# use this SerialComsPairSendInput.py with SerialComsPair_HardwareSerial_PC_UserInput

##Program layout
##This program does NOT use checksums of simplicity of coding. On the Arduino side set
##const bool USE_CHECK_SUM = false;
##const bool COMS_CONTROLLER = false;  # this side is the non-controller
##
##
##haveLineOfData() reads the COM port chars and returns true when a non-empty message is received
##  If we are clearToSend then discard any input. The other side should not be sending!!
##  check for timeout
##  collect input line
##  discard any extra data after end of input line. Only one line at a time
##  set clearToSend and return true if have non-empty line, else false
##
##sendNextMsg() send textToSend to the other side, if and only if clearToSendFlag is TRUE
##  replaces \n with space and sends to the other side followed by terminating \n
##  if the textToSend is too long the the Arduino side the whole message is ignored
##  and the connection will timeout
##
##checkConnectionTimeout()  check if there has been any message from the otherside within the connectionTimeout setting
##    sets clearToSendFlag = False  
##    
##When there is nothing to send each side exchanges empty messages i.e. just newline chars, to synchronize send/recieve
##
##Globals
##  connectionTimeout  in python this is in secs, in Arduino it is in mS
##  clearToSendFlag True/False initially False, True when connected AND a message has just been received from the other side. Set to false once a message is sent
##  textToSend  the message to be sent next when sentNextMsgFlag is true and connected is true.  textToSend is cleared when sent
##  textReceived the message just recieved. Does not include the terminating newline. Is cleared by next call to haveLineOfData()
##  charsReceived,  the chars received sofar for the next message. Only used internally by haveLineOfData()
##  timeLastMsgRecived  used to check for timeout if no messages received for connectionTimeout
##  
##
      
import serial
import time
import sys

connectionTimeout = 0.25 #  in python this is in secs, in Arduino it is in mS
clearToSendFlag = False # True when connected AND a message has just been received from the other side. Set to false once a message is sent
textToSend = "" #  the message to be sent next when sentNextMsgFlag is true and connected is true.  textToSend is cleared when sent
textReceived = "" # the message just recieved. Does not include the terminating newline. Is cleared by next call to haveLineOfData()
charsReceived = "" #  the chars received sofar for the next message. Only used internally by haveLineOfData()
timeLastMsgRecived = time.time() #  used to check for timeout if no messages received for connectionTimeout

startTime = time.time()

#========================
    # the functions
def setupSerial(baudRate, serialPortName):
    global  serialPort
    serialPort = serial.Serial(port= serialPortName, baudrate = baudRate, timeout=0, rtscts=False)
    print("Serial port " + serialPortName + " opened  Baudrate " + str(baudRate))

#========================
def checkConnectionTimeout():
    global clearToSendFlag, timeLastMsgRecived, connectionTimeout

    if time.time() - timeLastMsgRecived > connectionTimeout:
        timeLastMsgRecived = time.time()
        clearToSendFlag = False;
  
#========================

def sendNextMsg():
    global clearToSendFlag, textToSend
    
    checkConnectionTimeout()
    if (not clearToSendFlag):
      return # wait until connected and synced with otherside
    
    textToSend.replace("\n"," ")
    if len(textToSend) > 0:
        print("%.0fmS " % (1000.0*(time.time()-startTime)),end="");print("sent text '",end=""); print(textToSend,end=""); print("'");
        
    textToSend += "\n"
    serialPort.write(textToSend.encode('utf-8')) # encode needed for Python3
    textToSend = "" # clear for ext msg
    clearToSendFlag = False  # stop other sends until the other side responds

#========================

def haveLineOfData():
    # returns True if have received non-empty msg else False
    global receivedText, charsReceived, timeLastMsgRecived, clearToSendFlag
    if (clearToSendFlag):
        #ignore any data if we should be sending
        while serialPort.inWaiting() > 0:  # have something to read
            serialPort.read()
    
    # sets connected and clearToSendFlag to as necessary
    checkConnectionTimeout()
    
    receivedText = ""
    if serialPort.inWaiting() == 0:
        return False
    
    foundEOL = False
    while serialPort.inWaiting() > 0:  # have something to read
        x = serialPort.read().decode("utf-8") # decode needed for Python3
        if x == '\n':
            foundEOL = True
            break
        else:   
            charsReceived += x
            
    if foundEOL:
        #clear out any following data
        while serialPort.inWaiting() > 0:  # have something to read
            serialPort.read()
        timeLastMsgRecived = time.time() # reset timeout
        clearToSendFlag = True; # can send now
        
        if len(charsReceived) == 0:
            return False # empty msg returns False
        
        # else have non-empy msg and are connected
        receivedText = charsReceived
        charsReceived = ""
        return True

    # else still waiting for whole line
    return False

#==================


#====================
#====================
    # the program

setupSerial(9600, "COM5")

textToSend = input("Enter an integer to send to Arduino. ") # first cmd to send
while True:
  if haveLineOfData(): # valid response, could be just an empty line with no data
    print("%.0fmS " % (1000.0*(time.time()-startTime)),end="");print(" Received Data '",end=""); print(receivedText,end=""); print("'")
    # process textReceived here. can set textToSend in response as well if you want to
    textToSend = input("Enter integer to send ")
    if len(textToSend) == 0:
        textToSend += " " # don't send an empty msg as the other side won't respond 

  # Can overwrite textToSend here if you want to send something else
  sendNextMsg(); # send textToSend text if connected, else wait for connection. Clears textToSend after it is sent ready for next one

  # to just send data ignoring textReceived
##  if len(textToSend) == 0: # textToSend will be empty when is have been sent
##    textToSend = input("Enter cmd to send ")
##    if len(textToSend) == 0:
##        textToSend += " " # don't send an empty msg as the other side won't respond