import serial
import sys
import random
import time
import binascii

#Global variables
seq = 0         #Sequence number
packetSize = 18     #Number of random bytes to be sent with the packet
delay = 0.5 #Time delay (in milliseconds) between sending of packets

#COM port default settings
baudRate = 19200
dataBits = serial.EIGHTBITS
parityBit = serial.PARITY_NONE
stopBits = serial.STOPBITS_ONE

#Command line arguments
comPort = -1    #Must be set

#Functions
def ConstructPacket():
    global seq
    i = 0
    if seq > 255:
        sec = 0
    outgoingPacket = bytearray()
    outgoingPacket.append(seq)
    while (i < packetSize):
        outgoingPacket.extend(random.sample(xrange(255),1))
        i += 1
    seq += 1
    return  outgoingPacket

def SendPacket():
    serial.write(outgoingPacket)

def ReceiveResponse():
    incomingPacket = bytearray()
    if serial.inWaiting() == packetSize+1:
        incomingPacket = serial.readlines()
    return incomingPacket

#Command line argument handling
for i in range(0, len(sys.argv)):
    if sys.argv[i] == '-com':
        comPort = int(sys.argv[i+1])
    elif sys.argv[i] == '-delay':
        delay = int(sys.argv[i+1])
    elif sys.argv[i] == '-packetsize':
        packetSize = int(sys.argv[i+1])

if comPort < 0:
    raise Exception("COM port must be > 0")
if delay < 0:
    raise Exception("Delay must be > 0")
if packetSize < 0:
    raise Exception("Packet size must be > 0")

#Open serial port
tempPort = '\\.\COM' + str(comPort)
serial = serial.Serial(port=tempPort, baudrate=baudRate, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, timeout=None)

while 1:
    serial.flushInput()
    startTime = time.time()
    time.sleep(delay)
    outgoingPacket = ConstructPacket()
    SendPacket()
    incomingPacket = ReceiveResponse()
    totalTime = time.time() - startTime
    if outgoingPacket != incomingPacket:
        print "Packet sent and packet received do not match. Script terminating."
        print "Sent: " + outgoingPacket
        print "Received: " + incomingPacket
        sys.exit(1)
    else:
        print "Packet turnaround time: " + str(totalTime)