Monday 31 January 2011

Evalbot I2C & Nunchuk lib

After few long evenings I created I2C library for Evalbot from Texas Instruments. I wanted use I2C module which can be connected to J0 and PJ1 pins which are perfectly accessible but I had no luck with initialization of them.

So the second try was about using another I2C module connected to pins PB2 and PB3. These pins are also on expansion connector but I don't have the other side of the connector so I soldered near the pull-up resistors and the audio codec.

Short tutorial, pictures and libraries are on the homepage

Sunday 30 January 2011

ARM Webradio

Internet radios are great. There are so many stations, some are even without commercials and speaking.. just music. I was playing with idea to create webradio because there's not much devices of this kind on the market. My approach is different and I'm trying to implement software based Helix MP3 decoder... but with no luck so far..

Fortunately there are more skilled people than me and created perfect designs... What I don't like is that you have to use VS1053 decoder chip because ARM CortexM3 running even @ 30MHz is powerful enough to do software decoding. I hope that sooner someone do the design without external hardware decoder.

ARM webradio project @ Google Code

Small USB AVR programmer using USBasp

A year ago I created a new layout for USBasp programmer because I wanted really small sized device. I have changed pakage of some resistors and capacitors to SMD, so the parts could stick better together and use smaller area on PCB. I don't know how but  I was lucky to fit it all inside small Tic-Tac mint box.

The whole project and files are here

Slot car finally completed ... somehow

Tonight I was fighting with prepared board from Freescale for slot car competition (Freescale Race Challenge). This year is the car smaller, but board remains the same, so I had to use some force and hot glue gun to put all in the place :) After some hardware issues I was able to flash the sample application over USB mass storage bootloader.

Now I have to learn all about Coldfire MCF51JM128RM because I'm not familiar with them. Also I have to play with accelerometer, it's sensitivity and filter algorithms.

I'm planning some hardware modifications, optical encoders...

Saturday 29 January 2011

Evalbot I2CS1

Finally I have some time to play with Evalbot. But now I'm having difficulties with I2C. For the easier acces you can map the I2CS1 (the second one I2C module) to PJ0 and PJ1 pins. They are accesibley with standard breadboard-like pich, much easier than solder wires to small resisotors near Audio chip if you don't have the small connector for expansion board... When I do some progress, I'll make a post about it.

Friday 28 January 2011

Freescale Race Challenge

I'm attending the Freescale Race Challenge this year. The goal is to create an autonomic driven slot car. You can use your hardware inside the car or use the PCB from Freescale and tune it to your needs. It contains Coldfire MCU, microSD card slot, driver for motor and accelerometer. This platform is new to me. But I would like to play with their architecture.

I add some sensors and buttons to the design and start developing. The school contest round is in March so there's not much time.

Here I found some english text about this contest.

Tuesday 25 January 2011

Simple hello world by LED for LM3S9B92 and LM3S6965

You can download sample project for this chips and/or development boards. Makefile is for Codesourcery G++ compiler. The sample is using Systick interrupt.

LuminaryMicro Evalbot kit arrived!

I was surprised, when this package arrived. I didn't expected what it could be. When I opened it I was really happy. This Evalbot cost me only $25 instead of full price $150 :) So it took 3 months from order to delivery. I'll take a look on the kit later because of exams in school.

I already have one kit from LuminaryMicro - LM3S6965. But not on wheels :) This new kit has also USB on-the-go support  and small I2S audio codec. I was developing a MP3 internet radio player with older kit, but now it looks like all I need to do is wait until someone do MP3 player for me on this new kit :)

In few days I'll post how to configure arm-none-eabi compiler for this Evalbot and older LM3s6965 kit. I was using IAR compiler but I think that opensource GCC is better for opensource projects.

Monday 24 January 2011

Simple DC/DC step-down module

Today I designed and made step-down converter with pins like the 78xx stabilizers have. So it's perfect for breadboard design or replacement for 78xx stabilizer. Unfortunatelly it's using small SMD inductor so it cannot give you more than about 350mA. But it can handle the input voltage to 40V and don't get too hot like linear stabilizers. So no need for cooling :) You can use online calculator to change output voltage or change values of parts so you can get higher current.

Go to the article 

Saturday 22 January 2011

MOS 6502

If you want to know more about this special processor that powers event bender, look at video below. Michael Steil had a very interesting presentation about it. He's quite fast in the begining of presentation but he explained everything from complete basics to mechanical reverse engeneering of the chip.

Bunch of electronic parts

I finally have what I ordered :) Connectors and a lot of SMD parts. Some for my thesis or another projects. I've ordered some capacitors in SMD 0603. They are so small that my tweezers almost cannot pick them :)

There's image from wikipedia for comparison.

I also ordered 3pin conectors with a key on them so it's not possible to connect the plug incorrectly. I was always nightmare to figure out in what direction I have to insert digital thermometer DS18B20 because if you do it wrong, you destroy it :) I hope in brighter tommorrows without that old pinheads.

Friday 21 January 2011

Cool minicomputer

I've found an interesting czech project. Ok it's another wrist-watch like computer :) But this one has bluetooth connectivity and runs almost completely on Lua scripting language. On the video it seems quite fast but there's not any information about hardware. That's sad. The sourcecode is opened but the hardware looks like "closed-source".. maybe later..

Hackerspaces around

It's a bit late, but finally there are some new hackerspaces in my country. One hackerspace BrmLab in Prague is a bit further than I need. Fortunatelly someone is preparing hackerspace in Brno, so I'm excited when they find a place to meet. It's not far from Zlín since we have a new highway :) Complete list of hackerspaces is on official site.

Thursday 20 January 2011

Step-down DC/DC converter: Say goodbye to 78xx linear stabilizers

 For last couple of months I've been playing with DC/DC converters. Mainly step-down converters. I really like them. I had a linear stabilizer in my circuit and the device's consumption was 1,2W. When I changed my design to use DC/DC step-down converter - the consumption was 400mW - 3 times lower! I'm actually designing small modules with usual MC34063 chips. In standard PDIP version and SMD. I've ordered them very cheaply on eBay from China instead of expensive order here in Czech Republic :)
Dave Jones on his videoblog have very nice lessons on how to start with DC/DC converters. Maybe it's time to give a peace and cool place for that old and heating 78xx linear stabilizers, what do you think? :)

Wednesday 19 January 2011

Free book of Digital signal processing

For anone interested in DSP there's a free online book. I'm still waiting for the right moment (or free time) to start read it. The book is online but you can download each chapter in PDF.

Chip and pin security on bank cards is broken

I like a lot attempts to hack consumer devices. This bank card trick is something more than that but still very interesting. Student from Oxford created a device that stands between real bank card and paying terminal. With this device you simply don't have to enter pin. Just write something like four zeros and the transaction will work..

Omar's thesis and info is on his site.

Also there's a video from congress about this topic.

Let's start here

Hi everyone. Last days I was thinking that it would be nice if I can tell something valuable to other people. People that are interested too in electronics, programming, microcontrollers, opensource software etc..

We'll see how far this will go :)