It should be simple: find a nice large display like Viewsonic’s 37-in N3752w, connect it to a compact motherboard like VIA Technologies’ EPIA EX15000G, and network it with Belkin’s 300Mbps N1 technology.
Actually, it is fairly straighforward. But I turned to Logic Supply, a major distributor of Mini-ITX platforms, to find out about the problems and solutions that developers are running into when it comes to digital signage applications.
What You See
The most obvious component is Viewsonic’s 37-in N3752w HDTV display with a 1366-by-768 resolution. It can support 480i, 480p, 720p, and 1080i video. Video inputs include VGA, HDMI (with HDCP and audio support), composite, component and S-video. There is also a built-in ATSC/NTSC tuner. I liked the latter when testing the system as a TV, since it tunes both digital and analog channels at the same time instead of switching modes manually.
The N3752w’s display is impressive. It has a 1000:1 contrast ratio and a viewing angle of 170 degrees. It is relatively bright (500 cd/m2) and the anti-glare, anti-reflective coating improves viewing in bright rooms. I found the N3752w to deliver excellent performance over a range of multimedia content, from movies and television to graphic and slide presentations.
The built-in Speakers and dual 10-watt Dolby Digital sound system is sufficient for small- to medium-sized rooms. It can be driven by external inputs including the VIA EX motherboard.
An infrared remote is provided and most options are also available from the side-mounted control system. These may be options that developers may want to disable depending upon where the display will be employed.
The unit can be wall-mounted using a standard 200mm-by-400mm VESA mount. It is also possible to mount a control unit like the one we built on the rear, but it will not be possible to flush-mount the display on the wall. Of course, it is possible to place the control unit nearby but not immediately adjacent to the display.
The N3752w is obviously targeting HDTV home environments but it works equally well for digital signage applications.
Hardware Backend
The N3752w can be driven from cable input but a more programmatic source using a PC platform. Typically the latter will not have the same peripheral complement unless the systems are employed in a kiosk-style environment. In this particular example we forego the use of keyboards and mice.
This is reflected in the case chosen for the task: the Serener GS-L05 case. It has no front-panel connectors. The only thing on the front panel is a pair of LEDs. The rear of the unit exposes the standard Mini-ITX connectors that use a standard cover plate.
The GS-L05 Mini-ITX case is designed for fanless operation. Its top cover is finned aluminum. It can handle a range of motherboards like VIA’s EX series used in this system. It requires removal of the normal heatsink that the motherboard is delivered with. This is replaced with a heat pipe system that draws heat away from the processor for dissipation via the cover.
As you might have noticed, the configuration requires relatively precise clearances and the interior is tight. That’s where Logic Supply comes into play. I worked with them on system specifics, but had them deliver the actual product. They installed the motherboard, memory and compact power supply (See Tiny Mini-ITX Power Supply) and then added the heat pipe. The power supply has an external power brick as well.
The VIA EPIA EX15000G runs a VIA C7 1.5GHz processor with a VIA CX700M2 chipset. It can handle up to 1Gbyts of DDR2 533 DIMM RAM. We used half this amount. The built-in display adapter is the VIA UniChromeTM Pro II 3D/2D AGP graphics with MPEG-2/4 and WMV9 video decoding acceleration. There is an on-board VIA VT1625M HDTV Encoder and the output connectors include a DVI, composite, component and S-video. The VIA VT1708A High Definition Audio Codec can drive the RCA stereo audio outputs or the S/PDIF coaxial or optical connector. I used the RCA stereo and DVI connections for this project since those were cables I had available.
The motherboard includes the VIA VT6107 10/100 Mbps Fast Ethernet Controller. A 1Gbit/s Ethernet connection is optional. The motherboard also has a range of internal headers for audio and video. There is an LPC header and a connector for an LVDS panel. The PS/2 interface goes unused and the back panel USB connections were used for the initial software installation and for wireless support. Logic Supply did add a power switch on the back of the unit.
I did not take advantage of the 1394 Firewire interface or the pair of SATA interfaces because this was a totally solid-state solution. Instead, Logic Supply installed a 4Gbyte Emphase FDM4000I flash disk in the IDE socket. This not only provides a more reliable system but it can be less expensive. 4Gbytes is more than sufficient for operating systems like Windows XP or Linux with enough free space for a good deal of multimedia content, although not enough for a full-length movie.
If you decide to use a wired network you can take advantage of the Ethernet adapter’s PXE boot support. It is possible to set up the boot sequence to use this and fallback to the IDE flash drive. Of course, you might want to put the unit where wired connections are not available, in which case wireless is the way to go. Unfortunately, wireless PXE is not an option so the alternative is to always boot from the IDE flash drive.