I had great difficulty getting my Arduino Opta set up and working using the Arduino PLC IDE – whatever I tried I got the “Cannot download Sketch file (error code: 1)” error.

I finally had success using the plain Arduino IDE to do the initialization and then switching to the Arduino PLC IDE. The final step was changing the Modbus address to 247.

It probably shouldn’t be that tricky….

For a while I’ve been tinkering around with a simple project – an Arduino-based temperature (and humidity) monitor that outputs a webpage on my home LAN. The Arduino I used was the Freetronics EtherTen, a quality product.

Check out the code at https://github.com/gjhmac/TempMonHTTP.

// ————————————————————————————————————————————————
// Project:   DataLogger
// Version:   0.4
// Date:      26 August 2018
// Author:    Greg Howell <gjhmac@gmail.com>
// ————————————————————————————————————————————————
// Version    Date              Comments
// 0.4        26 August 2018    Modified code to only log to the SD card if the new value is different to the old value
// 0.3        30 June 2018      Added debugging and diagnostics on serial port, sped up ADC for analogue read (128kHz -> 1MHz), fixed “A REF”
// 0.2        26 April 2018     Addition of switch to enable/disable logging to SD card and LED to indicate logging status
// 0.1        17 February 2018  Initial Development
//
// ————————————————————————————————————————————————
// Description:
//  – Logs analog0 value to a text file on the SD card along with date/time stamp in CSV format
//  – Maintains date/time via DS1302 Real Time Clock
//  – Builds with Arduino 1.8.5
// ————————————————————————————————————————————————

// #includes
#include <SPI.h>    // Serial Peripheral Interface
#include <SD.h>     // SD Cards
#include <DS1302.h> // DS1302 RTC

const int chipSelect = 4;
const int buttonPin = 5;  // Pin 5 is the button to enable/disable logging (digital input)
const int ledPin =  6;    // Pin 6 is the LED indicate logging status (digital output)

const byte PS_128 = (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);
const byte PS_16 = (1 << ADPS2);

int buttonState = 0;      // initialise button state to off
int oldsensor;            // variable to store the previous sensor value (used in loop())

// Init the DS1302
// Pin 2 = RST
// Pin 3 = DAT
// Pin 4 = CLK
DS1302 rtc(2, 3, 4);
// ————————————————————————————————————————————————
// setup()
// ————————————————————————————————————————————————
void setup() {

  ADCSRA &= ~PS_128;  // remove prescale of 128
  ADCSRA |= PS_16;    // add prescale of 16 (1MHz)

  analogReference(EXTERNAL);  // Analogue reference set to “A REF” pin

  pinMode(buttonPin, INPUT);  // Initialize the pushbutton pin as an input
  pinMode(ledPin, OUTPUT);    // Initialize the LED pin as an output

  rtc.halt(false);            // Set the clock to run-mode
  rtc.writeProtect(false);    // and disable the write protection

  Serial.begin(9600);

  // Use following lines once to set clock if battery fails (modify to suit)
  //rtc.setDOW(SUNDAY); // Set Day-of-Week to FRIDAY
  //rtc.setTime(21, 50, 0); // Set the time to 12:00:00 (24hr format)
  //rtc.setDate(26, 8, 2018); // Set the date to August 6th, 2010

  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

  // Print current system date from RTC at start up
  Serial.print(“System date: “);
  Serial.println(String(rtc.getDateStr()) + “,” + String(rtc.getTimeStr()));

  Serial.print(“Initializing SD card…”);

  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println(“Card failed, or not present”);
    // don’t do anything more:
    while (1);
  }
  Serial.println(“card initialized.”);
}
// ————————————————————————————————————————————————
// loop()
// ————————————————————————————————————————————————
void loop() {
  String dataString = “”;                 // make a string for assembling the data to log
  int sensor = analogRead(A0);            // read analogue
  dataString += String(sensor);           // construct string with analogue signal
  buttonState = digitalRead(buttonPin);   // read button state

  // Logging enabled
  if (buttonState == HIGH) {
    File dataFile = SD.open(“datalog.txt”, FILE_WRITE);

    // if the file is available, write to it
    if (dataFile) {

      // if the new data is different to the old data write it to file
      if (sensor != oldsensor) {
        // Write data to serial output
        Serial.println(String(rtc.getDateStr()) + “,” + String(rtc.getTimeStr()) + “,” + dataString);
        Serial.println(String(sensor) + “,” + String(oldsensor));
        // Write data to SD card
        dataFile.println(String(rtc.getDateStr()) + “,” + String(rtc.getTimeStr()) + “,” + dataString);
        dataFile.close();
      }
      else {
        dataFile.close();
      }
    // set logging LED to high
    digitalWrite(ledPin, HIGH);
  }
  // if the file isn’t open, print an error
  else {
    digitalWrite(ledPin, LOW);
    Serial.println(“error opening datalog.txt”);
  }
}
  // Logging disabled
  else {
    // set logging LED to low
    digitalWrite(ledPin, LOW);
  }
  // set the old sensor value to the current sensor value (read at top of loop())
  oldsensor = sensor;
  // Wait before repeating 🙂
  delay (500);
}