huanyxj
Newbie level 3
Now I have a difficult USB problem that I cannot solve, so I have to ask help.
There are three questions.First,how large the resistors on the DH/DL line should be? In my design 24 ohm resistors were used firstly,but my usb device cannot work normally.Now I use a 30 ohm resistors,and the device can work.So I donot understand what effects result from the resistors on the DH/DL line and how large they should be.
The second is that what the usb cable may bring bad factors for usb device?
There are several pictures printed in test,first is the signal waveforms occured in the condition that usb transceiver used 24 ohm resistors on the DH/DL line . The second is that the signal waveform occured in the condition that I use ordinary usb cable connect host and device. The third is that the signal waveform occured in the condition of stardard full-speed usb cable was used.
There is another question that there are some great jitters in the rise and fall times.I donot know why they look like that and what make it.
I want to know as soon as possible, please help me![/img][/quote]
There are three questions.First,how large the resistors on the DH/DL line should be? In my design 24 ohm resistors were used firstly,but my usb device cannot work normally.Now I use a 30 ohm resistors,and the device can work.So I donot understand what effects result from the resistors on the DH/DL line and how large they should be.
The second is that what the usb cable may bring bad factors for usb device?
There are several pictures printed in test,first is the signal waveforms occured in the condition that usb transceiver used 24 ohm resistors on the DH/DL line . The second is that the signal waveform occured in the condition that I use ordinary usb cable connect host and device. The third is that the signal waveform occured in the condition of stardard full-speed usb cable was used.
There is another question that there are some great jitters in the rise and fall times.I donot know why they look like that and what make it.
I want to know as soon as possible, please help me![/img][/quote]
