Looking for some guidance on subject ... getting USB Host to work (Overo
J4-32,33,34,35) on a custom Overo expansion board. We're using the Tobi as
our basline USB Host connection back to a Linux PC (terminal), then
switching-over to our custom setup. Initially we had not had VBUS connected
as this is a self-powered application; we're only using USB Host for the
console connection during system integration.
Our initial cut at this had the custom expansion board connected to USB OTG
(Overo J1-36, 37) and no connection to USB Host. Now via a custom Gumstix
Breakout Board we've direct-connected a USB type A to mini cable to the J4
pins. VBUS is there from the PC terminal as observed via breaking-out leads
and viewing on a scope, but DP & DM are dead; no signals observed on scope,
no terminal activity. This breakout scheme was validated on the Tobi, so we
believe the cable works.
Looking at Tobi schematic we've observed some overload protection, ESD
protection, and dual-choke. There's also a power switch in series with the
VBUS line from the mini-jack controlled via GPIO_168 ... CPEN (not sure of
full name) which I believe has to do with the OMAP enabling/disabling or
providing a Tobi reset for the port? Our expansion board currently does not
replicate these Tobi features, and we've observed that the Pinto USB
connector interface is fairly straight forward.
Looking for some pointers on diagnosing a dead USB Host from Overo.
Thanks in advance,
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