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