Re: [Gumstix-users] which signal level to place on USBH_VBUS

[Andy W. <an...@si...>]

See the notes after Table 7 in version 1.11 of the Overo signals
reference document:

"Note: The Overo COM exports two signals related to USB Host power:

1. GPIO168_USBH_CPEN: This GPIO signal is, by convention on Gumstix
expansion boards, used as an active-high enable signal to trigger a
circuit that provides +5V to the USBH_VBUS pins of the COM. It is not
necessary to switch USBH_VBUS in this manner.

2. USBH_VBUS: This signal (input to the COM) should be held at +5V when
using the USB Host interface; the USB332x data
sheet(http://www.smsc.com/media/Downloads_Public/Data_Sheets/3320.pdf).
When designing expansion boards, ensure this line has adequate
over-voltage and over-current protection."

Regards,
Andy

On Tue, 2013-06-04 at 05:13 -0700, kris duff wrote:
> Hi,
> 
> On my custom design, I work with a USB cinterion GPRS modem.
> Everything were going fine but now I`m having problems with the
> device. On overo fire I get the following error : ehci-omap
> ehci-omap.O: detected XactErr len 0/8 retry ...  On overo earthstorm I
> get :  
> 
> cdc_acm 1-2:1.12: out of memory (write buffer alloc)
> [   27.647644] cdc_acm: probe of 1-2:1.12 failed with error -12
> 
> Last week it was working fine. 
> 
> I guess my design is ok since there is no smoke, but there is one
> little thing I`m not sure about is the level needed for the usbh_vbus.
> I connected 3.3V on this pin (sys_en buffered to 3v) but since the usb
> standard signal level is 5V should I connect 5V on this pin ?  Since
> the gumstix is sensitive to input voltage level, I'm scared to try it
> at 5V. 
> 
> Thank you
> 
> 
> Kris
> 
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