Spark Logic

FT232RL USB-to-UART bridge connection guide

FT232RL USB-to-UART bridge SSOP-28 wiring guide with power, signal assignments, and bench checks.

SSOP-28

28 contacts Current package

FTDI · 5.3 mm nominal body width · 0.65 mm lead pitch

Wire USB power with a 3.3 V UART

Required

Use the USB bus-powered configuration and feed VCCIO from 3V3OUT. Ground TEST and all ground leads. Leave the oscillator pins open for the internal clock and use the power filter and connector treatment in Figure 6.4.

4.7 µF in parallel with 100 nF between Filtered 5 V and ReturnFiltered 5 V4.7 µF in parallel with 100 nFReturn
100 nF at 3V3OUT and VCCIO between 3.3 V I/O supply and Return3.3 V I/O supply100 nF at 3V3OUT and VCCIOReturn

Bench checks

  • Check VCC is above 4.0 V when using the internal clock. Verify VCCIO is close to 3.3 V.
  • Check that the host detects the serial port before the loopback test.

FTDI FT_000053, version 2.12, §3.2 and Fig. 6.4.

Connection scenarios

Test the UART in loopback

Unplug USB and jumper the bridge transmit output to its own receive input. Plug USB back in, open the enumerated port and disable local echo and flow control.

Bench checks

  • Send a short string at 9,600 bit/s, 8 data bits, no parity and 1 stop bit. The received bytes should match the transmitted bytes.
  • Remove the jumper before connecting another UART. Cross the two data lines, share ground and check the logic levels first.

FTDI FT_000053, version 2.12, UART signal descriptions. Loopback is a bench test.

SSOP-28 wiring map

Highlighted contacts are used in the required step or selected circuit. Select a contact to inspect it.

Top view. Match pin 1 to the package mark. The numbers advance counterclockwise.
Selected pin details

11 · CTS#

Input · Inputs

Clear to Send, active low.

FTDI FT_000053, version 2.12, §3.2

Electrical limits · Pin in the reference

Models and documents

The interactive map covers FT232RL in SSOP-28. FT232RQ in QFN-32 has different pin numbers. Use the FT232R datasheet §3.3 for that package.

FT232RL
5.3 mm nominal body width · 0.65 mm lead pitch