User manual

LPC3250 Developer’s Kit v2 - User’s Guide

Page 37

4.22 SP13: UART-to-USB Bridge

There is a UART-to-USB bridge on the board. This is to simplify connection to a PC because serial

ports are not so common any more, especially not on laptops. The USB port also offers the possibility

to power the board. It is UART#5 that is connected to the USB channel. This UART is commonly used

as the console channel for applications. Printf() output is for example typically directed to this UART

channel.

The UART-to-USB bridge is based on the chip FT232RL from FTDI. A driver is typically needed to be

installed on the PC side. The driver creates a virtual COM port on the PC that represents the UART

channel. Any program on the PC can connect to this COM port for communication with the LPC3250

UART channel. There are two LEDs (Transmit – LED38 and Receive – LED37) that signal

communication activity.

It is possible to automatically enable service mode (for program download via UART). By inserting two

jumpers in JP20, the RTS signal can control signal GPI_01 and DTR can control reset. By pulling

GPI_01 low during a reset cycle, service mode is entered. Note that some terminal programs controls

the DTR/RTS signals so that the board is always in reset and/or always enter service mode. It this is

the case, just remove both JP20 jumpers.

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

Figure 21 – UART-to-USB Bridge

Signals

LPC3250

GPIO16_TXD

U5_TX

GPIO17_RXD

U5_RX

GPIO10

GPI_01

USB mini-B Connector

J25

Transmit LED

LED38

Receive LED

LED37

Automatic ISP

JP20

Default: not inserted