PsychoPy-Arduino Exercise #2
Using the calibrated Arduino light sensor to measure the duration
of a screen stimulus (i.e., brief WHITE screen stimulus).

In Arduino Exercise #1, we build a PsychoPy project to calibrate the 
Black and White levels of the Arduino light sensor.  In Exercise #2,
we will extend this project with code to allow us to measure the
duration of a video screen stimulus.

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Intro Routine
-------------

Cusom code|Begin Experiment Tab
-------------------------------

Add the following global variable declaration:

	#screen duration global
    usdDuration = 0.0
	
NEXT, CREATE/ADD 4 NEW ROUTINES TO YOUR PSYCHOPY PROJECT.
NAME THEM: 'BlackScreen', 'WhiteScreen' and 'BlackScreen2'

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BlackScreen Routine
-------------------
Add a Polygon/Rectangle component the fills the entire screen.
Set its fill color to Black and its time duration to infinity.
Add the following custom code component to send a command to the
Arduino microconroller.

Custom code component|Each Frame Tab
------------------------------------
	#send Duration Measurement request to Adruino
	if frameN == 5:
		arduino.write(bytes('d','utf-8'))

	#exit routine after 15 frames
	if frameN == 15:
		continueRoutine = False

-------------------
WhiteScreen Routine
-------------------
This routine generates the stimulus whose duration will be measured.
Create a Polygon/Rectangle component that fills the entire screeen.
The rectangle should fill the entire screen and its fill color = White.
Set its Start Time to Frame=0 and its duration to 10 frames.
No custom code used in this routine.

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BlackSreen2 Routine
-------------------
Create a Polygon/Rectangle that fills the screen. Set the fill color to
Black and the duration to 2 seconds.  
Next, create a custom code component and add the following code snippets
to the appropriate code tabs:

Custom code component|Each Frame Tab
------------------------------------
	#collect Arduino Duration data (if available)
	#then exit BlackScreen2 routine
	if arduino.in_waiting > 0:
		serial_input = arduino.readline()
		if len(serial_input) > 0:
			serial_str = serial_input.strip().decode()
			serial_data = int(serial_str)
			usdDuration = serial_data
			print("DURATION (micros):", serial_str)
		continueRoutine = False  #exit BlackScreen2 routine

	#exit routine if no Arduino response within 60 frames
	if frameN > 60:
		arduino.write(bytes('s','utf-8'))  #abort Duration measurement
		usdDuration = 0.0
		print("WHITE SCREEN timed-out")
		continueRoutine = False  #exit BlackScreen2 routine

Custom code component|End Routine Tab
-------------------------------------
	#log the Duration Measurement
	thisExp.addData('Duration', usdDuration)
	
Custom code component|End Experiment 
------------------------------------
	#Close serial port connection to Arduino
	arduino.close()

After successfully testing the project outlined above, check the PsychoPy 
console and/or the PsychoPy output file for the results of the duration
measurement.