mirror of
https://github.com/naruxde/revpimodio2.git
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Sven Sager
3294c5e980
Revised various sections across multiple documentation files to reflect updated methods (`run_plc` replacing manual setup with `cycleloop`) and adjust for new default parameters (e.g., `autorefresh`). Enhanced descriptions for timers, Cycletools usage, and new method explanations. Removed outdated or redundant examples and updated system requirements. Signed-off-by: Sven Sager <akira@narux.de>
6.7 KiB
6.7 KiB
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Basics
Core concepts and fundamental usage of RevPiModIO.
Contents
Programming Paradigms
RevPiModIO supports two complementary programming approaches:
Cyclic Programming - Execute a function at regular intervals, similar to PLC programming.
Best for deterministic timing, state machines, and time-critical control
Runs your function every cycle (typically 20-50ms)
See :doc:`cyclic_programming` for details
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Event-Driven Programming - Register callbacks triggered by hardware state changes.
Best for user interactions, sporadic events, and system integration
Consumes CPU only when events occur
See :doc:`event_programming` for details
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Both approaches can be combined in a single application. See :doc:`advanced` for examples.
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Unknown interpreted text role "doc".Getting Started
Basic Instantiation
Create a RevPiModIO instance to access your hardware:
import revpimodio2 rpi = revpimodio2.RevPiModIO(autorefresh=True) # Your code here rpi.exit()
Configuration Parameters
rpi = revpimodio2.RevPiModIO( autorefresh=True, # Auto-sync process image (recommended) monitoring=False, # Read-only mode syncoutputs=True, # Load output values on init debug=False # Enable debug messages )
autorefresh - Automatically reads inputs and writes outputs. Set to True for most applications.
monitoring - Read-only mode. Use when monitoring without controlling hardware.
syncoutputs - Load current output values on startup. Prevents outputs from resetting.
debug - Enable debug logging for troubleshooting.
Cycle Timing
Default update rates depend on your hardware:
- Core 1: 40ms (25Hz)
- Core3/Connect: 20ms (50Hz)
- NetIO: 50ms (20Hz)
Adjust cycle time to match your needs:
rpi = revpimodio2.RevPiModIO() rpi.cycletime = 100 # Set to 100ms rpi.autorefresh_all()
Important: Faster cycle times consume more CPU. Choose the slowest cycle time that meets your requirements. Default values will fit most needs.
Error Handling
Configure I/O error threshold:
maxioerrors = 10 # Raise exception after 10 errors # Check error count if rpi.core.ioerrorcount > maxioerrors: print("Warning: I/O errors detected")
Core Objects
rpi.io - Input/Output Access
Access all configured IOs from piCtory:
# Direct attribute access value = rpi.io.button.value rpi.io.led.value = True # String-based access rpi.io["button"].value # Check existence if "sensor" in rpi.io: print(rpi.io.sensor.value) # Iterate all IOs for io in rpi.io: print(f"{io.name}: {io.value}")
IO Properties
Each IO object has these properties:
- .name - IO name from piCtory
- .value - Current value (read/write)
- .address - Byte address in process image
- .type - IO type (INPUT=300, OUTPUT=301, MEMORY=302)
- .defaultvalue - Default value from piCtory
rpi.core - System Control
Access Revolution Pi system features:
LED Control
# Using constants rpi.core.A1 = revpimodio2.GREEN rpi.core.A2 = revpimodio2.RED rpi.core.A3 = revpimodio2.OFF # Individual colors rpi.core.a1green.value = True rpi.core.a1red.value = False
System Status
# CPU information temp = rpi.core.temperature.value freq = rpi.core.frequency.value # piBridge status cycle_time = rpi.core.iocycle.value errors = rpi.core.ioerrorcount.value
Watchdog
# Toggle watchdog rpi.core.wd_toggle() # Watchdog IO object rpi.core.wd.value = True
See :doc:`advanced` for complete watchdog management examples.
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Access specific hardware devices:
# By name dio = rpi.device.DIO_Module_1 # By position first = rpi.device[0] # Iterate for device in rpi.device: print(device.name)
Signal Handling
Graceful Shutdown
Handle SIGINT and SIGTERM for clean program termination:
rpi = revpimodio2.RevPiModIO(autorefresh=True) # Enable signal handling rpi.handlesignalend() # Run main loop rpi.mainloop()
Custom Signal Handler
Implement custom cleanup logic:
def cleanup(signum, frame): print("Shutting down...") rpi.setdefaultvalues() rpi.exit() rpi.handlesignalend(cleanup) rpi.mainloop()
Simple Examples
Read Input, Control Output
import revpimodio2 rpi = revpimodio2.RevPiModIO(autorefresh=True) # Read input and control output if rpi.io.button.value: rpi.io.led.value = True else: rpi.io.led.value = False rpi.exit()
LED Control
import revpimodio2 rpi = revpimodio2.RevPiModIO(autorefresh=True) # Control status LEDs rpi.core.A1 = revpimodio2.GREEN rpi.core.A2 = revpimodio2.RED rpi.exit()
Iterate All IOs
import revpimodio2 rpi = revpimodio2.RevPiModIO(autorefresh=True) # Print all IOs and their values for io in rpi.io: print(f"{io.name}: {io.value}") rpi.exit()
Best Practices
Use Descriptive IO Names
Configure descriptive names in piCtory:
# Good - Clear intent if rpi.io.emergency_stop.value: rpi.io.motor.value = False # Poor - Generic names if rpi.io.I_15.value: rpi.io.O_3.value = False
Always Clean Up
Always call rpi.exit() to clean up resources:
rpi = revpimodio2.RevPiModIO(autorefresh=True) try: # Your code here pass finally: rpi.exit()
Check IO Existence
Verify IOs exist before accessing:
if "optional_sensor" in rpi.io: value = rpi.io.optional_sensor.value else: print("Sensor not configured")
See Also
:doc:`cyclic_programming` - Cyclic programming patterns
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:doc:`event_programming` - Event-driven programming patterns
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:doc:`advanced` - Advanced topics and best practices
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:doc:`api/index` - API reference
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