Open hardware level shifters from Olimex provide editable KiCad designs for interfacing embedded boards operating at different logic voltages, from 1.65V to 5.5V.
Olimex has released two open-source hardware modules, BB-LVL-SHIFT and UEXT-LVL-SHIFT, to help developers connect embedded devices operating at different logic voltages. Both designs include publicly available schematics and KiCad source files, allowing hardware developers to inspect the circuits, adapt the layouts and reuse the designs in their own projects. The modules address different requirements: BB-LVL-SHIFT targets breadboard prototyping with two signal lines, while UEXT-LVL-SHIFT translates signals across the complete UEXT connector.
The BB-LVL-SHIFT is a compact, 15 × 13mm module that provides bidirectional level shifting across two signal lines, supporting voltages from 1.8V to 5.5V and signal speeds up to 1Mbps. Its pre-soldered header pins allow it to be plugged directly into a breadboard or connected using jumper wires. The module is intended primarily for low-speed I²C and UART interfaces, such as connecting 5V sensors to 3.3V microcontrollers, including ESP32, Raspberry Pi Pico and STM32 boards. Both sides must have their respective power supplies and a common ground connected for correct operation.
The larger UEXT-LVL-SHIFT measures 40 × 22mm and provides two UEXT connectors with level shifting for UART, SPI and I²C signals. It supports target logic voltages from 1.65V to 5.5V, enabling compatible UEXT peripherals to interface with systems operating at different voltage levels. The manufacturer specifies I²C speeds up to 1Mbps, with maximum SPI and UART signal rates of 75Mbps at 1.8V, 180Mbps at 2.5V and 420Mbps at 5V. The target-side UEXT connector must supply the appropriate voltage so that the circuit can translate signals correctly.
The two modules offer different approaches to a common embedded hardware problem. BB-LVL-SHIFT is suited to quick experiments involving two I²C or UART lines, whereas UEXT-LVL-SHIFT is designed for systems that need to translate all signals carried by the UEXT interface, including SPI. This can simplify connections between development boards, sensors, displays, storage devices and other peripherals without requiring developers to design a separate level-shifting circuit for each project.
Olimex has published the KiCad source files and schematics for both modules on GitHub, making the hardware designs available for examination and modification. Developers can access the BB-LVL-SHIFT repository and the UEXT-LVL-SHIFT repository to explore the designs. The boards are also available commercially, with single-unit prices listed at €3.95 for BB-LVL-SHIFT and €4.95 for UEXT-LVL-SHIFT. Their open hardware files provide a starting point for adapting voltage translation circuits to custom embedded systems.
