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Arduino FreeRTOS Mutex Examples

In this section, we will explain using an example to demonstrate mutexes in Arduino using freeRTOSThere are two freeRTOS Mutex examples in this tutorial, the first example demands some hardware (LCD) While the second does not need any hardware, you can try out both if you have the resources.

In the last tutorial, we considered in detail: semaphores and mutexes and we also established the difference between binary semaphores and mutexes.
Just for a review:Recall that a mutex is a locking mechanism that implements the take and gives functionality in itself, unlike a binary semaphore. See this tutorial if you have not before continuing.
Example 1: Protecting the LCD Resource Using Mutex in freeRTOS
Program Description

In this program, we Demonstrated the use a 16x2 LCD display to implement a mutex.

The LiquidCrystal library works with all LCD displays that are compatible with the Hitachi HD44780 driver. you can usually tell them by their 16-pin interface.


* LCD RS pin to digital…

Internet: Overview and Basic Concepts

The term “internet” is currently a very common term in our present day lexicon and not too many people try to really consider what it really is. In this post, we will be learning about the internet. How it came about and how it works.

In this article, we will be considering some basic sections of this large scale network called the internet. The Internet of things redirects here.

What is the internet?

The internet commonly called the internetworking of networks is a high capacity public switched network that is operated by a group called the Internet Service Providers.

Internet Service Providers
These are the group that makes the internet available for people to use, they are broadly divided into two groups:
1. Backbone Operators
2. Internet Resellers
The internet comprises of hundreds of backbone networks.

Backbone Operators: The backbone operators are the big guys on the internet, they maintain the backbone networks.

A backbone network is a high capacity packet switched network that is made up of LANs and WANs for data exchange and uses high-performance routers interconnected by high capacity transmission services. This high capacity transmission service is commonly produced by CISCO.

The backbone link is the interconnection of different backbone networks, the high transmission services we mentioned above is what is used in creating this backbone links. Interconnecting backbone routers can take place in the following ways:

    1. Private lines or

    2. ATM (Asynchronous Transport Mode)

In private lines, transmission services are mostly synchronous operating at 155Mbps.

ATM is Asynchronous Transfer Mode, the data transfer mode is asynchronous and can support access rates up to 622Mbps with better advantages over private lines.

Network Access Points: These are special connection facilities that are used for interconnecting backbone networks. However, backbone networks can peer to create another one-to-one connection between themselves in order to avoid the congestions that always take place at the Network Access Points.

Internet Resellers: This group of the ISP provides or establishes operating centers (Point of Presence) around the world. In doing this, some elements come into play. These elements involved in PoP configuration include:

  • Lan switch

  • Backbone router

  • Access Router

  • Remote Access Servers

  • Users: Dedicated users, Dial-in user, Email server, customer web server, etc

Lan Switch: Provides connection to the backbone routers
Access Routers: Supports dedicated connection from big customers (dedicated users)
Remote Access server: Connect to the Public Switched Telephone Network and channels traffic to the Backbone routers through the LAN switch

Internet Access

Internet access refers to the ways by which you can access/connect to the internet. There are two major divisions with regards to internet access.

These are:

  • Symmetrical access: Same bandwidth capacity is provided for both uplink (upstream) and download(downstream) channels

  • Asymmetrical access: Larger bandwidth is provided for downstream than upstream since it is noted that the ratio of downloads to uploads is like say 40:1.

In connecting. to the internet, most people only know the usual dial-up modem but there are other ways you can access the internet.

  1. Cable modem

  2. Satellite Access

  3. Wi-max

  4. Dedicate Access

How an Internet connection is made (Internet Sessions)

An internet session is a period from the moment one log into the internet (say a website) to the time the user closes his browser.

In this section, we explain what happens when you access a URL (Uniform Resource Locator) on your browser.

When you key in a URL say (e3guy.com), your device has a unique IP Address that will be used to connect to the internet. The IP Address is a 32-bit binary number written as a series of four decimal numbers separated using a full stop.

When you key in the URL, your request is sent to a domain name server, the domain name server searches for the URL in its table and returns the IP address. (The URL you searched for is actually an IP address).

Domain Name servers are arranged in a hierarchical order such that if the local DNS server could not find the URL entry, the request is moved to the next DNS in the hierarchy until the IP address is seen.

When the IP address is received from the DNS, an IP packet is generated, a to and fro address is inserted into the packet and  TCP connection request is forwarded to the network, to receive the web page request. the router is in charge of forwarding IP packets to their destination. the Web page is then downloaded over the TCP connection in a series of packets. Once the page is downloaded, the TCP connection is terminated.

Corporate Challenges with the internet

Just as the challenges of the  internet of things, The internet is an amazing technology, however, it's strength provided the greatest challenge ever: the ability to grant access to anyone, anywhere anytime brought about issues of concern for corporate bodies who need to be sure of who accesses what information.

The need to have some performance level guarantees and ensure authentication and privacy led to the development of some additional facilities over the internet. These facilities provided some additional advantages of security and Quality of Service over the internet. In this section, we will be considering only two of such:

  1. Virtual Private Networks (VPN)

  2. Multi-Protocol Label  Switching (MPLS)

Dial-Up Virtual Private Network (Dial-Up VPN)

The VPN was established to solve the problem of authentication, security and privacy. There are four major elements in the dial-up vpn:

  • Internet backbone which may be the same with the request, or different from it.

  • Authentication server which ensures it is the right user by verifying the username and password for instance

  • Firewall Server which filters connections

  • VPN Client software that helps create an encrypted connection to ensure privacy

Multi-Protocol Label  Switching

The MPLS is used by many organizations today to secure their network. The MPLS added two essential elements into the conventional IP (Internet Protocol)

  • Virtual Circuit: The Virtual Circuit made the connectionless or stateless IP to possess a state. Using a technique called Label Switched Path. In MPLS, all of the packets received and sent for a particular internet session must be made on a virtual circuit called the Label switched path. Once this circuit is established, no other connection is allowed to use that path until the current session is ended.

  • Capacity Determination: With this feature, a connection will only be made once it has ensured that there is sufficient capacity available to meet the connection requirements. Since the capacity is known, it becomes easy to add performance prediction with respect to time, delay and packet losses.




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