User manual

LPC3250 Developer’s Kit v2 - User’s Guide

Page 33

4.20 SP11: USB Channel 1

The USB1 interface is not supported since there is one on-chip USB interface on the LPC3250

and this is connected to the USB2 interface on the OEM base board. For reference, the

information about the interface is described below. The interface cannot be used.

The USB1 interface offers a USB Host or USB OTG interface. Only one of these interfaces can be

used at a time, i.e., both cannot be used simultaneously. There is an external USB OTG transceiver,

U31. This transceiver is used for OTG specific signaling but also for controlling the 1.5Kohm pull-up

and 15Kohm pull-down resistor control that is needed for USB Host/Device. If just USB Device is

needed, it is possible to insert a jumper in JP15 to statically attach a 1.5Kohm pull-up resistor to the

USB-DP signal. LED31 can be used to signal USB-up state.

USB Host power is controlled via distribution switch U20. Pads 1-2 on SJ5 are by default connected to

always enable +5V on VBUS channel 1. LED34 light whenever +5V is present on VBUS1. VBUS

feedback via GPIO46 is by default disconnected as well as status feedback from the distribution switch

via GPIO51.

In case VBUS1 shall be actively controlled from the OEM Board, R190 and R198 must be soldered

and pad 2-3 on SJ5 must be connected. Further, GPIO43/46/51 must not be used for other tasks in the

design.

It is possible to force USB Host detection when using the USB OTG interface by inserting a jumper on

JP16.

See picture below for locating relevant components. The table below lists signal connections.

Figure 19 – USB Channel#1

Signals

LPC3250

USB1-DP

Not connected

USB1-DM

Not connected

USB-A Connector

J20

USB mini-AB Connector

J19

Force USB Host

J16

Force USB Connect

J15

MIC2555 Expansion

JP30

Power Control

SJ5

USB1-Up LED

LED31

USB1 VBUS Power

LED34