USB headset detection

Rask Ingemann Lambertsen rask at sygehus.dk
Sat Mar 14 01:10:44 CET 2009


On Sun, Mar 08, 2009 at 09:18:35PM +0000, Andy Green wrote:
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> Somebody in the thread at some point said:
> 
> |    1. Charger (maybe with Y-cable) connected. Detected by 47 kOhm seen
> on ID
> |    pin. Set USB mode to host and turn off USB power supply.
> |
> |    2. USB headset connected. Detected by ? Set USB mode to host and
> turn on
> |    USB power supply.
> |
> |    3. USB host connected. Detected by ? Set USB mode to device and
> turn off
> |    USB power supply.
> 
> "?" here is meant to be ID pin level.  But we don't supply a USB device
> breakout cable which would consistently do the right thing to ID, so it
> means we can't make decisions based on ID level like a normal OTG setup.

   Actually, "?" was meant to be some, as of yet undetermined, detection
based on the power and data pins. But there are at least three problems that
come to my mind:

   1) We (probably) can't detect a USB host if USB power is enabled, both
because of the 15 kOhm pulldowns and because the PMU won't see the external
power.

   2) We most likely won't be able to detect a USB device without providing
power to it.

   3) We (probably) can't detect a USB device if we're set for USB device
mode. Likewise with a USB host if we're set for USB host mode.

   But it sure would be nice if it worked automatically. I'll have a look at
the s3c2442 user's manual to see if there's any sort of help from that side.

-- 
Rask Ingemann Lambertsen
Danish law requires addresses in e-mail to be logged and stored for a year




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