Do you need more GPIO for your Pi Pico project? A creative keyboard maker named HealthyCabinet found a way to unlock up to four new GPIO pins on the Raspberry Pi Pico or Pi Pico W. It requires a bit of soldering work, but nonetheless, it’s a surprisingly simple modification.

Out of the box, both the Raspberry Pi Pico and wireless Pi Pico W feature 26 GPIO headers, which line the outsides of the circuit board. But as reported by Hackster.io, crafty maker HealthyCabinet discovered that 26 GPIO pins aren’t enough for some projects—HealthyCabinet needed just one more pin to replace a mechanical keyboard’s MCU with the Pico microcontroller.

After a look at the Pi Pico datasheet, HealthyCabinet noticed that four extra pins are utilized for semi-non-essential internal board functions:

• GP1029: IP Used in ADC mode (ADC3) to measure VSYS/3
• GPI025: OP Connected to user LED
• GPI024: IP VBUS sense – high if VBUS is present, else low
• GPI023: OP Controls the on-board SMPS Power Save pin

Because HealthyCabinet’s project runs on USB power, it doesn’t require VBUS sense (GPI024). It also doesn’t need the power indicator LED (GPI025), which is primarily a quality of life feature.

After removing the resistors connected to these pins, HealthyCabinet soldered 26AWG wires in their place for easy GPIO access. Tests with a multimeter and a CircuitPython program confirm that these pins are still functional and controlled through software.

HealthyCabinet explains that, if a user needs even more GPIO pins, they can free the SMPS mode switch (GPI023) and VYSY voltage meter (GP1029). But the first modification requires a wire to ground or the 3v3 pin (for power equivalent to board-level voltage), and the former option requires dedicated USB power.

Unfortunately, modifications to the Pi Pico firmware are required to take full advantage of these extra pins. HealthyCabinet doesn’t have a GitHub for this mod, but you can read all about it on the Raspberry Pi subreddit.

Source: HealthyCabinet (Reddit, Imgur) via Hackster.io