Add code to read out response time from the box, not relying on system time.

[guillermoaguilar]

Add code to read out response time from the box, not relying on system time.

[dekuenstle]

Thanks, @guillermoaguilar! Do you have some code snippet/example/reference on how to to this?

[guillermoaguilar]

Yes, our implementation in HRL is an adapted copy of the example provided by the official documentation by VPixx., here below:

from pypixxlib.datapixx import DATAPixx3
from psychopy import core

#connect to VPixx device
device = DATAPixx3()

#First, let's make a dictionary of codes that correspond to our buttons. This is in decimal.
#Note 1: these codes ARE NOT UNIVERSAL. You can check what your own button codes are using the PyPixx Digital I/O demo
#Note 2: these codes are for single button presses only. If two buttons are pressed at the same time this will generate a unique code, which we will ignore
buttonCodes = {65527:'blue', 65533:'yellow', 65534:'red', 65531:'green', 65519:'white', 65535:'button release'}
exitButton = 'white'

myLog = device.din.setDinLog(12e6, 1000)
device.din.startDinLog()
device.updateRegisterCache()
startTime = device.getTime()
finished = False


#let's create a loop which checks the schedule at 0.25 s intervals for button presses.
#Any time a button press is found, we print the timestamp and button pressed.
#If a designated exit button is pressed, we disconnect.
while finished == False:
    #read device status
    device.updateRegisterCache()
    device.din.getDinLogStatus(myLog)
    newEvents = myLog["newLogFrames"]

    if newEvents > 0:
        eventList = device.din.readDinLog(myLog, newEvents)

        for x in eventList:
           if x[1] in buttonCodes:
                #look up the name of the button
                buttonID = buttonCodes[x[1]]

                #get the time of the press, since we started logging
                time = round(x[0] - startTime, 2)
                printStr = 'Button pressed! Button code: ' + str(x[1]) + ', Button ID: ' + buttonID + ', Time:' + str(time)
                print(printStr)
                if buttonID == exitButton:
                    finished = True
    core.wait(0.25)

#Stop logging
device.din.stopDinLog()
device.updateRegisterCache()

The important lines are the device.getTime() which gets the time from the box and stores it, that is, the box's clock time at the start of the query, and then after a button is pressed, get from the Log data the time, which is stored as the first element (x[0]) in a list of events x.

I'll try to incorporate this in your code...

[dekuenstle]

Thanks!
I probably misleadingly expressed myself in our conversation:
We already read the internal time-difference from the box (see here and here), but we do not yet match this to the ViewPixx's frame onset time.
I'm not sure if this is actually a problem, if you get the device time right after the frame flip, e.g., window.flip; buttonbox.start().