# Hardware To Software

Theory, hardware, software and code

## Circular menu in arduino redux

Seems like the old circular menu class is now incompatible with the new Arduino 1.0 GUI version.
Rober Wagner from the arduino forum described the incompatibility. He also sent to us an email and we thank him for the contribution.
The circular menu seems to interest a lot of people so we decided to “port” the circular menu class into the new Arduino 1.0 GUI.
We will try to describe the class in the future.
Now before starting have a look at the documentation of the “old circular menu”.
As always you have to construct the three button configuration on your breadboard.
The down button is on digital port 7 the right button on digital port 6 and the enter button at digital port 5.
In order to find out how to connect buttons on your arduino please read the “arduino and memory how to” tutorial.

Written by tasos

April 29th, 2012 at 11:45 pm

## Voltage dividers explained

Voltage Divider

The voltage divider is a circuit that produces an Vout that is a fraction of an Vin.
The two resistors in series can be seen as a single potentiometer.
This circuit will be heavily used in our website so we have decided to do a standalone article for this circuit.

From the Ohms law we know that V=I*R
From the Kirchhoff’s current law (first rule) we know  ΣI=0 So we have I1=I2+I3
From the Kirchhoff’s voltage law (second rule) we know that ΣV=0 So we have Vin=V1+V2
Observe that V2=Vout

Written by tasos

October 4th, 2011 at 3:17 am

Posted in Hardware,Theory

Tagged with ,

Creating menus for embedded devices is often challenging.
Usually you have very little resources and complicated menus can not be an option.

More buttons offer more possibilities but also a more complex user interface and more hardware resources.

Why more hardware resources?

Going back at the “arduino and memory how to” article we have used the button change example.
One button use one pin as input pin from our arduino processor.
So for more buttons you need more pins.

There are methods that you can “bypass” this problem as we will see in next articles but anyway more buttons = more cost.

Written by tasos

September 22nd, 2011 at 12:04 pm

## Learn how to make at home an etching solution

The etching is the technique that a strong acid chemical solution “eats” the unprotected copper.

So the etching method can be used for the production of printed circuit boards (PCB) since acid can be used to remove the unwanted copper from a copper clad.
A nice and easy method in order to make printed circuits at home is to use the so called : “toner transfer method”. This method will be discussed in another article.
For now keep in mind that you have a copper clad (fr4) with the circuit “printed” (with toner) on it.

So this printed copper board can be etched with an acid solution called etchant.
This acid solution will eat all the unprotected toner and the remained, protected by the toner, copper will be our final printed circuit.

Written by tasos

September 15th, 2011 at 10:07 pm

Posted in Hardware,Theory

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## How to assemble a low cost firewall with professional capabilities

Selecting a firewall is not a trivial decision.  Generally all firewalls are software-based. The embedded firewalls are simply very limited-capability programs running on a low-power CPU in order to obtain lower power consumption. You have to list your needs and select the software and then the dedicated hardware that can handle them. As first step we need to list our needs for the firewall.

Written by tasos

August 15th, 2011 at 11:56 pm

Posted in Hardware

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