Arduino and Python Temperature Logger

TempLogger.cpp

#include <OneWire.h>
#include <DallasTemperature.h>

// pin setups
int latchPin = 8;
int clockPin = 12;
int dataPin = 11;
int tempPin = 7;
char recMsg = '0';

// librraries for connecting to sensor
OneWire oneWire(tempPin);
DallasTemperature tempSens(&oneWire);

// characters for displaying on 7-seg display 0-9
byte numberSet[10] = {
  B01111011, B01000001, B00110111, B01100111,	// 0,1,2,3
  B01001101, B01101110, B01111110, B01000011,	// 4,5,6,7
  B01111111, B01101111 // 8,9
};


void setup() {
  // init serial
  Serial.begin(9600);
  // init temp sensor
  tempSens.begin();
  
  pinMode(latchPin, OUTPUT);
  
  // set display to 00
  displayNumb(0, 0); 
}

void loop() {
  
  while(Serial.available() > 0) {
    recMsg = Serial.read();
  }
  
  if (recMsg!='0') {
    // request temp from sensor
    tempSens.requestTemperatures();
    float t = tempSens.getTempCByIndex(0);
  
    // send temp to serial
    Serial.print(t);
  
    // cast temp to float (only have 2 digits to use on display)
    int rT = (int)t;
  
    // get units of temp
    int units = rT % 10;
  
    // get tens value of temp
    rT = rT/10;
    int tens = rT % 10;
    
    // display temp
    displayNumb(units, tens);
    
    recMsg = '0';
  }
}

void displayNumb(int a, int b) {
  // get the code for the numbers
  byte bitsA = numberSet[a];
  byte bitsB = numberSet[b];
  
  // set ready to shift out
  digitalWrite(latchPin, LOW);
  
  // shift units
  shiftOut(dataPin, clockPin, bitsA);
  // shift tens
  shiftOut(dataPin, clockPin, bitsB);
  
  // shift out data
  digitalWrite(latchPin, HIGH);
}

// shift the data out to the shift registors
void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {
  int i=0;
  int pinState;
  
  // set pinmodes for shift
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);

  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);
 
  // iterate over each bit in the myDataOut byte
  for (i=7; i>=0; i--)  {
    digitalWrite(myClockPin, 0);

    if ( myDataOut & (1<<i) ) {
      pinState= 1;
    }
    else {	
      pinState= 0;
    }

    digitalWrite(myDataPin, pinState);  
    digitalWrite(myClockPin, 1);
    digitalWrite(myDataPin, 0);
  }

  digitalWrite(myClockPin, 0);
}

TempLogger.py

#/usr/bin/python

import serial
import threading
import time
from datetime import datetime

def temp_logger(ard):
  # send msg to arduino
  ard.write('T')
  
  # wait a second for reply
  time.sleep(1)
  
  # read 5 bytes from arduino (string sent)
  temp = ard.read(5)
  print temp
  
  # open file for writing data
  f = open('pythontemp_logger.txt', 'a')
  
  now_time = datetime.now()
  str_now_time = now_time.strftime("%H:%M:%S")
  f.write(str_now_time + ',' + temp + '\n')
  f.close()
  
  # start the timer again
  global t
  t = threading.Timer(20.0, temp_logger, [ard])
  t.start()
  

# entry point
if __name__ == '__main__':
  print 'INIT: starting task'
  
  # attempt to make serial connection to arduino
  try:
    arduino = serial.Serial('/dev/tty.usbserial-A600agDn', 9600)
  except:
    print 'ERROR: whilst opening serial port'
    exit(0)
  
  # wait 2 seconds for arduino to reset
  time.sleep(3)
  
  # start the initial timer
  t = threading.Timer(20.0, temp_logger, [arduino])
  t.start()