Communication between Arduino and Raspberry Pi over USB - usb

Question

I have an Arduino connected over USB with a Raspberry Pi. A Python program is sending a value over USB, then the arduino receives it and turns the LED on. The Arduino is sending a analogue value from A0 to the Python program on the Raspberry. But Python receives sometimes 024, 24 or 4 instead of 1024. How can I fix this? Here is my code:
http://www.bitsharr.com/Hsoxw7nG
Arduino Code:
int led = 13;
char charIn;
int sensorPin = A0; // select the input pin for the potentiometer
int sensorValue = 0; // variable to store the value coming from the sensor
long previousMillis = 0;
long interval = 1000;
// the setup routine runs once when you press reset:
void setup() {
// initialize the digital pin as an output.
pinMode(led, OUTPUT);
Serial.begin(9600); //This initializes the USB as a serial port
}
void loop() {
if (Serial.available()) {
delay(5); // warten bis alle Daten da sind
while(Serial.available() > 0) {
charIn =(char) Serial.read();
if (charIn == '1') {
digitalWrite(led,HIGH);
delay(5000);
digitalWrite(led,LOW);
}
}
}
Python Code:
#!/usr/bin/python
# -*- coding: utf-8 -*-
from serial import Serial
ser = Serial('/dev/ttyUSB0', 9600)
x=ser.readline()
ser.write('1')
print(x)
def cleanup( str ):
result = ""
for c in str:
if( (c >= "0") and (c <= "9") ):
result += c
return result
print( cleanup(x))
#ser.write("1")
sensorValue = analogRead(sensorPin); //Reads the voltage of the resistor.
Serial.println(sensorValue); //Writes the voltage on the Serial port.
}

Answer 1

For starters, you are using Arduino code in your Python code.
sensorValue = analogRead(sensorPin); //Reads the voltage of the resistor.
Serial.println(sensorValue); //Writes the voltage on the Serial port.
How would your computer know what values are on your Arduino? You need to move this into the Arduino code. I can't tell you where: you never specified exactly what you want to accomplish with this code.
Some more problems with your code:
#ser.write("1") should be ser.write("1")
These two lines aren't bad but they're a bad coding practice to include because you don't use them:
long previousMillis = 0;
long interval = 1000;
But python receives sometimes 024, 24 or 4 instead of 1024.
The Arduino never sent anything; there is no serial.print(); or serial.println();! I don't know how you are receiving data. If you make the edits to your code above and/or specify exactly what you want to do (i.e. Send a 1 to the Arduino, turn a LED on, get sensor data back every five seconds, if the data is above 50%, turn the light off) and still don't know what to do, feel free to comment for clarification.