Copyright © 2011 Future Technology Devices International Limited

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Document No.: FT_000329

FT232BL

Clearance No.: FTDI#

171

9 LED Interface Configuration

Figure 9.1 Dual LED Configuration

Figure 9.2 Single LED

Configuration

The FT232B has two IO pins dedicated to controlling LED status indicators, one for transmitted data the

other for received data. When data is being transmitted / received the respective pins drive from tri-state

to low in order to provide indication on the LEDs of data transfer. A digital one-shot timer is used so that

even a small percentage of data transfer is visible to the end user.

Figure 9.1 shows a configuration using two individual LED’s – one for transmitted data the other for

received data.

In figure 9.2, transmit and receive LED indicators are wire-OR’ed together to give a single LED indicator

which indicates any transmit or receive data activity.

Another possibility (not shown here) is to use a 3 pin common anode tri-color LED based on the circuit in

Figure 9.2 to have a single LED that can display activity in a variety of colors depending on the ratio of

transmit activity compared to receive activity.

Note that the LED’s are connected to VCCIO.