Chip Safety Net

Under the Hood - June 23, 2008

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