Breadboard Card

The Breadboard Card (also called the MCU Dev Card) is a Tool Card from HW Media Lab LLC that carries a Seeed Studio XIAO module in a Framework Expansion Card form factor¹. Designed to work with the DockFrame modular USB-C hub or standalone via USB-C, it provides a development platform with breadboard-friendly 2.54 mm headers and a downstream USB-C port for prototyping¹².

In Development

The Breadboard Card is in pre-production as of July 2026. The DockFrame Crowd Supply campaign page is now live and accepting signups, marked as "launching soon"³. HW Media Lab's first Crowd Supply product, the WebScreen secondary display, successfully funded at over twice its goal⁴. All DockFrame hardware and software will be open-sourced after the campaign closes¹⁵.

Design

The card uses a Seeed Studio XIAO socket with 2.54 mm through-hole strips, compatible with any XIAO-family module sharing the 21 × 17.5 mm footprint and 14-pin castellated layout¹. The socket approach allows module recovery (bricked firmware, blown GPIO) and future module upgrades without redesigning the card¹.

Compatible XIAO modules¹:

Module	Core	Radio
XIAO SAMD21	Cortex-M0+ @ 48 MHz	None
XIAO RP2040	Dual Cortex-M0+ @ 133 MHz	None
XIAO RP2350	Dual Cortex-M33 / RISC-V @ 150 MHz	None
XIAO RA4M1	Cortex-M4 @ 48 MHz (+FPU)	None
XIAO ESP32-C3	RISC-V @ 160 MHz	WiFi + BLE
XIAO ESP32-C5	RISC-V @ 240 MHz	WiFi + BLE
XIAO ESP32-S3	Dual LX7 @ 240 MHz	WiFi + BLE
XIAO nRF52840	Cortex-M4F @ 64 MHz	BLE
XIAO nRF52840 Sense	Cortex-M4F @ 64 MHz	BLE + sensors
XIAO BLE	Cortex-M4F @ 64 MHz	BLE
XIAO MG24	Cortex-M33 @ 78 MHz	BLE + Matter + Thread

Power Protection

Both 5 V and 3.3 V rails have a TPS2553 current-limited switch (~1.65 A trip), protecting against shorted breadboard jumpers or wrong-way LEDs without bringing down the host¹.

USB-C Ports

Two USB-C connectors serve different roles¹:

• J3 (plug, male): Connects to the DockFrame hub (or any USB-C host), pulls 5.1 kΩ Rd on CC pins as UFP/sink
• J7 (receptacle, female): Downstream port for prototyping — USB 2.0 data passthrough from the XIAO, CC pins intentionally floating (USB-A-style devices work; strict USB-C peripherals requiring Rp will not enumerate)

Software

Any development environment supporting the XIAO module works — Arduino, PlatformIO, ESP-IDF, MicroPython, CircuitPython, Rust, TinyGo, Embedded Swift, Zephyr, FreeRTOS, NuttX¹. The XIAO enumerates as USB CDC at 115200 baud through the hub. The card is invisible at the firmware layer — it is a power harness and USB conduit¹.

Specifications

Specification	Details
Socket	Seeed Studio XIAO (14-pin castellated, 21 × 17.5 mm)1
Module included	XIAO ESP32-C51
Header pitch	2.54 mm (0.1"), 11-position strips1
Protected rails	+5 V, +3V3 (TPS2553 OCP at ~1.65 A)1
Downstream port	USB-C receptacle (USB 2.0 passthrough)1
Protection	PTC fuse, ESD diodes, load switches1
BOM	55 unique parts1
License	Open source (CERN-OHL-S hardware, MIT firmware)5
Source	HW-Lab-Hardware-Design-Agency (GitHub)5

Related Projects

Project	Description
DockFrame	HW Media Lab's modular USB-C hub hosting this card
Multimeter Card	Isolated multimeter in the same Tool Card format
Power Supply Card	Programmable bench supply in the same Tool Card format
RP2040 Expansion Card	RP2040-based development card with Qwiic port
RP2350 20-pin GPIO Expansion Card	RP2350A GPIO breakout card

Footnotes

1. Building a Breadboard in a Framework Expansion Card — HW Lab Blog ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷

2. DockFrame — HW Media Lab LLC ↩

3. DockFrame on Crowd Supply — Crowd Supply ↩

4. HW Lab's DockFrame Heads to Crowd Supply With Swappable Tool Cards — It's FOSS (July 2026) ↩

5. HW-Lab-Hardware-Design-Agency — GitHub ↩ ↩² ↩³