Electronic Design

Embedded PC Targets Digital Signage

VIA Technologies’ vmpc vm7700 (Fig. 1) is essentially a fanless PC in a slick, compact package (180mm by 298mm by 26mm) designed for mounting on the backside of a large-screen display (Fig. 2) — typically an LCD display like the Viewsonic’s N2751w (See Viewsonic N2751w Delivers Stunning HDTV And Perfect PC Video). Rear-mounting is made possible by the MIS-D 100 (100 mm by 100 mm) VESA Mount holes on the vm7700. VIA provides an adapter since many large-screen displays like the N2751w typically have MIS-F 200mm by 400mm mounting holes — though it should work equally well with small LCD displays. The vm7700 is actually small enough to be hidden near a display and incorporates tiny advantages like a screw-on power connector. Inside the system (Fig. 3) is a custom motherboard with a 1 GHz VIA C7 or VIA Eden ULV processor hidden under a heat sink that’s attached to the metal case, providing an excellent heat dissipation platform. The system, which can handle up to a gigabyte of memory, is rated for operation from 0°C to 45°C. Support chips incorporate the VIA UniChrome Pro II AGP graphics engine with MPEG-2 / 4 and WMV9 hardware decoding acceleration. The motherboard has a single socket for a 533 MHz DDR2 SO-DIMM. Disk storage includes a 2.5-in hard disk drive or a flash memory hard disk. The system also supports network booting for diskless operation. Peripheral interfaces include Gigabit Ethernet, optional Wireless LAN 802.11b/g with an external antenna, two PS/2 ports, a COM port, four USB 2.0 ports, plus audio ports. The video connections include DVI-D, VGA, and S-Video. While it also comes with an infrared input port for an external IR sensor, I used a USB-based IR adapter with MythTV for remote control support. There is a power adapter inside the box that is driven by an external 12V power brick. The power cable screws into the system, preventing accidental disconnects that occur with so many other compact systems. The system I received was running a copy of Ubuntu Linux. Windows XP and XP Embedded are also options. Having Ubuntu already installed made testing significantly easier. It was simply a matter of connecting a keyboard, mouse, and the Viewsonic N2571w HDTV. The system was delivered with Wi-Fi support so getting network access was simply a matter of setting the SSID and network password. Ubuntu was installed with VIA’s own video driver, which provides access to hardware acceleration. This allows video applications like Mplayer to handle streaming video without overloading the 1GHz processor. The driver was able to handle the 16:9 aspect ratio that is now the norm for digital signage applications. Constructing a simple digital signage application is relatively easy. Remote management and monitoring can be accomplished via SSH or VNC. I prefer setting up one VNC session for the main display and another that is virtual and, therefore, not visible on the display. The latter is used for real-time management, while the former lets you see what’s actually on display. As with many systems, though, the hardware-accelerated video only shows up on the actual display. Most multimedia applications like Mplayer have plenty of command-line options, allowing the user to easily create scripts to present content. Typically, cron jobs can handle timed deployment. I also tried running MythTV on the system, but I had to switch to the OpenChrome driver. It seems that MythTV uses xvmc and doesn’t check to see if the video driver supports this feature. In any case, the MythTV client worked quite nicely. In fact, I used my remote boot support to run this version of Ubuntu with OpenChrome. But note that the vm7700 isn’t suitable as a MythTV backend since there’s no way to add a TV capture card. The platform matches some VIA-based Mini-ITX systems I’ve built, so I have no doubt Windows XP will provide an equally stable and flexible platform. Overall, I’m impressed with the vm7700. Digital signage applications don’t usually require high-performance compute engines, but they do need to deliver streaming video — something this system can handle. The ability to use wired or wireless networking makes it a good candidate for remote booting and management, and facilitates delivery of content via the network. Related Links VIA Technologies Viewsonic

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