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10 <h1>Pierogi Documentation</h1>
13 The Pierogi universal infrared remote controller is a single self-contained
14 app capable of sending IR commands to a wide variety of devices.
15 At the moment, it is oriented towards television, VCR, DVD, and Blu-ray
16 devices, but a few other types of device have had their command sets entered.
20 In this app, each family of related infrared commands is collected into a
21 "keyset". As manufacturers commonly reuse a given set of commands rather
22 than re-invent the wheel each time they come out with a new product, many
23 devices can share the same keyset.
27 Pierogi also follows the classic concept of a universal remote, by having
28 a common set of buttons that are reused for each device. So, for example,
29 the "power" button has the same name and is located in the same position,
30 no matter what keyset is currently in use -- even if that keyset has a
31 different name for "power", or has no "power" command at all. (Check out
32 the <a href="http://en.wikipedia.org/wiki/Universal_remote">Universal
33 Remote wiki</a> for a description of universal remote controls, which
34 includes a special mention of the N900!)
38 So in short, to use Pierogi, you first select an appropriate keyset, then
39 press the appropriate buttons to control the target device. More detail on
40 the features of Pierogi is provided below.
43 <h2>Using Pierogi</h2>
46 The current Pierogi design is built around a tabbed window, each tab containing
47 a group of related buttons. Depending on the keyset that has been selected,
48 some of these buttons will be active, others inactive. Active buttons are ones
49 which have been associated with a command in the current keyset. Pressing an
50 active button will begin repeating the associated command; letting up on the
51 button will stop the command.
55 Keysets can be chosen using the "Select Keyset" option in the drop-down menu.
56 If you have a particular keyset you use often, it can be stored in the
57 "favorites" tab for quick access.
62 <p>The Main tab contains just the power, volume, and channel buttons. It is
63 intended to be a quick way to get to the most important, commonly used
64 controls. The name of the current keyset is also provided in this tab.</p>
68 <p>The Utility tab contains a selection of commonly useful controls, such as
69 "Mute", "Sleep", "Input", "Closed Captions / Subtitles", and the color buttons.
70 This tab is intended to be a quick way to reach the most frequently used
71 buttons; as such, the selection may be updated in future versions of Pierogi.
76 <p>This tab provides a numeric keypad and a handful of associated commands,
77 intended mainly for use with televisions. The "Prev Channel" button should
78 take you to the previously selected channel, if any. The "Dash" button
79 should allow you to specify a digital subchannel, as in "16-4". The "+100"
80 button is used for television sets which normally expect only two digits
81 per channel; using this button allows you to enter a third digit. The "-/--
82 Double Digit" button is used on very old televisions that normally expect
83 channels to be represented by just a single digit; pressing this should
84 allow you to enter a second digit.</p>
88 <p>This tab contains buttons used to enter and exit a menu, navigate within
89 a menu, and select menu entries. The "Menu" button is meant to enter the
90 main system menu of a given device; "Guide" is a content-related menu available
91 on many modern devices; and "Disc Menu" is used to access the menu interface
92 provided with DVD and Blu-Ray media.</p>
96 <p>Many of the most important playback commands are represented on this tab.
97 "Play", "Pause", and "Stop" are the most common ones, along with "Reverse"
98 (often called rewind) and "Fast Forward". A variety of other less common
99 navigation controls are included, along with the "Eject" command.</p>
103 <p>This is another page of media buttons, containing a mix of commands useful
104 for DVD players, VCRs, audio devices, and possibly other devices. The content
105 of this page may change in the future.</p>
109 <p>This page contains several more TV-oriented buttons, including controls for
110 picture-in-picture, teletext, and some graphics and audio controls. The
111 content of this page is subject to change.</p>
113 <h3>Favorite Tab</h3>
115 <p>As there are numerous keysets available in Pierogi, a "Favorite" tab has
116 been implemented. To add a favorite keyset to the tab, first select that
117 keyset from the "Select Keyset" window. Then, navigate to the Favorite tab
118 and press "Add Current Keyset".</p>
120 <p>Once you have added some keysets to the favorites list, you can tell
121 Pierogi to use one by simply selecting that keyset from the list.</p>
123 <p>A keyset can be removed from the list by selecting it and pressing
124 "Remove Selected Keyset".</p>
126 <h3>Select Keyset Window</h3>
128 <p>The Select Keyset window presents a list of all the keysets currently
129 available in Pierogi. As this list is fairly long, buttons have been added
130 at the top of the window that allows you to choose the make and/or type of
131 device you are trying to control; all keysets not associated with the chosen
132 make or type will be hidden. To use a keyset, simply select it from the list,
133 and then close the window (by pressing the return arrow at the top right of
136 <h2>Design Rationale</h2>
138 <p>Here I collect my thoughts on the how and why of creating Pierogi.</p>
140 <h3>Hasn't this been done before?</h3>
142 <p>Yes, remote control software has already been written for the N900. In
144 <a href="http://irreco.garage.maemo.org/">Irreco / QtIrreco</a> project
145 creates beautiful virtual remote controls. I've also used the
146 <a href="http://thp.io/2010/raemote/">Raemote</a> widget to control my Apple
147 computers. But these programs have their shortcomings; in particular, they
148 are not universal. Each simulated remote control in QtIrreco is a completely
149 separate animal. I would like to have a standard set of buttons that I can
150 use on all sorts of different hardware.</p>
152 <h3>What's up with LIRC?</h3>
154 <p>Just as QtIrreco and Raemote do, I want to leverage the work of the
155 <a href="http://www.lirc.org/">Linux Infrared Remote Control</a> project.
156 The LIRC project is by far the most influential open-source effort working
157 with consumer IR. And the N900 comes with a device driver made
158 specifically for their server! But, you see, I have a problem. I
159 don't want to do things the way LIRC wants to do things.</p>
161 <p>The N900 is different from other Linux systems using IR -- rather than
162 being the machine at which you point a remote control, this machine <i>is</i>
163 the remote control. This is not what LIRC was designed for; the heart of the
164 LIRC project is a server that will sit and wait for messages to arrive from
165 the IR system. Although it can also broadcast IR data back out (when using
166 hardware that supports 2-way IR communication), that is not its primary
169 <p>I believe there are three disadvantages to using the LIRC server as it
170 currently exists. First, there isn't much point to running a daemon on
171 the N900 to manage the IR device; no messages are ever going to come in from
172 the output-only hardware on the N900, so why sit and listen for them?</p>
174 <p>The second problem is somewhat larger. LIRC uses configuration files to
175 describe the command set for each remote control. And there are a lot of them.
176 A whole lot. We're talking thousands of files here, and each file can describe
177 many remote controls. This is not a problem for Raemote or Irreco, as they
178 only need to deal with one config file at a time. But if you're aiming to
179 manage the whole lot of them, you need to find a way to deal with the
182 <p>The third problem is more subtle, but really tough to crack. You see, the
183 whole point of LIRC is to take the commands it receives from the IR port and
184 translate them into something recognizable. As such, each config file provides
185 a mapping from numeric commands to human-readable strings. This is a
186 serious problem, if your interest is in finding similar commands in
187 different config files! Take, for example, the "power"
188 button found on most remote controls. In some config files, the string for
189 this is "power". Others have "Power", or "POWER". You can also find "pwr",
190 "PWR", "ON/OFF", "ON-OFF", "ONOFF", "POWER_ON_OFF", "KEY_POWER", "Operate",
191 "Standby", and who knows what else. And, you've gotta be careful not to get
192 confused by strings like "SUBTITLE_ON/OFF" or "TV_ON_TIMER". How is an app to
193 know which key to map all these strings to?</p>
195 <h3>So how is Pierogi different?</h3>
198 Pierogi attempts to answer these problems. First, it talks directly to the
199 /dev/lirc0 device, no server middleman needed. Yes, you can use Pierogi
200 without the LIRC daemon running; in fact, there's no need to ever install it.
201 Second, Pierogi is built
202 around the concept of the "keyset"; all IR codes that can share the same
203 protocol without interfering with one another are combined into a single
204 family of related commands. In short, this reduces the quantity of data
205 available from LIRC config files to something much more manageable.</p>
207 <p>The third problem mentioned above is a bit harder to solve; I'm currently
208 mapping each LIRC string to a corresponding Pierogi key by hand. Naturally,
209 this process will be fraught with errors; I intend to keep updating Pierogi
210 as these errors are found and fixed.
213 <h2>Internal Design Notes</h2>
215 <p>If you're interested in the ugly details of the code, read on!</p>
217 <h3>What's up with the name of this app?</h3>
219 <p>Lately I've been naming my projects after tasty foods. In particular,
220 I've been working my way through the pasta-oriented dishes. (My previous
221 project, "Linguine", has gotten bogged down, so I moved on to this one...)</p>
225 <p>I'm a C++ kind of guy, it just makes sense to me to use a C++ kind of
226 interface. The Qt classes have everything you need to set up a decent UI,
227 and Qt Creator makes coding up a project for the N900 relatively
228 painless. Check it out for yourself at
229 <a href="http://qt.nokia.com/">the Qt webpage</a>.
232 <h3>The simplest device ever!</h3>
234 <p>If you ever wanted to learn how to work with device drivers on Linux, the
235 N900's infrared port is the device you want to start with. It's not
236 much more than a flashlight: You turn it on. You turn it off. You turn it on
237 again. You turn it off again. You really can't get much simpler than that.
238 Interaction with the "/dev/lirc0" device involves no more than handing
239 it an array of integers: the first integer being an amount of time to keep the
240 light lit (in microseconds), the second being an amount of time to leave it
241 switched off, the third on, the fourth off, and so on.</p>
243 <p>Well, ok, so it involves just a little bit more than that. You don't want
244 to leave the light stuck in the "on" state when you are finished, so the driver
245 demands that the last item in every array be an "on" amount -- after finishing
246 that timer, the IR will stay off until the next command arrives.
250 Also, in an attempt to weed out any confusing signals from natural IR sources
251 in the environment, consumer IR devices are "pulsed" at a particular
252 frequency. So you're really turning a strobelight on and off, not just a
253 flashlight. When the receiver sees that the light is coming from a strobelight
254 pulsing at the desired frequency, it can be assured that that signal came from
255 an actual remote control. The N900's device driver allows you to set the
256 frequency anywhere between 20000 Hz and 500000 Hz. 38000 Hz seems to the most
257 popular frequency used by modern remote controls, at least from what you find
258 in LIRC config files. Also, you can set how long each pulse needs to be held,
259 in terms of a percentage: 25% means turning the light on for just one quarter
260 of the pulse, 33% means leaving it on for one third, etc. This is called the
261 "duty cycle", and can be anywhere between 0 and 100 percent. LIRC's default
262 duty cycle is 50 percent.
265 <p>And that's about it. I've been using a
266 <a href="http://svn.jacekowski.org/host_mode/trunk/drivers/input/lirc/lirc_rx51.c">web page</a>
267 that lists the source code for the IR device driver. I'm not sure if there's
268 a better location out there for N900 source code, but this seems accurate
271 <h3>You did <i>what</i> to the LIRC daemon?</h3>
274 Well, ok, yeah, I've cannibalized the transmission code out of the LIRC
275 server and dumped it into my app. Sort of. I can't really keep my hands off
276 of code once I've seen it, so I've rewritten it in C++, reorganizing it in
277 an object-oriented manner along the way.</p>
280 As I have progressed in adding support for additional IR protocols, I'm
281 beginning to see why the authors of the LIRC made the attempt to compress
282 every possible IR protocol into a straightforward count of individual IR
283 pulses. The total number of IR protocols in use is amazing, and many of them
284 (through oversight or due to the longevity of their use) are mind-numbingly
285 complicated to deal with. Still, I believe that separating the major protocols
286 into their own code paths results in code that is easier to understand and
287 maintain; I'm slowly moving away from the LIRC's system to my own as time
292 In any case, I owe the LIRC authors a deep debt of gratitude for their
293 efforts. If you are one such author, thank you. As Pierogi is more-or-less
294 derived directly from their work, it is also licensed under the same terms,
295 the GNU General Public License (GPL) version 2 or later.
300 <p>I've fallen in love with the Gentleface Mono Icon Set. Of the creative
301 commons icon sets available, theirs stands head and shoulders above the rest.
302 Find their work at <a href="http://www.gentleface.com">www.gentleface.com</a>.
306 <p>A set of links to some resources I've used while writing the code.</p>
309 <li>The center of the Linux infrared world, the
310 <a href="http://www.lirc.org/">Linux Infrared Remote Control</a> project.
312 <li>A <a href="http://en.wikipedia.org/wiki/Consumer_IR">Wiki page</a> with
313 general info on consumer IR
315 <li>A <a href="http://www.sbprojects.com/knowledge/ir/index.php">good introduction</a>
316 to the theory and practice behind consumer IR devices
318 <li>A <a href="http://en.wikipedia.org/wiki/RC-5">Wiki for the RC-5 protocol</a>
320 <li>Some <a href="http://www.sbprojects.com/knowledge/ir/nec.php">Info on the NEC protocol</a>
322 <li>Some <a href="http://www2.renesas.com/faq/en/mi_com/f_com_remo.html">More info on the NEC protocol</a>
324 <li>An introduction to the <a href="http://www.sbprojects.com/knowledge/ir/sirc.php">Sony SIRC protocol</a>
326 <li>An excellent collection of <a href="http://www.hifi-remote.com/sony/">Sony command codes</a>
328 <li>An in-depth investigation of the <a href="http://www.adrian-kingston.com/IRFormatPioneer.htm">Pioneer IR Protocol</a>
330 <li>Link to (what appears to be) source code for the N900's
331 <a href="http://svn.jacekowski.org/host_mode/trunk/drivers/input/lirc/lirc_rx51.c">/dev/lirc0 device driver</a>.
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