serial communication write(comand) and read(result)

[ricardons]

Hi

maybe someone could have a look at my code or suggest a better one (or another place to look for)


I need to do serial communication with a device: write to device and listen to what it is saying

I should write a command (send some bytes). I finish my command sendind byte 0XFF (chr(255)) 3 times in a row
Then the device sends me a reply that i have to read. This reply also finishes after 3 times 0XFF

I wrote this

import serial

ser = serial.Serial(

    port='/dev/ttyAMA0',
    baudrate=9600,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS,
    timeout=1
)
ser.reset_output_buffer()

print('Serial connected')

def nxRead(value):
    #first i need to send a 'command' (for example 'sendme X.value'
    command = 'sendme X.value'
    ser.write(command.encode('latin-1'))
    ser.write(chr(255).encode('latin-1')) # 0xFF
    ser.write(chr(255).encode('latin-1')) # 0xFF
    ser.write(chr(255).encode('latin-1')) # 0xFF

    #by now the device should have understood my request and will send me a reply byte by byte, finishing with 0XFF 0XFF 0XFF 

    reply = [] 
    count =0
    t3FF = False # the termination has not stopped

    while t3FF == False:
       r = ser.read().decode('latin-1)
       c = ord(r)
       reply.append(c)
         
           if c == 0xff:
               count = count + 1
               if count == 3:
                   t3FF = True
                   return
           else:
               count = 0
    return s

It's not working, why?

[mpd]

Be more specific. What isn't working right? Any errors or exceptions? Is it doing the wrong thing? Is it doing nothing at all? Do you know if the device is receiving your messages? I don't know this package but I know a lot of I/O libraries perform buffering, does the Serial object have a flush() method?