Build a Raspberry Pi I/O Breakout Cable & Plugboard Adapter – Step‑by‑Step Guide

Welcome to the second post in our So Make It series, where we dive into the nuts and bolts of Raspberry Pi hardware hacking. This guide is designed for beginners and explains every detail needed to create a short, reliable I/O breakout cable that connects the 26‑pin header on older Raspberry Pi models to a plug‑board adapter.

Why Build This?

Connecting to the Pi’s 26‑pin header can be messy without a proper breakout. A short, well‑constructed cable protects the Pi’s delicate Broadcom chip from excessive capacitive load, keeps signal integrity high, and gives you the flexibility to switch between projects by simply swapping the plug‑board.

Step 1: Gather the Parts

All components are inexpensive and widely available. The RS‑Online part numbers are listed for reference, but the same items can be sourced from eBay, Amazon or local electronics stores.

• 26‑pin, 0.1″ (2.54 mm) pre‑assembled socket with strain relief – RS 323‑7902
• 26‑pin, 0.1″ straight header (PCB‑mount) – RS 827‑7772 (longer lengths can be trimmed)
• 13‑pin, 0.1″ straight header (PCB‑mount) – RS 767‑1110 (aim for ≥8 mm pins; extend by pushing through plastic if needed)
• Short 26‑pin, 0.05″ (1.27 mm) flat ribbon cable (or an old floppy/IDE cable) – RS 289‑9925
• Single‑sided, 0.1″ pitch Veroboard (stripboard) – RS 01‑393

Optional: If you’re on a budget, a cut‑down floppy cable with one socket can suffice, but it will be longer and less reliable.

Step 2: Trim the Double‑Row Header

Using precision side cutters, count 13 pin pairs and cut cleanly through the plastic base. Avoid damage to the pins.

Step 3: Trim the Single‑Row Headers

Repeat the trimming process for each of the two 13‑pin single‑row headers.

Step 4: Extend the Pins

With long‑nose pliers, gently push each pin until it’s flush with the plastic base. A 10 mm extension is typical and improves routing flexibility.

Step 5: Prepare the Stripboard

Cut the Veroboard to a 13 × 4 hole rectangle. Keep the copper side facing up and align the holes so that the copper traces run perpendicular to the headers.

Step 6: Isolate the Copper Traces

Use a fine rotary tool or a sharp blade to cut a groove through the copper, separating the top and bottom rows of the double‑row header. Precision here prevents unwanted short circuits.

Step 7: Clean the Copper

Remove oxidation with fine wire wool or a brass polish (e.g., Brasso). Clean the surface in water and dry before soldering to ensure good wetting.

Step 8: Soldering Tips

Choose lead‑free silver‑tin solder for safety, and apply a flux pen for extra flow. Heat the iron to about 400 °C and use a chisel‑shaped tip for through‑hole work. Keep the tip hot, apply solder before each joint, and be careful not to over‑heat the plastic headers.

Follow the soldering sequence: (1) attach the 26‑pin socket to the cable, (2) solder the two 13‑pin headers to the Veroboard, (3) connect the cable to the socket, (4) secure the Veroboard onto a board or enclosure. Test continuity with a multimeter before powering the Pi.

Final Test

Once assembled, plug the cable into your Raspberry Pi and connect the plug‑board adapter. Verify each pin’s voltage and continuity. This setup now supports I²C, UART, SPI, and GPIO projects with minimal interference.