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By prittenhouse

The serial connection from my Artemis Dev kit to my Win10 laptop works great with the supplied USB cable. When I add a USB extension cable in between, the serial connection stops working (that is, I don't get any Serial messages).

The Device Manager shows the COM port and says it is working properly
The Artemis drive shows up in both cases, so at least some form of communication is still working.

I have tried two different extension cables and got the same results. Both cables work fine for other boards.

Has anyone else run into this issue?

User avatar
By prittenhouse
I did some more testing and noticed that the V_USB was glitching down to 3.6V from a nominal 5.1V. I suspect there is a short inrush current that is causing the voltage to droop across the longer USB cables. The glitch was only about 8uSec and the 3.3V only nudged down a little during the glitch (which I think explains why the Artemis itself continues to operate fine).

Both the Artemis and the interface chip are spec'd to run well below 3.6V so I don't think its a brown-out issue. Since the interface chip is connecting and disconnecting repeatedly, what I think is happening is the USB voltage is dropping below the limit used to signal that the cable has been unplugged. That causes the IF chip to drop the connection. When the voltage comes back up the IF chip reconnects.

I was able to work around the issue by adding a 10uF cap between V_USB and ground.
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