# srv_util_01_v153.py
    # LX-824HV Testing v1.0  tlfong01 2020sep15hkt2133
    
    # Contents
    
    # Serial UART LoopBack Program v0.62 (Minimal)
    # Serial UART LoopBack Program v0.98 (Multiple ports USB and on board UYART Ports)
    # HiWonder serial bus servo LX-824HV LewanSoul command testing (2020sep15)
    
    # Serial UART LoopBack Program v0.99 - https://penzu.com/p/f2cb232e
    # serial_loopback_test_v062.py tlfong01 2020jun03hkt1447
    # Rpi4B buster (r2020feb13), python 3.7.3 (r2019dec20), thonny v3.2.7 (r2020jan22)
    
    from   time import sleep
    import serial
    
    serialPort0 = serial.Serial(port = '/dev/serial0',
            baudrate = 9600,
            parity = serial.PARITY_NONE,
            stopbits = serial.STOPBITS_ONE,
            bytesize = serial.EIGHTBITS,
            timeout= 1)
    
    def setSerialPortBaudRate(serialPort, baudrate):
        print('   Begin setSerialPortBaudRate(), ...')
        print('     Serial port =', (serialPort0.name + ','), 'Buad rate =', baudrate)
        serialPort.baudrate = baudrate
        print('   End   setSerialPortBaudRate(), ...')
        print('')
        return
    
    def serialPortWriteBytes(serialPort, writeBytes):
        serialPort.write(writeBytes)
        return
    
    def serialPortReadBytes(serialPort, maxBytesLength):
        readBytes = serialPort.read(maxBytesLength)
        return readBytes
    
    def serialPortWriteWaitReadBytes(serialPort, writeBytes, maxBytesLength, waitSeconds):
        serialPort.flushInput()
        serialPort.flushOutput()
        serialPort.write(writeBytes)
        sleep(waitSeconds)
        readBytes = serialPortReadBytes(serialPort, maxBytesLength)
        print('     bytes written = ', writeBytes)
        print('     bytes read    = ', readBytes)
        return readBytes
    
    def repeatWriteBytes(serialPort, writeBytes, waitSeconds, repeatCount):
        print('     Begin repeatWriteOneByte(), ...') 
        for i in range(repeatCount):
            serialPortWriteBytes(serialPort, writeBytes)             
            sleep(waitSeconds)
        print('     End repeatWriteOneByte().')
        return
    
    def serialPortLoopBack(serialPort, writeBytes):
        print('   Begin serialPortLoopBack(), ...')
        maxBytesLength = 64
        waitSeconds    = 0.0
        serialPortWriteWaitReadBytes(serialPort, writeBytes, maxBytesLength, waitSeconds) 
        print('   End serialPortLoopBack()\n')
        return
    
    def repeatSerialPortLoopback(serialPort, writeBytes, repeatTimes):
        print('     Begin repeat serialPortLoopBack()')
        print('       repeating', repeatTimes, 'times, <Ctrl> C to abort, ...')
        maxBytes = 64
        waitSeconds = 0.0
        
        serialPort.flushInput()
        serialPort.flushOutput()
        
        for count in range(repeatTimes):
            serialPort.write(writeBytes)
            # sleep(waitSeconds)
            readBytes = serialPort.read(maxBytes)
    
        print('      End repeat serialPortLoopBack()')
        return
    
    def testRepeatSerialPortLoopback(serialPort, writeBytes, repeatTimes):
        print('   Begin testRepeatSerialPortLoopback(), ...')
        
        print('     Serial port =', (serialPort0.name + ' '))
        print('     WriteBytes  =', writeBytes)
        print('     RepeatTimes =', repeatTimes)
        print('     Now repeating', repeatTimes, 'times, <Ctrl> C to abort, ...\n')
        
        repeatSerialPortLoopback(serialPort, writeBytes, repeatTimes)
        print('    End   testRepeatSerialPortLoopback(), ...\n')
        return
     
    # ### Main ### 
    
    # Set serial serialPort0 115200bd
    setSerialPortBaudRate(serialPort0, 115200)
    
    # Loopback bytes object b'xyz123\r\n'
    serialPortLoopBack(serialPort0, b'xyz123\r\n')
    
    # Loopback reuest Vin command b'\x55\x55\x01\x03\x1b\xe0'
    serialPortLoopBack(serialPort0, b'\x55\x55\x01\x03\x1b\xe0')
    
    # Testing Rpi send/receive LeWanSoul request/reply bytes to/from LX-824HV
    
    requestVin = b'\x55\x55\x01\x03\x1b\xe0'
    repeatTimes = 10000000
    testRepeatSerialPortLoopback(serialPort0, requestVin, repeatTimes)
    
    # End of program
    
    '''
    
    ### Sample output tlfong01  2020sep15hkt2132 ###
    
       Begin serialPortLoopBack(), ...
         bytes written =  b'UU\x01\x03\x1b\xe0'
         bytes read    =  b'UU\x01\x03\x1b\xe0UU\x01\x05\x1bS\x14w'
       End serialPortLoopBack()
    
       Begin testRepeatSerialPortLoopback(), ...
         Serial port = /dev/serial0 
         WriteBytes  = b'UU\x01\x03\x1b\xe0'
         RepeatTimes = 10000000
         Now repeating 10000000 times, <Ctrl> C to abort, ...
    
         Begin repeat serialPortLoopBack()
           repeating 10000000 times, <Ctrl> C to abort, ...
    
    '''   
    
    # End