Posts Tagged ‘embedded’

Mxgui

September 22, 2011

Ok, here’s the new library for Miosix: Mxgui. As the name suggests, it’a a GUI library for microcontrollers, designed to work with the Miosix kernel.

Source code is here, while documentation here.

What can it be used for? 3D rendering on a microcontroller, for example.

Mxgui examples from fede.tft on Vimeo.

Miosix 1.54 released

October 3, 2010

After a lot of time spent coding, here’s the new release of Miosix, my OS kernel for microcontrollers.

New features include:

  • Porting for ST’s Cortex M3 microcontrollers
  • Preliminary implementation of the POSIX thread API (pthreads)
  • Improved statistics on memory usage and debugging messages
  • Bug fixes and other enhancements

If you’re interested, download the new release here: http://www.webalice.it/fede.tft/miosix/index.html

Digital voltmeter for power supply

October 2, 2010

This summer I finally found some time to fix my power supply.

It’s a rather old but relieable unit, and I have no intention of replacing it. Basically, it still works except for the voltage meter on the front panel. Over time, the pointer developed an offset of around 1V, which is visible in this image where the power supply is turned off. Instead of indicating exactly zero volt, the pointer is below the beginning of the scale.

This, together with the fact that today’s microcontroller require 3.3V to operate (while the voltmeter only has an 1V resolution), forced me to always use a multimeter when using it, to be able to precisely set the output voltage.

The solution I found was to simply replace the analog voltmeter with a digital one. Instead of using a voltmeter chip like the ICL7107 that usually require the measurement ground to be separated from the supply ground, these days it is easier to build a voltmeter using a microcontroller.

That’s because even the cheap and simple micros now have at least a 10 bit ADC which is more than enough for a voltage meter in the rage 3..15V (which is the range of my power supply). Since the task is easy there was no need to use an ARM microcontroller as I usually do, but instead an ATtiny26 proved more than enough, despite only having 2KBytes of FLASH and 128Bytes of RAM.

This is the result:

The circiut is simple, a 78L05 is used to reduce the 20V found in the power supply to 5V to power the microcontroller. A voltage divider made with 1% precision resistors is connected from the power supply input to an ADC capable GPIO on the microcontroller, and three LED displays show the voltage with 0.1V resolution.

The LED displays are ofcourse multiplexed so that the ATtiny, despite its low number of GPIOs, can drive the display with no other glue logic except for current limiting resistors.

Around 100 lines of C++ code keep the whole thing working.

STM32 GPIOs and Template Metaprogramming

December 23, 2009

I posted a new article on my website.

It talks about a performance optimized and high level way of handling STM32 GPIOs using Template Metaprogramming.

OLED displays are getting better every day

October 18, 2009

OLED is a display technology that attracted me from the beginning.

The advantages are:

  • Wider viewing angle (near 180 degrees)
  • Lower response time (order of microseconds, not milliseconds like LCDs)
  • Better contrast compared with LCDs
  • Power consumption depends on the actual number of pixels lit, so it can be lower than LCDs
  • Piexls directly emit light, no need of a backlight
  • Can be made flexible

I used OLED displays in two of my projects, the multi function watch, which uses a 96×64 pixel monochrome yellow OLED, and the Miosix player, with a 128×128 pixel 262K color OLED, and can confirm the advantages of this technology.

However, the reason of this blog post is this video I found on youtube:http://www.youtube.com/watch?v=f8S8tbQMp2k. It looks like another advance in OLED technology. Other than being flexible, it has another advantage: it is much more resistant than an LCD. I hope it will be mass produced soon :)

Using C++ on microcontrollers code size tricks

October 11, 2009

I posted a new article on my website.

It talks about some tecniques to minimize the code size when using GCC and C++ with microcontrollers. It also includes a fully functional template project for an LPC2138 microcontroller.

FPGA!

September 27, 2009

This is a quick post, more information will follow later. I’m entering the world of reconfigurable hardware :D

Here’s an image of the FPGA board I’ve designed:

fpga

It has an xc3s200 spartan 3 FPGA. It’s not one of the newest nor one of the biggest FPGAs around, but you can synthesize a Microblaze 32bit CPU in it and still have room for other logic.

And there are more good news: Xilinx provides a version of their IDE for Linux, and I even managed to program the FPGA using my JTAG cable and urJTAG.  Here’s an image of urJTAG correctly recognizing the two chips in the JTAG chain:

fpga_screenshot

Until now I’ve only written two simple VHDL programs, one that does an and gate, which is probably the equivalent of the “Hello world” for an FPGA, and one that divides the 50MHz clock on the board by 2^26, and uses the resulting ~1Hz frequency to blink a led. Both work as expected on the FPGA board.

So many interesting things to do, and so little time to do them… it’s 27 September and on 30 September I’ll have to go back to university… This year I had to write my thesis, and that resulted in no spare time during summer… :(

Miosix kernel released

September 23, 2009

After one year of development in the spare time, I released the Miosix kernel under an open source license.

I published the kernel source code, the schematic of the Miosix board, the doxygen documentation, instructions for compiling the kernel, and my thesis.

Read about it here: http://www.webalice.it/fede.tft/miosix/index.html.


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