Testing mail from commandline

Miscellaneous, 
echo "This is the main body of the mail" | mail -s "Subject of the Email" -a "From: [email protected]" [email protected]
telnet iot-parts.com 25
mailMAIL FROM:[email protected]
RCPT TO:[email protected]
DATA
telnet localhost 143
a login "username" "password"

     Test using imaps port (assuming you haven't disabled imaps port):
     # openssl s_client -connect imap.example.com:993

     Test using imap port and STARTTLS command (works also with imap port):
     # openssl s_client -connect imap.example.com:143 -starttls imap

b select inbox
c list "" *
e logout

Setup Free SSL Certificate on your Server

Miscellaneous, ,

Please note : This article (and the repo mentioned here) is deprecated. Certbot now recommends installation through Snap. For more details please see – https://certbot.eff.org/docs/install.html.
More info at: https://launchpad.net/~certbot/+archive/ubuntu/certbot

Electronic Frontier Foundation (EFF) provides Let’s Encrypt SSL Certificates through their  Certbot service. They don’t provide any Organization Validation (OV) or Extended Validation (EV)  certificate. As per plans, from January 2018, they will provide wildcard certificates also.

The Let’s Encrypt Policy and Legal documents can be found here : https://letsencrypt.org/repository/  and the FAQ page is at https://letsencrypt.org/docs/faq/

Below are the steps to install the free SSL certificate on an Ubuntu server running Apache

apt-get install software-properties-common
add-apt-repository ppa:certbot/certbot
apt-get update
apt-get install certbot
certbot certonly --standalone --standalone-supported-challenges http-01 -d <server fqdn>

It will ask, “Temporary” or “Standalone” server. Choosing temporary is fast and easy.
After that it will ask a few more general question like, email id for contact etc. Once all details supplied it will install the certificate and show the path where the certificates and key file is stored. Please make a note of the path for later use or reference.

The certificates are valid for 90 days only. After the 90 days it has to be renewed. What can be done to solve this is to set a cron that will automatically renew the certificate after every 60 days or so. Steps to set cron below

Open Cron file using

crontrab -e

Now put the following line to renew the certificate automatically every 2 months

0 0 1 */2 * certbot renew --noninteractive --post-hook "systemctl restart mosquitto apache2"

Save and exit Cron file.

All set for a secured connection.

 

Steps for other Servers can be found here https://certbot.eff.org/

How to Setup MQTT Server on a Windows 10 Desktop

Arduino, Miscellaneous, PHP
  1. Download the Win32 installer from the below link (I couldn’t successfully installed the CygWin version)
    https://mosquitto.org/download/
  2. Once downloaded, install the package
  3. During the start of the installation process it will show links from where some dependencies will have to be downloaded
  4. Copy/Open the links
  5. Once the installation finishes go to the websites opened in the previous step
  6. Download the OpenSSL installer and the pthreadVC2.dll file
  7. Install the OpenSSL
  8. Copy the pthreadVC2.dll file to the directory where mosquitto executable has been installed. Normally C:\Program Files (x86)\mosquitto
  9. Open folder where OpenSSL got installed (normally C:\OpenSSL\) and open the lib folder (normally C:\OpenSSL\lib)
  10. Copy ssleay32.lib and libeay32.lib into the folder where mosquitto executable has been installed.
  11. Please note – while copying the files Windows might ask for giving Admin permission. Go ahead.
  12. At this point Mosquitto should be ready to run————————————————————–
  13. Now testing mosquitto
  14. Open a Command Prompt
  15. Goto the folder where mosquitto is installed
  16. Give command mosquitto.exe -v -c mosquitto.conf
  17. The server should now start listening on port 1883
  18. Now open another Command Prompt
  19. Give the command mosquitto_sub -h localhost -t channel1/data1
  20. Open a third Command Prompt and give the command mosquitto_pub -h localhost -t channel1/data1 -m “test data”
  21. In the command prompt where we used mosquitto_sub (step 18 and 19) will show the message “test data” sent from the third command prompt.
  22. Reaching this point means mosquitto is working fine———————————————-
  23. To secure the transmission we can username and password authentication
  24. Open a command prompt with Admin privileges
  25. Goto the folder where Mosquitto is installed
  26. Create a password file (for the first time only) using the command mosquitto_passwd.exe -c passfile.txt username
  27. It will ask for password. Give the password and confirm the password
  28. After this point further users can be added using the below command mosquitto_passwd.exe -b passfile.txt username password
    Please note – this time we supplied the password also along with the username
  29. Now edit the config file (mosquitto.conf normally located in C:\Program Files (x86)\mosquitto) to enforce only authenticated data transfers
  30. Uncomment allow_anonymous and set it false
  31. Uncomment password_file and put the password file name after it. It will look like password_file passfile.txt
  32. Now onwards all sub and pub requests will have to be with username and password of a user whose details exists in the password file. Examples below 
    mosquitto_pub -h localhost -t channel1/data1 -m "test data" -u john -P johnpass 

mosquitto_sub -h localhost -t channel1/data1 -u jane -P janepass
  33. Access control can be done using a acl file or using mosquitto-auth-plug (https://github.com/jpmens/mosquitto-auth-plug)
  34. There should be a aclfile.example inside your mqtt directory. If not then also no problem we will shortly see the contents of the file below.
  35. Create a file with any name. Here we will use aclFile.txt
  36. In the mosquitto.conf file uncomment acl_file and put the name of your acl file after that. It will look something like acl_file aclFile.txt
  37. Example content of aclFile.txt as below 
     # user jane given full permission to channel1/data1 and only read permission to channel1/data2
user jane
topic channel1/data1
topic read channel1/data2

# user jane given full permission to both data1 and data2 channel
user john
topic channel1/#

Please put in your suggestions in comment.

MQTT on Windows  — Download link of Word File containing the above steps. WordPress had made some filenames missing. So uploaded the original word doc. 

Arduino as an Oscilloscope

Arduino

Yes an Arduino can be used as Oscilloscope without any additional hardware.

Burn this code to Arduino

const int probePin = A0;
 
void setup() {
  //Setup serial connection
  Serial.begin(9600); 
}
 
void loop() {
  //Read analog pin
  int val = analogRead(probePin);
 
  //Write analog value to serial port:
  Serial.write( 0xff ); //can be skipped                                                    
  Serial.write( (val >> 8) & 0xff ); //the higher 8 bits                                            
  Serial.write( val & 0xff ); //the lower 8 bits
}

Download Processing from https://processing.org/download/  This tool will be used to run a C code that will plot the graphs.

Now run this C code in Processing

/*
 * Oscilloscope
 * Gives a visual rendering of analog pin 0 in realtime.
 * 
 * This project is part of Accrochages
 * See http://accrochages.drone.ws
 * 
 * (c) 2008 Sofian Audry ([email protected])
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */ 
import processing.serial.*;

Serial port;  // Create object from Serial class
int val;      // Data received from the serial port
int[] values;
float zoom;

void setup() 
{
  size(1280, 480);
  // Open the port that the board is connected to and use the same speed (9600 bps)
  port = new Serial(this, Serial.list()[0], 9600);
  values = new int[width];
  zoom = 1.0f;
  smooth();
}

int getY(int val) {
  return (int)(height - val / 1023.0f * (height - 1));
}

int getValue() {
  int value = -1;
  while (port.available() >= 3) {
    if (port.read() == 0xff) {
      value = (port.read() << 8) | (port.read());
    }
  }
  return value;
}

void pushValue(int value) {
  for (int i=0; i<width-1; i++)
    values[i] = values[i+1];
  values[width-1] = value;
}

void drawLines() {
  stroke(255);
  
  int displayWidth = (int) (width / zoom);
  
  int k = values.length - displayWidth;
  
  int x0 = 0;
  int y0 = getY(values[k]);
  for (int i=1; i<displayWidth; i++) {
    k++;
    int x1 = (int) (i * (width-1) / (displayWidth-1));
    int y1 = getY(values[k]);
    line(x0, y0, x1, y1);
    x0 = x1;
    y0 = y1;
  }
}

void drawGrid() {
  stroke(255, 0, 0);
  line(0, height/2, width, height/2);
}

void keyReleased() {
  switch (key) {
    case '+':
      zoom *= 2.0f;
      println(zoom);
      if ( (int) (width / zoom) <= 1 )
        zoom /= 2.0f;
      break;
    case '-':
      zoom /= 2.0f;
      if (zoom < 1.0f)
        zoom *= 2.0f;
      break;
  }
}

void draw()
{
  background(0);
  drawGrid();
  val = getValue();
  if (val != -1) {
    pushValue(val);
  }
  drawLines();
}

This is not replacement for an actual oscilloscope. It is a simple one that can used to monitor signal levels and voltages.

Burning Arduino Bootloader to Atmega8 or other Atmega

Arduino, , , , , ,

This is for all who are having problems in burning the Arduino Bootloader on an Atmega8 or any other Atmega Processor using a Arduino Board like Arduino Uno.

  1. The processor for the first time burning will have to be used with an external oscillator. I was trying without the external oscillator (was depending on the internal oscillator -  setup the fuses also properly) and was banging my head. 
  2. The Arduino Uno (or any other board that you are using) will have to be burned with the ArduinoISP code. (Files -> Examples -> ArduinoISP -> ArduinoISP)
  3. Don't bother about the Chip Configurations (and/or binary) that are available on the net, especially if you are looking to use the external oscillator. None works properly.Find a board from the existing list that uses the same Processor. 
  4. For Atmega8 use the "Arduino NG or older" from the boards list. That board should also work for Atmega168
  5. If you are using a 8MHZ crystal then open the "boards.txt" files under "Program Files (x86)\Arduino\hardware\arduino\avr".  And edit the "atmegang.build.f_cpu". Change it to "8000000L".
  6. If you will be using the Internal Oscillator then you will have to change the fuse values to proper ones in the above board configuration.
  7. I had problems with high bitrate while burning. So I changed it to "9600" (atmegang.upload.speed=9600).
  8. After you are done with the configurations and connections use the option "Burn Bootloader" under Tools in the Arduino IDE

 

I also found tutorials where it was suggested to remove the processor from board (UNO board) which is being used as programmer. Don’t do that.

Putting the chip in an UNO board didn’t work for me. I don’t know why but it didn’t.

What I found is the Atmega8 works best with the external oscillator. With an internal oscillator I was having problems after running the chip continuously for quite some time.

 

The connections with an Arduino UNO
------------------                --------------------------
Arduino Uno                         Atmega 8 or other
------------------                --------------------------
10                                      Reset  (1 on Atmega8)
11                                      MOSI   (17 on Atmega8)
12                                      MISO   (18 on Atmega8)
13                                      SCLK   (19 on Atmega8)
And the AVCC pin should be externally connected to VCC, even if the ADC is not used.

 

And like many suggested on the Internet already, a standalone programmer is the best. I got a USBasp from eBay.

And I guess it is better to invest in a 328p processor due to limited resource of Atmega8 chip. More or less same price.

Atmega8 IC can be used as standalone IC, that is without using the whole Arduino board. Please see this article for details : Using Atmega8 or Atmega328p directly without using Arduino boards and Atmega8 to Arduino pin mapping

 

Eagle PCB Library for ESP8266 ESP-12

Eagle PCB, , ,

Eagle PCB Library for ESP-12

Please note though the library file is named as esp-12e, but it is for esp-12. The ESP-12E version will be published soon.

Somehow I couldn’t find a proper a library on the internet. I found only one but that had wrong pin spacing.

Download the esp-12e eagle library here

For more details on ESP-8266 visit this link

ESP8266 Hello World   ESP-8266 AT Commands  GPS Tracker using NEO 6M and ESP-12

 

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