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Preview: olpa, OSS developer

olpa, OSS developer

advocating olpa's open source developments

Last Build Date: Sat, 30 Sep 2017 15:07:41 +0000


Cleaning the signal from EEG-SMT

Sat, 30 Sep 2017 15:07:41 +0000

An disappointment after getting EEG-SMT working: the resulting measurement is just a noice. It is a challenging task for a beginner to understand what is going wrong. Check software First I made sure that the signal isn’t modified somehow on the way. EEG-SMT uses the version P2 of the firmware for ModularEEG, which is available […]

Display signal from OpenEEG EEG-SMT

Sun, 10 Sep 2017 12:56:20 +0000

There is a number of software intended for EEG works. The EEG-SMT quick start guide suggests Electric Guru, BrainBay and OpenVibe, but it implies the use of a legacy operating system instead of Linux. This post extends the quick start to have Linux notes. The content: * Install OpenVIBE * Connect STM-EEG to Linux * […]

Affordable EEG and neurofeedback: OpenEEG, EEG-SMT

Sat, 09 Sep 2017 17:36:07 +0000

My old interest is to influece the brain to make it working more efficient. One of the approaches is to learn complete relaxation, or in other word meditation. The book “Meditation für Skeptiker” by Ulrich Ott suggests a scientific evidence for this claim, and I decided to try. I tried and failed. I wasn’t able […]

Format dvd+rw before writing data

Sun, 13 Aug 2017 14:28:08 +0000

Writing a DWD+RW under Linux should be simple, something like: $ wodim speed=2 dev=/dev/sr0 -v -data ubuntu-16.04.3-desktop-i386.iso However, in my case it fails. Some background knowledge suggests to format the disc first, but blanking the disc fails too. Solution is: format the disc with another utility: $ dvd+rw-format -blank /dev/sr0 After this step, writing does […]

AWS response status is always 200

Sat, 29 Jul 2017 09:36:46 +0000

There is a task, which can’t be avoided when developing serverless applicatoins on Amazon Web Services: How to return a custom status code from a REST API? One of the approaches is to use “prefix mapping”, like for example is shown in this amazon blog post: Error Handling Patterns in Amazon API Gateway and AWS […]

mocking microservices for functional tests

Sat, 04 Feb 2017 12:27:31 +0000

Here are a few links which helped me to understand what to use to mock microservices with REST API. Just for a case, I’ve choosen wiremock because I need Java and saboteur functionality. A summary on approaches for microservices testing: Working Locally with Microservices. TDD of Python microservices by Michał Bultrowicz at EuroPython 2016. Slides. […]

python Selenium in Ubuntu 16.04

Thu, 22 Dec 2016 09:03:41 +0000

Selenium is a web browser automation software. In Ubuntu 16.04 it doesn’t work out of the box, and external components should be installed. In this post I note how to install them locally without affecting the system. First, I create a virtual environment named selenium: $ mkdir ~/opt $ cd ~/opt $ virtualenv selenium $ […]

experience report with TDD

Thu, 03 Nov 2016 10:21:04 +0000

I’ve seriously tried TDD in a real project, writing tests before code and following the red-green-refactor cycle. Short summary: * I believe in TDD now; * training and practice are required to learn TDD, reading books is not enough; * the initial time investment is big. The promise of TDD is that the profit appears […]

how to move anything in rviz in ros

Wed, 26 Oct 2016 13:20:52 +0000

Rviz A 3d visualization environment for robots. Sounds intriguing and useful, but the first steps in it are painful. In particular, moving anything is surprisingly a very hard task for a novice who doesn’t know about the right way. Now I have enough experience to describe what to do: Moving things in rviz.

vi editing mode set global

Tue, 18 Oct 2016 05:19:02 +0000

The Linux command line and other software based on readline library support vi editing mode. After I worked on a new system with the default settings for a while, I noticed that I miss this mode very much. It took some time to remember how I setup it on the main system. Grepping files for […]

fast throw-away git repository

Mon, 22 Aug 2016 19:42:51 +0000

Based on the article How to Run Your Own Git Server, I’ve constructed a small list for fast git setup for temporary projects. Server: $ mkdir -p /the/server/repository/dir $ cd /the/server/repository/dir $ git init --bare Client: $ cd /my/project/directory $ git init # Note: without --bare $ git add, commit etc $ git push --set-upstream […]

DANTE e.V. Frühjahrstagung 2016

Wed, 20 Apr 2016 11:51:43 +0000

I was a speaker at the TeX users meeting in Wuppertal, with the talk “Erfahrung und Vorhersagen für automatisches XML-nach-PDF-Publizieren mit TeX” (experience and prediction for automatical from-XML-to-PDF publishing using TeX). For many years we hear the phrase “TeX can be used for XML publishing”. Unfortunately, due to a few technical problems this phrase is […]

python libxml2 dita

Thu, 21 Jan 2016 08:29:51 +0000

python libxml2 dita For correct transformation of DITA files (XML-standard for modular documentation), it is necessary to pull information from DTD (document type definition). In my python code, sometimes I did get this information and sometimes not. Now I’ve tracked the source of instability and corrected the code. Sample python code: import libxml2 import libxsltmod […]

Printing unusually sized PDFs

Mon, 21 Dec 2015 16:02:04 +0000

The PDF is of some non-standard landscape layout, the printer is an usual A4 printer, the software can’t handle the mix correctly. The solution is to tune the dimensions of the PDF pages manually. First, rotate to the portrain orientation: pdftk non-standard-landscape.pdf cat 2-85E output rotated.pdf I wanted only a few pages (from 2 to […]

le-tex transpect: how to use docbook-to-docx stylehseets

Thu, 10 Dec 2015 07:38:55 +0000

For XML to DocBook to .docx conversion, I found that “le-tex transpect” framework has solved many technical issues already, so I overcame the “not invented here syndrome” and decided to rely on this tool. To tune the stylesheets for own needs, I created a github copy of the repository: docxtools. To run the stylesheets outside […]

Generating Excel XML, avoiding “found unreadable content”

Wed, 30 Sep 2015 12:03:55 +0000

In theory, changing content of an Excel file is easy: * Parse XML from the zip-file * Change XML * Save XML into the zip In practice I got the error: >>Von Excel wurde unlesbares Inhalt in … gefunden. Möchten Sie den Inhalt dieser Arbeitsmappe wiederherstellen?< < (English: "Excel found unreadable content...") After long debug, […]

Tkinter sample application for a long operation

Thu, 09 Jul 2015 12:54:42 +0000

In the year 2001 I started to experiment with GUI applications in Python. The experience was summarized and published in the article “A complete Python Tkinter sample application for a long operation“. Now, in the year 2015, a programmer have sent me an updated code. With the minimal changes, which mostly are update of the […]

fast-disable css in firefox

Fri, 17 Apr 2015 07:20:39 +0000

Sometimes I want to read a web page without its design “improvements”. In many case it is enough to switch off css, and in firefox this functionality is built-in. Shift+F7 to get the developer tools. Thanks stackoverflow for the hint.

Workaround for: CTR mode needs counter parameter, not IV

Fri, 20 Feb 2015 11:04:23 +0000

After upgrading the local Linux system, my python paramiko (ssh protocol implementation) program stopped working, with the error message: CTR mode needs counter parameter, not IV Internet search gave no solution. Therefore, it was a time to experiment. A logical consequence from the error message is that somewhere should be used only “IV” or only […]

using freebidi from python using ctypes

Mon, 08 Dec 2014 11:42:10 +0000

GNU FriBidi is an implementation of the Unicode Bidirectional Algorithm (bidi). There is a Python binding PyFribidi, but it is not complete. What I need is not a visual presentation of a string, but information where direction is changing. This function is not provided by the binding, therefore I’ve made an alternative using ctypes. Download: […]