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original in en Guido Socher
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Guido likes Linux because it is a really good system to
develop your own hardware.
Abstract:[Here you write a little summary]
The tuxgraphics ethernet board can be very useful
all over the house to take measurements or control
devices. Ethernet network cables are however sometimes
difficult to add. The solution is wireless: WiFi also
known as 102.11a, 102.11g, 102.11n.
How to get tuxgraphics ethernet board in the graden pavilion or cabana
connected to the home network using WiFi?
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It would be possible to connect an AVR microcontroller
to a WiFi card. The challenge is however the encryption.
There are not only a number of different encryption algorithms
but it is as well a challenge to implement all of them
in a microcontroller.
Off the shelf WiFi AP-clients and WIFI Bridges
There is a lot of completion in the market for WiFi electronics
and all of those devices are mass produced. I bought recently a
new Longshine WA-45 WIFI AP-client for 35 dollar.
The price is to low that it becomes impossible to compete
with that. The best solution is therefore to use such an off the shelf WiFi
You can find a variety of those WiFi AP-clients in
any specialized supermarket for computer and electronics. They are usually
sold as "WiFi Bridge and Access Point". On the box it will normally say
"WIFI Access Point" or "WIFI Bridge" but NOT "WIFI Router". On the
back of the box you might see some explanation saying that you need in addition
a router to connect to the internet and that this system can be used
to connect existing ethernet devices to a wireless network.
How to use a WiFi Bridge
A WiFi Bridge allows you to connect more than one Ethernet
board to the Wifi network. They are generally a bit more
expensive as the below AP-clients but you can as well connect
more devices at the same time. The configuration is straight forward.
You configure the network (SSID) to connect to and the type of
encryption. After that you just attach devices via Ethernet cables and it looks
from the device point of view as if it was connected to a wired LAN.
Trendnet TEW-640MB, 4 RJ45 Lan ports.
How to use a WiFi AP-client
Those "WIFI Access Points" can normally be configured to work in
a couple of different modes:
We are after the "AP-Client" mode. An AP-Client allows you to
connect exactly one client (tuxgraphics ethernet board in our case) via
WIFI. If you want to connect more than one in the same physical location
then use a WiFi Bridge.
- WIFI AP (Access Point)
- WDS (Wireless Distribution System) Bridge with AP or without AP function.
This is used to enable wireless interconnection of multiple APs.
This works usually only if you have two or more WDS bridges of the same type.
- AP-Client. An AP-Client will transform any IEEE 802.3 device (wired network device)
into an 802.11b/g/n wireless client. This mode is also known as Gaming Console WIFI
Adapter or Wireless-Client mode.
Those "WIFI Access Points" are small boxes with a single ethernet rj45 jack and an antenna.
You configure them to connect to a given WIFI network identified
by its name (SSID).
Here is how they look like. Most of them work very well.
Longshine WA-45, works very well.
Level 1 wap0006, works very well.
A product to avoid is the D-LINK DWL-2100A. It can not be used to connect
a server to a WiFi network as it does not handle initial Ethernet ARP broadcasts correctly.
AP-client, wireless client configuration
The setup is from a hardware point of view very
simple. You just connect the AVR ethernet board to AP-client adapter with a
The configuration might be a bit more complicated. In
most cases you will have to connect in your computer with
an ethernet cable and then access a configuration web page
at a factory pre-set IP address.
The details depend on the manufacturer but I can give a few
tips. You want the WiFi AP-client to be as "dumb" as possible.
It should be a "wireless cable" to the AVR ethernet board.
The AP-client configuration should normally require only the following
parameters. If the menu system asks for more parameters then
you are probably in the wrong mode.
- Mode: AP-client.
- Band: 802.11 A/G/N, select the band that is compatible with your already
existing WIFI network.
- ESSID of the AP to connect to. The "name" of your already existing WIFI network.
- WLAN MAC: Some AP-clients might requires this and others not. The idea
is that there could be bigger WIFI networks with multiple APs and you want to
select one of the APs by its MAC address. If this option is
needed then go to your already existing WIFI router and check what the MAC
address on the WIFI side is.
- A page with security and encryption related settings.
- A page with LAN IP setup. Here you configure the IP address
under which the AP-client can be reached for configuration purposes. This
page has nothing to do with the IP address of the ethernet board you
want to attach. A good AP-client has a field called "clone MAC" where
you can specify the MAC address under which the board shall be visible
in the WiFi LAN. Set it to the MAC address of the board that you plan to attach.
Once you think that the configuration is complete I suggest to
take a PC, shut down the PCs WIFI interface and connect it to the WIFI AP-client adapter. Check if it gets
a new IP address from the DHCP server insider you WiFi Router (not
the AP-client) and check on the PC what that address is. Then go
to a different PC in the network and ping that address.
Connect the tuxgraphics ethernet board once this
this test was successful.
Reliability of WiFi
We all love WiFi because it can provide network access at a decent speed
all over the house. There are however temporary reliability issues related to
interference with other devices such as the neighbors WiFi system or
cordless phones and some toys for children. Cordless phone are particularly
problematic because you can not see them when scanning for other interfering
WiFi networks. There is as well a problem with penetration through
iron enforced concrete walls or aluminum foil vapor barriers used
in wooden houses.
Nothing beats the reliability of a wired ethernet cable but
we all use WiFi because it has an aspect of convenience.
- The tuxgraphics avr ethernet board is available in our online shop: shop.tuxgraphics.org
The tuxgraphics ethernet board provides a web server with the possibility
to control hardware and read sensors. It is not a web server for
downloading files but one for controlling hardware.