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Digital Line Set

This block sets a GPIO digital line to HIGH or LOW. Use it to control digital outputs like relays, LEDs, and motors.

Digital Line Set Block

Overview​

The Digital Line Set block controls GPIO (General Purpose Input/Output) digital output pins, enabling direct hardware control for relays, indicators, and actuators.

Configuration​

  • GPIO Line: Which digital pin to control
  • State: HIGH (1) or LOW (0)

Use Cases​

Common digital output scenarios:

Relay Control​

Control AC/DC loads:

Turn ON pump: Digital Line Set = HIGH
Turn OFF pump: Digital Line Set = LOW

LED Indicators​

Show device status:

Status OK: Green LED = HIGH, Red LED = LOW
Status Error: Green LED = LOW, Red LED = HIGH

Motor Control​

Control DC motors:

Motor Forward: Pin A = HIGH, Pin B = LOW
Motor Reverse: Pin A = LOW, Pin B = HIGH
Motor Stop: Pin A = LOW, Pin B = LOW

Solenoid Valves​

Control fluid flow:

Valve Open: Solenoid = HIGH
Valve Closed: Solenoid = LOW

GPIO Configuration​

Configure GPIO lines:

  • Output Mode: Push-pull or open-drain
  • Initial State: State at power-on
  • Pull Resistor: Internal pull-up/pull-down
  • Drive Strength: Current capability

Dynamic Control​

Set state dynamically:

  • Use variables for state
  • Calculate state from conditions
  • Control based on sensor readings
  • Implement logic patterns

Timing​

Control timing:

  • Instant on/off switching
  • Debounce delays

Multiple Outputs​

Control multiple pins:

  • Create separate blocks for each pin
  • Coordinate multiple outputs
  • Implement sequences
  • Parallel control

State Persistence​

Remember output state:

  • Save state to settings
  • Restore on reboot
  • Default state on startup
  • Power-fail safety

Linking to Variables​

Link GPIO to variables:

  • Automatic hardware variable created
  • Set variable to control output
  • Variable shows current state
  • Bidirectional synchronization

Applications​

Home Automation​

Light Control: GPIO -> Relay -> Light
Lock Control: GPIO -> Solenoid -> Door Lock
Fan Control: GPIO -> Relay -> Fan

Industrial Control​

Pump Control: GPIO -> Contactor -> Pump Motor
Valve Control: GPIO -> Solenoid -> Pneumatic Valve
Alarm: GPIO -> Horn/Beacon

Robotics​

Motor Driver: GPIO -> H-Bridge -> DC Motor
Servo Enable: GPIO -> Servo Controller
Gripper: GPIO -> Solenoid -> Pneumatic Gripper

Safety Considerations​

Implement safety features:

  • Watchdog timeout to safe state
  • Emergency stop input
  • Interlock logic
  • Fail-safe defaults

Sequences​

Implement output sequences:

1. Digital Line Set: Valve 1 = HIGH (open)
2. Delay 2 seconds
3. Digital Line Set: Pump = HIGH (on)
4. Wait for level sensor
5. Digital Line Set: Pump = LOW (off)
6. Delay 1 second
7. Digital Line Set: Valve 1 = LOW (close)

Troubleshooting​

Common GPIO output issues:

  • Output not working: Check wiring and pin configuration
  • Insufficient current: Use external driver/relay
  • Wrong voltage: Verify logic levels
  • Flickering: Check power supply and connections

Best Practices​

GPIO control best practices:

  1. Document pin assignments
  2. Implement safety interlocks
  3. Use appropriate drivers for loads
  4. Add protection circuits
  5. Test emergency stop
  6. Initialize to safe state
  7. Monitor output status

Hardware Examples​

Control Relay Module​

GPIO Pin -> Relay Module Input
Relay Common -> Load Hot Wire
Relay NO -> Load Return

Control LED​

GPIO Pin -> 330Ω Resistor -> LED Anode -> Cathode -> Ground

Control DC Motor (via transistor)​

GPIO Pin -> Base Resistor -> NPN Transistor -> Motor -> Power Supply

See Also​