# Stream Deck+ Button Detection Algorithm

algo.md

Stream Deck+ Button Detection Algorithm

This document describes the algorithm used to detect button presses and releases on the Stream Deck+ device.

Data Format

The Stream Deck+ sends 14-byte packets for button events. The first byte (data[0]) determines the event type:

• 1: Button or encoder event
• 2: Touchscreen event
• 3: Dial event

For button events (data[0] == 1), the data format is as follows:

[1 0 8 0 X Y Z W V U T S R Q]

Where:

• X (data[4]): Button 0 state (1 = pressed, 0 = released)
• Y through Q (data[5] through data[12]): Buttons 1-7 states (1 = pressed, 0 = released)

Button Detection Algorithm

1. Button 0 Detection:

   • Press: Check if data[4] == 1
   • Release: Check if data[4] == 0 and button was previously pressed

2. Buttons 1-7 Detection:

   • For each position i from 5 to 12:
     • Calculate button number: buttonNum = i - 4
     • Press: Check if data[i] == 1
     • Release: Check if data[i] == 0 and button was previously pressed

3. State Tracking:

   • Maintain an array lastKeyStates[8] to track the previous state of each button
   • Update state only when a change is detected
   • Use state tracking to prevent duplicate press/release events

Example Data

Button 0 press:

[1 0 8 0 1 0 0 0 0 0 0 0 0 0]

Button 0 release:

[1 0 8 0 0 0 0 0 0 0 0 0 0 0]

Button 1 press:

[1 0 8 0 0 1 0 0 0 0 0 0 0 0]

Button 1 release:

[1 0 8 0 0 0 0 0 0 0 0 0 0 0]

Implementation Notes

1. The algorithm uses a polling frequency of 20Hz (50ms intervals)
2. Raw data is only printed when an actual button event is detected
3. Button numbers are zero-based (0-7)
4. Array bounds checking is implemented to prevent index out of range errors
5. The algorithm handles both press and release events for all buttons

Edge Cases

1. Multiple Button Presses: The algorithm can detect multiple buttons pressed simultaneously
2. Rapid Presses: State tracking prevents duplicate events during rapid button presses
3. Out of Range: Button numbers >= 8 are skipped to prevent array index errors
4. Encoder Events: The algorithm distinguishes between button and encoder events by checking data[1] and data[2]