Document No.: FT_000329
FT232BL/BQ USB UART IC Datasheet Version 2.2
Clearance No.: FTDI# 171
9 LED Interface Configuration
Figure 9.1 Dual LED Configuration
Configuration
Figure 9.2 Single LED
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.
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