Source code for caproto.ioc_examples.io_interrupt

#!/usr/bin/env python3
import termios
import fcntl
import sys
import os
import threading
import atexit

from caproto.server import pvproperty, PVGroup, ioc_arg_parser, run

[docs]def start_io_interrupt_monitor(new_value_callback): ''' This function monitors the terminal it was run in for keystrokes. On each keystroke, it calls new_value_callback with the given keystroke. This is used to simulate the concept of an I/O Interrupt-style signal from the EPICS world. Those signals depend on hardware to tell EPICS when new values are available to be read by way of interrupts - whereas we use callbacks here. ''' # Thanks stackoverflow and Python 2 FAQ! if not sys.__stdin__.isatty(): print('[IO Interrupt] stdin is not a TTY, exiting') return fd = sys.stdin.fileno() oldterm = termios.tcgetattr(fd) newattr = termios.tcgetattr(fd) newattr[3] &= ~termios.ICANON & ~termios.ECHO oldflags = fcntl.fcntl(fd, fcntl.F_GETFL) print('Started monitoring the keyboard outside of the async library') # When the process exits, be sure to reset the terminal settings @atexit.register def reset_terminal(): print('Resetting the terminal settings') termios.tcsetattr(fd, termios.TCSAFLUSH, oldterm) fcntl.fcntl(fd, fcntl.F_SETFL, oldflags) print('Done') termios.tcsetattr(fd, termios.TCSANOW, newattr) fcntl.fcntl(fd, fcntl.F_SETFL, oldflags | os.O_NONBLOCK) # Loop forever, sending back keypresses to the callback while True: try: char = except IOError: ... else: if char: print(f'New keypress: {char!r}') new_value_callback(char)
[docs]class IOInterruptIOC(PVGroup): keypress = pvproperty(value='', max_length=10) # NOTE the decorator used here: @keypress.startup async def keypress(self, instance, async_lib): # This method will be called when the server starts up. print('* keypress method called at server startup') queue = async_lib.ThreadsafeQueue() # Start a separate thread that monitors keyboard input, telling it to # put new values into our async-friendly queue thread = threading.Thread(target=start_io_interrupt_monitor, daemon=True, kwargs=dict(new_value_callback=queue.put)) thread.start() # Loop and grab items from the queue one at a time while True: value = await queue.async_get() print(f'Saw new value on async side: {value!r}') # Propagate the keypress to the EPICS PV, triggering any monitors # along the way await self.keypress.write(str(value))
if __name__ == '__main__': ioc_options, run_options = ioc_arg_parser( default_prefix='io:', desc='Run an IOC that updates via I/O interrupt on key-press events.') ioc = IOInterruptIOC(**ioc_options) run(ioc.pvdb, **run_options)