This is to vent my frustration with USB on ts7800. I'm trying
to deploy systems with Maxon BP3 3g usb wireless modems (sierra
wireless chipset). These work on ts7200 & x86 fine. But don't work
connected to a ts7800 with 2.6.21-ts(oct102008) +airprime or with
2.6.30-rc7(http://ts78xx.digriz.org.uk/)+option. The option module failes
immediately giving messages like this: "option: option_instat_callback:
error -71" which apparently indicates a low-level USB problem. I've tried
multiple ts7800 boards and multiple USB modems.
Fortunately if a (non-powered) USB hub is interposed the modem seems to
work reliably. But the extra power consumption of the hub is annoying
because my systems are solar-powered.
More frustrating is audio. I capture sound using custom-built usb sound
boards based on AVRs and previously using Griffin iMics. Again these work
with ts7200 (same EABI kernel & userland) & x86 but fail with ts7800s
running both 2.6.21-ts and 2.6.30-rc7. As far I can tell the problem
is not ALSA, it seems to be a low level hardware/software bug in the
ts7800's USB. If a (non-powered) USB hub is interposed, sound capture
sometimes works but it depends on the hub, the sampling rate and other
configuration details. I can't make it reliable enough for my purposes.
I don't need sound playback - but it also seem to have problems.
I haven't seen any problems with USB storage devices on the ts7800 but I
don't use them much. The above problems occur if you power the devices
separately or via the ts7800.
So the moral is, don't count on non-storage USB devices working on
a ts7800. In particular USB audio is likely to fail. And interposing
a hub might help. As consequence I'm looking for alternative low power
boards with SATA+USB 2.0. This one looks interesting:
http://www.logicpd.com/sites/default/files/1013568A_OMAP-L138_eXperimenter_Brief.pdf
More suggestions welcome.
Andrew
|