FT232RL USB to TTL adapter: specs and pinout
A USB-to-serial adapter board using the FTDI FT232RL chip. Figures below are for the chip; the adapter board (voltage selector jumper, header order, protection) is not covered by an official document.
Specs
| Spec | Value | Source |
|---|---|---|
| Function | USB to asynchronous serial UART, 300 baud to 3 Mbaud, at TTL levels | source Features, p.1 |
| Chip supply VCC | 4.0-5.25 V with internal oscillator; 3.3-5.25 V with an external crystal | source Table 5.2, p.18 |
| UART and CBUS I/O supply VCCIO | 1.8-5.25 V (sets the logic level of TXD, RXD and handshake pins) | source Table 5.2, p.18; Table 3.2 |
| Supply current | 15 mA typical, normal operation | source Table 5.2, p.18 |
| 3V3OUT output | 3.0-3.6 V, up to 50 mA to external logic | source Table 5.2; Table 3.2 pin 17 |
| Buffers | 128 byte receive, 256 byte transmit | source Features, p.1 |
| Ambient temperature (power applied) | -40 to 85 C | source Table 5.1, p.17 |
| Absolute maximum VCC | -0.5 to 6.00 V | source Table 5.1, p.17 |
Power
| Value | Source | |
|---|---|---|
| Supply | Chip VCC 4.0-5.25 V (internal oscillator); adapter-board input: not covered by an official document | source Table 5.2, p.18 |
| Current | 15 mA typical (chip, normal operation) | source Table 5.2, p.18 |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
Rows are FT232RL chip pins. The adapter board's own header labels, order and 5 V/3.3 V selector are not covered by an official document; read them from the silkscreen.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 1 | TXD | FT232RL SSOP-28 chip pin: transmit data output | source Table 3.4 | |
| 5 | RXD | FT232RL SSOP-28 chip pin: receive data input | source Table 3.4 | |
| 2 | DTR# | FT232RL SSOP-28 chip pin: data terminal ready output / handshake | source Table 3.4 | |
| 3 | RTS# | FT232RL SSOP-28 chip pin: request to send output / handshake | source Table 3.4 | |
| 11 | CTS# | FT232RL SSOP-28 chip pin: clear to send input / handshake | source Table 3.4 | |
| 4 | VCCIO | FT232RL SSOP-28 chip pin: 1.8-5.25 V supply for the UART and CBUS pins | source Table 3.2 | |
| 20 | VCC | FT232RL SSOP-28 chip pin: 3.3-5.25 V device core supply | source Table 3.2 | |
| 17 | 3V3OUT | FT232RL SSOP-28 chip pin: 3.3 V output from the internal regulator, up to 50 mA | source Table 3.2 | |
| 7, 18, 21 | GND | FT232RL SSOP-28 chip pin: ground | source Table 3.2 |
Build with it
Project ideas for the FT232RL USB to TTL adapter. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- ESP-01S flashing setup: Use this only if the adapter's own markings show 3.3 V logic; power the ESP-01S from the separate 3.3 V supply, because 3V3OUT on the chip is limited to 50 mA. If the board is fixed at 5 V, do not connect it to the ESP-01S.
- Pico USB serial debug console: The Pico's UART pins are 3.3 V: connect only an adapter whose own markings show 3.3 V logic. Do not feed 5 V from the adapter into the Pico's pins.
- Bare ESP32 module flashing rig: Use an adapter whose markings show 3.3 V logic; the module is powered from the breadboard supply, not from the adapter.
- A serial sensor logger that sends temperature readings to a laptop with a Pro Mini 5V, a DHT22 sensor and a USB to serial adapter: The Pro Mini has no USB chip, so this adapter gives it both the serial link and the programming connection. Use the adapter at 5 V logic only if its markings say so, and read the header order from the silkscreen. A board with its own USB serial (such as an Uno) would clash with an adapter on pins 0 and 1.
Common mistakes
- Chip note: the UART logic level follows VCCIO (VCCIO tied to 3V3OUT gives 3.3 V levels, tied to VCC gives 5 V levels). Whether the stocked board has a selector jumper is not documented: read the board's own markings, and on a fixed 5 V board do not connect it to an ESP-01S, an ESP32 or a Pico (source: link, Table 3.2 pin 4).
- 3V3OUT supplies up to 50 mA only, which is not enough to power a Wi-Fi module; power the target separately (source: link, Table 3.2 pin 17).
- TX goes to the target's RX and RX to TX; the chip's TXD is an output and RXD an input (source: link, Table 3.4).
Not covered by the official source
- Adapter board (jumper, header order, connector) not covered by an official document.
- Datasheet is Version 2.07 (2010); a newer FTDI revision may exist.
Sources
- link (FTDI FT232R USB UART IC Datasheet Version 2.07, FT_000053; copy hosted on a mirror)