User manual

LPC3250 Developer’s Kit v2 - User’s Guide

Page 36

GPIO26

USB-VBUS-CTRL from USB OTG transceiver on LPC3250 OEM board

GPIO55

GPI_02

GPIO66

USB-ID to USB OTG transceiver on LPC3250 OEM board

4.21.1 USB Channel 2 as USB Host

When USB channel #2 is used as USB Host, JP17/JP18/JP19 shall all be set in position 2-3.

J22 is the connector to use when USB Host is used. In order to provide +5V to the external USB

device connected to this connector (J20), channel B of U20 must be enabled. VBUS2 is enabled by

GPIO26 (active low). Over-current status back is provided via GPIO55. LED35 lights green when +5V

is available on J22. The VBUS2 signal is also feed back to GPIO54.

JP31 has no effect.

LED33 can signal that an external USB device has been connected.

4.21.2 USB Channel 2 as USB Device

When USB channel #2 is used as USB Device, JP17/JP18/JP19 shall all be set in position 1-2. Also a

1.5Kohm pull-up resistor is needed on the USB DP data signal. GPIO28 controls this. Alternatively,

SJ4 pin 2-3 can be connected to always enable this pull-up resistor. LED32 lights when the pull-up

resistor is enabled.

J21 is the connector to use when USB Device is used. This is a USB-B connector. The VBUS signal is

also feed back to GPIO54.

LED35 is has no meaning.

JP31 has no effect.

4.21.3 USB Channel 2 as USB OTG

When USB channel #2 is used as USB OTG, pull-up and pull-down resistors are controlled via the

USB OTG chip on the LPC3250 OEM board. Note however that 15Kohm pull-down resistors are

always connected (R187/R188). If this is a problem, remove these resistors.

J32 is the connector to use when USB OTG is used.

JP17/JP18/JP19 shall all be set in position 2-3.

JP31 shall be inserted.

LED32/33 have no meaning.