UART Expansion Card

The UART Expansion Card is a community-designed expansion card providing a USB-to-UART serial interface for any Framework laptop¹. Designed by Josh Cook (jyancat) of i2cLabs, it uses a CH340C bridge IC with switchable voltage and logic levels between 3.3 V and 5 V¹²³.

Design

The card uses the CH340C USB-to-UART bridge, selected for its simplicity and low cost¹². A jumper selects between 3.3 V and 5 V logic levels, making it compatible with both modern and legacy microcontrollers¹³. A 6-position pin socket breaks out GND, CTS, VCC, TX, RX, and DTR³.

The card extends slightly beyond the chassis to accommodate through-hole headers for stability¹. It comes assembled with a 3D-printed case in black, white, or silver³.

Specifications

Specification	Details
Bridge IC	CH340C12
Logic levels	3.3 V / 5 V (jumper-selectable)13
Breakout	GND, CTS, VCC, TX, RX, DTR (6-pin socket)3
Connector	Standard 2.54 mm header socket1
Case	3D-printed (black / white / silver)3
Source	jyancat/UART-Expansion-Card (GitHub)2
License	CERN-OHL-S-2.02
Store	i2cLabs3
Price	$22 AUD3

Availability

The card is sold assembled and tested through i2cLabs for $22 AUD³. Josh Cook assembled an initial batch of 25 units in mid-2022 and reported positive reception from buyers¹.

Related Projects

Project	Description
RP2040 Expansion Card	Josh Cook's RP2040-based development card
RS-232 Expansion Card	Medved's RS-232 serial card using MCP2221 + MAX232
EC Card 2	UART-based EC debug expansion card
RS-485 Expansion Card	Medved's RS-485 half-duplex card

Footnotes

1. UART Expansion Card — Framework Community (Josh_Cook, June 2022) ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

2. jyancat/UART-Expansion-Card — GitHub (CERN-OHL-S-2.0) ↩ ↩² ↩³ ↩⁴ ↩⁵

3. UART Expansion Card — i2cLabs store ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰