Auxiliary power and USB

Hello

I would like to use the USB host function of the Beagleboard (using the USB OTG port).
I plugged a 5VDC power supply on the auxiliary power.

When I start the Beagleboard, I receive only symbol caracters in the console, like if the parameters of the serial connection in the terminal were not correct.
When I use the USB OTG to power the board it works.

I tested the power supply, the voltage is 5.3V.

Is the power so sensitive ?
Do I need to make a Y usb cable to power to be able to use the USB OTG as power input and plug the DATA on a USB HUB ?

Thank you in advance

Regards,

Guillaume Duteil

Guillaume,

The power from the OTG port is only about 100mA as stated in the Reference Manual. To use powered devices on the USB port using the OTG, you must have a powered hub.

To use the HOST function of the beagleboard, you must have a clean 5V supply connected to the DC jack. If you plug the OTG port into the PC, it will act as a client and not a host. You must be DC powered to be a host using the OTG port.

Gerald

Guillaume,
> From: beagleboard@googlegroups.com [mailto:beagleboard@googlegroups.com] On Behalf Of Guillaume
> Duteil
> Sent: Wednesday, August 27, 2008 4:05 PM
> To: beagleboard@googlegroups.com
> Subject: [beagleboard] Auxiliary power and USB
>
>
> Hello
>
> I would like to use the USB host function of the Beagleboard (using the
> USB OTG port).
> I plugged a 5VDC power supply on the auxiliary power.
>
> When I start the Beagleboard, I receive only symbol caracters in the
> console, like if the parameters of the serial connection in the terminal
> were not correct.
> When I use the USB OTG to power the board it works.
>
> I tested the power supply, the voltage is 5.3V.
>
> Is the power so sensitive ?
I have a rev A.5 board and been messing around with voltages over last weekend.

5V is the voltage required. I have it powering up at 3.75 odd volts too (powered by 3 NiMh batteries) and at 5.1v(with a 2500mA variable power supply). This is plugged to power port thru a toggle switch. I can send a snap of my mods if anyone is interested (pretty similar to mods by Koen done here: http://www.flickr.com/photos/koenkooi/2512038988/in/pool-beagleboard

I believe this supplies the VBAT supply to Twl4030, probably Gerald can correct me on the acceptable voltage ranges..(DM seems to tell me the valid range is 2.8 to 4.6 - not sure of any other circuits b/w input voltage and actual vbat though..)

USB power is 5v. max amperage varies from 100mA for a bus powered hub to around 500 mA for a root hub. I think a self powered hub can hit upto 400mA (apologies that my USB knowledge is rusty at the moment)..

There are other quirks with USB power that I ran into with the Zoom.

100mA is the only safe amount to draw from a USB port without it enumerating.
Some PCs don't enforce this and allow more current, even over 500mA but
some do. So even with a self powered hub, it all depends on the hardware.

On paper, the USB spec says up to 100mA is available before enumeration
and after enumeration it is up to the host software to accept or deny
any addition requested amount. So drawing >100mA is dependant upon the
USB port used. All of this probally don't apply to most of those AC to
USB phone cable charger or 12V to USB phone cable charger things.

-- Hunyue

BeagleBoard requires a well-regulated +5V supply. Beware of cheap
bricks, as they may produce more than +5V and endanger the
BeagleBoard. For example, U1 (TI TPS2141) has maximum recommended
5.5V (6V absolute max).

Make sure the +5V supply is solid with an oscilloscope. A voltmeter
may read an average +5.3V while the actual voltage oscillates between
a higher and lower value due to inadequate capacitors in a cheap power
supply.

John

I'm having a similar problem in that when I plug in an external 5VDC I get the
symbol characters (but occasionally I can get the letter I typed at the
keyboard, maybe 1 in 20, seemingly totally random), but when I try to power
off of USB OTG port, I get nothing. I've used my null modem cable a lot on
Sun Sparc's, and set up a test between a Linux box and a Windows box (minicom
and hyperterm) set to 115200 n81 (no handshaking) and they talk together
fine, but neither one will talk to the beagleboard. :frowning:

Bad board??? Any suggestions would be appreciated!

What is the configuration of your IDC to DB9 cable?

I would start here under the serial questions. http://elinux.org/BeagleBoardFAQ

Gerald