Beagleboard stable USB EHCI hack
Occasionally, the USB EHCI controller on a
Rev C3 Beagleboard stops working until the system is rebooted. It is
usually triggered by heavy traffic, e.g. due to a WLAN dongle or a USB
thumbdrive. It was apparently fixed properly in Rev C4, but if you're
stuck with a C3 board the following hack may solve the problem for
The error is due to noise on the VDD2 power rail (1.8 V). Too many
events occuring simultaneously may cause the power rail to dip, which in turn
causes the USB PHY to panic. One way to lower the probability of this
is to increase the capacitance of the power rail near the USB PHY.
As you can see in the picture, I've soldered a 10 uF electrolytic
capacitor across C97, thus increasing the capacitance from 10 uF to
20 uF. The capacitor is oriented with the positive side towards the
SD card slot, but you may want to verify this yourself using a voltmeter
on a running system.
Be careful, and don't blame me if you mess it up. But if you do, you now
have a valid reason to buy a Rev C4 board. =)
The capacitance hack was suggested in this
usenet thread, along with much other speculation.
Posted Thursday 13-May-2010 15:35