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

Question

So i am reading (and displaying with a tkinter textbox) data from a serial connection, but i can't process the returning data as i would like to, in order to run my tests. In more simple terms, even though the machine response = 0x1 is displayed, i can't read it from the global serBuffer.

Before displaying it to the textbox i would read from inside the test function and then check if the response was in the string, but now that i pass the read data(strings) to a global variable and then try to read it, it doesn't seem to work, UNLESS i remove the serBuffer = "" from readserial. That results in a new issue though. When i press the button to send the command it sends it, but only receives the response after the second time i 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.

Picture with the desired response ( that the test function doesn't read 0x1 and always returns FAIL)

Picture with the non-desired response ( that 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 every time after).

import tkinter as tk
import serial
from serial import *


serialPort = "COM3"
baudRate = 115200
ser = Serial(serialPort, baudRate, timeout=0, writeTimeout=0) #ensure non-blocking


#make a TkInter Window
mainWindow = tk.Tk()
mainWindow.wm_title("Reading Serial")
mainWindow.geometry('1650x1000+500+100')




scrollbar = tk.Scrollbar(mainWindow)
scrollbar.pack(side=tk.RIGHT, fill=tk.Y)

log = tk.Text ( mainWindow, width=60, height=60, takefocus=0)
log.pack()

log.config(yscrollcommand=scrollbar.set)
scrollbar.config(command=log.yview)

#make our own buffer
#useful for parsing commands
#Serial.readline seems unreliable at times too
serBuffer = ""
ser.write(b'\r\n')

def readSerial():
    while True:
        c = (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

            # add the line to the TOP of the log
            log.insert('1.1', serBuffer)
            serBuffer = ""  # empty the buffer
        else:
            serBuffer += c  # add to the buffer

    mainWindow.after(100, readSerial)  # check serial again soon

def test():
    command = b" test command \r\n"
    ser.write(command)
    global serBuffer
    time.sleep(0.5)
    if "0x1" in serBuffer:
        print('PASS')
        return 'PASS'
    else:
        print('FAIL')
        return 'FAIL'

button = tk.Button(mainWindow, text="Pone Test", font=40, bg='#b1c62d', command=test)
button.place(relx=0.8, rely=0, relwidth=0.1, relheight=0.05)


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

mainWindow.mainloop()

Answer 1

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!

Answer 2

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)