PORTS Forum
Ports and Interfaces => USB => Topic started by: nvd on April 19, 2013, 09:57:36 am
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Hi All,
Our 2.0 device is undergoing Compliance test.
A failure is reported in one scenario --
2.0 device(Our device) is connected to 3.x host(renesas golden host) through a 1.x hub.
When we connect our device through a FS hub to renesas host, then the hub itself is not getting detected.
When our device is powered OFF, then the hub is getting detected. Again powering On the device, hub is lost.
Our device is Self powered and the hub is most likely Bus powered.(Not sure about the hub at the moment)
Chapter9 and class specific tests are passing with 3.0 host when no hub is used.
In addition, the Device is reported to be working OK when connected to EHCI host through 1.x hub.
Chapter9 and class specific tests are passing with EHCI host.
I don't have any logs which can help to debug this.
Could you please provide some insight on what might be happening?
Regards,
nvd
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Even self-powered devices can draw bus current. Be sure your device draws no more than 100 mA. Be sure bMaxPower in the configuration descriptor = 50 (to request 100 mA) or more than 2x the mA needed (but less than 50).
A hardware analyzer would probably offer a clue.
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First thing I would do is measure the current on the bus, an Ammeter might work for that.
The more fancy analysers like the LeCroy Voyager can do voltage/current measurements against time, that would tell you if you have an inrush problem. An oscilloscope could also be used for the inrush measurements, other wise you'd need an ammeter which told you peak current (which I don't think I've ever seen one of those).
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Thanks! That helped.