USB control of underwater camera
Posted 29 September 2012 - 11:30 AM
Assuming one can get the bulkhead done for USB, I believe it is 3 meters ( EDITED, I measure my cable it is 3 meters ) max before signal corruption will occur. That is the longest wire I have uses for USB base GPS module and the data is not as big as you would use for camera photo files. The module only send NMEA GPS data to my laptop.
Being digital, if wire too long we probably get missing bits and get corrupted file, if analog we probably get distortion but use-able data.
The data cables for USB 1.x and USB 2.x use a twisted pair to reduce noise and crosstalk. USB 3.0 cables contain twice as many wires as USB 2.x to support SuperSpeed data transmission, and are thus larger in diameter.
The USB 1.1 Standard specifies that a standard cable can have a maximum length of 3 meters with devices operating at Low Speed (1.5 Mbit/s), and a maximum length of 5 meters with devices operating at Full Speed (12 Mbit/s).
USB 2.0 provides for a maximum cable length of 5 meters for devices running at Hi Speed (480 Mbit/s). The primary reason for this limit is the maximum allowed round-trip delay of about 1.5 μs. If USB host commands are unanswered by the USB device within the allowed time, the host considers the command lost. When adding USB device response time, delays from the maximum number of hubs added to the delays from connecting cables, the maximum acceptable delay per cable amounts to 26 ns. The USB 2.0 specification requires cable delay to be less than 5.2 ns per meter (192,000 km/s, which is close to the maximum achievable transmission speed for standard copper wire).
The USB 3.0 standard does not directly specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG 26 wires the maximum practical length is 3 meters (9.8 ft).
Let me know if your experiment works yah.....
Edited by SPP, 29 September 2012 - 11:34 AM.
Posted 02 October 2012 - 11:04 AM
I was thinking about doing the same thing some years ago, but found it wasn t practical.