Mixing a 3.3 V microcontroller with a 1.8 V sensor or a 5 V peripheral is one of the most common problems on a hobbyist's bench. On 19 October 2026, Olimex released two small boards for it. BB-LVL-SHIFT is a two-line breadboard module. UEXT-LVL-SHIFT sits between two UEXT connectors and shifts every signal on the bus. Both are listed as open-source hardware, and the product pages show both as In Stock.

Neither board is complicated, and that is the point. For a maker with a drawer of UEXT modules or a breadboard full of mixed-voltage parts, what matters is the voltage range, the speed and the price. Here is what Olimex's own pages say about each.

BB-LVL-SHIFT: two lines, breadboard format

Olimex's product page says BB-LVL-SHIFT provides bi-directional level shifting between two lines from 1.8 to 5.5 V and is ideal for I2C and UART signals. In its 19 October announcement, the company names the pairs it has in mind: SDA/SCL for I2C or TX/RX for UART.

The specs Olimex lists on the product page are:

  • Channels: two, bi-directional
  • Voltage range: 1.8 V to 5.5 V
  • Signal speed: up to 1 Mbps
  • Size: 15 x 13 mm
  • Headers: pre-soldered
  • Design files: KiCad sources and schematic published

The pre-soldered headers make a difference for a part this small: the board is ready to push into a breadboard straight out of the bag. According to the announcement, the 1 Mbps ceiling covers standard, fast and fast-mode-plus I2C, as well as typical UART baud rates. The announcement also stresses that you must connect ground and the power supply on both sides, not just the signal lines, so the shifter knows which voltage levels it is translating between.

Olimex's page does not name the translator chip on BB-LVL-SHIFT. We have not checked the schematic, so we are not naming one either.

UEXT-LVL-SHIFT: the whole connector

UEXT is Olimex's own 10-pin expansion connector. It carries UART, SPI, I2C and power on one header, and the announcement describes it as found on many Olimex boards. UEXT signals are at 3.3 V. UEXT-LVL-SHIFT has two UEXT connectors. One faces the host. The other faces a target that may run at a different voltage. The product page describes it as a UEXT-to-UEXT level shifter for 1.65 V to 5.5 V targets with full signal level shifting. The announcement post spells this out as "full level shifting on all UEXT signals: UART, SPI and I2C".

Olimex quotes these speed limits:

  • I2C: up to 1 Mbps
  • SPI and UART: max 75 Mbps at 1.8 V, 180 Mbps at 2.5 V, 420 Mbps at 5 V
  • Size: 40 x 22 mm

One wiring detail needs attention. Olimex notes that the target UEXT connector must provide the target voltage on its power pin, so the shifter can reference the correct logic level on that side. The target side has to supply its own reference voltage.

The bill of materials in the OLIMEX/UEXT-LVL-SHIFT GitHub repository (Rev A) lists three SN74LVC2T45DCUR translators in VSSOP-8 (U1 to U3), four BSS138 FETs, a 47 µF capacitor and the two UEXT connectors. Texas Instruments' SN74LVC2T45 product page describes the part as a dual-bit, dual-supply, noninverting bus transceiver. Both of its supplies run from 1.65 V to 5.5 V. That matches the 1.65 V lower limit Olimex gives for this board. The BOM does not say which signals use the translators and which use the FETs, and we have not confirmed the exact signal-to-part mapping.

Two voltage floors, and why they differ

The headline of the Open Source For You write-up gives 1.65 V to 5.5 V for the pair, though its body text correctly gives 1.8 V to 5.5 V for BB-LVL-SHIFT. According to Olimex's own pages, the two boards have different minimums. BB-LVL-SHIFT is rated from 1.8 V and UEXT-LVL-SHIFT from 1.65 V. The 0.15 V difference only matters at the bottom of the range, but a project with a 1.65 V to 1.8 V rail sits right in that gap. Check the rating for the specific board before you design around it.

Licensing

The UEXT-LVL-SHIFT repository is split into DOCUMENTS and HARDWARE/UEXT-LVL-SHIFT_Rev_A folders, and each part of the project has its own licence:

  • Hardware: CERN Open Hardware Licence v2, Strongly Reciprocal
  • Software: MIT
  • Documentation: CC BY-SA 3.0

The repository also says the silkscreen credits to Bernardo Kastrup and Dean Belfield must remain. CERN OHL-S is a strongly reciprocal licence: if you modify the design and distribute the result, you have to publish your changes under the same terms. For BB-LVL-SHIFT, the product page lists published KiCad sources and a schematic.

What It Means for Makers

Who it is for. BB-LVL-SHIFT is for anyone prototyping on a breadboard who needs to connect one I2C bus or one UART across a voltage boundary. Olimex's own example is connecting 5 V I2C sensors to 3.3 V boards such as ESP32, Raspberry Pi Pico or STM32, or talking to 1.8 V devices from 3.3 V or 5 V microcontrollers. UEXT-LVL-SHIFT is for people who already use Olimex boards and UEXT modules and want to reach a target at a different voltage without rewiring the bus by hand. With full shifting on UART, SPI and I2C and SPI rates in the tens to hundreds of Mbps, Olimex says SPI is not a bottleneck for fast SPI displays, flash memories or ADCs.

What you get. Both boards come with Olimex's own figures for voltage range and data rate and with published KiCad sources and schematics. The UEXT version also has a CERN OHL v2 hardware licence on its GitHub repository.

Price and availability. Prices below are as listed on the Olimex product pages when we checked on 21 October 2026, two days after the launch. Both boards are listed as In Stock, so they are shipping now and are not pre-order or crowdfunding products.

  • BB-LVL-SHIFT: EUR 3.95 each; EUR 3.75 at 10 to 49 pcs; EUR 3.56 at 50 to 10000 pcs.
  • UEXT-LVL-SHIFT: EUR 4.95 each; EUR 4.70 at 10 to 49 pcs; EUR 4.46 at 50 to 10000 pcs.

Neither board is new technology, and Olimex does not claim it is. These are inexpensive, documented parts for a common bench problem, sold by a vendor that publishes its design files.

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