GPIO Adapter PCB for Seeedstudio XIAO Plus

Unlocking All 20 GPIOS on the Seeed Studio XIAO Plus Series with a Custom Adapter PCB

Seeed Studio recently released new members of their popular XIAO lineup, this time with 20 accessible GPIOs — a huge upgrade for makers needing more I/O in a tiny footprint. These new boards inclu

• XIAO ESP32S3 Pl
• XIAO nRF52840 Sense Plus
• XIAO nRF52840 Plus

While having 20 GPIOs is fantastic, the side and underside pin configuration makes it tricky to access all of them using standard breadboards or perfboards. To fix this, I designed a GPIO Adapter PCB that breaks out all pins for easy prototyping.

In this post, I’ll walk you through the two soldering methods I used to attach the XIAO Plus to the adapter PCB: hand soldering and hot plate reflow.

Method 1: Hand Soldering the XIAO Plus

Hand soldering is straightforward and doesn't require special tools — just a steady hand and some patience.

Tools You'll Need:

• A fine-point soldering iron tip
• Solder
• IPA (Isopropyl Alcohol) for cleaning
• Optional: magnifying glass or microscope

Steps:

Start with One Pad — Heat one corner pad and apply a small amount of solder to hold the board in place

Align the XIAO Plus on the Adapter PCB — Carefully place the board on the PCB to align all edge pads with their respective pads, and heat the corner pad

Solder the Remaining Edge Pads — Work your way around, soldering all visible pads.

Clean the Joints — Use IPA to clean off flux residue.

Add Header Pins — Finally, solder the header pins for breadboard compatibility

Limitation:

You cannot solder the underside pads using just a soldering iron. That’s where the hot plate method comes in!

Method 2: Hot Plate Reflow Soldering

This method allows you to solder both edge and underside pads — perfect for complete GPIO access.

Tools You’ll Need:

PD 65W Mini Hot Plate

RELIFE RL-404S Solder Paste (138°C melting point)

Steps:

Apply Solder Paste — Add a tiny amount of solder paste to each pad on the adapter PC

Place the XIAO Plus — Carefully align and place the board on top of the paste.

Heat Things Up — Set the hot plate to 150°C and let it preheat.

Reflow Time — Place the PCB on the hot plate and watch as the solder melts (you’ll see it shine up).

Cool Down — Remove the PCB and let it cool naturally.

Add Header Pins — Now that all pads (including the bottom ones) are connected, solder the headers.

Final Thoughts

With this simple adapter PCB and one of the soldering methods above, you can unlock the full potential of the 20 GPIOs on the XIAO Plus series. Whether you’re building advanced sensor arrays, motor controllers, or just want more room to experiment — this setup makes it all possible.