Date: Tue, 6 Nov 2007 14:42:27 +0100 From: Bernd Walter <ticso@cicely12.cicely.de> To: Krassimir Slavchev <krassi@bulinfo.net> Cc: freebsd-arm@freebsd.org, ticso@cicely.de Subject: Re: Detecting USB devices at startup? Message-ID: <20071106134227.GK4593@cicely12.cicely.de> In-Reply-To: <47306BDD.70206@bulinfo.net> References: <472F1A97.3090308@bulinfo.net> <20071105.080609.1723237322.imp@bsdimp.com> <47303B8E.2040403@bulinfo.net> <20071106125853.GJ4593@cicely12.cicely.de> <47306BDD.70206@bulinfo.net>
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On Tue, Nov 06, 2007 at 03:27:57PM +0200, Krassimir Slavchev wrote: > Bernd Walter wrote: > > On Tue, Nov 06, 2007 at 12:01:50PM +0200, Krassimir Slavchev wrote: > >> Yes, It looks like a power issue but the power supply used in the > >> development board is very good designed (LM2576 is used). I will measure > >> power line again. Also the PWM frequency might interfere with PLL. > >> I will try to find powered hub to make tests. All usb hubs on the market > >> are bus-powered :( > > > > I can ensure you: there are self powered hubs. > > If in doubt buy a seven port, they can't work bus powered. > > Ok, I will look for bigger hub. I'm still a bit surprised, since there are so many noname hubs with fat wallwarts. > > Is the LM2576 really used for USB? > > http://www.harerod.de/centipad/documents/CentiBOB201psk_color.pdf > Look at sheet 2. > > > This is a very beefy thing just for a single port and everything else > > in a AT91RM9200 system is running at 3,3V or lower. > > On my board I use such a 257x regulator for 3,3V, separate linear > > regulators from 3,3V to supply the 1.8V for core and switch and > > another linear regulator directly from input for 5V to USB. > > There is another voltage regulator TPS767D301. > http://www.harerod.de/centipad/documents/CentiPad_Programmers_Model_205.pdf > Look at sheet 13. Interesting, so they run everything linear regulated from 5V. Sounds like a lot of power loss, but their board is different and maybe they have more 5V components. My board only needs 5V for USB, so I never saw the need for efficient 5V and prefered efficient 3,3V, which is also quite loaded from the switch. -- B.Walter http://www.bwct.de http://www.fizon.de bernd@bwct.de info@bwct.de support@fizon.de
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