maemo.org - Talk - View Single Post - N900 will not allow USB OTG!

	joerg_rw	2010-05-20 , 18:40
	Posts: 2,222 \| Thanked: 12,651 times \| Joined on Mar 2010 @ SOL 3	#925

Originally Posted by blue_led

for what reason bme read an idle/unused asic ( bq24xxx ) ?
as i understand from specs in charge or boost mode for sustaining those functions, some activity on i2c bus is needed.
if NO CHARGE mode why i2c read / writes activity ?. this useless activity drain the precious battery.
i will look closer on specs for a decent reason.

if vbus sensing for mode selection pop-up is needed instead of pulling status of BQ24k vbus sensing from 4030 via interrupt is preferred.

popup usb mode selection is not in bme or mce . what code is doing this selection ?

i wish a new one with:

pc suite mode ( never used )
mass storage
host ( docking station )
printer for photos ( pict bridge )
.....

VBUS sensing is to sense attachment of N900 to a host, while 1707 PHY pullup of D(+/-, depending FS, LS) is for sensing attachment of a device to N900.
Quite obviously attachment of a device to N900 can not be detected unless N900 is in hostmode.
So any popup requester offering a hostmode option ("host ( docking station )") is rather nonsense.

The whole hassle about VBUS-supply from N900 is just because we are not in a clean plain hostmode, and tricking the OTG statemachine from B-state into A-state includes a rather complex negotiation scheme about which of both OTG devices supposed to form the session is responsible now for providing VBUS power (if any of both) - so the OTG statemachine has quite a number of useless and partially nonfunctional tests like OTG_STATE-A_VBUS_RISE etc pp (exact names may differ), and we need to do a lot of messing around with VBUS supply to make these useless tests succeed.
For a plain vanilla correctly implemented hostmode, all those tests are moot and should be disabled.

and again what I believe will become my mantra and signature for the next few dozen posts:
We need to put "echo host >mode" to work, we need to switch PHY chip to host config which is 2* pulldown R.

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