An embedded developer called Tod Kurt, has designed a capacitive touch control surface for the Raspberry Pi Pico. The device, named picoslidertoy, has 25 individual sensors capable of sensing basic touch controls as well as more intricate linear and rotary slide controls. The picoslidertoy interfaces with a Raspberry Pi Pico, utilizing up to 25 of its general-purpose input/output (GPIO) pins. It offers three distinct types of touch-sensitive input controls. These include nine buttons, along with a pair of rotary sliders and three linear sliders, enabling users to track finger movements along circles or lines rather than just single points of contact.
For those interested in exploring the project further, design files, source code, and 3D print files for an enclosure are accessible on GitHub. The picoslidertoy presents versatile applications, serving as a USB MIDI control surface, a USB Macropad keyboard with analog controls, or even a USB gamepad. Programming options include CircuitPython with touchio or Arduino with the TouchyTouch library, with several example firmware apps provided. Two versions of the picoslidertoy are available: a black PCB production version with aligned cutouts for standard 0.91" I2C OLED and all SMD resistors pre-soldered, and a green PCB prototype version with no components soldered and slightly off I2C OLED cutouts. Both versions feature a minimal 3D-printable enclosure to minimize spurious readings in capacitive touch projects like this. More detailed build instructions are forthcoming.
What sets the picoslidertoy apart is its direct integration of 25 capacitive touch sensors with the Raspberry Pi Pico, bypassing the need for an external touch chip. Kurt emphasizes the simplicity of extracting "analog" values from the touch sensors, although he acknowledges ongoing efforts to ensure stability in these readings. The picoslidertoy is available for purchase on Kurt's Tindie store, offered either as a kit for $11 or fully assembled for $16 (excluding the Raspberry Pi). Additionally, a $36 bundle includes a fully assembled variant with a Raspberry Pi Pico clone board and an SSD1306-based I2C OLED.
