Circuit Issues
Templates
#0165InterfaceDRC cleanv1.0

UART level translator 3.3 V ↔ 5 V

Two-channel UART level translator between a 3.3 V microcontroller and a 5 V device (or any two logic levels from 2 to 5.5 V): one buffer per direction, each powered from the side it drives, with TTL-level, 5.5 V-tolerant inputs. Series resistors on every input and output limit fault currents and ringing. Used as the 5 V UART side of the heat-pump / AC link.

3D render of the 0165 UART level translator 3.3 V ↔ 5 V KiCad design block
3D render (KiCad 10)
3D render of the 0165 UART level translator 3.3 V ↔ 5 V KiCad design block
3D render, top view (KiCad 10)
Schematic of the 0165 UART level translator 3.3 V ↔ 5 V KiCad design block
Schematic (KiCad 10)

Key specifications

  • Two independent supplies, 2–5.5 V each
  • One channel each way: MCU TX → device RX, device TX → MCU RX
  • 5.5 V-tolerant inputs, push-pull outputs
  • UART speeds well above 1 Mbit/s

Design notes

  • Push-pull, one direction per line: for UART and other one-way signals, not for I²C.
Coming soon

This block is not available yet. It is released once its checks are complete. Planned price: €29.

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Planned package contents

  • KiCad 10 design block

    Schematic and PCB layout fragment; symbols and footprints embedded

  • BOM (CSV)

    Manufacturer part numbers and LCSC codes

  • Schematic PDF + README

    Interface, specs, population options and design notes

  • 3D models

    STEP models of the special parts; standard parts use KiCad’s 3D library

  • template.yaml

    Machine-readable interface and limits

PCB Composer

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About PCB Composer

Development status

Block ID0165
Block name0165-uart-level-translator-3v3-5v
Version1.0
StatusDRC clean – Schematic and layout pass the KiCad rule checks; not yet verified on hardware.
Open review items4 (0 blocking)
PCB layoutRule-checked layout fragment
FormatKiCad 10 design block (schematic + PCB)
Last change2026-11-03

Interface

Hierarchical labels the block exposes to the rest of your design.

NetDirectionDescription
+BUF_IN_SUPPower inSupply of the MCU side (e.g. 3.3 V)
+BUF_OUT_SUPPower inSupply of the device side (e.g. 5 V)
BUF_OUT_DOInputFrom the MCU UART TX
BUF_OUTOutputTo the device RX, at the device-side level
BUF_INInputFrom the device TX, up to 5.5 V
BUF_IN_DIOutputTo the MCU UART RX, at the MCU-side level

FAQ

Which KiCad version do I need?

KiCad 10. The files are saved in the KiCad 10 format and are meant to be placed with KiCad’s Design Blocks feature (schematic block, then “Apply Design Block Layout” on the PCB).

Do I need the Circuit Issues part library?

No. Symbols are embedded in the schematic and footprints in the PCB, so the block opens on its own. Parts carry manufacturer part numbers and LCSC codes.

Is the layout production-ready?

The layout fragment passes the KiCad design rule check. Route it into your board and run DRC with your own fab rules.

Can I use the template in a commercial product?

The licence terms are published together with the first release.

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