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Next Generation Interfaces Compared
Next Generation interfaces include Ethernet, USB, Camera Link, CoaXpress standards, and Thunderbolt3. The camera interfaces have shaped the growth of the machine vision industry and further more aspiring to do so in the future.
USB 3.2
USB 3.2 uses both sides of a Type-C connector to support two USB 3.1 links in parallel, this specification enables transfer speeds up to 20 Gbit/sec. The only difference between Generation 1 and Generation 2 is in the transition from USB 3.0 to USB 3.1. it is maintained in USB 3.2.
Key differences between Generation 1 and Generation 2
- The signalling rate differs, Generation 2 doubles the signalling rate from 5 Gbit/sec to 10 Gbit/sec
- Encoding efficiency, Generation 1 uses 8/10b encoding while Generation 2 uses a more efficient encoding of 128/132b.
- Maximum cable length, Generation 1 links provide 4 Gbit/sec of real-world throughput, while Generation 2 links support up to 9.7 Gbit/sec. Generation 2 links support real-world transfer speeds much closer to the signalling rate.
- The maximum cable length of Generation 1 links is five meters, while Generation 2 links are limited to one meter. The short cable length of USB 3.2 Generation 2 is likely to limit its widespread adoption until affordable active optical cables become available.
Take Note
- A USB 3.2 interface will not be faster than USB 3.1. Even though less efficient encoding of USB 3.1 Generation 1 were doubled, it would still be about 20% slower than a USB 3.1 Generation 2 connection. The differences in maximum cable length for each generation mean that users select a cable with an appropriate length for their interface’s generation.
- USB supports Direct Memory Access (DMA), which enables image data to stream from a camera directly into system memory. This is ideal for embedded applications with limited memory bandwidth and CPU power.
Thunderbolt3
Thunderbolt interface has not yet made any other changes in the machine vision industry, like USB 3.2. However, it promises a useful combination of up to 40Gbit/sec, ease of use, and familiar USB-C connectors.
It will also be able to support USB Power Delivery specification, enabling it to deliver up to 100W of power. The current cable length is limited to only 50 cm which may constrain adoption of this interface until reliable and affordable active optical cables become available.
If we are to talk about the maximum signaling speed across a Thunderbolt3, that is 40Gbit/sec, the real-world throughPut will appear significantly lower.
Intel recently announced that all their new chipsets will support Thunderbolt3. They have also relaxed licencing requirements to encourage third-party manufacturers to adopt the interface. They want to drive adoption of Thunderbolt3 but the challenge is there are currently no Thunderbolt3 machine vision cameras.
USB 3.1 vs USB Type-C
It’s important to note the difference between standards like USB 3.1, 3.0 and USB 2.0 and ports or plugs such as USB-A, B or C. The version of the USB standard indicates the speed and the function of the cable. USB Types are the shape of the cable plugs and the shape of their ports in your computer or device.
USB Type-A is the familiar rectangular port. It is the largest USB port and is often found on computers and car chargers. The device that has the USB Type-A port is almost always the host device.
USB Type-B port is a square-shaped plug that is often used on external hard drives and printers. There are also mini and micro USB Type-B ports that are commonly found on portable devices: smartphones and tablets. Mini USB ports tend to be on things like cameras and older devices.
USB Type-C, also known as USB-C, is simply a new shape of port and cable plug, with many benefits. The first is reversibility. The difficulty of plugging in a USB device is a universal staple of Internet humor. Even when looking it is not easy to plug in a USB cable correctly.
Since the new USB Type-C connector is reversible, you can plug it in either way, it doesn’t matter. Also, if you have a computer and a device that both have USB-C ports you can plug either end of the cable into the PC, and the other in the peripheral.
USB Type-C is about the same size as micro USB connections, so it’ll fit in even the smallest of devices. On addition to that, Type-C USB is great for charging. Bi-directional power means that not only can your device charge a peripheral, but if it runs low, the peripheral could charge the host device.
USB 3.1 vs USB 3.0 vs USB 2.0
USB 3.0 was introduced over half a decade ago, that was November 2008. It significantly increased the speeds of data transfer. USB 2.0 was only capable of a theoretical maximum data transfer rate of 480 megabits per second, while USB 3.0 was capable of 5 gigabits per second, approximately 10 times faster.
During those days, very few computers had USB 3.0 ports, and some only had a few alongside USB 2.0 ports. To contrast between USB 2.0 and 3.0, the USB 3.0 ports had a blue connector or tongue inside.
USB 3.1 was released just a few years ago, in July of 2013. Since then, device manufacturers have been working tirelessly to bring the new standard to the products around your home. The data transfer speed of USB 3.1 is incredible, 10Gbps. This rivals the speed of Ethernet and the original Thunderbolt. However, there are few devices that are capable of such high data transfer speeds.
Note that:
The version such as 2.0, 3.1 of USB describes the data speed and power supply specifications of a cable or connection, while the type of USB eg A, B, C describes the physical shape of the port and connector.
For instance, Type-A connector can accept USB 3.1, 3.0, 2.0 and even 1.0 cables and devices, regardless of which version of USB the port supports. The lowest version of USB among the cables and devices will determine the data transfer speed on a port-by-port basis.