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AM1808 USB0_VBUS

Inderjit Bains
Expert 2745 points

Regarding this post:

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/t/110587.aspx

If USB0_VBUS is not to be connected to +5V, and SYSCFG -> CFGCHIP2 register is used to enable USB host-only, what should USB0_VBUS be tied to?

Also, if I do decide to connect USB0_VBUS to +5V, can the 5.5V absolute maximum spec be exceeded if a 1K series resistor is used?

  • 0
    Expert 2745 points

    Read more on this:  it looks like CFGCHIP2 -> USB0OTGMODE will need to be set to 0x3 to "Override phy values to force USB host operation with VBUS low."  So VBUS can be pulled low:  1K pulldown or direct to GND?  Also, does this only need to be done once (bootloader or Linux?), or will the PHY periodically reset it to a default value?

  • 0 in reply to Inderjit Bains
    Expert 2745 points

    Changed the following in board-da850-evm.c:

    #ifdef    CONFIG_USB_MUSB_HOST
        cfgchip2 |=  CFGCHIP2_FORCE_HOST;

    to:

    #ifdef    CONFIG_USB_MUSB_HOST
        cfgchip2 |=  CFGCHIP2_FORCE_HOST_VBUS_LOW;

    USB does not work at all with the above change.  Oddly, it does work with CFGCHIP2_FORCE_HOST, even when VBUS is pulled low (1K to GND).

    Can anyone explain this?