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  13  <h1>
  14      <a href="https://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
  15
  16  </h1>
  17
  18 </div>
  19
  20
  21     <h3>Entries tagged "linuxcnc".</h3>
  22
  23     <div class="entry">
  24       <div class="title">
  25         <a href="https://people.skolelinux.org/pere/blog/LinuxCNC_MQTT_publisher_component.html">LinuxCNC MQTT publisher component</a>
  26       </div>
  27       <div class="date">
  28          8th January 2023
  29       </div>
  30       <div class="body">
  31         <p>I watched <a href="https://yewtu.be/watch?v=jmKUV3aNLjk">a 2015
  32 video from Andreas Schiffler</a> the other day, where he set up
  33 <a href="https://linuxcnc.org/">LinuxCNC</a> to send status
  34 information to the MQTT broker IBM Bluemix.  As I also use MQTT for
  35 graphing, it occured to me that a generic MQTT LinuxCNC component
  36 would be useful and I set out to implement it.  Today I got the first
  37 draft limping along and submitted as
  38 <a href="https://github.com/LinuxCNC/linuxcnc/pull/2253">a patch to the
  39 LinuxCNC project</a>.</p>
  40
  41 <p>The simple part was setting up the MQTT publishing code in Python.
  42 I already have set up other parts submitting data to my Mosquito MQTT
  43 broker, so I could reuse that code.  Writing a LinuxCNC component in
  44 Python as new to me, but using existing examples in the code
  45 repository and the extensive documentation, this was fairly straight
  46 forward.  The hardest part was creating a automated test for the
  47 component to ensure it was working.  Testing it in a simulated
  48 LinuxCNC machine proved very useful, as I discovered features I needed
  49 that I had not thought of yet, and adjusted the code quite a bit to
  50 make it easier to test without a operational MQTT broker
  51 available.</p>
  52
  53 <p>The draft is ready and working, but I am unsure which LinuxCNC HAL
  54 pins I should collect and publish by default (in other words, the
  55 default set of information pieces published), and how to get the
  56 machine name from the LinuxCNC INI file.  The latter is a minor
  57 detail, but I expect it would be useful in a setup with several
  58 machines available.  I am hoping for feedback from the experienced
  59 LinuxCNC developers and users, to make the component even better
  60 before it can go into the mainland LinuxCNC code base.</p>
  61
  62 <p>Since I started on the MQTT component, I came across
  63 <a href="https://yewtu.be/watch?v=Bqa2grG0XtA">another video from Kent
  64 VanderVelden</a> where he combine LinuxCNC with a set of screen glasses
  65 controlled by a Raspberry Pi, and it occured to me that it would
  66 be useful for such use cases if LinuxCNC also provided a REST API for
  67 querying its status.  I hope to start on such component once the MQTT
  68 component is working well.</p>
  69
  70 <p>As usual, if you use Bitcoin and want to show your support of my
  71 activities, please send Bitcoin donations to my address
  72 <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
  73
  74       </div>
  75       <div class="tags">
  76
  77
  78         Tags: <a href="https://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="https://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="https://people.skolelinux.org/pere/blog/tags/linuxcnc">linuxcnc</a>, <a href="https://people.skolelinux.org/pere/blog/tags/robot">robot</a>.
  79
  80
  81       </div>
  82     </div>
  83     <div class="padding"></div>
  84
  85     <div class="entry">
  86       <div class="title">
  87         <a href="https://people.skolelinux.org/pere/blog/Automatic_LinuxCNC_servo_PID_tuning_.html">Automatic LinuxCNC servo PID tuning?</a>
  88       </div>
  89       <div class="date">
  90         16th July 2022
  91       </div>
  92       <div class="body">
  93         <p>While working on a CNC with servo motors controlled by the
  94 <a href="https://en.wikipedia.org/wiki/LinuxCNC">LinuxCNC</a>
  95 <a href="https://en.wikipedia.org/wiki/PID_controller">PID
  96 controller</a>, I recently had to learn how to tune the collection of values
  97 that control such mathematical machinery that a PID controller is.  It
  98 proved to be a lot harder than I hoped, and I still have not succeeded
  99 in getting the Z PID controller to successfully defy gravity, nor X
 100 and Y to move accurately and reliably.  But while climbing up this
 101 rather steep learning curve, I discovered that some motor control
 102 systems are able to tune their PID controllers.  I got the impression
 103 from the documentation that LinuxCNC were not.  This proved to be not
 104 true.</p>
 105
 106 <p>The LinuxCNC
 107 <a href="http://linuxcnc.org/docs/html/man/man9/pid.9.html">pid
 108 component</a> is the recommended PID controller to use.  It uses eight
 109 constants <tt>Pgain</tt>, <tt>Igain</tt>, <tt>Dgain</tt>,
 110 <tt>bias</tt>, <tt>FF0</tt>, <tt>FF1</tt>, <tt>FF2</tt> and
 111 <tt>FF3</tt> to calculate the output value based on current and wanted
 112 state, and all of these need to have a sensible value for the
 113 controller to behave properly.  Note, there are even more values
 114 involved, theser are just the most important ones.  In my case I need
 115 the X, Y and Z axes to follow the requested path with little error.
 116 This has proved quite a challenge for someone who have never tuned a
 117 PID controller before, but there is at least some help to be found.
 118
 119 <p>I discovered that included in LinuxCNC was this old PID component
 120 at_pid claiming to have auto tuning capabilities.  Sadly it had been
 121 neglected since 2011, and could not be used as a plug in replacement
 122 for the default pid component.  One would have to rewriting the
 123 LinuxCNC HAL setup to test at_pid.  This was rather sad, when I wanted
 124 to quickly test auto tuning to see if it did a better job than me at
 125 figuring out good P, I and D values to use.</p>
 126
 127 <p>I decided to have a look if the situation could be improved.  This
 128 involved trying to understand the code and history of the pid and
 129 at_pid components.  Apparently they had a common ancestor, as code
 130 structure, comments and variable names were quite close to each other.
 131 Sadly this was not reflected in the git history, making it hard to
 132 figure out what really happened.  My guess is that the author of
 133 <a href="https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/components/at_pid.c">at_pid.c</a>
 134 took a version of
 135 <a href="https://github.com/LinuxCNC/linuxcnc/blob/master/src/hal/components/pid.c">pid.c</a>,
 136 rewrote it to follow the structure he wished pid.c to have, then added
 137 support for auto tuning and finally got it included into the LinuxCNC
 138 repository.  The restructuring and lack of early history made it
 139 harder to figure out which part of the code were relevant to the auto
 140 tuning, and which part of the code needed to be updated to work the
 141 same way as the current pid.c implementation.  I started by trying to
 142 isolate relevant changes in pid.c, and applying them to at_pid.c.  My
 143 aim was to make sure the at_pid component could replace the pid
 144 component with a simple change in the HAL setup loadrt line, without
 145 having to "rewire" the rest of the HAL configuration.  After a few
 146 hours following this approach, I had learned quite a lot about the
 147 code structure of both components, while concluding I was heading down
 148 the wrong rabbit hole, and should get back to the surface and find a
 149 different path.</p>
 150
 151 <p>For the second attempt, I decided to throw away all the PID control
 152 related part of the original at_pid.c, and instead isolate and lift
 153 the auto tuning part of the code and inject it into a copy of pid.c.
 154 This ensured compatibility with the current pid component, while
 155 adding auto tuning as a run time option.  To make it easier to identify
 156 the relevant parts in the future, I wrapped all the auto tuning code
 157 with '#ifdef AUTO_TUNER'.  The end result behave just like the current
 158 pid component by default, as that part of the code is identical.  The
 159 <a href="https://github.com/LinuxCNC/linuxcnc/pull/1820">end result
 160 entered the LinuxCNC master branch</a> a few days ago.</p>
 161
 162 <p>To enable auto tuning, one need to set a few HAL pins in the PID
 163 component.  The most important ones are <tt>tune-effort</tt>,
 164 <tt>tune-mode</tt> and <tt>tune-start</tt>.  But lets take a step
 165 back, and see what the auto tuning code will do.  I do not know the
 166 mathematical foundation of the at_pid algorithm, but from observation
 167 I can tell that the algorithm will, when enabled, produce a square
 168 wave pattern centered around the <tt>bias</tt> value on the output pin
 169 of the PID controller.  This can be seen using the HAL Scope provided
 170 by LinuxCNC.  In my case, this is translated into voltage (+-10V) sent
 171 to the motor controller, which in turn is translated into motor speed.
 172 So at_pid will ask the motor to move the axis back and forth.  The
 173 number of cycles in the pattern is controlled by the
 174 <tt>tune-cycles</tt> pin, and the extremes of the wave pattern is
 175 controlled by the <tt>tune-effort</tt> pin.  Of course, trying to
 176 change the direction of a physical object instantly (as in going
 177 directly from a positive voltage to the equivalent negative voltage)
 178 do not change velocity instantly, and it take some time for the object
 179 to slow down and move in the opposite direction.  This result in a
 180 more smooth movement wave form, as the axis in question were vibrating
 181 back and forth.  When the axis reached the target speed in the
 182 opposing direction, the auto tuner change direction again.  After
 183 several of these changes, the average time delay between the 'peaks'
 184 and 'valleys' of this movement graph is then used to calculate
 185 proposed values for Pgain, Igain and Dgain, and insert them into the
 186 HAL model to use by the pid controller.  The auto tuned settings are
 187 not great, but htye work a lot better than the values I had been able
 188 to cook up on my own, at least for the horizontal X and Y axis.  But I
 189 had to use very small <tt>tune-effort<tt> values, as my motor
 190 controllers error out if the voltage change too quickly.  I've been
 191 less lucky with the Z axis, which is moving a heavy object up and
 192 down, and seem to confuse the algorithm.  The Z axis movement became a
 193 lot better when I introduced a <tt>bias</tt> value to counter the
 194 gravitational drag, but I will have to work a lot more on the Z axis
 195 PID values.</p>
 196
 197 <p>Armed with this knowledge, it is time to look at how to do the
 198 tuning.  Lets say the HAL configuration in question load the PID
 199 component for X, Y and Z like this:</p>
 200
 201 <blockquote><pre>
 202 loadrt pid names=pid.x,pid.y,pid.z
 203 </pre></blockquote>
 204
 205 <p>Armed with the new and improved at_pid component, the new line will
 206 look like this:</p>
 207
 208 <blockquote><pre>
 209 loadrt at_pid names=pid.x,pid.y,pid.z
 210 </pre></blockquote>
 211
 212 <p>The rest of the HAL setup can stay the same.  This work because the
 213 components are referenced by name.  If the component had used count=3
 214 instead, all use of pid.# had to be changed to at_pid.#.</p>
 215
 216 <p>To start tuning the X axis, move the axis to the middle of its
 217 range, to make sure it do not hit anything when it start moving back
 218 and forth.  Next, set the <tt>tune-effort</tt> to a low number in the
 219 output range.  I used 0.1 as my initial value.  Next, assign 1 to the
 220 <tt>tune-mode</tt> value. Note, this will disable the pid controlling
 221 part and feed 0 to the output pin, which in my case initially caused a
 222 lot of drift.  In my case it proved to be a good idea with X and Y to
 223 tune the motor driver to make sure 0 voltage stopped the motor
 224 rotation.  On the other hand, for the Z axis this proved to be a bad
 225 idea, so it will depend on your setup.  It might help to set the
 226 <tt>bias</tt> value to a output value that reduce or eliminate the
 227 axis drift.  Finally, after setting <tt>tune-mode</tt>, set
 228 <tt>tune-start</tt> to 1 to activate the auto tuning.  If all go well,
 229 your axis will vibrate for a few seconds and when it is done, new
 230 values for Pgain, Igain and Dgain will be active.  To test them,
 231 change <tt>tune-mode</tt> back to 0.  Note that this might cause the
 232 machine to suddenly jerk as it bring the axis back to its commanded
 233 position, which it might have drifted away from during tuning.  To
 234 summarize with some halcmd lines:</p>
 235
 236 <blockquote><pre>
 237 setp pid.x.tune-effort 0.1
 238 setp pid.x.tune-mode 1
 239 setp pid.x.tune-start 1
 240 # wait for the tuning to complete
 241 setp pid.x.tune-mode 0
 242 </pre></blockquote>
 243
 244 <p>After doing this task quite a few times while trying to figure out
 245 how to properly tune the PID controllers on the machine in, I decided
 246 to figure out if this process could be automated, and wrote a script
 247 to do the entire tuning process from power on.  The end result will
 248 ensure the machine is powered on and ready to run, home all axis if it
 249 is not already done, check that the extra tuning pins are available,
 250 move the axis to its mid point, run the auto tuning and re-enable the
 251 pid controller when it is done.  It can be run several times.  Check
 252 out the
 253 <a href="https://github.com/SebKuzminsky/MazakVQC1540/blob/bon-dev/scripts/run-auto-pid-tuner">run-auto-pid-tuner</a>
 254 script on github if you want to learn how it is done.</p>
 255
 256 <p>My hope is that this little adventure can inspire someone who know
 257 more about motor PID controller tuning can implement even better
 258 algorithms for automatic PID tuning in LinuxCNC, making life easier
 259 for both me and all the others that want to use LinuxCNC but lack the
 260 in depth knowledge needed to tune PID controllers well.</p>
 261
 262 <p>As usual, if you use Bitcoin and want to show your support of my
 263 activities, please send Bitcoin donations to my address
 264 <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
 265
 266       </div>
 267       <div class="tags">
 268
 269
 270         Tags: <a href="https://people.skolelinux.org/pere/blog/tags/3d-printer">3d-printer</a>, <a href="https://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="https://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="https://people.skolelinux.org/pere/blog/tags/linuxcnc">linuxcnc</a>, <a href="https://people.skolelinux.org/pere/blog/tags/robot">robot</a>.
 271
 272
 273       </div>
 274     </div>
 275     <div class="padding"></div>
 276
 277     <div class="entry">
 278       <div class="title">
 279         <a href="https://people.skolelinux.org/pere/blog/LinuxCNC_translators_life_just_got_a_bit_easier.html">LinuxCNC translators life just got a bit easier</a>
 280       </div>
 281       <div class="date">
 282          3rd June 2022
 283       </div>
 284       <div class="body">
 285         <p>Back in oktober last year, when I started looking at the
 286 <a href="https://en.wikipedia.org/wiki/LinuxCNC">LinuxCNC</a> system, I
 287 proposed to change the documentation build system make life easier for
 288 translators.  The original system consisted of independently written
 289 documentation files for each language, with no automated way to track
 290 changes done in other translations and no help for the translators to
 291 know how much was left to translated.  By using
 292 <a href="https://po4a.org/">the po4a system</a> to generate POT and PO
 293 files from the English documentation, this can be improved.  A small
 294 team of LinuxCNC contributors got together and today our labour
 295 finally payed off.  Since a few hours ago, it is now possible to
 296 translate <a href="https://hosted.weblate.org/projects/linuxcnc/">the
 297 LinuxCNC documentation on Weblate</a>, alongside the program itself.</p>
 298
 299 <p>The effort to migrate the documentation to use po4a has been both
 300 slow and frustrating.  I am very happy we finally made it.</p>
 301
 302 <p>As usual, if you use Bitcoin and want to show your support of my
 303 activities, please send Bitcoin donations to my address
 304 <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
 305
 306       </div>
 307       <div class="tags">
 308
 309
 310         Tags: <a href="https://people.skolelinux.org/pere/blog/tags/3d-printer">3d-printer</a>, <a href="https://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="https://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="https://people.skolelinux.org/pere/blog/tags/linuxcnc">linuxcnc</a>, <a href="https://people.skolelinux.org/pere/blog/tags/robot">robot</a>.
 311
 312
 313       </div>
 314     </div>
 315     <div class="padding"></div>
 316
 317     <div class="entry">
 318       <div class="title">
 319         <a href="https://people.skolelinux.org/pere/blog/Run_your_industrial_metal_working_machine_using_Debian_.html">Run your industrial metal working machine using Debian?</a>
 320       </div>
 321       <div class="date">
 322          2nd March 2022
 323       </div>
 324       <div class="body">
 325         <p>After many months of hard work by the good people involved in
 326 <a href="https://en.wikipedia.org/wiki/LinuxCNC">LinuxCNC</a>, the
 327 system was accepted Sunday
 328 <a href="https://tracker.debian.org/pkg/linuxcnc">into Debian</a>.
 329 Once it was available from Debian, I was surprised to discover from
 330 <a href="https://qa.debian.org/popcon.php?package=linuxcnc">its
 331 popularity-contest numbers</a> that people have been reporting its use
 332 since 2012.  <a href="http://linuxcnc.org/">Its project site</a> might
 333 be a good place to check out, but sadly is not working when visiting
 334 via Tor.</p>
 335
 336 <p>But what is LinuxCNC, you are probably wondering?  Perhaps a
 337 Wikipedia quote is in place?</p>
 338
 339 <blockquote>
 340 "LinuxCNC is a software system for numerical control of
 341 machines such as milling machines, lathes, plasma cutters, routers,
 342 cutting machines, robots and hexapods. It can control up to 9 axes or
 343 joints of a CNC machine using G-code (RS-274NGC) as input. It has
 344 several GUIs suited to specific kinds of usage (touch screen,
 345 interactive development)."
 346 </blockquote>
 347
 348 <p>It can even control 3D printers.  And even though the Wikipedia
 349 page indicate that it can only work with hard real time kernel
 350 features, it can also work with the user space soft real time features
 351 provided by the Debian kernel.
 352 <a href="https://github.com/linuxcnc/linuxcnc">The source code</a> is
 353 available from Github.  The last few months I've been involved in the
 354 translation setup for the program and documentation.  Translators are
 355 most welcome to
 356 <a href="https://hosted.weblate.org/engage/linuxcnc/">join the
 357 effort</a> using Weblate.</p>
 358
 359 <p>As usual, if you use Bitcoin and want to show your support of my
 360 activities, please send Bitcoin donations to my address
 361 <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
 362
 363       </div>
 364       <div class="tags">
 365
 366
 367         Tags: <a href="https://people.skolelinux.org/pere/blog/tags/3d-printer">3d-printer</a>, <a href="https://people.skolelinux.org/pere/blog/tags/debian">debian</a>, <a href="https://people.skolelinux.org/pere/blog/tags/english">english</a>, <a href="https://people.skolelinux.org/pere/blog/tags/linuxcnc">linuxcnc</a>, <a href="https://people.skolelinux.org/pere/blog/tags/robot">robot</a>.
 368
 369
 370       </div>
 371     </div>
 372     <div class="padding"></div>
 373
 374     <p style="text-align: right;"><a href="linuxcnc.rss"><img src="https://people.skolelinux.org/pere/blog/xml.gif" alt="RSS Feed" width="36" height="14" /></a></p>
 375     <div id="sidebar">
 376
 377
 378
 379 <h2>Archive</h2>
 380 <ul>
 381
 382 <li>2023
 383 <ul>
 384
 385 <li><a href="https://people.skolelinux.org/pere/blog/archive/2023/01/">January (3)</a></li>
 386
 387 <li><a href="https://people.skolelinux.org/pere/blog/archive/2023/02/">February (1)</a></li>
 388
 389 </ul></li>
 390
 391 <li>2022
 392 <ul>
 393
 394 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/02/">February (1)</a></li>
 395
 396 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/03/">March (3)</a></li>
 397
 398 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/04/">April (2)</a></li>
 399
 400 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/06/">June (2)</a></li>
 401
 402 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/07/">July (1)</a></li>
 403
 404 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/09/">September (1)</a></li>
 405
 406 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/10/">October (1)</a></li>
 407
 408 <li><a href="https://people.skolelinux.org/pere/blog/archive/2022/12/">December (1)</a></li>
 409
 410 </ul></li>
 411
 412 <li>2021
 413 <ul>
 414
 415 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/01/">January (2)</a></li>
 416
 417 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/02/">February (1)</a></li>
 418
 419 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/05/">May (1)</a></li>
 420
 421 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/06/">June (1)</a></li>
 422
 423 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/07/">July (3)</a></li>
 424
 425 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/08/">August (1)</a></li>
 426
 427 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/09/">September (1)</a></li>
 428
 429 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/10/">October (1)</a></li>
 430
 431 <li><a href="https://people.skolelinux.org/pere/blog/archive/2021/12/">December (1)</a></li>
 432
 433 </ul></li>
 434
 435 <li>2020
 436 <ul>
 437
 438 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/02/">February (2)</a></li>
 439
 440 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/03/">March (2)</a></li>
 441
 442 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/04/">April (2)</a></li>
 443
 444 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/05/">May (3)</a></li>
 445
 446 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/06/">June (2)</a></li>
 447
 448 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/07/">July (1)</a></li>
 449
 450 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/09/">September (1)</a></li>
 451
 452 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/10/">October (1)</a></li>
 453
 454 <li><a href="https://people.skolelinux.org/pere/blog/archive/2020/11/">November (1)</a></li>
 455
 456 </ul></li>
 457
 458 <li>2019
 459 <ul>
 460
 461 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/01/">January (4)</a></li>
 462
 463 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/02/">February (3)</a></li>
 464
 465 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/03/">March (3)</a></li>
 466
 467 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/05/">May (2)</a></li>
 468
 469 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/06/">June (5)</a></li>
 470
 471 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/07/">July (2)</a></li>
 472
 473 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/08/">August (1)</a></li>
 474
 475 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/09/">September (1)</a></li>
 476
 477 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/11/">November (1)</a></li>
 478
 479 <li><a href="https://people.skolelinux.org/pere/blog/archive/2019/12/">December (4)</a></li>
 480
 481 </ul></li>
 482
 483 <li>2018
 484 <ul>
 485
 486 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/01/">January (1)</a></li>
 487
 488 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/02/">February (5)</a></li>
 489
 490 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/03/">March (5)</a></li>
 491
 492 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/04/">April (3)</a></li>
 493
 494 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/06/">June (2)</a></li>
 495
 496 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/07/">July (5)</a></li>
 497
 498 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/08/">August (3)</a></li>
 499
 500 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/09/">September (3)</a></li>
 501
 502 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/10/">October (5)</a></li>
 503
 504 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/11/">November (2)</a></li>
 505
 506 <li><a href="https://people.skolelinux.org/pere/blog/archive/2018/12/">December (4)</a></li>
 507
 508 </ul></li>
 509
 510 <li>2017
 511 <ul>
 512
 513 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/01/">January (4)</a></li>
 514
 515 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/02/">February (3)</a></li>
 516
 517 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/03/">March (5)</a></li>
 518
 519 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/04/">April (2)</a></li>
 520
 521 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/06/">June (5)</a></li>
 522
 523 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/07/">July (1)</a></li>
 524
 525 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/08/">August (1)</a></li>
 526
 527 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/09/">September (3)</a></li>
 528
 529 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/10/">October (5)</a></li>
 530
 531 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/11/">November (3)</a></li>
 532
 533 <li><a href="https://people.skolelinux.org/pere/blog/archive/2017/12/">December (4)</a></li>
 534
 535 </ul></li>
 536
 537 <li>2016
 538 <ul>
 539
 540 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/01/">January (3)</a></li>
 541
 542 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/02/">February (2)</a></li>
 543
 544 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/03/">March (3)</a></li>
 545
 546 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/04/">April (8)</a></li>
 547
 548 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/05/">May (8)</a></li>
 549
 550 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/06/">June (2)</a></li>
 551
 552 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/07/">July (2)</a></li>
 553
 554 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/08/">August (5)</a></li>
 555
 556 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/09/">September (2)</a></li>
 557
 558 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/10/">October (3)</a></li>
 559
 560 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/11/">November (8)</a></li>
 561
 562 <li><a href="https://people.skolelinux.org/pere/blog/archive/2016/12/">December (5)</a></li>
 563
 564 </ul></li>
 565
 566 <li>2015
 567 <ul>
 568
 569 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/01/">January (7)</a></li>
 570
 571 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/02/">February (6)</a></li>
 572
 573 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/03/">March (1)</a></li>
 574
 575 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/04/">April (4)</a></li>
 576
 577 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/05/">May (3)</a></li>
 578
 579 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/06/">June (4)</a></li>
 580
 581 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/07/">July (6)</a></li>
 582
 583 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/08/">August (2)</a></li>
 584
 585 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/09/">September (2)</a></li>
 586
 587 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/10/">October (9)</a></li>
 588
 589 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/11/">November (6)</a></li>
 590
 591 <li><a href="https://people.skolelinux.org/pere/blog/archive/2015/12/">December (3)</a></li>
 592
 593 </ul></li>
 594
 595 <li>2014
 596 <ul>
 597
 598 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/01/">January (2)</a></li>
 599
 600 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/02/">February (3)</a></li>
 601
 602 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/03/">March (8)</a></li>
 603
 604 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/04/">April (7)</a></li>
 605
 606 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/05/">May (1)</a></li>
 607
 608 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/06/">June (2)</a></li>
 609
 610 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/07/">July (2)</a></li>
 611
 612 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/08/">August (2)</a></li>
 613
 614 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/09/">September (5)</a></li>
 615
 616 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/10/">October (6)</a></li>
 617
 618 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/11/">November (3)</a></li>
 619
 620 <li><a href="https://people.skolelinux.org/pere/blog/archive/2014/12/">December (5)</a></li>
 621
 622 </ul></li>
 623
 624 <li>2013
 625 <ul>
 626
 627 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/01/">January (11)</a></li>
 628
 629 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/02/">February (9)</a></li>
 630
 631 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/03/">March (9)</a></li>
 632
 633 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/04/">April (6)</a></li>
 634
 635 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/05/">May (9)</a></li>
 636
 637 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/06/">June (10)</a></li>
 638
 639 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/07/">July (7)</a></li>
 640
 641 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/08/">August (3)</a></li>
 642
 643 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/09/">September (5)</a></li>
 644
 645 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/10/">October (7)</a></li>
 646
 647 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/11/">November (9)</a></li>
 648
 649 <li><a href="https://people.skolelinux.org/pere/blog/archive/2013/12/">December (3)</a></li>
 650
 651 </ul></li>
 652
 653 <li>2012
 654 <ul>
 655
 656 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/01/">January (7)</a></li>
 657
 658 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/02/">February (10)</a></li>
 659
 660 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/03/">March (17)</a></li>
 661
 662 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/04/">April (12)</a></li>
 663
 664 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/05/">May (12)</a></li>
 665
 666 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/06/">June (20)</a></li>
 667
 668 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/07/">July (17)</a></li>
 669
 670 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/08/">August (6)</a></li>
 671
 672 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/09/">September (9)</a></li>
 673
 674 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/10/">October (17)</a></li>
 675
 676 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/11/">November (10)</a></li>
 677
 678 <li><a href="https://people.skolelinux.org/pere/blog/archive/2012/12/">December (7)</a></li>
 679
 680 </ul></li>
 681
 682 <li>2011
 683 <ul>
 684
 685 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/01/">January (16)</a></li>
 686
 687 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/02/">February (6)</a></li>
 688
 689 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/03/">March (6)</a></li>
 690
 691 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/04/">April (7)</a></li>
 692
 693 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/05/">May (3)</a></li>
 694
 695 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/06/">June (2)</a></li>
 696
 697 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/07/">July (7)</a></li>
 698
 699 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/08/">August (6)</a></li>
 700
 701 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/09/">September (4)</a></li>
 702
 703 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/10/">October (2)</a></li>
 704
 705 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/11/">November (3)</a></li>
 706
 707 <li><a href="https://people.skolelinux.org/pere/blog/archive/2011/12/">December (1)</a></li>
 708
 709 </ul></li>
 710
 711 <li>2010
 712 <ul>
 713
 714 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/01/">January (2)</a></li>
 715
 716 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/02/">February (1)</a></li>
 717
 718 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/03/">March (3)</a></li>
 719
 720 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/04/">April (3)</a></li>
 721
 722 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/05/">May (9)</a></li>
 723
 724 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/06/">June (14)</a></li>
 725
 726 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/07/">July (12)</a></li>
 727
 728 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/08/">August (13)</a></li>
 729
 730 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/09/">September (7)</a></li>
 731
 732 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/10/">October (9)</a></li>
 733
 734 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/11/">November (13)</a></li>
 735
 736 <li><a href="https://people.skolelinux.org/pere/blog/archive/2010/12/">December (12)</a></li>
 737
 738 </ul></li>
 739
 740 <li>2009
 741 <ul>
 742
 743 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/01/">January (8)</a></li>
 744
 745 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/02/">February (8)</a></li>
 746
 747 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/03/">March (12)</a></li>
 748
 749 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/04/">April (10)</a></li>
 750
 751 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/05/">May (9)</a></li>
 752
 753 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/06/">June (3)</a></li>
 754
 755 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/07/">July (4)</a></li>
 756
 757 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/08/">August (3)</a></li>
 758
 759 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/09/">September (1)</a></li>
 760
 761 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/10/">October (2)</a></li>
 762
 763 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/11/">November (3)</a></li>
 764
 765 <li><a href="https://people.skolelinux.org/pere/blog/archive/2009/12/">December (3)</a></li>
 766
 767 </ul></li>
 768
 769 <li>2008
 770 <ul>
 771
 772 <li><a href="https://people.skolelinux.org/pere/blog/archive/2008/11/">November (5)</a></li>
 773
 774 <li><a href="https://people.skolelinux.org/pere/blog/archive/2008/12/">December (7)</a></li>
 775
 776 </ul></li>
 777
 778 </ul>
 779
 780
 781
 782 <h2>Tags</h2>
 783 <ul>
 784
 785  <li><a href="https://people.skolelinux.org/pere/blog/tags/3d-printer">3d-printer (19)</a></li>
 786
 787  <li><a href="https://people.skolelinux.org/pere/blog/tags/amiga">amiga (1)</a></li>
 788
 789  <li><a href="https://people.skolelinux.org/pere/blog/tags/aros">aros (1)</a></li>
 790
 791  <li><a href="https://people.skolelinux.org/pere/blog/tags/bankid">bankid (4)</a></li>
 792
 793  <li><a href="https://people.skolelinux.org/pere/blog/tags/betalkontant">betalkontant (9)</a></li>
 794
 795  <li><a href="https://people.skolelinux.org/pere/blog/tags/bitcoin">bitcoin (12)</a></li>
 796
 797  <li><a href="https://people.skolelinux.org/pere/blog/tags/bootsystem">bootsystem (17)</a></li>
 798
 799  <li><a href="https://people.skolelinux.org/pere/blog/tags/bsa">bsa (2)</a></li>
 800
 801  <li><a href="https://people.skolelinux.org/pere/blog/tags/chrpath">chrpath (2)</a></li>
 802
 803  <li><a href="https://people.skolelinux.org/pere/blog/tags/debian">debian (188)</a></li>
 804
 805  <li><a href="https://people.skolelinux.org/pere/blog/tags/debian edu">debian edu (159)</a></li>
 806
 807  <li><a href="https://people.skolelinux.org/pere/blog/tags/debian-handbook">debian-handbook (9)</a></li>
 808
 809  <li><a href="https://people.skolelinux.org/pere/blog/tags/digistan">digistan (11)</a></li>
 810
 811  <li><a href="https://people.skolelinux.org/pere/blog/tags/dld">dld (18)</a></li>
 812
 813  <li><a href="https://people.skolelinux.org/pere/blog/tags/docbook">docbook (30)</a></li>
 814
 815  <li><a href="https://people.skolelinux.org/pere/blog/tags/drivstoffpriser">drivstoffpriser (4)</a></li>
 816
 817  <li><a href="https://people.skolelinux.org/pere/blog/tags/english">english (444)</a></li>
 818
 819  <li><a href="https://people.skolelinux.org/pere/blog/tags/fiksgatami">fiksgatami (23)</a></li>
 820
 821  <li><a href="https://people.skolelinux.org/pere/blog/tags/fildeling">fildeling (14)</a></li>
 822
 823  <li><a href="https://people.skolelinux.org/pere/blog/tags/freeculture">freeculture (34)</a></li>
 824
 825  <li><a href="https://people.skolelinux.org/pere/blog/tags/freedombox">freedombox (9)</a></li>
 826
 827  <li><a href="https://people.skolelinux.org/pere/blog/tags/frikanalen">frikanalen (20)</a></li>
 828
 829  <li><a href="https://people.skolelinux.org/pere/blog/tags/h264">h264 (20)</a></li>
 830
 831  <li><a href="https://people.skolelinux.org/pere/blog/tags/intervju">intervju (43)</a></li>
 832
 833  <li><a href="https://people.skolelinux.org/pere/blog/tags/isenkram">isenkram (16)</a></li>
 834
 835  <li><a href="https://people.skolelinux.org/pere/blog/tags/kart">kart (23)</a></li>
 836
 837  <li><a href="https://people.skolelinux.org/pere/blog/tags/kodi">kodi (4)</a></li>
 838
 839  <li><a href="https://people.skolelinux.org/pere/blog/tags/ldap">ldap (9)</a></li>
 840
 841  <li><a href="https://people.skolelinux.org/pere/blog/tags/lego">lego (5)</a></li>
 842
 843  <li><a href="https://people.skolelinux.org/pere/blog/tags/lenker">lenker (8)</a></li>
 844
 845  <li><a href="https://people.skolelinux.org/pere/blog/tags/linuxcnc">linuxcnc (4)</a></li>
 846
 847  <li><a href="https://people.skolelinux.org/pere/blog/tags/lsdvd">lsdvd (2)</a></li>
 848
 849  <li><a href="https://people.skolelinux.org/pere/blog/tags/ltsp">ltsp (1)</a></li>
 850
 851  <li><a href="https://people.skolelinux.org/pere/blog/tags/madewithcc">madewithcc (3)</a></li>
 852
 853  <li><a href="https://people.skolelinux.org/pere/blog/tags/mesh network">mesh network (8)</a></li>
 854
 855  <li><a href="https://people.skolelinux.org/pere/blog/tags/multimedia">multimedia (44)</a></li>
 856
 857  <li><a href="https://people.skolelinux.org/pere/blog/tags/nice free software">nice free software (13)</a></li>
 858
 859  <li><a href="https://people.skolelinux.org/pere/blog/tags/noark5">noark5 (23)</a></li>
 860
 861  <li><a href="https://people.skolelinux.org/pere/blog/tags/norsk">norsk (320)</a></li>
 862
 863  <li><a href="https://people.skolelinux.org/pere/blog/tags/nuug">nuug (198)</a></li>
 864
 865  <li><a href="https://people.skolelinux.org/pere/blog/tags/offentlig innsyn">offentlig innsyn (40)</a></li>
 866
 867  <li><a href="https://people.skolelinux.org/pere/blog/tags/open311">open311 (2)</a></li>
 868
 869  <li><a href="https://people.skolelinux.org/pere/blog/tags/opphavsrett">opphavsrett (75)</a></li>
 870
 871  <li><a href="https://people.skolelinux.org/pere/blog/tags/personvern">personvern (114)</a></li>
 872
 873  <li><a href="https://people.skolelinux.org/pere/blog/tags/raid">raid (2)</a></li>
 874
 875  <li><a href="https://people.skolelinux.org/pere/blog/tags/reactos">reactos (1)</a></li>
 876
 877  <li><a href="https://people.skolelinux.org/pere/blog/tags/reprap">reprap (11)</a></li>
 878
 879  <li><a href="https://people.skolelinux.org/pere/blog/tags/rfid">rfid (3)</a></li>
 880
 881  <li><a href="https://people.skolelinux.org/pere/blog/tags/robot">robot (17)</a></li>
 882
 883  <li><a href="https://people.skolelinux.org/pere/blog/tags/rss">rss (1)</a></li>
 884
 885  <li><a href="https://people.skolelinux.org/pere/blog/tags/ruter">ruter (7)</a></li>
 886
 887  <li><a href="https://people.skolelinux.org/pere/blog/tags/scraperwiki">scraperwiki (2)</a></li>
 888
 889  <li><a href="https://people.skolelinux.org/pere/blog/tags/sikkerhet">sikkerhet (59)</a></li>
 890
 891  <li><a href="https://people.skolelinux.org/pere/blog/tags/sitesummary">sitesummary (4)</a></li>
 892
 893  <li><a href="https://people.skolelinux.org/pere/blog/tags/skepsis">skepsis (5)</a></li>
 894
 895  <li><a href="https://people.skolelinux.org/pere/blog/tags/standard">standard (74)</a></li>
 896
 897  <li><a href="https://people.skolelinux.org/pere/blog/tags/stavekontroll">stavekontroll (7)</a></li>
 898
 899  <li><a href="https://people.skolelinux.org/pere/blog/tags/stortinget">stortinget (14)</a></li>
 900
 901  <li><a href="https://people.skolelinux.org/pere/blog/tags/surveillance">surveillance (64)</a></li>
 902
 903  <li><a href="https://people.skolelinux.org/pere/blog/tags/sysadmin">sysadmin (5)</a></li>
 904
 905  <li><a href="https://people.skolelinux.org/pere/blog/tags/usenix">usenix (2)</a></li>
 906
 907  <li><a href="https://people.skolelinux.org/pere/blog/tags/valg">valg (9)</a></li>
 908
 909  <li><a href="https://people.skolelinux.org/pere/blog/tags/verkidetfri">verkidetfri (20)</a></li>
 910
 911  <li><a href="https://people.skolelinux.org/pere/blog/tags/video">video (77)</a></li>
 912
 913  <li><a href="https://people.skolelinux.org/pere/blog/tags/vitenskap">vitenskap (4)</a></li>
 914
 915  <li><a href="https://people.skolelinux.org/pere/blog/tags/web">web (42)</a></li>
 916
 917 </ul>
 918
 919
 920     </div>
 921     <p style="text-align: right">
 922  Created by <a href="http://steve.org.uk/Software/chronicle">Chronicle v4.6</a>
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