从Python发送字符串到Arduino LCD

Question

I want to display a string on an Arduino LCD 16x2 using python, but I've encountered problems with serial communication.

Here is the code running in Arduino:

Arduino Code

#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
String stringa;
const unsigned long TimeOut = 10; // timeout 10 ms
String stringa1;
String stringa2;

void setup() {
  lcd.begin(16, 2);
  Serial.begin(9600);
}

void loop() {
  stringa = "";
  unsigned long T = 0; // timer
  T = millis(); // timer running
  while (millis() - T < TimeOut) {
    // waiting timeout
    while (Serial.available() > 0) {
      // receiving Serial
      stringa += char(Serial.read()); // add char
      T = millis(); // reset timer
    }
  }
  if (stringa.length() > 32) {
    lcd.setCursor(0, 1);
    lcd.print("stringa length: " + stringa.length());
    delay(2000);
    lcd.print("                ");
  } else {
    stringa1 = stringa.substring(0 , 16);
    stringa2 = stringa.substring(16);
    lcd.setCursor(0, 0);
    lcd.print(stringa1);
    lcd.setCursor(0, 1);
    lcd.print(stringa2);
    delay(5000);
  }
}

It works perfectly with Serial communication from Keyboard provided in Arduino IDE. But it doesn't work when I try to send a string using the Python script below:

Python Code

import serial
import sys
import time
arduino = serial.Serial('COM3', 9600, timeout=0)
stringa = 'hello'
arduino.write(bytes(stringa,'utf-8'))
arduino.close()

Where is the problem? I can't find a solution! Thanks.

Answer 1

Take a look at the difference between the timeouts in the C file above and the python script below.

The timeout is 10 milliseconds in your C file wheareas it's 0 in your Python script. Also check the result of the arduino.write() to make sure that it was successful.

Possibly implement something like the following:

import serial
import sys
import time
arduino = serial.Serial('COM3', 9600, timeout=10)
stringa = 'hello'
try:
    arduino.write(stringa.encode())
except OsError:
    print "Write failed!"
arduino.close()

If this does not work then try checking the serial ports between both the C file and the Python script. Make sure they are the same. Hope this helps!