Part Number:AM3354
We’re using the AM3354 USB host interface to talk to our daughter card that’s a USB Full Speed device. We’ve been running in this setup on production hardware for a few years using the Linux kernel version 3.2.0-00388-g7c13576 (I know, not supported. It was when this device started shipping). A new batch of boards with more recent lot AM3354’s now detect a Babble a high percentage of boot time. Nothing on the other hardware or software has changed, and we have never seen this with any previous lots. We have implemented the Babble recovery mode in the build, so this is normally detected and through the recovery/reset process the boot continues and the interface is fine from then on. The Babble appears to happen as the am3354 is determining the speed of the device (sensing the device pullups). This is not related to the 5v power or noise on the D+/- lines.
Has anything changed on recent lots of that Sitara part that would cause the Babble startup sense or timing to be different? We use the ZCZ package. Some lot ID's for reference:
55A9E0W - One example older package lot ID in which we never see a Babble.
74C7Z6W - A newly purchased part with lot ID that will see a Babble in a high percentage of boots (20%+).
With initial testing, this seems to be repeatable for that new lot of processors.
Thx...Steve