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REV B

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GPIO Card for Raspberry Pi 4 & 5

Slides Onto the 40-Pin Header, 24 x 56 mm

A narrow strip that slides onto the Pi's 40-pin header and stays there while you wire. Every pin numbered and named where your hands already are — not on a browser tab behind you. Front gives you the pin numbers and GPIO numbers; turn it over for the bus assignments.

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ChatGPT Image Oct 17, 2026, 09_13_11 PM — GPIO Card REV B - the 24 x 56 mm strip, front and back.

40 Pins, numbered both sides

24 × 56 Millimetres — it stays on the header

7 Function colours

3.3 V Logic — not 5 V tolerant

Fits Raspberry Pi 4 and Raspberry Pi 5 — the 40-pin header is in the same place on both
Slides onto the 40-pin header — 40 gold-plated holes on the exact 2.54 mm grid
Narrow enough to stay on — 24 x 56 mm, so it clears the connectors beside the header
Colour coded by function — 5V, 3.3V, GND, I2C, SPI, UART, PWM
Both numbering systems — physical pins 1–40 and BCM GPIO numbers
Bus names on the back — SDA, SCL, TXD, RXD, MOSI, MISO, SCLK, CE0, CE1 and the PWM pins
No soldering — 1.50 mm holes slide over the pins by hand and lift off the same way
A real PCB — FR-4, white soldermask, ENIG gold, full-colour both sides
3.3 V logic warning printed on the front where you will see it

The problem it solves

Why GPIO Card for Raspberry Pi 4 & 5 exists

Raspberry Pi GPIO projects often fail because users mix up physical pin numbers, BCM GPIO numbers, power pins and bus pins. GPIO Card makes the reference physical and keeps it on the header while the user wires.

Counting pins with a fingertip

The strip slides onto the header on 40 gold-plated holes, so every label sits right beside its own pin.

Pin 12 is not GPIO 12

Physical pin numbers 1 to 40 run down the outside and BCM GPIO numbers are on the labels, so the two never get mixed up.

Reading all forty labels

5V, 3.3V, GND, I2C, SPI, UART and PWM each have their own colour, so the pins you need are found at a glance.

Who it is for

Made for the bench, the classroom and the workshop

Raspberry Pi users

Wire sensors, LEDs and HATs without a browser pinout open behind you.

Beginners

See what every pin is before connecting anything to it.

Makers

Narrow enough to leave on the header, so it stays with the Pi instead of getting lost.

Teachers

One on every Pi means fewer "which pin is it?" questions in class.

Workshop leaders

Hand out a Pi and a strip together — the reference comes with the hardware.

STEM classrooms

Makes the idea of pins, buses and voltage levels physical and visible.

Specs

The numbers, at a glance

Fits Raspberry Pi 4 and Raspberry Pi 5 — slides onto the standard 40-pin header

Pinout The 40-pin assignments are identical on every 40-pin Raspberry Pi, so the reference itself is correct across the range

Not for Raspberry Pi 400 and Pi 500 — their header lies flat in the keyboard case and needs an adapter

Holes 40 plated holes, 1.50 mm finished, on the 2.54 mm grid — about 0.30 mm clearance per side over the header pins

Mounting No tools, no soldering. It drops over the pins and sits flat.

Outline 24.0 × 56.0 mm, 2.0 mm rounded corners

Thickness 1.6 mm FR-4

Front All 40 pins — physical pin number and GPIO number, colour-coded by function

Full specification

12 rows

Fit

Fits	Raspberry Pi 4 and Raspberry Pi 5 — slides onto the standard 40-pin header
Pinout	The 40-pin assignments are identical on every 40-pin Raspberry Pi, so the reference itself is correct across the range
Not for	Raspberry Pi 400 and Pi 500 — their header lies flat in the keyboard case and needs an adapter
Holes	40 plated holes, 1.50 mm finished, on the 2.54 mm grid — about 0.30 mm clearance per side over the header pins
Mounting	No tools, no soldering. It drops over the pins and sits flat.

Size

Outline	24.0 × 56.0 mm, 2.0 mm rounded corners
Thickness	1.6 mm FR-4

Print

Front	All 40 pins — physical pin number and GPIO number, colour-coded by function
Back	Bus assignments per pin: SDA, SCL, TXD, RXD, MOSI, MISO, SCLK, CE0, CE1 and the PWM pins
Warning	Printed on the front: 3.3 V LOGIC ONLY — NOT 5 V TOLERANT

Build

Finish	ENIG gold on white soldermask, full-colour digital print both sides, no silkscreen
Revision	GPIO CARD REV B · 2026-10

// Every header, pin by pin

Pinout

4 pins

Filter to one header, or search for the pin you are looking for.

ODD Left column — odd pins

Pin	Name	Function	Note
1	3V3	3V3
3	GPIO2 SDA	I²C
5	GPIO3 SCL	I²C
7	GPIO4	GPIO
9	GND	GND
11	GPIO17	GPIO
13	GPIO27	GPIO
15	GPIO22	GPIO
17	3V3	3V3
19	GPIO10 MOSI	SPI
21	GPIO9 MISO	SPI
23	GPIO11 SCLK	SPI
25	GND	GND
27	ID_SD	Reserved	HAT EEPROM — leave alone
29	GPIO5	GPIO
31	GPIO6	GPIO
33	GPIO13 PWM	PWM
35	GPIO19 PWM	PWM
37	GPIO26	GPIO
39	GND	GND

EVEN Right column — even pins

Pin	Name	Function	Note
2	5V	5V
4	5V	5V
6	GND	GND
8	GPIO14 TXD	UART
10	GPIO15 RXD	UART
12	GPIO18 PWM	PWM
14	GND	GND
16	GPIO23	GPIO
18	GPIO24	GPIO
20	GND	GND
22	GPIO25	GPIO
24	GPIO8 CE0	SPI
26	GPIO7 CE1	SPI
28	ID_SC	Reserved	HAT EEPROM — leave alone
30	GND	GND
32	GPIO12 PWM	PWM
34	GND	GND
36	GPIO16	GPIO
38	GPIO20	GPIO
40	GPIO21	GPIO

// How you use it

One side to find the pin, one to find the bus

Front — where is it?

Physical pin number on the outside, GPIO number beside the hole. Colour tells you the function at a glance: red 5 V, orange 3V3, blue I²C, teal UART, green PWM, purple SPI.

Back — what is it?

The same 40 rows, named by bus: SDA and SCL, TXD and RXD, MOSI, MISO, SCLK, CE0, CE1, and the four PWM pins. Blank rows are ordinary GPIO with nothing special on them.

It stays put

It slides down over the pins and sits on the header, so it does not slide off while you are counting pins with your other hand.

// What is on the back

The four buses, at a glance

I²C bus 1

SDA = GPIO2 · pin 3 · SCL = GPIO3 · pin 5

SPI0

MOSI = GPIO10 · MISO = GPIO9 · SCLK = GPIO11 · CE0 = GPIO8 · CE1 = GPIO7

UART

TXD = GPIO14 · pin 8 · RXD = GPIO15 · pin 10

Hardware PWM

GPIO12, 13, 18, 19

Reserved

Pins 27 / 28 — HAT EEPROM (ID_SD / ID_SC).

Before you wire

Raspberry Pi GPIO notes

GPIO Card is a reference only — it carries no power and connects nothing. These notes are about the Raspberry Pi pins it labels.

Raspberry Pi GPIO is 3.3V onlyEvery GPIO pin works at 3.3V logic.
Not 5V tolerantA 5V signal wired straight to a GPIO pin can damage the Pi. Pins 2 and 4 are 5V supply rails, never a signal level.
Fit it the right way roundPin 1 on the strip goes over pin 1 on the header. Turned round, the labels sit next to the wrong pins.
Power off while re-wiringMove jumper wires with the Pi switched off.

On the board · Not 5 V tolerant

It is printed on the front, where you see it before wiring — not buried in a manual.

Logic Every GPIO is 3.3 V. A 5 V sensor output wired straight to a GPIO can damage the SoC.

Pins 2, 4 5 V rails — supply only, never a signal level. The Pi does give you 5 V; it just will not accept it back on a GPIO.

Pins 27, 28 Reserved for HAT identification. Use them as ordinary GPIO and HAT auto-detection breaks.

Downloads

Files for this board

Documents and production files for this board. Sizes are shown so nothing large downloads by surprise.

Documents Guides, pinouts and handouts

PDF PDF guide PDF · 8.2 KB ↓ PDF Pinout reference PDF · 8.5 KB ↓ PDF Classroom handout PDF · 5.2 KB ↓

FAQ

Questions people ask

Which Raspberry Pi does it fit?

Raspberry Pi 4 and Raspberry Pi 5. The strip is deliberately short so it clears the connectors that sit just past pin 40 on both boards. The 40-pin assignments are identical on every 40-pin Raspberry Pi, so the reference is correct more widely — but the Pi 400 and Pi 500 keep their header flat inside the keyboard case, so the strip will not seat on those.

Does it need soldering?

No. The 40 holes are 1.50 mm, about 0.30 mm wider per side than the header pins, so it slides on by hand and lifts off the same way. Nothing is soldered to it and nothing is connected electrically — the plated rings are decorative.

Does it stay on while a HAT is fitted?

No. It uses the same pins a HAT wants, so the strip comes off first. It is for the wiring stage, not for running.

Why does it say not 5 V tolerant?

Because it is the mistake that kills a Pi. Every GPIO is 3.3 V logic — a 5 V sensor output wired straight to a GPIO can damage the SoC. Pins 2 and 4 do supply 5 V, which is exactly why the warning says LOGIC: you can draw 5 V, you cannot feed it back into a GPIO.

What are pins 27 and 28 for?

ID_SD and ID_SC, reserved for HAT identification EEPROM. Use them as ordinary GPIO and you break HAT auto-detection, so the strip names them rather than leaving them blank.

What happened to the old card?

REV A1 was a credit-card-sized version. It was replaced by this strip, which is narrow enough to stay on the header without covering the board or fouling the connectors beside it.

Goes with