Category: Electronics

FPGA arrived

Just arrived from China, a small cheap FPGA: Altera Cyclone-II (EP2C5T144).

The device itself is the least capable of all the Cyclone II FPGAs, but its seriously cheap at only $13. And its big enough to hold a basic CPU core. This is what it looks like (9V battery included for scale):

FPGA1

The USB Blaster has to be bought separately but only costs an additional $3. Unfortunatly the DC jack is for 5V, its unregulated unlike Arduinos. Bummer. And I dont have any 5V adapter with a 5.5mm plug so I have to make one myself.

Here are the specs for the board itself (and others of the same family, its the smallest one, EP2C5):

cyclone_specs

So now Im mostly ready to start designing and testing my own CPU. Ive already started some basic designing since a couple of nights back. Gaining some insights and making early design choices.

I still havent committed to wether the data bus should be 8-bit or 16-bit. Id like to make it 16-bit but that means a whole lot of wires (since its ultimately imagined as a breadboard design). Now that I think of it maybe I should make a first test design with address bus and data bus both being 8-bit.

Sorting integrated circuits

Today I received an order of compartmentalized plastic boxes for sorting things into. And so I sorted what I have so far. Some compartments are empty because the chips are still in my shopping cart at Digikey. And some are in the mail on the way here from China (Aliexpress).

Small compartments but can pack up to 20 chips into one if its just packed well. If thats not enough then the dividers can be removed to expand compartments sideways. The horizontal dividers are fixed. Vertical dividers on the compartment right at the lock mechanism is also fixed. But all in all, a cheap, neat, easy solution for sorting integrated circuits.

logics

Link to the Aliexpress item. Shipping took 19 days from China to Sweden by China post registered air mail.

BreadLED, again

My second attempt upped the neatness factor a little bit. I also changed the resistor to 2kΩ to dim the led a bit and maybe save a bit of power.

Top one is first attempt, bottom one is second attempt.

nr2_breadled1nr2_breadled2

Chinese chip connection…

“Psst. Hey dude. Over here…”

A chinese man in the shadows beckons me to come over. When I do, he opens his coat to show me the lining covered with little bags full of INTEGRATED LOGIC CIRCUITS.

The mans name is Ali. Ali Express. And while he claims his goods are the best, straight from the factory, it can sometimes be something entirely different. But, most of the time it gets the job done.

Ali has been my supplier for a while now. Sometimes his wares are scruffy but it’s usually not an outright disappointment.

Today he dropped another small bag at our secret drop box. It was filled with… well, see for yourself. Plastic cases or foam was not included ofcourse. Alis wares usually comes wrapped in horrible kitchen plastic foil. Cringeworthy stuff having near static sensitive devices. But hey, it’s cheap.

All of this for 11 dollars, 13 cents. Shipping included. But Ali made a mistake this time, I only ordered and paid for 2x ATTINY85s, but I received 5x.

My uncle also dropped by today and left a few (three) PIC16C84-04/P chips as well. So now I’m all set up with MCUs for a while. No more excuses, it’s time to get around to doing something useful…

chipgood1

Breadboard prepped LED´s

Always with the breadboard tinkering you want to throw in an LED here and there to give visual cues about whats happening but always there is that pesky need for a current limiting resistor.

Well, here is my take on a solution for that “problem”.

First you cut one leg off the LED, solder the appropriate resistor on there, then solder the two legs onto a header pin pair; thus…

ledresist

And then, to add stability and to prevent the legs from being shorted together, enter the hot snot magic dispenser…

ledsnotted

Ofcourse this doesnt look very neat, which is why the final step is to squeeze on some heatshrink tube…

ledtubed

Ideally a speck of paint should be applied on one of the header pins to highlight the polarity of the LED but I dont have paint laying around right now, so its good enough for now.

And please dont complain about how ugly the soldering and snotting is. Im doing the best I can with only one functional hand (yes Im disabled). If you like the idea it’d be cool to hear and see if you made your own.

Optimizing the LedControl library

vlcsnap-2017-02-05-23h54m51s351.png

After hooking up eight LED matrices in series, I could see that the LedControl library wasnt up to the task. After digging through the source code I realized what a peice of junk it was.

I had to do better myself. And did. I even ended up writing my new routine in assembler. Better optimized than even the code gcc managed to produce.

Source code in the form of an Atmel Studio project,
is available here: http://joonicks.eu/arduino/LedControl.zip

 

Current limiting circuit YouTube

snapshot

Finally got around to making a demonstration video of my current limiting and short circuit protection circuit.

Using a LED as a dummy load might not have been the best idea but at least it visualizes the concept in a simple way.

The circuit is intended as an extra protection layer between a power supply and the circuit that uses it. Instead of blowing fuses or magic smoke in case of overcurrent or short circuit, this concept circuit could be tuned to protect the power supply quite well and cheaply.

Though in case of bigger normal loads, the transistor cant be a flimsy BC547. With any luck it might manage a few hundred mA but at 500 mA it’d probably burn up pretty quick.