phenomenon:
Raspberry Pi or 3b + 4b stuck two free drive USB camera
The camera toward the light will time out newspaper
Light toward camera does not reported
problem:
Power is not enough
Toward the light may trigger a USB camera's exposure compensation leads to larger power
solve:
Use hub with additional power supply
Select timeout error occurs when calling camera under linux, there may be a camera (especially USB2.0 camera) is inserted at 2.0 interface, insufficient power supply capacity of the port. If you troubleshoot other problems yet to be resolved, you can see there is no problem port.
The last parameter V4L2 the select function is timeout, timeout is used to set the timeout, set up after the timeout, if select in the absence of file descriptors available to monitor the situation, we will wait for the timeout, more than this time select returns error.
When faced select timeout errors, not only consider the transfer of large timeout time, in fact, this is a temporary solution, impossible to adjust the timeout great tune bigger and useless, and certainly there are still blocking the transmission of other classes The problem. It is a problem for a long time, and later thought, this will not be the dregs of the port does not work, changed the computer 3.0 interface, then no such problems, the Advisory camera manufacturers, their answer is USB2.0 camera transmission and power supply are doing together, and therefore not very stable, may affect each other when between data transmission and power supply, how about the influence I do not know, but this issue may wish to check the idea as an extra bar.
The main problem to be a reference, the (resolution 720P) Logitech c270 operating state approximately 0.2A, a single design usb2.0 interfaces are typically conserved current 0.5A, usb3.0 1A, so a single port security bottom tow 2 is no problem If your camera with night vision, then if the power will soar at night, this should be analyzed, according to the actual situation but this situation can also be used with a power supply port usb hub solutions.
The problem is not connected to four cameras, the first auxiliary power supply + charger can get.
