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AM335X USB

eric chow1
Prodigy 30 points

hi

My schematic design will be like this picture:

 My expectation would be like this:

        USB0 designed  for usb boot, USB0_DRVBUS used as GPIO;

        USB1 as a host , is designed for program update, USB1_DRVBUS used as GPIO too.

Since usb connector is far away from the chip, so i connect USBx_VBUS  directly to system power supply VCC+5V0, and VCC+5V0 is also connect to the power pin of USB1's connector.

Will the design as the picture described satisfy my expectation? thanks.

  • 0
    TI__Guru**** 393215 points
    Hi Eric,
     
    For USB0 you must take the USB0_VBUS sigmal from the USB connector VBUS. For USB1 I strongly recommend that you use a power switch driven by USB1_DRVVBUS. USB1_VBUS should be taken again from the USB connector. You can check the GP EVM schematic (http://processors.wiki.ti.com/images/d/d0/AM335X_gpevm_ZCZBASEBOARD_3H0002_REV1_4A.zip, page 12, bottom of page) for the proper connections.
  • 0 in reply to Biser Gatchev-XID
    Prodigy 30 points

    hi, Biser,

          I really need pin USB1_DRVBUS/GPIO3_13 used as GPIO3_13, and  for cost-down , there will be

    only a PTC instead of a usb power switch. what should i do then? thanks

  • 0 in reply to eric chow1
    TI__Guru**** 393215 points
    In Host mode the USB PHY switches on VBUS through the USB_DRVVBUS pin, then expects a valid voltage on the USB_VBUS pin. This is hardware controlled. There may be software workarounds but I'mm not a software expert and cannot say if/how this can be done.
  • 0 in reply to Biser Gatchev-XID
    TI__Guru**** 177101 points

    You can use the following patch if USB1_VBUS is directly tied to 5V for host-only mode.

    diff --git a/arch/arm/mach-omap2/omap_phy_internal.c b/arch/arm/mach-omap2/omap_phy_internal.c
index 13bfef3..e41b224 100644
--- a/arch/arm/mach-omap2/omap_phy_internal.c
+++ b/arch/arm/mach-omap2/omap_phy_internal.c
@@ -288,8 +288,17 @@ void ti81xx_musb_phy_power(u8 id, u8 on , bool wkup)
                                                TI816X_USBPHY0_NORMAL_MODE;
                        usbphycfg &= ~TI816X_USBPHY_REFCLK_OSC;
                } else if (cpu_is_am33xx()) {
-                       usbphycfg &= ~(USBPHY_CM_PWRDN | USBPHY_OTG_PWRDN);
-                       usbphycfg |= (USBPHY_OTGVDET_EN | USBPHY_OTGSESSEND_EN);
+                       usbphycfg &= ~(USBPHY_CM_PWRDN | USBPHY_OTG_PWRDN | USBPHY_OTGVDET_EN);
+
+                       /* HACK: EVM USB1 port is in host-only mode, clear its
+                        * USBPHY_OTGVDET_EN bit to ignore first VBUS sensing.
+                        * Change 1 to 0 if USB0 port is in host-only mode.
+                        */
+                       if (id == 1)
+                               usbphycfg |= USBPHY_OTGSESSEND_EN;
+                       else
+                               usbphycfg |= (USBPHY_OTGVDET_EN | USBPHY_OTGSESSEND_EN);
+
                        usbwkupctrl = AM33XX_USB_WKUP_CTRL_DISABLE;
                }
        } else {