Saturday, July 27, 2013

Pre-Blog Projects Revisted pt. 1

I was digging through old photos on my ImageShack profile and decided to talk about them. There is no particular order, but each has a story to go along with it.

Shown below is from when I was working with the z80 (as if I ever stopped). I pulled this z80 from a dead Sega Genesis and built it onto a breadboard to test the functionality. It turns out whatever was wrong with the Genesis was not the z80. The testing circuit was simpl; executing NOPs (no Operations) by connecting all Data pins to ground via a pull resistor. This caused the Address pins to run from $0000 to $FFFF bit by bit and since each Address pin was connected to an LED, the LEDs would light up (very quickly mind you) as a binary counter. The only LEDs I couls see flashing were the high erbits becuase the lower bits were mush too fast.

Also shown is a memory chip which remained unattached, an AY-3-8910A Programmable Sound Generator IC, a CTS256A-AL2 Text-To-Speech Controller IC which has gone unused because I do not have the SPO256-AL2 companion voice synth IC. And lastly, in the bottom corner is just a simple xtal running through NAND gates to clean up the signal.



Here is one of my favorite projects! This was a simple Atmega microcontroller based logic Analyzer which I redesigned around very strict limitations. Original credit to:
http://www.serasidis.gr/circuits/mini_logic_analyzer/miniLogicAnalyzer.htm
The limitations were that I wanted it to fit inside of a nintendo gameboy, run on 4x AA batteries like the gameboy and use the battery contacts, battery compartment, power switch and screen location from the gameboy itself.

First came the board. The gameboy has a rather small square mainboard which has several specific mounting holes. All measurements were done very crudely with a clear mm ruler...I sure wish I had a digital caliper. Luckily, everything fit (the second time). The board shown is the board that I printed myself with the transfer method as it is called. you may print your circuit onto a clear coated paper (I use magazine pages) and then iron the image onto a copper clad board, clean and immerse into an etchant solution. Maybe I will write up a tutorial at some point, but it is pretty straight forward. Since this was not my first board to have etched myself, it turned out wonderfully. Some boards...did not. But alas; I am persevering!Notice my old logo etched on the right. ;)

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Here is the same board after being populated by hand and placed into the gameboy. "BA-DING" ... just kidding. At least the LED shows power is applied. The microcontroller is on the underside since I designed it to fit into a socket. Another restriction that I just remembered was that I wanted to use the gameboy's buttons to navigate through the program. The bottom of the board is suppose to hold ordinary push buttons, but I did not fit them so that I could wire up the GB's.

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LOOK IT WOR......thanks China for the crappy LCD screen. >_>
Yes, the text is indeed upside-down, but at least I managed to get it working. This happens to be the second problem with this particular LCD. The first was that it runs on 5v, not 3.3 like the datasheet stated. Also, the control pins were all sorts of switched around. With a little retrcing of my board design, I had that sorted out as well. My favorite problem (sarcasm) was that the LED backlight happened to be high-enabled rather than low...so if I had not caught that as soon as I did, they probably would have been damaged.

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Add the case and logic probes (minus one)...and...Ta-da! A working logic Analyzer!

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The above mishap from China isn't true for all electronics though. The USB ISCP below works very well. The only problem is that the ZIF socket is hardly ever used. It is used for a few Serial programmable microcontrollers and eproms. The only eproms I use are parallel programmable for which I use a different programmer.

On either side of the programmer are my sockets to program the microcontrollers (written on the sides of the boards). YES, I realize that having these boards entirely kills the 'S' in ISCP, but few of my designs fit an ISCP connector...

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Here is a smaller project: two guitar pedal boards. These board were suppose to use the PT2399 IC to create a variable echo effect, but I never found all of the needed components so the board were stores away in one of my many crap-boxes.

Each board controls an analog mono audio signal and connectos two potentiometers for control. on the right of the board is where a 7805 voltage regulator would fit and at the center is where the chip would have been socketed. Again, I degin all of my boards using Eagle CAD and then print them onto a PDF so that the vectorized image remains thew highest quality and static size.

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This is a print of a gameboy cartidge programmer designed my Reiner Zeigler to be used with modified cartridges or other commercial carts. It allows for you to read and write not only ROMs, but also RAM data if present. This board is the reason why I built the Atmega 8515 programmer above.

Reiner designed two version of the board; one for USB and one for Serial. I tried my hand at the USB because at the time, I didn't have a serial connector on the desktop I built...as is one of the few disappointing facts about new computers.

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lastly is the board after etching. It turned out terribly! This was the first board I had ever etched so I can't really complain. It was a learning experience and nothing more. Since nearly all of the data and addressing pins bled together, the board was tossed and I tried again later on after redesigning the board to accommodate my barbaric etching methods. I think the problem was that I didn't iron it long enough and with enough pressure. Some of the plastic ink peeled off or bled together.

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