Sophisticated graphics have hit the embedded systems world and are increasingly demanded by military, aerospace, industrial, and medical applications. The problem, of course, is that graphics are challenging even in the desktop world. In embedded designs, they present unique issues that include very specific, non-standard functionality.
Take an airplane cockpit. It may need to drive three or more screens, each displaying different information deriving from, and possibly combined from, different sources. A tank may have a similar requirement, but what’s displayed on the screen in the tank is likely to be different because (at the very least) the tank has to do without windows. Meanwhile, a control room might have six tiled screens on a wall that could be combined into a single large image or present up to six separate images.
Applications like these may share little in common, except the use of a display. The information to be displayed may arrive through existing video streams or from elsewhere in the form of raw data. It may go out as one or more video streams, or it may be sent as raw information somewhere else to be further processed. Input and output video streams may be transported as a number of different video formats or over some other channel like USB 3.0 or Ethernet. They may need to drive monitors or analog displays, and they may need to do so over modern HDMI cables or old-fashioned RGB signals.
The actual processing may be as diverse as the possible signals. Requirements may be as straightforward as frame grabbing, AES128 encryption, or compression using a standard like H.264, or it may require a general-purpose graphics processor to implement specific custom processing. Different systems employ these functions in custom combinations. And most of them have severe size and/or weight constraints that mandate the most compact possible implementation.
These functions can be implemented on mezzanine cards affixed to a standard carrier board like Eurocard (VPX, CPCI, or VME) or COM Express baseboards. But the card must accommodate a large number of video channels (inbound and outbound) and formats as well as the ability to exchange data quickly over a format like PCI Express (PCIe). Graphics standards like SDI can signal at speeds over 3 Gbps, and intercard data may need to move at speeds exceeding 5 Gbps. Finally — and perhaps most critically — space is best economized if multiple modules can be placed on the carrier cards.
These parameters can be compared for the most common mezzanine boards, ranging from the aging PMC card; its updates, the XMC and the FPGA-oriented FMC cards; and the MXM 3.0 format (specifically geared towards video in laptops). A quick inventory of these formats, shown in black in Table 1, readily shows that high-end graphics and video processing exceed their capabilities, and that an alternative is needed. The existing standard form factors (black) cannot meet the needs of advanced graphics designs, meaning that a new form factor (MXC, in blue) is needed.
The new MXC form factor from Wolf Industrial Systems, shown in blue in the table, specifically targets the high-end video requirements of analog, digital, and broadcast SMPTE inputs and outputs, video mixing and overlay, H.264 compression, and AES128 encryption.
The MXC Form Factor
The most fundamental MXC characteristic is its size: it’s small enough to fit two modules on a 3U-sized card and four can fit on a 6U card. This isn’t simply a matter of outer dimensions, since at 85x70mm for a Type A card, it would appear to be similar in size to an 82x70mm Type A MXM 3.0 card. The difference is the connector arrangement: the few extra millimeters required by the MXM card edge connector makes it impossible to fit two on a 3U card (or four on a 6U card).
The next obvious characteristic of the MXC form factor is the sheer number of pins — 500. The pin arrangement is shown in Figure 1, and it is specifically geared for graphics and video applications. Banks of signals are available for analog or digital video in and out channels and can be configured for RS170, RGB, DP, DVI, TMDS, LVDS and SMPTE (SD-SDI to 3G-SDI) video formats. Together, as many as four different video input signals can be mixed and overlaid on up to eight different video outputs.
Video output data can be simultaneously compressed, encrypted and delivered through USB 3.0, PCIe or Ethernet 10/100/1G/10G connections. VPX carriers or baseboard-level systems using multiple MXC modules can communicate using 16 lanes of switched PCIe 2.1 or separate video interconnect busses, drastically reducing the effort required to interface video data sources that weren’t necessarily designed to talk to each other.
On 3U VPX/MXC carrier boards, 32 PCIe lanes switch between the two MXC modules, enabling them to DMA each other or to communicate to the backplane. This makes it possible to create high-performance multi-board system solutions (Figure 2). Four modules on a 6U card can work together on a sophisticated display algorithm using the bandwidth of 96 switched PCIe lanes. This PCIe interconnect provides a highspeed, efficient, standard way of moving data at 80 Gbps for 3U VPX/MXC carriers and 160 Gbps for 6U VPX/MXC carriers.
The achievable signaling speeds are drastically affected by the quality of the connector, visible in Figure 3. Video signals may need to travel at over 3 Gbps; the so-called Generation 2 PCIe revision has doubled the original PCIe rate to 5 GT/s (Gigatransfers/ second, equating to 5 Gbps for a single lane), and it is anticipated that this speed will increase with future generations of PCIe. Because the MXC card uses a Samtec Searay connector, it can handle up to 10-Gbps signaling, providing headroom for today’s speeds and extending the useful lifetime of the card as signaling speeds increase in the future.
Such high-speed signals require careful grounding, so each differential pair has its own ground. The power supply needs are also minimized since the MXC card requires only two power supplies (5V and 3.3V). With no components on the actual cards requiring a higher voltage, power design can be significantly simplified. Power consumption is reduced as well.
Finally, MXC is a rugged form factor. The Searay connector is rigid and reliable, as is the removable heat plate (shown in Figure 4), which allows customers a simple interface for convection or custom conduction cooling. Both are designed to withstand severe shock, vibration, and environmental extremes. MXC board designs conform to RAIC design standards, MIL-STD-810 compliance, and are designed to IPC Class 3 solderability standards, providing an overall module that will stand up to the harsh operating conditions — -40°C to 85°C and high humidity — to which these systems are likely to be subjected.
Examples of modules that can be interconnected and configured in numerous ways include:
• A video processing card featuring an 800-MHz AMD Radeon E6760 GPU with 1 GB of 700-MHz GDDR5 memory and the ability to output six independent video outputs in combination of DisplayPort, LVDS, TMDS, HDMI 1.4a, DVID, or VGA;
• A module that can compress and output HD-SDI uncompressed video at 1080P60, as well as output compressed H.264 and encrypted AES128 video over PCIe, USB or Ethernet, with additional FPGA space available for customized features;
• A GPGPU card with an AMD Radeon E6760 parallel processor using OpenCL1.1 SDK providing 560 GigaFLOPS of processing power;
• A four-channel frame grabber with two NTSC/PAL/SECAM inputs and two VGA inputs; and
• A video mixer with TMDS, RGB analog and two SMTPE video inputs for mixing or overlay.
While a need will remain for the standard card formats in the domains where they dominate, designers are increasingly looking for alternatives like the MXC card for sophisticated, high-performance applications involving the management and creation of multiple video streams.
Standard COTS form factors — and in particular, COTS Open-VPX and VPX-REDI standards with their various interconnect capabilities and system compatibilities — will always govern the military, industrial, medical, and aerospace domains. The MXC form factor fully embraces the modern serial-fabric Eurocard 3U and 6U form factors with Open VPX and VPX-REDI MXC carrier boards, making it possible to create very sophisticated video graphic systems on a single VPX board. Likewise, MXC cards can provide excellent video graphics companion modules for designers building COM Express baseboards.