Do you need more GPIOs for your Pi Pico project? A creative keyboard maker called 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 it’s a surprisingly simple mod nonetheless.
Out of the box, both the Raspberry Pi Pico and the wireless Pi Pico W feature 26 GPIO headers, which line the outside of the circuit board. But as reported hackster.ioAstute 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 looking at the Pi Pico datasheet, HealthyCabinet noted that four additional pins are used 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, low otherwise
- GPI023: OP Controls the integrated SMPS Power Save pin
Since the HealthyCabinet project runs on USB power, it does not require VBUS sense (GPI024). You also don’t need the power indicator LED (GPI025), which is primarily a quality of life feature.
After removing the resistors attached to these pins, HealthyCabinet soldered 26 AWG wires in their place for easy GPIO access. Testing with a multimeter and CircuitPython program confirms that these pins are still working and controlled through software.
HealthyCabinet explains that if a user needs even more GPIO pins, they can free up the SMPS mode switch (GPI023) and the VYSY voltage meter (GP1029). But the first mod requires a ground wire or the 3v3 pin (for power equivalent to board-level voltage), and the first option requires dedicated USB power.
Unfortunately, modifications to the Pi Pico firmware are required to take full advantage of these additional 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