Implement an Always Idle Cashless Terminal - Python

import serial import os import time STATUS = { "INACTIVE" : "c,STATUS,INACTIVE", #In this state the device has never been contacted by the VMC "DISABLED" : "c,STATUS,DISABLED", # The device has communicated with the VMC but waiting to be enabled "ENABLED" : "c,STATUS,ENABLED", # Device enabled by the VMC, waiting for a vending request "VEND" : "c,STATUS,VEND", # The device gets c,STATUS,VEND,<amount>,<product ID> when a product has been selected on the VMC "IDLE" : "c,STATUS,IDLE", # Session goes back to IDLE when the device is waiting for the VMC to end session "DISPENSED" : "c,VEND,SUCCESS", #This message is received when the vending machine has successfully dispensed the product "FAIL2DISPENSE" : "c,ERR,VEND 3", #This message is received when the vending machine couldn't dispense the product (e.g coffee machine out of water, or coil machine with empty coil) } AUTHORIZE_VEND = "C,VEND," # Prefix to send to authorize a vend request in VEND state (e.g. C,VEND,<requested_amount>) DENY_VEND = "C,STOP" #Message to send to deny a vend request from the vending machine #### Serial Port functions to interact with MDB USB/Pi Hat def openSerial(): global ser ser = serial.Serial() #Create Serial Object ser.baudrate = 115200 #Set the appropriate BaudRate ser.timeout = 50 #The maximum timeout that the program waits for a reply. If 0 is used, the pot is blocked until readline returns ser.port = '/dev/ttyACM0' # Specify the device file descriptor, on windows use "COMX" ser.open() #Open the serial connection def write2Serial(msg): global ser #DEBUG print("Sending " + msg) ser.write((msg+"\n").encode()) #Write the message to send encoded in Binary ser.flush() def readSerial(): global ser s = ser.readline().decode("ascii").strip("\n").strip("\r") # Read the response if s: #DEBUG print("Read:" + s) return s return "" #### Utilities ########################### #Function to print to console def print2Console(msg): clearConsole() print("\r" + msg,end="\r") #Function to clear the console to wipe previous messages def clearConsole(): if os.name in ('nt', 'dos'): #Windows os.system("cls") else: os.system("clear") #Linux #### Cashless API Related Functions ###### def initCashlessDevice(): write2Serial("C,0") #It is advised to shut down cashless while initializing write2Serial("C,1") if __name__ == '__main__': openSerial() initCashlessDevice() while True: time.sleep(1) #Wait for 1 second rcv = readSerial() if rcv == STATUS["INACTIVE"] or rcv == STATUS["DISABLED"]: print2Console("Waiting for vending machine...") elif rcv == STATUS["ENABLED"]: print2Console("Please select product on vending machine.") elif STATUS["VEND"] in rcv: vendAmt = rcv.split(",")[3] #c,STATUS,VEND,<amount>,<product_id> prodId = rcv.split(",")[4] #In case the product ID Is to be used for anything clearConsole() while True: i = input("\rPress v to pay " + vendAmt + " or x to cancel") if i == "v": write2Serial(AUTHORIZE_VEND + vendAmt) print2Console("Waiting product dispense...") break elif i == "x": write2Serial(DENY_VEND) print2Console("Transaction ancelled by user.") break clearConsole() continue elif rcv == STATUS["DISPENSED"]: print2Console("Product dispensed!") elif rcv == STATUS["FAIL2DISPENSE"]: print2Console("Product failed to dispense.") elif rcv == STATUS["IDLE"]: print2Console("Transaction finished.") else: continue