point.value Vs point.lastValue

[bbartling]

So I think I understand when using connect that point.lastValue returns the last value of the Pandas series df.

• Does point.value perform a fresh read request and point.lastValue is just what was found during last poll of the point?

But just curious why my script operates like this....I notice different things happening when I switch point.value Vs point.lastValue in my code below inside the def printData(): recurring task.

For example is I just use point.value the code will loop through all four points from the 2 devices and print each sensor reading as expected, 4 sensors in total from 2 different devices. The nan readings are correct I just have a wire missing off the controller on my test bench at the moment:

2022-09-24 09:43:01,291 - INFO    | Ready!
2022-09-24 09:43:01,292 - INFO    | Device defined for normal polling with a delay of 10sec
2022-09-24 09:43:01,292 - INFO    | Polling started, values read every 10 seconds
{'TEST1': 71.53999328613281}
{'TEST1': nan}
{'TEST2': nan}
{'TEST2': nan}
{'TEST1': 71.53999328613281}
{'TEST1': nan}
{'TEST2': nan}
{'TEST2': nan}
{'TEST1': 71.49999237060547}
{'TEST1': nan}
{'TEST2': nan}
{'TEST2': nan}
{'TEST1': 71.50999450683594}
{'TEST1': nan}
{'TEST2': nan}
{'TEST2': nan}
{'TEST1': 71.12999725341797}
{'TEST1': nan}
{'TEST2': nan}
{'TEST2': nan}
{'TEST1': 71.49999237060547}
{'TEST1': nan}

But when I use point.lastValue its like the code is stuck only returning one sensor reading over and over. Looks like this:

2022-09-24 09:36:31,159 - INFO    | Device defined for normal polling with a delay of 10sec
2022-09-24 09:36:31,160 - INFO    | Polling started, values read every 10 seconds
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}
{'TEST1': 70.89999389648438}

Here's my code, is this because a time.sleep or something is hosing up BACnet polling processes? Its the same thing I noticed in my other issue that is closed that you helped with some code....

import BAC0
from BAC0.tasks.RecurringTask import RecurringTask 
import time

bacnet = BAC0.lite()

furnace_obj_list = [('analogInput', 2),
                    ('analogInput', 3)]

hotwaterhtr_obj_list = [('analogInput', 2),
                    ('analogInput', 3)]


furnace = BAC0.device('12345:2',
                        201201,
                        bacnet,
                        object_list=furnace_obj_list,
                        segmentation_supported=False)


hotwaterheatr = BAC0.device('12345:6',
                        201202,
                        bacnet,
                        object_list=hotwaterhtr_obj_list,
                        segmentation_supported=False)


time.sleep(3)

devices = [furnace,hotwaterheatr]


def printData():
    for device in devices:
        for point in device.points:
            #print(point)

            data = {
                #device.properties.name : point.lastValue
                device.properties.name : point.value
            }
            print(data)

            time.sleep(10)


def main():
    task1 = RecurringTask(printData,delay=60)
    task1.start()

    while True:
        time.sleep(0.01)


if __name__ == "__main__":
    main()


bacnet.disconnect()
print('disconnected')

[ChristianTremblay]

Sleep is bad... the thread are stopped... This is why in the while loop, I use a very small delay in the sleep function. This way, after 0.01sec, if the thread needs to run, there is a chance for it to do so.

try this

import BAC0
from BAC0.tasks.RecurringTask import RecurringTask 
import time

bacnet = BAC0.lite()

furnace_obj_list = [('analogInput', 2),
                    ('analogInput', 3)]

hotwaterhtr_obj_list = [('analogInput', 2),
                    ('analogInput', 3)]


furnace = BAC0.device('12345:2',
                        201201,
                        bacnet,
                        object_list=furnace_obj_list,
                        segmentation_supported=False)


hotwaterheatr = BAC0.device('12345:6',
                        201202,
                        bacnet,
                        object_list=hotwaterhtr_obj_list,
                        segmentation_supported=False)


# will tolerate this one... but you could test if it is really required.
time.sleep(3)

devices = [furnace,hotwaterheatr]


def printData():
    for device in devices:
        for point in device.points:
            #print(point)

            data = {
                #device.properties.name : point.lastValue
                device.properties.name : point.value
            }
            print(data)

           #time.sleep(10)


def main():
    task1 = RecurringTask(printData,delay=60)
    task1.start()

    while True:
        time.sleep(0.01)


if __name__ == "__main__":
    main()


bacnet.disconnect()
print('disconnected')