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alexz
Joined: 17 Sep 2004
Posts: 133
Location: UK
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| USBN9603 Hardware question |
 Posted: Wed Nov 03, 2004 3:31 am |
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May be this is not the right place to ask this question, but I know there are a lot of people with knowledge visit this forum.
I am using the PIC16F877 to control the USBN9603 for the USB control .
As written in the specification, the 'D+' signal should be pulled up to 3.3v through the 1.5k resistor to get the Full Speed operation.
The problem is that once I have done that, the voltage on the D+ side of the resistor is zero and not close to 3v as expected.
On the 3.3v side of the resistor the voltage is 3.3v as expected.
I know that the host should recognize one of the D+ or D- signals high, in order to start the enumeration and also get the interrupt in the PIC.
That's why it is essential to have the D+ high, if I am not wrong.
The question is: what voltage should I expect on the D+ ?
If the zero volts I have got at the moment is correct, why do not I get the interrupt in the PIC then?
If the zero volts is not right, how can I correct that?
Thanks a lot.
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Alex |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Wed Nov 03, 2004 7:01 am |
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| Quote: | If the zero volts is not right, how can I correct that?
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Look for a short. |
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alexz
Joined: 17 Sep 2004
Posts: 133
Location: UK
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| Posted: Wed Nov 03, 2004 7:06 am |
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| Mark wrote: | | Quote: | If the zero volts is not right, how can I correct that?
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Look for a short. |
So,do you mean that it should be around 3v at the D+ signal?
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Alex |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Wed Nov 03, 2004 7:12 am |
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| Quote: | So,do you mean that it should be around 3v at the D+ signal?
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I have no idea! I just used a bit of common sense. I have no idea about that chip but it is highly doubtful that it could pull the line to "0" volts. If you said 0.3 volts or higher, then I might change my statement. But 0 volts, I would look for a short. |
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alexz
Joined: 17 Sep 2004
Posts: 133
Location: UK
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| Posted: Wed Nov 03, 2004 7:14 am |
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60mV 
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Alex |
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