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2.4 GHz Inverted F Antenna Eagle Library

ISM radios for microcontroller are becoming quite popular in last years, and if you are designing with wireless radios you have a wide choice of transceiver in both sub-gigahertz an 2.4 GHz bandwidth.

If you choose to go for 2.4 GHz, you’ll have the benefits of a wide choice of radios, relaxed constraints in protocol design and a small size antenna.

Focusing on the antenna, 2.4 GHz radios usually have a differential output which have to be adapted to a 50 Ohm single-ended signal suitable for Wi-Fi antennas, which can be connected to the radio using an RP-SMA connector or directly embedded into the PCB.

This post shows a printed antenna design, kindly provided by TI/Chipcon, suitable for 2.4 GHz ISM radios. You’ll also find a link for an Eagle library with some tuning variant.

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Network Statistics with iptables and rrdtool

Netfilter is a powerful tool when it comes to select traffic on a Linux router.

When you set up a chain of rules with iptables, you are also get set of traffic counters with each rule you set, which can be used to see how many times the rule have matched.

If you place a chain of rules without any jump, the packet get counted and goes forward the chain, so that you can write a set of rules just to get some statistic of selected pattern of traffic in your network.

In this post I’ll show how to write some simple rule, get the data on a rrdtool database and plot a traffic graphic out of it.

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Network Activity LED with Linux LED Subsystem

This is a nice userspace application I use on my router to control the Internet connection status LED in “smart” way.

The idea is simple, instead of just randomly blink the LED when there is some activity on the network, this application checks for the total bytes transferred on the network interface, and blinks the LED every 100KB of data.

That behavior is borrowed from modern electric counter, which have a LED that blinks every predefined number of Watt/hour.

That’s useful because you can quickly have an idea of the bandwidth utilization of your connection by just checking how often the LED blinks, so you can instantly identify a low-bandwidth constant traffic by a high-bandwidth traffic.

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IPv6 Stateful Firewall with netfilter/ip6tables

IPv6 is coming!

Ok, that was just a provocation. If you have some interest in networking technologies you’ll know for sure that stable IPv6 implementation are around for many years now but very few providers give the user IPv6 connectivity. You can follow the IPv6 deployment status around the world on this Wikipedia page.

Anyway, for those of you who are lucky enough to have a real IPv6 connection, it’s time to add the “6” to some network utility, and that includes ip6tables!

This script is a stateful firewall for an IPv6 standalone and router installation, which provides the same level of security given by an IPv4 NAT router.

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IPv6 Tunnel Broker on GNU/Linux Routers

IPv6 connectivity is slowly spreading around the net day after day. Sooner or later you may want to get IPv6 connectivity to your home, as some providers already does with brave users.

If your ISP does not give you native IPv6 connectivity you can still get your own IPv6 access in a number of ways.

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Iptables Stateful Firewall and NAT Routing

Network packet filtering! Whether is your home or your company, modern networks have many systems connected. Even a small domestic network can provide connectivity to many devices of different kinds: PCs, laptops, printers, smartphones, game consoles, your neighbor’s laptop (wait… what?!), NASes, media players, TVs…

If you have some basic knowledge in networking, you’ll probably want a way to control all the traffic going through your network, and if you are running a GNU/Linux system, you probably already have what you need… Netfilter!

What you’ll find here are some examples of common Netfilter (iptables) configurations and some scripts I use as a base for my firewalls and network installations.

These are really useful if you need some advanced firewall configuration and you choose to run your own GNU/Linux system as a router instead of a commercial one. Also, these scripts may come in handy if you need to quickly replace a broken router with a spare PC.

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Five Port Fast Ethernet Managed Switch

This project is the complete design of a 5 port fast Ethernet switch, based on the Micrel KSZ8995M switch IC with integrated PHY and an ATMega168 8-bit microcontroller.

The hardware was originally developed in 2009, because I needed a compact, VLAN capable switch to expand the functionality of an NSLU2, which has just a single Ethernet port and that I was using as router for my home network.

Features

  • Complete VLAN support
  • Auto MDIX on all ports
  • Programmable port rate limiting
  • Integrated MIB counters
  • TTL UART interface for external access of switch configuration


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