Diy Y usb cable

[mansr]

11 hours ago, Speedskater said:

Not NIT PICKING at all!

'earth is a way, way overused term.  There are many points in a system that might be casually called earth. Only one of those points is the correct one.

The term "earth" should only be used for points in a circuit with a low-impedance connection to the actual earth, typically via the mains safety ground.

[mansr]

1 minute ago, sandyk said:

It's STILL NIT PICKING.

Words have meanings. Get used to it.

[mansr]

9 minutes ago, sandyk said:

 his isn't the appropriate Forum to discus this kind of subject.

Neither does it have any relevance to the question originally asked by the OP.

Oh, look. More irony.

[mansr]

24 minutes ago, R1200CL said:

I like it 😀

 

So how long does it have to be in order to comply with the USB specifications ? .....

There is no minimum length.

[mansr]

1 minute ago, R1200CL said:

So where is the 90 ohm located ? In the cable or the plugs ?

90 Ω is the characteristic impedance, not DC resistance.

[mansr]

28 minutes ago, R1200CL said:

Several entries in that table are wrong. HDMI, DisplayPort, DVI, and PCIe should all be 100 Ω. The figures there are taken from an NXP application note referencing an Intel design guide which recommends using slightly lower values for PCB traces in specific applications. Don't trust Wikipedia.

[mansr]

36 minutes ago, R1200CL said:

@mansr

The use of a twisted ethernet cable as USB was the interesting part here.  So I guess the value for ethernet was correct. 

Yes, Ethernet is 100 Ω. That's (barely) within the acceptable range for USB 2.0.

 

Quote

And next question is, why do one have to comply with the specifications?

And more important what happens if you don’t ?

Then you get signal reflections which, if bad enough, cause transmission errors.

 

Quote

Bits are bits 😂

Only if they are received correctly. Impedance matching is one part of ensuring that they are.

[mansr]

2 hours ago, marce said:

the faster the signal (this is the signals rise time) the more critical the impedance control.

And for this reason, picosecond rise times on signals with fairly low edge rate (like S/PDIF) isn't necessarily a good idea.

[mansr]

35 minutes ago, R1200CL said:

Did you just made an argument why USB is likly to be superior to S/PDIF ?😀

No.