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How to calibrate touch screen display on STM32 board

Touch screen displays are a common choice in many microcontroller projects. Touch capability won’t take additional space – it sits on top of LCD to directly interact with objects you see on screen. To get this working, touch screen coordinates must match screen coordinates. So could be sure when you touch the point on screen you point where you want. The touch screen is an analog device. It is made of two flexible resistive sheets with a gap between them. When the screen is touched, a connection between sheets is made, and thus a measurement of voltage drop is taken. Normally resistive touch screen has a four-wire configuration. And normally, a specialized IC is used to take measurements and send data to MCU for processing. In our case, we are dealing with the ADS7843 touch screen controller, but in other systems, this works the pretty the same way. The fact is that the touch screen controller reads screen ADC values and passes them via the SPI interface. So all you get is raw ADC readings that are not lined up with LCD coordinates. As you know, LCD screens can be of different resolutions, different orientations, so data gathered from resistive…

What microcontroller development boards I have

During this time, I’ve been purchasing or building various microcontroller boards. Most of them were used to try things out or because they were cheap to get. So I thought, why not blow dust away and see what we have here. Maybe there will be some fresh thoughts on where to use them. Probably I should spare a few words about each of them.

Facts about Raspberry Pi that make it popular

Is there anyone who didn’t hear about Raspberry Pi? It’s like the second thing after Arduino. And this is the result of the right idea at the right time. Many Linux boards around that don’t cost a fortune, but they didn’t make it to the masses. And mainly, they were used by advanced users who know Linux well enough. Raspberry Pi pros Raspberry Pi changed things pretty drastically. And there are several key factors why:

Basic touch screen routines up and running

STM32103ZET6 prototyping board comes with LCD having touch screen capability. It is a great way to interact with the device. Practically speaking Touch screen is a resistive film that can be accessed as a regular potentiometer which value depends on the touchpoint. Depending on voltage drop, it is possible to calculate the coordinates. There is a touch screen controller that takes most of the hard work – it has an internal ADC that measures the voltage and sends a value to the microcontroller using one of the selected interfaces (I2C or SPI). There is a typical ADS7843 controller used in the board, which talks to the microcontroller using SPI. After playing around, I’ve put a messy code that reads touch screen coordinates. It is a glued code from various sources, so it is only to fix some results. Currently, the code reads many values, then averages to get rid of most garbage, and then calculates screen matching coordinates. This is the trickiest part to do. You can do this empirically by reading min and max ADC values for each axis and then calculate coordinates using formulas:

Online signature healthcare

Who wants to spend their precious time? Everyone wants fast and efficient services from public services, especially in health and insurance areas. Instead of wasting your time in a long queue, you should use an electronic signature in healthcare. Yes, it is a fact that you do not have time to go to the hospital or insurance office to sign the documents. Therefore, do not be left behind. You will find and enjoy the benefits of having such a beneficial item. Besides saving your time and cutting the useless formal procedures, you also start the greener process—no need to print the papers anymore if you have online signature healthcare.

Reading serial data from chipKIT UNO32 using Python3 and pyserial

Python is great programming (scripting) language that is supported on all platforms. Embedded enthusiasts love it because of the variety of modules that connect things to the internet and other crazy stuff by writing only a few code lines. Today my interest was to read serial data using Python 3.3 and the pyserial module. Python 3.3 is still fresh, and there is a majority of modules that need to be ported from Python 2 to Python 3, but I hope soon they will here. The serial module seems to be working fine in Windows 7 x64, and I decided to share my experience. First of all download and install Python 3 (current release is Python 3.3) Just be sure to include “Add python.exe to Path” so you could run Python anywhere on your computer. We won’t go into details on how to set up this tool. It is pretty robust. After setup, python install is placed in C:\Python33. To test if things work OK open the command prompt and type python; you should see the python prompt:

Way of playing AVI files on iPad

AVI (Audio-Video Interleaved) video format is a standard format around the internet. Windows introduced this format in 1992. AVI files carry audio and video data that are played synchronously. Audio and video can be compressed with different codecs and stored in a single .avi file. That can be played with Windows played or another player with the right codecs. If you are MAC used and carry the iPad around, you probably noticed a problem with playing AVI files on these devices. Apple is stuck to MP4 format, which actually is more advanced because it can carry more information than audio and video. 3D graphics, subtitles, and still images also can be packed along in a single file. All benefits and disadvantages you may find on the internet. The user may find a problem playing one or another format on his machine. As we mentioned, without unique apps, there can be a problem playing .avi files on the iPad. Instead of struggling to find one good AVI player probably, it is worth converting them to mp4. There are many video converters available to download. For instance, Aimersoft.com produces an excellent free video converter called Video Converter Ultimate. It supports all standard…

Updating STM32 C template with CMSIS V3

So far, we’ve been using an old template with CMSIS version 1.30. Since then, it was updated several times by adding new Cortex processor families, fixing several bugs, and adding new features. They also changed the folder structure of CMSIS to be more generic. And there is a CMSIS DSP library integrated. With it, you can do complex math tasks using only a few lines of code. So why not upgrading our software template for Sourcery Codebench G++ toolchain with new CMSIS. First of all, download the latest CMSIS package from arm.com/cmsis. You will have to register to access download files—package with CMSIS, DSP library, and documentation weights about 45MB. Since we are working with ST32 microcontrollers, you also need to download STM32F10x Standard Peripheral Library from STMicroelectronics.

Using SVN for embedded projects. Part 1.

Writing software is a complex task. In every microcontroller program, you usually try to reuse previously registered libraries, downloaded code, and other data that is being updated. What if you are developing something in the team? How do you keep track of everything? Storing project files in directories eventually gets messy – finally, you lose track of what’s done. For instance, sometimes, you have written an LCD library and used it in several microcontroller projects. But eventually, you found a bug or optimized code. Usually, you would have to copy new library files in every project to keep updated. This is hard when you already have dozens of projects. There is one way to stay organized by using version control software. In this case, we will talk about SVN. Subversion (SVN) is an open-source system that allows controlling files and folders, keep track of changes made during the time. Simply speaking, SVN is a virtual file system that keeps track of every change in files, and directories. It’s a clever way of storing project files whether you are working alone or in a team. Using this system-wise, you will always have things organized and never lose the version of your…