This is a simple open hardware project for a USB-to-TTL serial adapter based on the FTDI FT232RNL chip. The main feature of this adapter is its automatic voltage level detection, supporting TTL I/O levels from 1.8V to 5V without requiring manual jumper selection.
There are many USB-to-TTL adapters available on the market, such as:
However, most of them require the user to manually set the voltage level using jumpers or switches. This can be inconvenient or even risky if the user forgets to set, or does not know exactly the correct voltage, potentially damaging the target device.
- Based on FTDI FT232RNL USB-serial bridge.
- Supports 1.8V to 5V TTL I/O levels.
- No jumpers or switches required to select voltage.
- Uses TI TXU0202 dual-channel voltage level translator for automatic level adaptation.
- Only RX and TX signals are used (no RTS/CTS or other control signals).
- Two mirrored TTL connectors with inverted RX/TX pinout for flexible wiring
- All schematic symbols and footprints have fields populated for automated assembly on JLCPCB
This adapter eliminates the need for manual voltage configuration. Thanks to the TXU0202 level shifter, the adapter automatically adapts to the voltage of the connected target device. This makes it safer and easier to use, especially when working with multiple devices operating at different logic levels.
The board provides two 1x4 pin headers on the TTL side, with the same signals but mirrored RX/TX orientation. This simplifies usage with different target pinouts.
[ VCC_TTL | TX | RX | GND ] ← Connector A
[ VCC_TTL | RX | TX | GND ] ← Connector B (mirrored)
This layout helps avoid the common issue of crossed RX/TX lines between the adapter and the target device.
There are indications in the silkscreen to identify the VCC_TTL and GND pins.
This project includes files suitable for production with JLCPCB:
- usb_uart_1V8_bom_top.csv and usb_uart_1V8_bom_bot.csv: Bill of materials, with fields compatible with JLCPCB's parts selection tool (only top side populated)
- usb_uart_1V8_cpl_top.csv and usb_uart_1V8_cpl_bot.csv: Pick-and-place files (only top side contains components)
- All schematic symbols and footprints include LCSC part numbers, JLC footprints and assembly attributes
This project was developed using KiCad 9.0.1.
- KiCad design files are on he root dir of the repo
usb_uart_1V8.pretty/: local footprint librarygerber/: Production-ready Gerber + drill files, packed in grb_usb_uart_1V8.zip
Here is a photo of of of the assembled board in revision v0.1
This project is licensed under the CERN-OHL-S v2 open hardware license. See LICENSE.CERN-OHL-S_v2.txt for more information.
Feel free to open issues or submit pull requests if you find bugs or want to suggest improvements.
This project was inspired by the analysis in this blog post: https://www.electrothinks.com/2024/02/ft232rl-usb-to-serial-uart-module.html