Python send data Serial to Microcontroller STM32F4

Question

So this is the script I am using to send each 2 seconds for four time the Time in microsecond to the microcontroller stm32f4 but unfoturnately it only sends some numbers(from 1-->4) which are not the same as when I do a print,it is like random numbers .

import time 
import serial from datetime 
import datetime from time 
import gmtime, strftime

ser = serial.Serial(
    port='/dev/ttyACM0',
    baudrate=115200,
    parity=serial.PARITY_NONE,
    stopbits=serial.STOPBITS_ONE,
    bytesize=serial.EIGHTBITS

)
ser.writeTimeout = 0 
ser.isOpen() 

TM1 = int(round(time.time()*1000000))   
ser.write(str(TM1).encode())
#ser.write( str(TM1)+"            \r\n")
time.sleep(2) 
TM2 = int(round(time.time()*1000000))
ser.write(str(TM2)+"            \r\n") 
time.sleep(2)
TM3 = int(round(time.time()*1000000))
ser.write(str(TM3)+"            \r\n") 
time.sleep(2) 
TM4 = int(round(time.time()*1000000)) 
ser.write(str(TM4)+"            \r\n")

StarSheriff · Accepted Answer · 2016-05-30 10:17:26Z

1

I cannot see anything obviously wrong at first sight. I have a almost identical snippet of code running here that works. My guess would be that the settings of the serial port do not match. Double check that the baudrate, parity and stopbit settings match.

Second guess would be a mess-up with encodings. Have you set your default encoding in python to utf-8? If so you could try

ser.write(str(TM1).encode('ascii'))

Posting the output you get would help as well.

Edit: to avoid the microcontroller skipping some characters. You could use a small function like this. (I used that to send commands to a sensor that had the same issues. When I sent a command like this `ser.write("start logging") it would receive something like "sart lgging".

def write_safe(cmd):
    for x in cmd:
        ser.write(x)
        sleep(0.05)
    ser.write('\r\n')

edited May 30, 2016 at 10:17

answered May 30, 2016 at 9:23

StarSheriff

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4 Comments

Z.Yong Over a year ago

It is the same . The settings matches. For example i print the TM1 : 1464600660433102 and output on console is : 164064312 I changed the beaudrate to 9600 so it sends now more numbers

StarSheriff Over a year ago

Ok, what you get looks to me like your micro-controller is skipping some characters/bytes. Might be from the stop bit (but you said the settings are matching), or that your uc is not ready to receive the next byte. You can try to send each character with a delay in between to isolate the problem.

Z.Yong Over a year ago

How to send each character with a delay in between?

StarSheriff Over a year ago

for example: for c in str(TM1): ser.write(c) time.sleep(0.5) Of course each command in its own line, I am not yet used to the editors on SO.

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