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144 lines
9.3 KiB
HTML
144 lines
9.3 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Strict//EN">
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<html><head>
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<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
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<meta http-equiv="Content-Language" content="en-us"><title>Product</title>
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<link rel="stylesheet" type="text/css" href="../style.css"></head>
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<body style="background-color: rgb(255, 255, 255);">
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<h3>Lua Code Examples</h3>eLua distros come bundled with nice and fun
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(yes! we have games too! :) Lua programs examples in the File System.
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They are also included in the eLua
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source code distribution, under the /romfs subdirectory. <br>Lua example programs for eLua are also presented and commented here. <br>As previously explained, you can run them directly from eLua's file
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system or you can use the eLua shell and send them via XMODEM, as
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described <a href="using.html#shell">here</a>.<br><br>
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<h3><a name="hello"></a>hello.lua: the ubiquitous "Hello, World!"</h3>
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<p><strong>Runs on: </strong><br>All Targets</p><p><strong></strong>
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<strong>Description:<br></strong>To call this a "program" is a gross overstatement, but it's a
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tradition, so we respect it :) It just prints "Hello, World!" on the terminal and
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returns to the shell. Download it only if you feel too lazy to fire up
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the lua interpreter inside eLua and write it yourself :)</p><p><strong>Commented Source Code:</strong><br></p><p>print("Hello World")</p>
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<h2><br></h2><h3><a name="info"></a>info.lua: getting the platform data</h3>
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<p><strong>Runs on: </strong><br>All targets except i386</p><p><strong>Description:<br></strong>
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This isn't really more advanced than "Hello, World!", but it does show
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an eLua specific module: the platform data module (pd). You can read
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more about the platform modules in the eLua source distribution
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(docs/platform_modules.txt). The program will display the platform
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name, the CPU name, the board name and the CPU clock and then will exit
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to the shell.</p><p><strong>Commented Source Code:</strong></p><p><span style="font-family: Courier New;">-- Uses module pd to access platform data and print it on the Terminal</span><br style="font-family: Courier New;"><span style="font-family: Courier New;">print( "I'm running on platform " .. pd.platform() ) </span><br style="font-family: Courier New;"><span style="font-family: Courier New;">print( "The CPU is a " .. pd.cpu() )</span><br style="font-family: Courier New;"><span style="font-family: Courier New;"><span>print( "The board name is " .. pd.board(</span>) )</span><br></p><p></p>
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<h3><a name="led"></a>led.lua: the old LED blinker, the new eLua way</h3>
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<p><strong>Runs on: </strong><br>All targets except i386</p><p><strong>Description:<br></strong><strong></strong>
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Now we get to do something "more embedded": blink a LED. The code ilustrates a few interesting eLua features:</p>
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<ul><li><p>cross platform code: the code assigns a different pin
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to the LED starting from the board name. You can see how the platform
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data module makes it very easy to write such portable code.</p></li><li><p>uart, pio, tmr, pd modules: they are all used here.</p></li></ul>
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<p>Watch it blink, then press any key to return to the eLua shell.</p><p><strong>Commented Source Code:</strong></p>
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<h3><a name="hangman"></a>hangman.lua: taking advantage of your terminal</h3>
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<p><strong>Runs on: </strong><br>All Targets except i386</p><strong></strong>
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<strong></strong><p><strong>Description:<br></strong>By far the geekiest example from the eLua distribution (or would it be morse.lua? :), it makes use of
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the term module (docs/terminal_support.txt) to let the user play a
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BSD-like "hangman" directly in his terminal emulator. Run the example
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and enjoy. Currently it has a very small list of words, as this was
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written mainly as a proof of eLua's capabilities, but it's very easy to
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add new words/replace the existing ones. A screenshot can be seen <a href="http://elua.berlios.de/other/elua_hangman.png">here</a>.</p><p></p>
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<h3><a name="pwmled"></a>pwmled.lua: LED blinker, advanced class</h3><p><strong>Runs on: </strong><br>EK-LM3S8962, EK-LM3S6965</p><strong></strong>
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<strong></strong><p><strong>Description:<br></strong>
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This uses the PWM module to fade the on-board LED in and out, in an
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infinite loop. Not much to say here, the code is very simple, yet the
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results are quite spectacular. Press any key to end the sample and
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return to the shell.</p><p></p>
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<h3><a name="tvbgone"></a>tvbgone.lua: yes, eLua can do real time!</h3>
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<p><strong>Runs on: </strong><br>EK-LM3S8962, EK-LM3S6965</p><strong></strong>
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<strong></strong><p><strong>Description:<br></strong>This is more complex, but also very important for eLua, because it
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proves that real time applications (with relatively strict timing
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requirements) can run from eLua directly. It's the famous TV-B-Gone
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project adapted from <a href="http://www.ladyada.net/make/tvbgone/">LadyAda's kit</a>.
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If you're not familiar with TV-B-Gone, it knows how to do one thing
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very well: power off your TV :) Basically it contains a lot of remote
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control codes (for a lot of TVs) that are continously sent via an IR
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LED. This code uses the PWM module (new in eLua 0.4) and it also does
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file I/O from Lua, since the remote control codes are kept in a
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separate file (which is also part of the ROM file system). To read the
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binary file, the "pack" module (also new in 0.4) is used. To ensure
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that we don't get any unexpected delays, the Lua garbage collector is
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turned off. Take a look at this sample, it's both a very good proof of
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the capabilities of eLua and a good learning resource. To use it on any
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of the Cortex boards (EK-LM3S8962 or EK-LM3S6965) connect an IR LED
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with a resistor between the "PWM2" and "GND" pins of the extension
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connector. Get close to your TV and press the "select" button on your
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board to start sending the IR codes. The on-board LED stays lit while
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the codes are transmitted and shuts off afterwards. Press the "down"
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button on your board to exit the application and return to the shell.</p><p></p>
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<h3><a name="piano"></a>piano.lua: because PWM is great</h3><p><strong>Runs on: </strong><br>EK-LM3S8962, EK-LM3S6965, SAM7-EX256</p><strong></strong>
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<strong></strong><p><strong>Description:<br></strong>
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Yet another use for the PWM module, this sample can be used to "play"
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notes via the on-board speaker using the PC keyboard. The on-screen
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keyboard shows what keys you must press for different notes, and you
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can set your octave and inter-note delay. Press ESC to end your eLua
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musical session :) A screenshot can be seen <a href="http://elua.berlios.de/other/elua_piano.png">here</a>.</p><p></p>
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<h3><a name="bisect"></a>bisect.lua: floating point at its best</h3>
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<p><strong>Runs on: </strong><br>All Targets</p><strong></strong>
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<strong></strong><p><strong>Description:<br></strong>This is taken directly from the official Lua distribution, and it's
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here to show that eLua can do floating point just like on a desktop
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machine, albeit slower. Run it on your target, then run it again, but
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this time on the PC, and compare the results. Yes, they are identical.</p><p></p>
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<h3><a name="morse"></a>morse.lua: because PWM is great, part II</h3>
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<p><strong>Runs on: </strong><br>EK-LM3S8962, EK-LM3S6965, SAM7-EX256</p><strong></strong>
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<strong></strong><p><strong>Description:<br></strong>This uses the same PWM module for Morse code generation. Just enter a
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text, and listen to it getting Morsed on your board's speaker and on a blinking Led. The
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letters and Morse codes are also shown on the terminal. Use '+' and
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'-'' to change the frequency, up and down arrows to change the speed,
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's' to mute/unmute, and ESC to exit.</p><p></p>
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<h3><a name="lhttpd"></a>lhttpd.lua: only with (e)Lua ...</h3>
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<p><strong>Runs on: </strong><br>EK-LM3S8962, EK-LM3S6965<strong></strong>
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<strong></strong><br></p><p><strong>Description:<br></strong>This is one of those things that can show the real potential of a
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language (and hopefully the real potential of eLua in this case). As
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you have probably guessed by now, it's a web server written in Lua.
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Except that it is much more than this: it's a scripting web server! That's
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right, you can embed parts of Lua code into your pages, and the server
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will parse them and replace the Lua code with its output. To output
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something from Lua code embedded in a web page, simply use "print" in
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your Lua code. You can also write your pages completely in Lua (again,
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using "print"), the server knows how to handle this too. When is the
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last time you heard about a scripting web server in 256k of Flash/64k
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of RAM? </p><p>The full list of features is given below:</p>
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<ul><li>completely written in Lua</li><li>can handle a single connection at a time (for now)</li><li>can serve text and images (so far)</li><li>gets its files from the ROM file system (this will be extended when more filesystems are added)</li><li>can
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execute embedded Lua code and replace it with its output (via "print"
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statements). Embed Lua code in your HTML files between tags, make sure
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your HTML file extension is ".pht", and the server will preprocess it
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and replace the Lua code with its output</li><li>if a file with
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".lua" extension is requested, it doesn't send the file, but executes
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it and sends its output (via "print" statements)</li></ul>
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<p>This is still work in progress, but it already works quite well.
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Take a look at romfs/index.pht and romfs/test.lua from the source
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distribution for an example of how to include Lua code in your HTML
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files.</p><p></p><p></p><p></p></body></html>
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