Interface uitleg

• Camera Link

Is a serial communication protocol designed for computer vision applications based on the National Semiconductor interface Channel Link. It was designed for the purpose of standardizing scientific and industrial video products including cameras, cables and frame grabbers. The standard is maintained and administered by the Automated Imaging Association or AIA, the global machine vision industry's trade group. 

Transmission Protocol

The base Camera Link standard uses 28 bits to represent up to 24 bits of pixel data and 3 bits for Video Sync signals. These consist of Data Valid, Frame Valid, and Line Valid bits. The data is serialized 7:1, and the four data streams and a dedicated clock are driven over five LVDS pairs. The receiver accepts the four LVDS data streams and LVDS clock, and then drives the 28 bits and a clock to the board The camera link standard calls for these 28 bits to be transmitted over 4 serialized differential pairs with a serialization factor of 7. The parallel data clock is transmitted with the data. Typically a 7x clock must be generated by a PLL or SERDES block in order to transmit or receive the serialized video. To deserialize the data, a shift register and counter may be employed. The shift register catches each of the serialized bits, one at a time, then registers the data out into the parallel clock domain - once the data counter has reached its terminal value.

Base Configuration

The "Base" Camera Link configuration carries signals over a single connector/cable. The cable used is a MDR ("Mini D Ribbon") 26-pin Male Plug Connector, optimized by 3M for the LVDS signal. In addition to the 5 LVDS pairs transmitting the serialized video data (24 bits of data and 4 framing/enable signals), the connector also carries 4 LVDS discrete control signals and 2 LVDS asynchronous serial communication channels for communicating with the camera. At the maximum chipset operating frequency (85 MHz), the base configuration yields a video data throughput of 2.04 Gbit/s (255 MB/s)

Medium/Full Configuration

The Camera Link specification includes higher-bandwidth configurations that provide additional video data paths over a second connector/cable. The "Medium" configuration doubles the video bandwidth, adding an additional 24 bits of data and the same 4 framing/enable signals present in the "Base" configuration. This yields a 48-bit wide video data path capable of throughput up to 4.08 Gbit/s (510 MB/s). The "Full" configuration adds another 16-bits to the data path, resulting in a 64-bit wide video path that can carry 5.44Gbit/s (680 MB/s).

Other Extended Configurations

Some camera and data acquisition hardware manufacturers have extended the bandwidth of the interface beyond the limits imposed by the Camera Link interface specification. These formats extend the width of the "Full" configuration by reassigning some of the redundant framing/enable signals to produce a data path width of up to 80-bits, which further increases the video bandwidth.

• GigE vision

GigE Vision® is a new camera interface standard developed using the Gigabit Ethernet communication protocol. GigE Vision ® is the first standard to allow for fast image transfer using low cost standard cables over very long lengths. With GigE Vision® , hardware and software from different vendors can interoperate seamlessly over GigE connections.

The standard was developed for industry, by a talented group of companies representing every sector of the vision industry. The Automated Imaging Association (AIA) oversees the ongoing development and administration of the standard.

GigE Vision® offers many benefits including

 * High bandwidth (1000 Mbps) allows large uncompressed images to be transferred quickly in real time
* Uncompromised data transfer up to 100 meters in length
* Standard gigabit Ethernet hardware allows single/multiple camera connection to single/multiple computers
* Low cost cables (CAT5e or CAT6) and standard connectors
* Highly scalable to follow the growth of Ethernet bandwidth. As 10GigE becomes mainstream, GigE Vision® will be the fastest connection in the industry
* Standard hardware, cables allow easy, low cost integration

Technical Details of the GigE Vision™ Standard

The GigE Vision™ standard has four elements:

1. The GigE Vision™ Control Protocol (GVCP), which runs on top of Universal Datagram Protocol (UDP) IPv4. It defines how to control and configure compliant devices such as cameras, specifies stream channels and provides mechanisms for cameras to send image and control data to host computers.
2. The GigE Vision™ Stream Protocol (GVSP), which defines data types and describes how images are transmitted over GigE.
3. The GigE Device Discovery Mechanism, which defines how cameras and other compliant devices obtain IP addresses.
4. An XML description file based on the emerging GenICam™ standard, which provides the equivalent of a computer-readable datasheet to allow access to camera controls and image stream.

• IEEE 1394

The IEEE 1394 interface is a serial bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used by personal computers, as well as in digital audio, digital video, automotive, and aeronautics applications. The interface is also known by the brand names of FireWire (Apple Inc.), i.LINK (Sony), and Lynx (Texas Instruments). IEEE 1394 replaced parallel SCSI in many applications, because of lower implementation costs and a simplified, more adaptable cabling system. The 1394 standard also defines a backplane interface, though this is not as widely used.

History and development

FireWire is Apple Inc.'s name for the IEEE 1394 High Speed Serial Bus. It was initiated by Apple and developed by the IEEE P1394 Working Group, largely driven by contributions from Apple, although major contributions were also made by engineers from Texas Instruments, Sony, Digital Equipment Corporation, IBM, and INMOS/SGS Thomson (now STMicroelectronics).

Apple intended FireWire to be a serial replacement for the parallel SCSI (Small Computer System Interface) bus while also providing connectivity for digital audio and video equipment. Apple's development began in the late 1980s, later presented to the IEEE,[2] and was completed in 1995. As of 2007, IEEE 1394 is a composite of four documents: the original IEEE Std. 1394-1995, the IEEE Std. 1394a-2000 amendment, the IEEE Std. 1394b-2002 amendment, and the IEEE Std. 1394c-2006 amendment. On June 12, 2008, all these amendments as well as errata and some technical updates were incorporated into a superseding standard IEEE Std. 1394-2008.
Sony's implementation of the system, known as "i.LINK" used a smaller connector with only the four signal circuits, omitting the two circuits which provide power to the device in favor of a separate power connector. This style was later added into the 1394a amendment. This port is sometimes labeled "S100" or "S400" to indicate speed in Mbit/s.
The system is commonly used for connection of data storage devices and DV (digital video) cameras, but is also popular in industrial systems for machine vision and professional audio systems. It is preferred over the more common USB for its greater effective speed and power distribution capabilities, and because it does not need a computer host. Perhaps more importantly, FireWire makes full use of all SCSI capabilities and has high sustained data transfer rates, a feature especially important for audio and video editors. Benchmarks show that the sustained data transfer rates are higher for FireWire than for USB 2.0, especially on Apple Mac OS X with more varied results on Microsoft Windows.

Technical specifications

FireWire can connect up to 63 peripherals in a tree topology (as opposed to Parallel SCSI's electrical bus topology). It allows peer-to-peer device communication — such as communication between a scanner and a printer — to take place without using system memory or the CPU. FireWire also supports multiple hosts per bus. It is designed to support Plug and play and hot swapping. The copper cable it uses (1394's most common implementation) can be up to 4.5 metres (15 ft) long and is more flexible than most Parallel SCSI cables. In its six-circuit or nine-circuit variations, it can supply up to 45 watts of power per port at up to 30 volts, allowing moderate-consumption devices to operate without a separate power supply.

FireWire devices implement the ISO/IEC 13213 "configuration ROM" model for device configuration and identification, to provide plug-and-play capability. All FireWire devices are identified by an IEEE EUI-64 unique identifier (an extension of the 48-bit Ethernet MAC address format) in addition to well-known codes indicating the type of device and the protocols it supports.

Operating system support

Full support for IEEE 1394a and 1394b is available for Microsoft Windows XP, FreeBSD, Linux, Apple Mac OS 8.6 through to Mac OS 9[8], and Mac OS X as well as NetBSD and Haiku. Historically, performance of 1394 devices may have decreased after installing Windows XP Service Pack 2, but were resolved in Hotfix 885222 and in SP3. Some FireWire hardware manufacturers also provide custom device drivers which replace the Microsoft OHCI host adapter driver stack, enabling S800-capable devices to run at full 800 Mbit/s transfer rates on older versions of Windows (XP SP2 w/o Hotfix 885222) and Windows Vista. At the time of its release, Microsoft Windows Vista supported only 1394a, with assurances that 1394b support would come in the next service pack. Service Pack 1 for Microsoft Windows Vista has since been released, however the addition of 1394b support is not mentioned anywhere in the release documentation.

Node hierarchy

FireWire devices are organized at the bus in a tree topology. Each device has a unique self-id. One of the nodes is elected root node and always has the highest id. The self-ids are assigned during the self-id process, which happens after each bus reset. The order in which the self-ids are assigned is equivalent to traversing the tree in a depth-first, post-order manner.

Standards and versions

The previous standards and its three published amendments are now incorporated into a superseding standard, IEEE 1394-2008. The features individually added gives a good history on the development path.

FireWire 400 (IEEE 1394-1995)
A 6-circuit FireWire 400 alpha connector
The original release of IEEE 1394-1995 specified what is now known as FireWire 400. It can transfer data between devices at 100, 200, or 400 Mbit/s half-duplex data rates (the actual transfer rates are 98.304, 196.608, and 393.216 Mbit/s, i.e. 12.288, 24.576 and 49.152 megabytes per second respectively). These different transfer modes are commonly referred to as S100, S200, and S400.
Cable length is limited to 4.5 metres (14.8 ft), although up to 16 cables can be daisy chained using active repeaters; external hubs, or internal hubs are often present in FireWire equipment. The S400 standard limits any configuration's maximum cable length to 72 metres (240 ft). The 6-circuit connector is commonly found on desktop computers, and can supply the connected device with power.
The 6-circuit powered connector, now referred to as an alpha connector, adds power output to support external devices. Typically a device can pull about 7 to 8 watts from the port; however, the voltage varies significantly from different devices. Voltage is specified as unregulated and should nominally be about 25 volts (range 24 to 30). Apple's implementation on laptops is typically related to battery power and can be as low as 9 V and more likely about 12 V.

FireWire 800 (IEEE 1394b-2002)
A 9-circuit beta connector.
IEEE 1394b-2002 introduced FireWire 800 (Apple's name for the 9-circuit "S800 bilingual" version of the IEEE 1394b standard) This specification and corresponding products allow a transfer rate of 786.432 Mbit/s full-duplex via a new encoding scheme termed beta mode. It is backwards compatible to the slower rates and 6-circuit alpha connectors of FireWire 400. However, while the IEEE 1394a and IEEE 1394b standards are compatible, FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's alpha connectors, making legacy cables incompatible. A bilingual cable allows the connection of older devices to the newer port. In 2003, Apple was the first to introduce commercial products with the new connector.