blackarchon wrote:So do you think it may be a problem with the hardware rather than the software?
I have not looked at the schematics or layout of the electronics and therefore cannot be sure what is going on. It is suspicious that the noise level on the USB connection is high at the same time as the errors, but this might not be correlated with the errors in /var/log/messages. The HDMI chip firmware had to be tuned to get the PI through the CE tests. Therefore, I am not surprised that I can hear HDMI imaging noise. There are several others on the forum who have a reasonable or good knowledge of the layout and may be able to give a better diagnosis.
What do you mean by "I can hear HDMI imaging noises"?
Do you pick it up on a radio, or what?
The firmware tweak needed for EMC certification probably were only to do with a lower default drive level. These signals are notorious for EMC in that they are in the range that is tested for and are almost "monotone", and thus score high peaks on a spectrum analyser, especially if used with badly shielded cables.
If you want to experiment with "noise" on the USB (I'm guessing you must mean noise on the datalines), and power feedback over the uplink cable to your hub, then I suggest using a tiny piece of cellotape to cover pin 1 of the USB plug (see wikipedia for a description which pin is pin 1).
Another test is to measure with a multimeter if there is a voltage between the ground of the PI, and earth there is an AC voltage. Ground of the raspberry PI, is TP2. For earth, I suggest you use either the ground pin of your mains, or perhaps a waterpipe (not the Turkish variant mind you) but something electrically tied to earth.
If there is a lot of voltage there, something like half the mains voltage, its probable that there is a PSU used in the system that has two small capacitors tied between the mains lead, and the "ground pin" of the PSU, if that ground isn't really connected to earth it means that half the mains voltage is on GND of the system, which may well lead to strange problems.
be careful with tying TP2 to earth in this case, as you do not know how "hard" the voltage might be, I suggest you start with a 10K resistor in series just in case, then see if the voltage disappears.
Multimeters (good ones) typically have an impedance in the AC and DC voltage settings of about 11.11 Meg Ohm, (for 1:10 probes consisting a 100M resistor) so they wont act as shorts to ground during measurements like this.