Monday, October 8, 2012

Understanding what ASCII is.

If you do any sort of programming you will eventually run into ASCII codes.
So what are they?

Lets start by saying that a computer only understands numbers. specifically bits and bytes. Originally most computers were 8bit. Where 8bits or 1 Byte has a range of 0-255.

Since the computer can only under stand a number between 0-255 it cannot understand what "A" would mean. As a result computer programmers had to assign values to characters.

value     character
0           "SPACE"
1           A
2           B
3           C
...          ....
255       esc

Now the computer can take a string of number such as (2,1,3,0,2,1,3) and display it on the screen as a string. "BAC BAC". please note that these numbers are made up as an example.

The only problem was that every company and university had their own conversion tables. So if one sent their code to a different company it was hard to understand. Networking computers on different tables was also a problem. Say you wanted to send and email and it got converted using the wrong table it would be just a bunch of garbage on the other side.

Here is an example of the problem. 
Just check out paragraph 3 and look at the pic.

To fix the problem we needed a standard that all computers would have to use. That standard is ASCII or American Standard Code for Information Interchange



Tuesday, April 3, 2012

The Bells Oberon Mini Keg guitar amp!

I built this Oberon guitar amplifier for my brother's birthday present.

My brother is a bassist and like most guitarist he likes to play his acoustic bass at the beach with his buddies. His bass however is overpowered by acoustic guitars. He wanted a portable amp that would be loud and easy to carry around. I settled on a mini keg as they are durable and easy to acquire. Bells Oberon spelled the perfect keg. Oberon is a sure sign that summer has arrived and what better way to enjoy summer than with some beer and music at the beach.

We decided that using a rechargeable battery would be the best option. My brother works in the construction field, and as you might expect he has a number of cordless tools. With a little trimming I was able to get an entire DeWALT battery charger into the keg. This allows the keg to double as a charger.

The circuit uses the ubiquitous TDA line of chip amps. The tda2050 to be precice.

I followed this datasheet schematic.
I changed R4 for a 1k potentiometer that allowed me to set the gain for a guitar. I also added this simple passive equalizer.
The setup works better than I expected. The sound is deep and loud. My brother loves it and I hope to have video for you guys soon.

Saturday, March 24, 2012

Easier to compile Advmame.

How to get advmame on the rasberry pi.
I found a tip about using advmame instead of xmame and decided it was worth a try.
advmame has an awesome configure script that takes all the work out of editing makefiles.
It also runs a lot faster.

First you will need to have some sort of rasberry pi simulator I went with this method.
RPi on Virtual Box

As before
Use the following command to ensure your running on the arm kernal

uname -a

here is my output.

Linux rasberry-pi 3.0.4 #2 mon oct 17 17:39:42 ict 2011 armv61 GNU/Linux
If you dont have X set up install it by using the command

apt-get install lxde xorg python geany

Now we need to install some dependencies to build advmame. You may not need all of these. I put them together from a lot of tinkering.

apt-get install build-essential libgtk2.0-dev libgnome2-dev libsdl1.2-dev
apt-get install libxv-dev libxv1

Download the advmame source. I tried 106.1 without success.

extract the archive.
tar -zxvf advancemame-0.106.0.tar.gz
cd advancemame-0.106.0

Now we configure and compile.
make install
Pretty easy huh. Thanks to advmame team for all there work.