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On Button Input Pressed

This block is triggered when a button or digital input is pressed (goes LOW to HIGH or HIGH to LOW, depending on configuration).

On Button Input Pressed Block

Overview​

The On Button Input Pressed block detects button press events on GPIO digital input pins, enabling user input and sensor event detection.

Configuration​

  • GPIO Line: Which digital input pin to monitor
  • Trigger Edge: Rising edge (LOW to HIGH) or falling edge (HIGH to LOW)
  • Debounce: Debounce time in milliseconds

Button Wiring​

Active HIGH (Pull-Down)​

Button pressed: Pin goes from LOW to HIGH
GPIO Pin -> Button -> VCC
GPIO Pin -> Pull-down Resistor -> Ground
Trigger on: Rising edge

Active LOW (Pull-Up)​

Button pressed: Pin goes from HIGH to LOW
GPIO Pin -> Button -> Ground  
GPIO Pin -> Pull-up Resistor -> VCC
Trigger on: Falling edge

Debouncing​

Debounce eliminates false triggers from:

  • Mechanical button bounce
  • Electrical noise
  • Contact chatter

Typical debounce times:

  • 10-50ms for mechanical buttons
  • 5-10ms for electronic signals
  • Adjust based on testing

Use Cases​

Common button input scenarios:

User Control​

On Button Pressed:
- Toggle light on/off
- Cycle through modes
- Start/stop process
- Confirm action

Sensor Detection​

On Motion Sensor:
- Trigger alarm
- Turn on lights
- Log event

On Door Switch:
- Detect open/close
- Security monitoring

Industrial Inputs​

On Limit Switch:
- Stop motor
- Detect position
- Safety interlock

On Emergency Stop:
- Immediate shutdown
- Lock out controls

Button Types​

Momentary Buttons​

  • Pressed only while held
  • Spring return
  • Most common type

Toggle Switches​

  • Stays in position
  • Two stable states
  • Use for persistent state

Limit Switches​

  • Mechanical activation
  • Position detection
  • Safety applications

Input Configuration​

Configure input pins:

  • Pull-Up: Internal or external resistor to VCC
  • Pull-Down: Internal or external resistor to ground
  • Schmitt Trigger: Noise immunity
  • Input Mode: Standard or interrupt

Multiple Buttons​

Handle multiple buttons:

  • Create separate blocks for each button
  • Assign functions to each
  • Implement button combinations
  • Create button matrix (advanced)

State Tracking​

Track button state:

  • Count presses
  • Measure hold duration
  • Detect double-click
  • Implement long-press

Button Functions​

Toggle​

On Button Pressed:
    state = NOT state
    Digital Line Set: Output = state

Momentary Control​

On Button Pressed:
    Digital Line Set: Output = HIGH
On Button Released:
    Digital Line Set: Output = LOW

Counter​

On Button Pressed:
    count = count + 1
    If count >= 5:
        Trigger action
        count = 0

Long Press Detection​

Detect long button press:

On Button Pressed:
    Start timer (3 seconds)
    
On Timer Complete:
    If button still pressed:
        Execute long-press action
        
On Button Released:
    Stop timer
    If timer not expired:
        Execute short-press action

Hardware Considerations​

Pull Resistors​

  • Internal: 10-100kΩ (convenient)
  • External: 4.7-10kΩ (more reliable)
  • Choose based on noise environment

ESD Protection​

  • Buttons are user-accessible
  • Add ESD protection diodes
  • Use TVS diodes for sensitive inputs

Cable Length​

  • Long cables increase noise susceptibility
  • Use shielded cable
  • Add RC filter for debouncing
  • Consider differential signaling

Safety Critical Inputs​

For safety-critical buttons:

  • Redundant input checking
  • Fail-safe logic
  • Hardwired safety circuits
  • Regular testing

Interrupt vs Polling​

Interrupt (Default)​

  • Immediate response
  • Low CPU usage
  • Best for time-critical

Polling​

  • Regular checking
  • Simpler logic
  • Higher CPU usage

Troubleshooting​

Common button input issues:

  • False triggers: Increase debounce time
  • Missed presses: Decrease debounce or check wiring
  • Inverted logic: Change trigger edge configuration
  • Intermittent: Check connections and pull resistors

Best Practices​

Button input best practices:

  1. Always use debouncing
  2. Proper pull resistors
  3. Test in noisy environment
  4. Document button functions
  5. Provide user feedback (LED, beep)
  6. Implement safety checks
  7. Consider accessibility

Advanced Features​

Button Combinations​

If (Button1 pressed AND Button2 pressed):
    Execute special function

Mode Selection​

Press count 1: Mode A
Press count 2: Mode B  
Press count 3: Mode C
Hold 3 seconds: Settings menu

Button Matrix​

Multiple buttons with fewer pins (advanced)

Linking to Variables​

Button state can link to variables:

  • Automatic input variable created
  • Read variable for current state
  • Monitor state changes
  • Log button events

See Also​