USB 2.0

Already in the USB interface was developed by Intel and introduced onto the market as USB 1.0. The aim was to harmonise and simplify the different interfaces of the PC for peripheral devices (mouse, keyboard, modem, printer, scanner, ...). Due to the maximum data rate of 12 Mbit/s, the use in machine vision was unthinkable.

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The USB 2.0 interface was specified in and shortly afterwards integrated into mainboard chipsets. For a number of years, several USB 2.0 ports have been a standard in every PC. USB 2.0 corresponds to a data rate of 480 Mbit/s (approx. 40 MB/s net) which is sufficient for many applications. The voltage supply is also integrated in the cable. In case of industrial cameras, too, this interface is well established on the market and predominantly serves for cheap applications.

In the first chipsets for the next generation of USB were presented to an expert audience. USB 3.0, also called super-speed USB, is supposed to increase the transmission speed to up to 4.8 Gbit/s. A wide market launch is expected for . To which extent USB 3.0 is going to become prevalent for industrial cameras is not yet clear. Due to the high data rate even shorter cable lengths are to be expected in spite of more elaborate cables (one separately shielded pair of conductors each (shielded differential pair, SDP) for both transfer directions as well as a common shielding for the entire cable).

Advantages of USB 2.0 over analogue systems

FireWire and USB 2.0 have become a competition and gain particularly compared to the analogue image interface in recent years.

Advantages:

• The digital image transmission provides a loss-free signal transfer and therefore a better image than analogue image transfer.
• Omission of the expensive frame grabber card. Since , all PCs have provided several integrated USB interfaces.
• Extremely cheap standardised cable and connector technology with integrated voltage supply of the camera. They are significantly less expensive than analogue Hirose cables, but normally not lockable.

Characteristics of USB 2.0

• USB 2.0 provides a bandwidth of 480 Mbit/s, corresponding to an effective image data rate of 40 MB/s. This is sufficient performance in order to operate several cameras with standard resolution or higher on one computer and to inspect several parts per second.
• The technology offers hot plug / hot unplug: devices can be connected and detected during operation.
• Integrated voltage supply (5 VDC) for devices in the 4-pole cable. Devices complying with the USB specification may consume a total of 500 mA from the bus. Devices with a power of up to 2.5 W can therefore be supplied via the bus.
• According to the specification a USB cable must only be 4.5 m long at the maximum. By using high-quality cables, a length of approximately 10 m can be realised as well. If greater distances must be bridged, hubs can be connected in between.
• The thin flexible 4-pole cables have a simple design. In addition to two conductors for the voltage supply, two other conductors (D+ / D-) are required which are twisted. The data transmission is always symmetrical, one conductor transmits the data signal, the other always the inverted signal. The signal receiver evaluates the voltage difference of both signals. The signal level between 1 and 0 is thus twice as high, interferences can widely be eliminated. USB cables are therefore quite interference-free, have a thin cross-section and can easily be laid in an industrial environment.
• Data transmission is possible in both directions: camera control, triggering, parameterisation is equally possible during operation.
• The bus specification involves a central host controller, this master takes over the coordination of the connected peripheral devices called slaves. Up to 127 different devices can theoretically be connected to the USB bus: this is done in the form of a star topology. As always only one USB device can be connected to one USB socket, distributors (hubs) must be used. The network structure can be up to six levels deep. A daisy-chain operation like in case of FireWire is not permitted.
• Practical experience with USB camera systems in industrial facilities, however, reveal that operating several cameras, which simultaneously capture and send images, may lead to interferences and problems with overall cable lengths, etc. A particular bandwidth on the bus can indeed be exclusively assigned and guaranteed to a USB camera. This, however, is no longer available for any other connected device. For real multi-camera systems only one camera is ideally connected to one USB bus. Additional USB plug-in cards are cheap and easy to retrofit.

Disadvantages of USB 2.0

• Due to the master-slave principle of the USB bus, the camera is always a slave device and the host PC is the master device which must control the data traffic on the bus. In case of a triggered operation of the camera, the PC must request the images, which results in performance problems if several cameras with synchronous image acquisition are connected.
• Cables and plugs are unindustrial. Cables suitable for drag chains and robots are hardly available. The achievable cable lengths from 5 to 10 m without repeaters are often not sufficient for larger systems.
• USB as a standard defines the data traffic, plugs, signal level, etc., however, it does not natively support a standardised cross-manufacturer protocol for image transfer and camera control. Proprietary USB camera drivers must always be installed which bind the user to one hardware supplier.

Conclusion:
USB 2.0 provides the user with a practical interface which represents the cheapest solution for non-standardised image transfer for simple applications involving not too many cameras. Unfortunately it is not standardised, with the result that all manufacturers require their own USB driver. Ideal for use on laptop, PC and embedded devices (like Raspberry Pie Gen. 2 or Gen.3) less suitable for rough industrial environments or complex applications with many cameras. The cable length is limited.
Modern cameras are increasingly being developed on the basis of the USB3.x interface, which are mostly available as USB3 Vision devices and thus compatible with many cameras from other suppliers.

USB 2.0 Camera Module: 4 Things You Need to Know

USB 2.0 camera modules are widely used in various applications, ranging from surveillance systems and industrial automation to video conferencing and computer vision. They offer an easy-to-use and cost-effective solution for capturing high-quality images and videos. In this article, we will explore the key things you need to know about USB 2.0 camera modules.

1. Composition of USB 2.0 Camera Module

A USB 2.0 camera module typically includes the following components:

Image sensor:

This is the component that captures the image, it is usually a CCD (charge-coupled device) or CMOS (complementary metal-oxide-semiconductor) sensor.

Lens:

This component focuses the light onto the image sensor, it can be fixed or adjustable.

Image Processor:

This component processes the data from the image sensor and converts it into a digital signal that can be transmitted over USB.

USB controller:

This component manages the communication between the camera module and the host computer over the USB connection.

Power Management Unit:

This component manages the power supply to the camera module and can include a battery or a DC/DC converter.

Mechanical housing:

This component protects the internal components of the camera module and can include a mounting mechanism for attaching the camera module to a host device.

PCB:

The Printed Circuit Board (PCB) is where all the components are mounted, it connects all the components and allows them to communicate with each other.

Please note that the specific components and their composition of a USB 2.0 camera module may vary depending on the manufacturer and the intended application.

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2. Application of USB 2.0 Camera Module

USB 2.0 camera modules find extensive use in industrial and original equipment manufacturer (OEM) applications. They are commonly employed in machine vision systems for quality control, inspection, and process monitoring. USB 2.0 camera modules also serve as vital components in robotics, medical imaging, surveillance systems, and virtual reality applications.

A USB 2.0 camera module is a versatile device that can be used in a variety of applications. Some common applications include:

Video conferencing:

USB 2.0 camera modules are commonly used in desktop video conferencing systems to provide high-quality video and audio for remote meetings and collaborations.

Surveillance:

USB 2.0 camera modules can be used in surveillance systems to provide real-time video feeds for monitoring and security purposes.

Machine Vision:

USB 2.0 camera modules can be used in industrial and manufacturing settings for tasks such as quality control, inspection, and monitoring of production lines.

Robotics:

USB 2.0 camera modules can be used in robotics applications to provide visual input for navigation, object recognition, and other tasks.

Medical imaging:

USB 2.0 camera modules can be used in medical imaging applications such as endoscopy and microscopy to capture high-resolution images.

Automotive:

USB 2.0 camera modules can be used in automobiles for backup cameras, driver monitoring, and in-car entertainment systems.

Research and Development:

USB 2.0 camera modules can be used in research and development settings to capture images and videos for analysis and experimentation.

Gaming:

USB 2.0 camera modules can be used in gaming applications to provide real-time video feeds for motion detection and facial recognition in gaming.

Please note that USB 2.0 is an older standard and some newer camera modules might use USB 3.0 or even USB 4.0, it would be best to check and compare different options to find a camera module that best meets your needs.

3. Cost-Effectiveness:

USB 2.0 camera modules provide a cost-effective solution for many imaging applications. Compared to other camera interfaces, such as USB 3.0 or Gigabit Ethernet, USB 2.0 modules are generally more affordable. They offer a balance between performance, ease of use, and cost, making them suitable for a wide range of budget-conscious projects.

4. Limitations:

While USB camera modules offer numerous benefits, they have some limitations to consider. The USB 2.0 interface has a lower bandwidth compared to USB 3.0 or other high-speed interfaces, which can impact the maximum resolution and frame rate achievable. Additionally, USB 2.0 camera modules may not be suitable for applications requiring ultra-low latency or extremely high-resolution imaging.

Conclusion

USB 2.0 camera modules provide a convenient and cost-effective solution for capturing high-quality images and videos in various applications. With their plug-and-play functionality, software support, and integration options, they offer flexibility and ease of use. However, it's important to consider the resolution, frame rate, power requirements, and any limitations when selecting a USB 2.0 camera module for your specific project or application.