Custom code used in ArduinoLatency.psyexp project

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Python code used in the 'sample' Routine
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BEFORE EXPERIMENT TAB
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#connect to Arduino via USB serial port
import serial
import time
com_port = "COM18"  #Windows serial port address
#com_port = "/dev/cu.usbmodem14101"   #Mac serial port
try:
    arduino=serial.Serial(com_port,baudrate=115200,timeout=1.0)
    time.sleep(3.0)
    arduino.flushInput()
    arduino.flushOutput()
    arduino.write(bytes('p','utf-8')) # Ping arduino
    serial_data = arduino.read()     #wait for Ping reply character ('R')
    print("Serial port %s successfully openned." % (com_port))
except:
    print("Unable to open serial port: ", com_port)
    sys.exit()


BEGIN EXPERIMENT TAB
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import time
startTime = time.perf_counter()
endTime = time.perf_counter()
transportLatency = []
usdLatency = 0.0
strLatency = str(0)

BEGIN ROUTINE TAB
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#Ping Arduino microcontroller
startTime = time.perf_counter()
arduino.write(bytes('p','utf-8'))
#block until immediate reply detected
serial_data = arduino.read()
endTime = time.perf_counter()
#compute and save 2-way transport latency
usdLatency = (endTime-startTime) * 1000  #convert to millisec
transportLatency.append(usdLatency)  #results buffer
strLatency = str(round(usdLatency,3))

EACH FRAME TAB
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#End Routine after 200 msec
if t > 0.2:
    continueRoutine = False  #end routine after 200 msec
	
END ROUTINE TAB
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thisExp.addData("Latency", usdLatency) #append data to output file

END EXPERIMENT TAB
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#Shutdown serial connection to Arduino
arduino.close()


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Python code used in the 'Report' Routine
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BEGIN ROUTINE TAB
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import numpy as np
np_latencies = np.array(transportLatency)
mean_latency = np.mean(np_latencies)
strMeanLatency = "Mean = %.3f" % (mean_latency)
std_latency = np.std(np_latencies)
strStdLatency = "Std Dev = %.3f" % (std_latency)
min_latency = np.min(np_latencies)
strMinLatency = "Minimum = %.3f" % (min_latency)
max_latency = np.max(np_latencies)
strMaxLatency = "Maximum = %.3f" % (max_latency)
#
#save latency distribution to disk file
np.save('np_arduino_latencies.npy', np_latencies)
print("Mean latency ="+strMeanLatency)