# Hardware Support

> Original: [Hardware support](https://tttapa.github.io/Control-Surface/Doxygen/db/dd3/group__AH__ExtIO.html)

Hardware utilities in the `AH::` namespace for debouncing, filtering, and encoder reading.

## Button

Debounced button with state machine:

```cpp pico
AH::Button btn {5};
btn.begin();

// In loop:
btn.update();
if (btn.getState() == AH::Button::Falling)
    // pressed
if (btn.getState() == AH::Button::Rising)
    // released
```

States: `Pressed`, `Released`, `Falling` (just pressed), `Rising` (just released).

## FilteredAnalog

EMA-filtered analog input with hysteresis to reduce noise:

```cpp pico
AH::FilteredAnalog<10> pot {26};  // 10-bit, GPIO 26

// In loop:
if (pot.update())
    uint16_t value = pot.getValue();
```

## AHEncoder

Interrupt-driven quadrature rotary encoder:

```cpp pico
AH::AHEncoder enc {0, 1};  // pin A, pin B
enc.begin();

// In loop:
int32_t delta = enc.read();
enc.write(0);  // reset position
```

## GPIO on RP2xxx

cs-midi uses pico-sdk GPIO directly. Pin numbers are GPIO numbers (0-29 on RP2040, 0-47 on RP2350).

- Buttons use internal pull-ups (active low)
- ADC pins: GPIO 26-29 (ADC0-ADC3)
- Encoder pins: any GPIO with interrupt capability (all pins on RP2xxx)

## Extended I/O

Hardware expanders (MCP23017, MAX7219, shift registers) are not yet ported from Control Surface. Use direct GPIO pins for all inputs and outputs.