DS232BQ Version 1.8

© Future Technology Devices Intl. Ltd. 2005

Page 21 of 25

FT232BQ USB UART ( USB - Serial) I.C.

7.5 LED Interface

FT232BM

TXLED#

RXLED#

11

12

VCCIO

220R

220R

TX

RX

FT232BM

TXLED#

RXLED#

11

12

VCCIO

220R

LED

Figure 12

Dual LED Configuration

Figure 13

Single LED Configuration

The FT232BQ 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 12 shows a configuration using two individual LED’s – one for

transmitted data the other for received data. In Figure 13, the 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 13 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.

FT232BQ

FT232BQ