custom overo board and usb

[Florian Weimer-4]

Hi all,

 

I´m planning a custom baseboard for the overo and at the moment I'm looking at the summit schematics to get a clue about the usb wiring and I´m asking myself if the TPS61202 is only used to boost the input voltage. Since I´m using a 5V regulated DC-DC converter I thouhgt about not using the TPS61202  on my own board. The only thing that I don´t understand is the USBH_CPEN on the EN Pin of the TPS61202 . Is it also possible to supply USB_VBUS with 5V constantly (at least I don´t know what USBH_CPEN does)?

 

I´m also asking myself wether to use the OTG or Host port (I´d like to use an USB cam in the future). Could the Host port supply devices with 500mA? 

 

Regards,

Florian 

 

__________________________________________________

Dipl.-Ing. Florian Weimer

Institut für Flugmechanik und Flugregelung, Universität Stuttgart

Pfaffenwaldring 7a

70569 Stuttgart

 

Telefon:  +49 711 - 685 - 666 14
Fax:        +49 711 - 685 - 666 70
E-Mail:   florian.weimer@...

Internet: http://www.ifr.uni-stuttgart.de/

 

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[Søren Steen Christensen]

Hi Florian 
 
> The only thing that I don´t understand is the USBH_CPEN on the
> EN Pin of the TPS61202 . Is it also possible to supply USB_VBUS
> with 5V constantly (at least I don´t know what USBH_CPEN does)?
USBH_CPEN is controlled by SW and can switch off the USB_VBUS in case the
USB stack decides to do so for whatever reason (i.e. to reinitialize the USB
link completely and force a reenumeration). In case you already have a
stable 5V supply I would just add a current limiting switch controlled by
USBH_CPEN to your design. The current limit feature is important in order to
ensure that a short circuit on your USB plug won't bring down your internal
+5V supply, which I assume you use for other stuff as well?

> I´m also asking myself wether to use the OTG or Host port
> (I´d like to use an USB cam in the future).
> Could the Host port supply devices with 500mA? 
The USB host specification tells, that an USB Host port should be able to
supply up to 500mA and an OTG up to 100mA. That being said - The power is
drawn directly from your power supply through your switch, so you are
basically free to design whatever fits your need. In case you would like to
draw 1A or only allow 100mA you are free to do so - The OMAP won't stop you
doing it. In case of choosing 100mA you of cause isn't totally USB compliant
then (and you might run into trouble running your webcam :-).

I hope this helped you forward?
  Søren
 
---
SSC Solutions ApS - Denmark - www.ssc-solutions.dk


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