Yeop's IoT world

This time,  I used 3 raspberry pies to make a network for communicating gateway with end device. I am gonna put some sensors on the end device to get data but this time I didn't and send just message from end devices to gateway. One of Raspberry is gateway for network and it receives message from two other raspberry pies through MQTT. As soon as gateway get a message,  It makes a text file to save the messages. Let's see the code followed:



I used pi3_01 for gateway and the messages come from pi2 and pi3_02. Gateway always keep listening topic by using subscribe and each end device has their own topic. When gateway get a message, it saves the message to text file whose name is test.txt by using appendFIleSync. So gateway can save all message what end device send to it.

Moreover, this is end device code:


I made this device to send message and topic periodically(every 1 sec).  In next time, I will try to make a gateway program which can count how many messages gateway got and end devices which can publish a message and stop to send message if it send a message once.

This time, I controled led by using GPIO. This is basic knowledge to control GPIO. So this is one of steps for my project.
If it is first time for you to use GPIO and led diode, you need to download and install some packages.


1. Download GPIO package.
type it in terminal
$ git clone git://github.com/quick2wire/quick2wire-gpio-admin.git ~/gpio-admin


2. Go to direntory
$cd   ~/gpio-admin


3. Install package
$make
$sudo make install


4. Assign GPIO
$sudo adduser pi gpio
$3xec su -l pi


5. Download library to use GPIO
$npm install onoff


6. Make your code for Blink led. My code is followed:
7. node foo(your nodejs file name)




Reference:
윤성진(2016), 스마트IoT 및 실습, Korea university of technology & education

I tried to search how to read text file byte by byte but it was hard to search it. Most of posts shew how to read whole text file not byte by byte. Even if there are some information about the 'fs.read' in nodejs.org, that information was not enough for me because my knowledge is not enough to understand 'fs.read' with just grammar information. I googled many time to search some information how to read text file byte by byte and combined all sources what I searched. Finally, I succeed to read text file byte by byte. The code is following: