I didn't see any similar thread to this it would be very useful to have ours projects well documented step by step, why pay so much for "know-how"?
This thread is dedicated for those interested in building their own cables.
This will start with my latest project - USB A - B cable.
I needed USB cable which meet the USB 2.0 spec over longer runs, as we know the maximum cable length is 5m I'll be back to this later.
I always wondered why not use Ethernet cable as they are special designed to transmit digital data such as a USB cable through the current loop and it is also adapted for transporting the information at a much greater distance than the USB. So I chose the cable category (Fa) cat7 actually Cat7+is improved version of 7a, made by Swedish Supra Cables.
Supra Cat7+ spec.
The USB 2.0 standard defines a High Speed transfer rate of 480Mb/s.The transmission is done from a transmitter to a receiver through differential data line, to limit data reflection, the following must match:
- Transmitter output impedance
- Line characteristic impedance
- Receiver input impedance
The USB 2.0 standard defines a cable with 90Ω ± 10-15% differential impedance.The cable may have no more than 30 ns signal propagation delay on entire length.Cable is 4 wire.The data wires are 28 AWG twisted pair, the power wires are 20 to 28 AWG.The cable shielding must cover at least 65% overall.
The Supra cat7+ have everything what I need to build my own USB cable. Excellent screening characteristics 100% coverage(individual and overall screen) for minimal interference, low delay skew, bandwidth 1300Mhz, low capacitance and efficient noise rejection maintain signal integrity in the long run interconnects, PE- insulated wires with the exact 100 Ohm impedance design in wide range.
Note : This is a simple tutorial.
As you see, the Ethernet cable consists of four pairs of conductors, each of the conductor pairs has its own shielding, in addition to the outer shielding, we will need only three pairs, one twisted pair for the (data -), (data+), another pair will be combined together to reducing the resistance of wire and connected to the pin 4 GND and the same we will do with the Pin 1 +5vdc, the remaining pair needs to be cut off.
USB Connectors Pinout
1. +5 VCC
The braid is to be terminated (crimped) to the plug metal shells at both ends, as close to 360° as possible, to prevents EMI/RFI interference.
^ TEST BEFORE YOU PLUG ANYTHING IN ^
Done! Here you go 2.5m high quality USB A - B cable at low cost.
Hope this was helpful.
reference - some useful links:
P.S. About over longer cable runs: I tested so far 12 meters cable! (before I split it into shorter lengths) connected to my Burson Conductor DAC with MacBook pro, iMac and my very old Toshiba laptop streaming music up to 24/192kHz without any glitches or even single dropouts and finally tested the cable with the HP printer and it worked without hassle.
It shouldn't work! It gave me a lot to think about.The cable quality does matter and parameters such as characteristic impedance is the goal, rather than esoteric materials.
Edited by WALL-E - 5/28/13 at 2:10pm