I am trying to build a home automation system with Raspberry Pi connected to Arduino Uno via USB. Everything works but the Python script that I am using for reading variables from Arduino is always throwing exception the first time I run it after rebooting Raspberry Pi, so I can't make it start automatically after boot and I always have to have SSH open on my computer in order for it to work.
I am using Python to run C program with the wiringPi library http://wiringpi.com/reference/serial-library/, the C program writes to the serial, Arduino uses switch statement to return the requested data or to do something else (like flashing a LED). The returned data is written in a text file by the C program, which is then sorted in other text files by the Python script.
The interface is PHP displaying the data from the text files and sending commands to Arduino using another C program with the wiringPi library (it is almost the same as the first one).
This is the python script:
#!/usr/bin/python
import datetime
from datetime import datetime
import time
import sys
import os
while 1:
print "\n" + datetime.now().strftime('%d-%m-%y %H:%M:%S')
os.system("sudo ./fastUSB.o") #run C program
fastFile = open("/var/www/fastReader.txt", "r+") #opens the file written from C
fastValues = fastFile.read(14)
fastArray = fastValues.split()
fastFile.close()
os.remove("/var/www/fastReader.txt") #deletes the file so the old data is removed
createFastFile = open("/var/www/fastReader.txt", "w") #makes new one
createFastFile.close()
try: #puts the array in differen files
lightCurrent = open("/var/www/current/light.txt", "w")
lightCurrent.write(fastArray[0])
lightCurrent.close()
lightLog = open("/var/www/logs/lightLog.txt", "a")
lightLog.write(datetime.now().strftime('%d-%m-%y %H:%M:%S') + " - ")
lightLog.write(fastArray[0] + "\n")
lightLog.close()
print "Light level is " + fastArray[0]
except:
print "No"
try:
motionCurrent = open("/var/www/current/motion.txt", "w")
motionCurrent.write(fastArray[1])
motionCurrent.close()
motionLog = open("/var/www/logs/motionLog.txt", "a")
motionLog.write(datetime.now().strftime('%d-%m-%y %H:%M:%S') + " - ")
motionLog.write(fastArray[1] + "\n")
motionLog.close()
if fastArray[1] == '1':
motionState = "detected"
else:
motionState = "not detected"
print "Motion is " + motionState
except:
print "No"
This is the C program:
/*
Pi_Serial_test.cpp - SerialProtocol library - demo
Copyright (c) 2014 NicoHood. All right reserved.
Program to test serial communication
Compile with:
sudo gcc -o Pi_Serial_Test.o Pi_Serial_Test.cpp -lwiringPi -DRaspberryPi -pedantic -Wall
sudo ./Pi_Serial_Test.o
*/
// just that the Arduino IDE doesnt compile these files.
#ifdef RaspberryPi
//include system librarys
#include <stdio.h> //for printf
#include <stdint.h> //uint8_t definitions
#include <stdlib.h> //for exit(int);
#include <string.h> //for errno
#include <errno.h> //error output
//wiring Pi
#include <wiringPi.h>
#include <wiringSerial.h>
// Find Serial device on Raspberry with ~ls /dev/tty*
// ARDUINO_UNO "/dev/ttyACM0"
// FTDI_PROGRAMMER "/dev/ttyUSB0"
// HARDWARE_UART "/dev/ttyAMA0"
char device[]= "/dev/ttyUSB0";
// filedescriptor
int fd;
unsigned long baud = 9600;
int te = 1;
//prototypes
int main(void);
void loop(void);
void setup(void);
void setup(){
printf("%s \n", "Slow reader");
fflush(stdout);
//get filedescriptor
if ((fd = serialOpen (device, baud)) < 0){
fprintf (stderr, "Unable to open serial device: %s\n", strerror (errno)) ;
exit(1); //error
}
//setup GPIO in wiringPi mode
if (wiringPiSetup () == -1){
fprintf (stdout, "Unable to start wiringPi: %s\n", strerror (errno)) ;
exit(1); //error
}
}
void loop() {
if(te == 1) {
te = 0;
serialPuts (fd, "00010\n");
// you can also write data from 0-255
// 65 is in ASCII 'A'
//serialPutchar (fd, 5);
}
// read signal
if(serialDataAvail (fd)){
char tempChar = serialGetchar (fd);
FILE * writeTemp = fopen("slowReader.txt", "a");
printf("%c", tempChar);
fputc(tempChar, writeTemp);
fflush(stdout);
fclose(writeTemp);
}
}
// main function for normal c++ programs on Raspberry
int main(){
setup();
while(millis()<=1000) loop();
serialClose(fd);
return 0;
}
#endif //#ifdef RaspberryPi
When I run the Python script for the first time after reboot it is continuesly throwing the exceptions, then I stop it by pressing Ctrl+Z and when I run it again it is working. I tried stopping it with sudo pkill -f reader.py and it's not fixing it like stopping it with Ctrl+Z. Copying the code after while 1: before the while also doesn't fix it. It has to be stopped manually with Ctrl+Z in order to work.
Sending commands from the site to Arduino is also not working before I run the script for the first time. My guess is that when the script is ran for the first time after boot it is configuring the serial port, baud, etc. but it doesn't make sense to not be able to start, stop, start it automatically.
