7400 Competition Reminder: Entry deadline is October 31st

Just a reminder to all potential entries that the deadline is October 31st. You now have only 2 weeks to submit your entry. Good luck!

Build something that uses or abuses a logic chip and get amazing boards, tools, and other swag. The Open 7400 Logic Competition promotes awareness of the basic building blocks of modern circuits. Devious geeks ignited the computer revolution with discrete logic computers, what can you do? Details and entry form here.

uJ – a Java VM for microcontrollers


Dmitry Grinberg wanted to design a way to program MCUs that would be easy for beginners who don’t necessarily understand details of C such as pointers and memory management, yet don’t want to rely on common alternatives such as Arduino or PICAXE. He developed uJ: a Java VM for microcontrollers. “It implements the entirety of the Java bytecode and is written entirely in C, so that it may run on any processor. It has been tested and found functional on 8-bit AVR devices (ATmega64, Atmega128), some Microchip 16-bit PIC devices (dsPIC33FJ128GP802, dsPIC33FJ64GP802, PIC24FJ32GA002), and a few other architectures. It is quite efficient, fast, and usable for actual real-life situations. Minimum requirements? A few dozen K of code space and a few hundred bytes of RAM is all you need to get started.”

For more documentation, another demo video and to download the code visit Dmitry’s website.

Via the contact form.

Workshop Update for October 17th, 2012

Wish we had some exciting news, but today we’re just jugging wholesale, emails, and whatnot.

We did get a chance to update the Soldering Iron Driver documentation for an upcoming start of PCB sales at Seeed for $7. In that respect, we also started a 3D model of the same (pictured above).

We’re also working on a thousandth iteration of the 1.8” TFT breakout board. We got all flavors at this point – USB backpack, bare bones breakout board, breakout with voltage level translation, breakout with a PIC used for emulating HD44780 LCDs, etc…

Open 7400 prize: RaspberryPI from HubCityLabs

HubCityLabs hackerspace from Moncton,Canada is the latest sponsor of the Open 7400 Competition. Up for grabs is a Raspberry PI for a Canadian entry. This and other prizes could be yours, but only if you get your entry in soon!

Thank you to HubCityLabs for sponsoring the 2012 Open 7400 Logic Competition!

7400 competition entry: Data encryption and decryption system using 74xx logic gates

Nakul built a 7400 based data encryption and decryption device. It works on the cellular automaton algorithm:

Encryption and decryption plays a vital role in today’s digital world. So we thought of implementing an encrypting and decrypting device using only 74xx logic chips. The encryption algorithm is based on cellular automaton. Rule 30 of the cellular automaton produces can be used as a random number generator. A cellular automaton is basically an array containing 1s and 0s whose next value depends on the previous value of the array based on a particular rule.

Build something that uses or abuses a logic chip and get amazing boards, tools, and other swag. The Open 7400 Logic Competition promotes awareness of the basic building blocks of modern circuits. Devious geeks ignited the computer revolution with discrete logic computers, what can you do? Details and entry form here.

Via the contact form.

Nokia LCD Backpack free PCB build

Gege2b built a Nokia LCD Backpack free PCB. This board controls common Nokia LCDs like those sold by SparkFun via USB. It was intended to be produced, but problems with LCD supply shot it down. You can still get the populated board from Seeed for $9.50, but it doesn’t include the LCD.

If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.

HOW-TO: Access Bus Pirate v4 on-board I2C EEPROM


Bus Pirate v4 has an on-board 24xx64 8Kbyte data storage chip called an  EEPROM (IC3). It can be used to store various settings and preferences, but cooler, the EEPROM’s I2C interface can be accessed from within the Bus Pirate’s I2C mode. First time users can get familiar with the Bus Pirate without any added components!

Two 2K pull-up resistors (R8, R9) are connected to the I2C lines. The chip is powered at 3.3volts and gets a 0.1uF decoupling capacitor (C6) on the power supply pin.

24AA- series I2C EEPROM from Microchip come in a ton of sizes. AA parts work from 1.8volts to 5.5volts, while the 24LC- parts have a 2.5volt minimum requirement.

If you are a first time BP user please read Bus Pirate 101 tutorial first. Get familiar with I2C terminal commands from  I2C. Continue reading below on how to interface with the on board EEPROM.

Continue reading “HOW-TO: Access Bus Pirate v4 on-board I2C EEPROM”

GUINO Arduino GUI visualizer/debugger


madshobye devised this graphical debugging console for Arduino while serving as an artist in residence at Instructables. He wanted a graphical means of visualizing what was occurring in an Arduino program. “It can be a tricky task to debug and visualize realtime data on the Arduino board. You are usually stuck with the standard serial output, as the complexity of your Arduino code grows this makes it impossible to comprehend what is actually going on inside the board. To solve this I have created a little library that will enable you to create your own custom GUI for your Arduino projects.”

Visit this Instructables page for more details, video of the program in action, and downloads.

7400 Competition Reminder: Entry deadline is October 31st

Just a reminder to all potential entries that the deadline is October 31st. You now have only 2 weeks to submit your entry. Good luck!

Build something that uses or abuses a logic chip and get amazing boards, tools, and other swag. The Open 7400 Logic Competition promotes awareness of the basic building blocks of modern circuits. Devious geeks ignited the computer revolution with discrete logic computers, what can you do? Details and entry form here.

Workshop Update for October 16th, 2012

Bought new batteries for the camera. Lots of India planning and correspondence – please confirm if you are joining. Talked with DP friend Tully (from Shenzhen Geek Tour video) about our upcoming trip to Shenzhen.

We are designing a few more variations of a TFT breakout board, some with only 5v-3.3v level translators, some with microcontrollers on-board to handle the graphics.

7400 competition entry: 4-bit SAR analog to digital converter

Marco entered a 4-bit SAR ADC made from discrete logic chips 74xx & 40xx series for the Open 7400 Logic Competition.

The SAR (Successive approximations) works by comparing the analog value to be converted with a generated value with a method similar to the mathematical bisection method. More precisely, it starts comparing, by a simple difference, the input value with Vref/2 (it divides the full range Vref in two halves); if the result is > 0 the N-bit (called MSB) = 1, i.e. the input value is greater than Vref/2, otherwise N-bit = 0. Now it divides the “new range”, upper or lower half of Vref, in two halves by setting the (N-1)-bit = 1, keeping the previous N-bit, and it compares this value with the input voltage. If the result > 0 then (N-1)-bit = 1, otherwise (N-1)-bit = 0. It then goes on with the (N-2)-bit and so forth to the LSB. The conversion time is, at best, Tck*N. The generated value for the comparison is digital, so a DAC is needed to do the comparison with the analog input value.

Check out the video below.

Continue reading “7400 competition entry: 4-bit SAR analog to digital converter”

Crayola ColorStudio HD Pen hack

Hack a Crayola ColorStudio HD Pen and load it up with your own Arduino sketch. The pen uses a PIC microcontroller to pulse a reed relay which is picked up by the capacitive screen on the tablet. An app on tablet decodes the pulses, and changes the color of the paint brush.

Rob pried it open and replaced the PIC12F505 microcontroller with a ATtiny 44 pin compatible chip. He loaded it up with an Arduino sketch and got it to emulate the original device, as can be seen in the video above.

Having already made some custom PCB that use capacitive communication I immediately recognized the familiar sound of a reed relay being turned on and off when using the pen. Knowing that the device contains a relay it becomes clear how the app works, by pulsing this electromechanical component at a constant frequency this is detected by the tablet as a series of touches and distinguished from a standard finger touch. Having used the same technique in my boards I was able to reprogram the pen to be able to transmit data as is shown in the video.

Via Hacked Gadgets.

Eagle Parts: 74XX245 buffer footprint, because Murphy always strikes twice

This part from our Eagle library is a favorite. We use the 74xx245 buffer as a 5v to 3.3V level translator in many of our projects. Many of those projects went through a few revisions, ’cause we keep getting the directional control pin wrong.

Eventually we branded a legend for the “DIR” pin directly on the schematic symbol. It’s gonna smack your face if you even think about connecting it the wrong way!

Got cool schematic symbols you’d like to share? Leave a link, or talk about them in the comments.

#FreePCB via Twitter to 2 random RTs

Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters.

Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

Stellaris Launchpad hack adds LiPo capability


Philipp Stenkamp wanted to power his Stellaris Launchpad with a spare LiPo battery, but found as shipped this wasn’t a plug-and-play operation. “The Launchpad expects 4.75-5.25 VDC on VBUS, nothing that a single cell LiPo could provide. I know that the system voltage is 3.3 VDC and that the voltage regulator on the board has a very low dropout voltage, so powering the Launchpad with anything between 3.4-5.25 VDC should work well. The voltage of a single-cell LiPo ranges between 3.0-4.2 VDC, so let’s populate this header and plug a fully charged LiPo in it! Being a practical guy, I did just that. Guess what, nothing happened!” With a little research he discovered the way to making the Launchpad LiPo friendly was as simple as cutting a trace.

Visit Philipp’s webpage for project background and details on the risks and benefits of this hack.

Eridani Cortex M3 development board is on sale

Brian decided to close shop on the Cotex M3 development boards. His brainchild, the Eridani, is based on TI’s Stellaris LM3S3651 and features USB OTG functionality. He has stopped sales, and would like to sell off or trade leftover boards that need some rework.

I have a hand full of Eridani’s that need rework. I don’t however have the time to do the rework, basically if you have the ability to desolder a LQFP64 and resolder it you should have no issue making them work. You’ll also need an ARM JTAG (Bus Pirate should work with openOCD).

If you want a board PM me with an offer. It can be money or a cool project. US is strongly preferred both for cost of postage and also the customs form overhead.

Via the forum.

Raspberry Pi model B gets double the RAM

R-Pi’s 256MB just doesn’t cut it for your Java application? The Raspberry Pi foundation let us know that all outstanding Model B orders will be getting double the memory.

With this in mind, we’re pleased to announce that from today all Model B Raspberry Pis will ship with 512MB of RAM as standard. If you have an outstanding order with either distributor, you will receive the upgraded device in place of the 256MB version you ordered. Units should start arriving in customers’ hands today, and we will be making a firmware upgrade available in the next couple of days to enable access to the additional memory.