Home Brew Computers

Altair 8800 - Popular Electronics 1975 issue

2010-05-18T21:34:00.001-04:00

And the auction hasn't ended yet.....

iPhone Simulator - Folders

2010-04-15T21:31:00.004-04:00

Screenshot showing my "test" app inside a folder with Photos and Notes.

Pretty cool. This is the beta version of the iPhone (and iPad) 4.0 SDK which I installed just a few days ago. What does this have to do with homebrew? Nothing.

AVR Microcontrollers

2010-04-08T07:35:00.001-04:00

Last week while taking a break from working on my Apple 1 clone, and from working on the 6802 homebrew stuff, I started looking into AVR microcontrollers. I was really looking for an input device that someone else had already built for converting PS2 keyboard scancodes into ASCII.

I contacted one guy, but his device converts to ASCII serial out, and I need parallel. So while poking around for more info, I came across a couple of sample code snippets, using various microcontrollers to accomplish capturing keyboard input. Specifically the Atmel microcontrollers. This eventually led to the purchase of this book: "Embedded C Programming and the Atmel AVR". I figured it was time for me to start investigating these chips and maybe do a little tinkering, and maybe even build my own PS2 to ASCII keyboard converter, which I could then use on my Apple 1 clone project. So far, it is pretty interesting. I installed the C IDE but haven't done much with it yet. The IDE that comes with the book is called: CodeVisionAVR C Compiler Evaluation. More to come on that.

Jameco Keypad Encoder

2009-10-03T18:06:00.004-04:00

I've been researching how to build a hex keypad -- and found....

EDE1144 KEYPAD ENCODER

Keypad Encoder IC from Jameco

Would using this IC qualify me for cheating?

(And why am I having a hard time finding a keypad with keys 0-9 and A-F? Don't they make these anymore?)

How to discharge a capacitor

2009-10-03T14:17:00.003-04:00

Here is a simple example:

How to discharge a capacitor

PCB Boardhouses

2009-09-24T19:01:00.006-04:00

Nice list of boardhouses found here:

CadsoftUSA

Boardhouses

(These guys do the Eagle PCB software, Mac version available too)

Binary Box with Power Indicator and ON/OFF switch

2009-09-08T00:43:00.000-04:00

I recently hooked up the ON/OFF switch and power indicator (green LED upper right).

"Binary Box" Schematic

2009-09-08T00:06:00.000-04:00

As promised, here is the schematic for the "Binary Box".
You will need the following parts:

(5) 330 ohm resistors
(4) Red LEDs
(1) Optional Green LED for use as a power indicator
(1) TIL311 (or equivalent)
(5) On/Off switches (Toggle)
(1) 7404 IC (Inverter)

"Binary Box" prototype

2009-04-21T12:59:00.000-04:00

This was last weekend's project. This is my "Binary Box" prototype designed mainly for educational use so kids can learn binary to hex conversion. The circuit consists of (5) on-off switches, a 7404 hex inverter, a TIL311 display, (5) LEDs and (5) 330 ohm resistors. (Power switch hasn't been soldered yet). This circuit runs on +5v. As illustrated, you can see that a lit LED indicates a binary 1 if the switch is turned on. Off represents a binary 0. Images show my son giving the unit its first test run -> 1111 = 15 = F. 1001 = 9

EPROM Programmer settings for Excel 28c16 chip

2009-03-23T21:39:00.001-04:00

How to set up the Top2004 EPROM Programmer

1. For Exel 28C16 chip -

from the Option menu, select "Type"
On the far right of the dialog box, select the "FLASH/EE" radio button
in the manufacture list, select "EXEL"
in the Type list on the right, select 28C16

2. Burning - after placing the chip in the programmer:
select the Option menu, then "Run"
set the "Delay(mS/byte)" to 5ms, otherwise you will get "Error!" message

When BURNING chips, make sure the timing is set to 5ms or slower, anything faster (e.g. the default 2ms is too fast for this chip).

Click on the "Program" button
Then Verify

EPROM Programmer

2009-03-22T15:08:00.002-04:00

This is an EPROM burner I designed sometime in 2006. It was a complete experiment and my first real project that actually did something useful. There are no debouncing components, but this thing can program an EPROM successfully. I verified the data burned by checking with a Top2000 EPROM programmer which I purchased later on. I have the schematic which I will upload shortly.

Powers up and a solid signal!

2009-02-04T00:21:00.000-05:00

And here is the top view. Note the RESET and HALT switches.

Coffee. You can sleep when you're dead.

2009-02-04T00:16:00.000-05:00

I stayed up all night in late December 2008 and soldered for a few hours. The data lines are yellow, address lines are green. Power lines are red. Ground lines are black (ok, a couple are blue). You are looking at the wiring of the CPU, ROM, 74LS138 Address Decoder, and the 7404 inverter. With programmed ROM, this computer should be able to run and step through a program. Also wired are a HALT momentary switch, and a RESET momentary switch.

MC6847 Video Character Generator

2009-02-04T00:01:00.000-05:00

This is the MC6847 character generator. If you look to the right side of the breadboard you can see the amps/transistors to generate the correct output signal (which I left on the breadboard for my own reference before soldering) The circuit frequency is generated with a 4 pin crystal oscillator, running at the industry standard 3.58 MHz frequency.
Below the breadboard is the soldered version of the amp/transistor signal generator. You can see the RCA jack that is plugged into a NTSC LCD monitor. That was the first time I have ever created my own soldered board, and it worked the first time! Sloppy, but it works! This circuit also works with a composite monitor -- in my case, an old Commodore 64 monitor.
This circuit will generate Black and White only, but I am planning on adding an MC1372 so color can be generated. Although I slightly modified the amp circuit by using 2N4400 amps instead of the 2N2222, the design is by Joseph Norman. Thanks Joseph!

Clock Frequency IN and OUT

2009-02-03T23:50:00.000-05:00

The bottom image shows the square wave generated by the 1.0 MHz crystal oscillator before reaching the CPU. The top image shows the signal that is coming out of the 6802 CPU (pin 37 "E").
The signal shows that the frequency coming from pin 37 will be one-fourth the frequency that is sent into the CPU.

6802 CPU with 2 pin crystal oscillator

2009-02-03T23:35:00.000-05:00

It is difficult to see the difference, but this is the breadboarded version using a 2 pin crystal instead of the 4 pin crystal oscillator. You can see the 2 capacitors next to the crystal.

6802 CPU with 4 pin crystal oscillator

2009-02-03T23:27:00.000-05:00

This is a Motorola MC6802 CPU with a 1.0 MHz Crystal Oscillator (4 pin). I wanted to compare the signals generated by the 4 pin (which includes the oscillator) vs the 2 pin crystal. The 4 pin was a bit smoother.

Soldering CPU to ROM data lines

2009-02-03T23:19:00.000-05:00

This was back sometime in December 2008, wiring up the data lines from the CPU to the ROM. Note the lines leading to a location on the board where more data lines can be added to the bus in the future (e.g. when RAM is added) -- instead of going directly from the CPU to the ROM chip.

CentOS 5 Dev Environment for PHP + MySQL

2009-01-13T00:03:00.000-05:00

Setting up the CentOS 5.2 - Development Environment

Operating System: CentOS 5
Develpment Language: PHP
Integrated Development Environment: Eclipse + Zend Debugger
Version Control: Subversion (Eclipse Plugin)
Database: MySQL

===================================
download CentOS 5 from VMWare Virtual Appliances.

Extract the zip file, and load in VMWare, then start the virtual machine.
Verify you can ping the outside world (e.g. open a terminal window, then ping yahoo.com).
If you cannot ping the outside world, then you will need to configure your network settings using
the network control panel.

==================================
Reset the JRE Java location, and create a symbolic link to point to the newer 1.6xxx version:

cd /usr/bin
rm java (removes the symbolic link which points to an older version of the JRE)
ln -s /usr/java/jre1.6.0_11/bin/java java

===================================
Install PHP:

- open a terminal window
- yum install php

===================================
Install PHP IDE (Eclipse + Debugger)

Download the All-in-One Eclipse PDT + Zend Debugger Package from:

http://www.zend.com/en/community/pdt

(or google "eclipse zend debugger" to find this package)

After the file download completes, copy the pdt-xxxx.tar.gz file to
a location where you want to install it:
e.g. /opt or /usr/local

then copy the file to that location:
cp ~/Desktop/pdt-xxx.tar.gz ./

unzip the file:
gunzip pdt-xxx.tar.gz

extract the tar file:
tar -xvf pdt-xxx.tar

Check that the installation was successful:
cd eclipse
./eclipse &

The above should launch Eclipse IDE.

===================================
INstall the Zend Debugger Plug-in using the Software Updates area
in Eclipse:

From the Eclipse | Help menu select Software Updates...
Click on the Available Software tab and expand the "http://downloads.zend.com/pdt" leaf.
Select (check) the "Zend Debugger Features" checkbox, then click "Install..."

You will be prompted to restart Eclipse (which it will automatically)

Verify Zend Debugger was installed by going back to:

Help > Software Updates ...
Scroll down the list and you should see "Zend Debugger Feature" at the bottom of the list.

===================================
Install SVN (Subversion - source code version control system)

todo: ...

===================================
Install MySQL

todo: ...

CentOS 5.2 How to install PGAdmin PGAdmin3

2009-01-12T02:06:00.000-05:00

Trouble installing PGAdmin3 using yum install pgadmin3 ?
(The error is related to Missing gtk libs)

Install pgdg-centos-8.3-4.noarch.rpm first.
Then run:

yum install pgadmin3

2009-01-12T01:37:00.000-05:00

Old School TIL311 hex display (with latch). Expensive buggers, if you can still find them.

First Post

2009-01-12T00:53:00.001-05:00

homebrew hardware hacking