Issue processing data read from serial port, when displaying it in a Tkinter textbox

Comment: but only receives the response after the second time a press it, and every time after. So as a result i get a Fail if i run the test once, but i get a pass everytime after

Raise the first, timeout from 100 to 500 ore more.

        # after initializing serial, an arduino may need a bit of time to reset
        mainWindow.after(100, self.readSerial)

---

To find out the delay for the first response, try the following:

Note: You have to do this without running def readSerial, to prevent concurent empty the in buffer"

    command = b" test command \r\n"
    self.ser.write(command)

    delay = 0.0

    # wait until you get `.in_waiting` data.
    while not self.ser.in_waiting:
        time.sleep(0.1)
        delay += 0.1
        print('.', end='')
        if delay >= 10:
            print('BREAK after {} no in_waiting'.format(int(delay * 10)))
            break

    print('Delay:{}, in_waiting:{}'.format(delay, self.ser.in_waiting))

---

The following works for me.

Note: I use OOP syntax.

1. last_command

   serBuffer = ""
   last_command = None
   

2. Copy the ready read_buffer to last_command, empty only read_buffer

   def readSerial(self):
       while True:
           c = (self.ser.read().decode('utf-8', 'ignore'))  # attempt to read a character from Serial
           # was anything read?
           if len(c) == 0:
               break
   
           # get the buffer from outside of this function
           global serBuffer
   
           # check if character is a delimeter
           if c == '\r':
               serBuffer += "\n"  # don't want returns. chuck it
   
           if c == '\n':
               serBuffer += "\n"  # add the newline to the buffer
   
               global last_command
               last_command = serBuffer
   
               # add the line to the TOP of the log
               # log.insert('1.1', last_command)
               print('readSerial.last_command:"{}"'.format(bytes(last_command, 'utf-8')))
   
               serBuffer = ""  # empty the buffer
   
           else:
               serBuffer += c  # add to the buffer
               print('readSerial:"{}"'.format(bytes(serBuffer, 'utf-8')))
   
       self.after(100, self.readSerial)  # check serial again soon
   

3. Do test()

   def test(self, write=True):
       print('test(write={})'.format(write))
   
       if write:
           command = b" test command \r\n"
           self.ser.write(command)
           self.after(500, self.test, False)
   
       elif last_command is not None:
           print('last_command:{}'.format(bytes(last_command, 'utf-8')))
   
           if "0x1" in last_command:
               print('PASS')
           else:
               print('FAIL')
       else:
           # ATTENTION: This could lead to a infinit loop
           # self.after(500, self.test, False)
           pass
   

Output:

test(write=True)
readSerial:"b' '"
readSerial:"b' t'"
readSerial:"b' te'"
readSerial:"b' tes'"
readSerial:"b' test'"
readSerial:"b' test '"
readSerial:"b' test c'"
readSerial:"b' test co'"
readSerial:"b' test com'"
readSerial:"b' test comm'"
readSerial:"b' test comma'"
readSerial:"b' test comman'"
readSerial:"b' test command'"
readSerial:"b' test command '"
readSerial:"b' test command \n\r'"
readSerial.last_command:"b' test command \n\r\n'"
test(write=False)
last_command:b' test command \n\r\n'
FAIL

Note: I get FAIL, because there is no 0x1 in last_command as i use PORT = 'loop://' which echo what is writen!

I made some changes, check this one.

def readSerial():
    while True:
        c = (ser.read(1).decode('utf-8', 'ignore')) from Serial

        if len(c) == 0:
            break


        global serBuffer
        if c == '\r':
            serBuffer += "" 

        if c == '\n':
            serBuffer += "\n" 



            log.insert(tk.END, serBuffer)
            log.see(tk.END)
            log.update_idletasks()
            serBuffer = ""  
        else:
            serBuffer += c  

    mainWindow.after(500, readSerial)