DAQ_TRIGGER.SINGLE_SHOT_WAKE_UP

Typical use-cases for the different DAQ_TRIGGER modes of Worker_DAQ. Variations are possible.

The Worker_DAQ class instance will update once only, whenever it has received a so-called wake-up call. A wake-up can be requested by calling method QDeviceIO.wake_up_DAQ(). There are two distinct cases for which this mode can be used.

For device synchronization

The use-case outlined in the diagram above shows a stand-alone QTimer that periodically and simultaneously wakes up two different instances of Worker_DAQ, each communicating with a different peripheral I/O device. It is an easy way to sync the data acquisition between different devices, where the PC acts as a master.

Example:

from dvg_qdeviceio import QDeviceIO, DAQ_TRIGGER
from PyQt5 import QtCore

app = QtCore.QCoreApplication()

qdev_1 = QDeviceIO(my_device_1)
qdev_1.create_worker_DAQ(
    DAQ_trigger  = DAQ_TRIGGER.SINGLE_SHOT_WAKE_UP,
    DAQ_function = my_DAQ_function_1,
)

qdev_2 = QDeviceIO(my_device_2)
qdev_2.create_worker_DAQ(
    DAQ_trigger  = DAQ_TRIGGER.SINGLE_SHOT_WAKE_UP,
    DAQ_function = my_DAQ_function_2,
)

# We create the sync timer in the main thread in this example, but it is better
# for the timing stability to transfer the sync timer to a separate thread.
timer = QtCore.QTimer()
timer.setInterval(10)                       # 10 ms --> 100 Hz
timer.setTimerType(QtCore.Qt.PreciseTimer)  # ~1 ms granularity, resource heavy
timer.timeout.connect(qdev_1.wake_up_DAQ)
timer.timeout.connect(qdev_2.wake_up_DAQ)

qdev_1.start()
qdev_2.start()
timer.start()

while True:
    app.processEvents()  # Needed to have the sync timer tick

Alternative example (undocumented):

from dvg_qdeviceio import QDeviceIO, DAQ_TRIGGER

qdev_1 = QDeviceIO(my_device_1)
qdev_1.create_worker_DAQ(
    DAQ_trigger     = DAQ_TRIGGER.INTERNAL_TIMER,
    DAQ_function    = my_DAQ_function_1,
    DAQ_interval_ms = 10,  # 10 ms --> 100 Hz
)

qdev_2 = QDeviceIO(my_device_2)
qdev_2.create_worker_DAQ(
    DAQ_trigger  = DAQ_TRIGGER.SINGLE_SHOT_WAKE_UP,
    DAQ_function = my_DAQ_function_2,
)

qdev_1.worker_DAQ._timer.timeout.connect(qdev_2.wake_up_DAQ)
qdev_2.start()  # First make sure SINGLE_SHOT_WAKE_UP is up and running
qdev_1.start()  # and only then start INTERNAL_TIMER

For aperiodical triggering

… button press by the user … a process variable that crossed a threshold