Hidden Agenda is an open-source USB device that puts audio-pedal-style effects on keyboard and mouse input. Plug a keyboard or mouse into it, connect the pedal to a computer, and its software can alter what the computer receives—from cursor momentum and looping to repeated or remapped keystrokes.
What the Hidden Agenda pedal does
Built by Guy Dupont, Hidden Agenda sits between a USB keyboard or mouse and a computer. It intercepts the device’s USB human-interface-device (HID) input, applies a selected effect, then sends the modified events to the computer. With the pedal switched off, input passes through unchanged. The project’s hardware and implementation are documented at the Hidden Agenda project page.
The idea is to translate effects familiar from audio gear into changes to typing and pointer behavior. It is best understood as a creative maker project, not as a conventional productivity accessory.
How it connects and processes input
The documented layout has a USB-A port for the keyboard or mouse and a USB-C connection to the computer; that computer connection also powers the pedal. The design uses a Seeed XIAO RP2040 development board. TinyUSB and Pico-PIO-USB let the device handle USB host input from the peripheral while also acting as a USB device to the computer.
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In practical terms, the keyboard or mouse connects to the pedal rather than directly to the computer. The computer then receives the pedal’s output. This routing is central to how the effects work; it is not simply a software filter installed on the computer.
Controls: selecting and activating effects
The pedal’s controls are arranged like those on a guitar effects pedal: a rotary knob, a footswitch, and a mode toggle. The control mode determines whether the knob selects an effect or adjusts its parameter.
- Effect-select mode: turn the knob to choose an effect slot.
- Momentary mode: the effect operates only while you hold the footswitch.
- Latch mode: press the footswitch to toggle the effect on or off; turn the knob to change the selected effect’s parameter.
Mouse effects: changing pointer movement
Reverb adds cursor momentum
Mouse reverb makes the cursor continue moving after you stop moving the mouse, giving pointer movement a sense of momentum. Hackster’s example describes it as an audio-style reverb idea applied to the cursor: Hackster’s Hidden Agenda overview.
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Looper records and repeats a gesture
The looper records a mouse movement and plays it back continuously. Its documented speed range extends from reverse playback to faster-than-recorded playback, so the replay can change both direction and pace.
Distortion and noise filtering alter movement
At higher settings, the distortion/noise-filter effect introduces random cursor movement. At lower settings, it smooths movement with a low-pass filter. The same effect slot therefore produces markedly different behavior depending on its setting.
Crossover turns mouse actions into keyboard input
Mouse crossover maps mouse actions to keyboard input. The project also offers a crossover in the opposite direction for keyboard input, described below.
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Keyboard effects: changing keystrokes
Tremolo alternates letter case
Keyboard tremolo changes letter case, ranging from an uppercase/lowercase alternation to randomized case behavior.
Delay repeats keystrokes
Delay repeats a keypress at timed intervals. Its feedback control changes how the repetitions continue, echoing the adjustable repeats of an audio delay.
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Pitch shift and harmonizer remap typed characters
Pitch shift remaps typed keys to nearby characters. In Hackster’s example, pressing “b” can produce “c” or “a,” depending on the setting. Harmonizer behavior can produce multiple letters from an input key.
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Crossover turns keyboard input into mouse-style actions
Keyboard crossover converts keyboard input into mouse-style actions, complementing the mouse-to-keyboard crossover effect.
What hardware and cable are required?
The project documentation names the Seeed XIAO RP2040 as its microcontroller board and includes hardware and enclosure files. The author credits AmplifyFUN with sourcing, cutting, and printing the final enclosures. For the computer connection, the Etsy listing says a USB-C cable is required. The board is a component used in the project, not evidence that a complete commercial pedal is currently available.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Is Hidden Agenda for sale?
An Etsy listing describes a Hidden Agenda multi-FX pedal, but a listing alone does not establish current stock or whether the same seller continues to offer it. Check the listing directly for availability and the precise item being sold: Hidden Agenda multi-FX pedal on Etsy. The project’s open-source hardware files provide a separate route for makers who want to investigate building one.
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Is it useful for accessibility?
Some coverage has suggested that two effects might help people with movement disorders. That is a possibility, not a demonstrated medical benefit: the available coverage does not document clinical trials, user testing, or evidence that Hidden Agenda is an effective accessibility or treatment tool. A person considering it for access needs should treat its experimental effects as unvalidated and assess whether its altered input is usable for their particular tasks.
Who is this pedal for?
Hidden Agenda is most compelling for makers and people curious about unusual input behavior. Its physical footswitch and hardware-based USB routing distinguish it from software-only remappers, while its effects prioritize creative transformations over predictable everyday typing or pointing. It may be interesting to explore for alternative interaction, but the project does not establish comparative performance against remapping software or conventional accessibility tools.
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