How many FSCAM_CU135s can I connect to my system?
FSCAM_CU135 camera is tailor-made for cases in which multiple cameras are connected to a single host system. It is a transformative solution that is ready to make an indelible mark in industries such as photogrammetry, parking lot management and 3D document scanning.
Due to its high-powered cluster performance, one of the most commonly asked questions is, Exactly how many cameras can I connect to my system?. However, this question doesn’t have a single answer. But through this blog, we aim to give you a clearer picture.
The camera requires a maximum of 3.5 watts in USB 3.0 configuration. As per USB specification, each port in a host system can provide 4.5 watts. If you are about to connect multiple cameras to a single port through a USB Hub, then it is mandatory that the Hub is self-powered. Also, you should check the rating of Hub’s power adapter to know how much cameras it can accommodate.
Due to the above limitation, you can view the message in your system as shown below.
USB Tiered-Star Topology Restrictions
The USB topology has several hubs and functions. Functions can be any USB device, but the de-facto standard is for the topology to only allow only 7 tiers. The tiered-star representation is shown below.
Generally, all USB hosts has a root hub built into its system. This root hub forms the tier 1 of the topology. All other hubs and functions add on to the tier count and the maximum count is restricted to 7. Any hub or device that is connected above this tier 7 will not work.
There can also be cases where a single HUB purchased consisting of more than one hub connected in series internally. For example, if you purchase a 10-port hub, it is very likely to comprise multiple hubs that are connected internally as shown below:
In this case, each internal hub takes up a tier and utmost care should be taken not to connect another hub to its lowest tier. To verify the number of internal hubs, you can use device manager or USB Tree view applications. The device manager displaying 3 internal hubs is shown below.
An example representing the connection of 21 cameras with the help of two 10 port hubs and one 4 port hubs without violating the 7 tier restriction is shown below.
In case, if there is any violation in the number of tiers, a message will be thrown by the OS as shown below.
It is worth noting that some motherboard manufacturers include a USB Hub inside their system, which adds up to the tiers. Use USB Tree View application to make sure that the restriction is not violated.
According to the USB specification, the maximum number of devices that can be connected to USB host is 127. But as per our practical experiments, this is false.
Each processor has its own implementation in this restriction, and unfortunately it has not been properly documented.
Intel-based processors cite that the maximum number of devices is not a whole USB device but a single end point. Since each device has multiple end points, the practical maximum size is reduced. Another factor is the memory limitation, each PC can have limitation with respect to the memory allocated to the endpoints in BIOS.
The number of cameras that can be connected to a single USB host controller in Intel Processor based PC ranges from around 10 to 20.
In this case, you can expand the maximum number of cameras just by increasing the number of host controllers in that PC, with the help of PCIE expansion cards. An Intel PC where 45 FSCAM_CU135 cameras are connected is shown below.
In ARM-based system, the restrictions with respect to end point does not seem to be true. Even with a single host controller, you can connect about 50 cameras in this system. In any case, if you exceed the maximum devices that can be connected, you will receive the message as shown below.
And in device manager, a device cannot start symbol with a message will be displayed as shown below.
We hope that this blog provided you a better understanding of all the factors to be considered before understanding how many FSCAM_CU135 cameras can be connected to your system.