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59 lines
2.9 KiB
Plaintext
59 lines
2.9 KiB
Plaintext
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(NOTE: view this file with a monospaced font)
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04. Adding a new platform to eLua
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================================================================================
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If you want to add a new platform to eLua, the first thing you need to check is
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if the platform has enough resources to run Lua. Roughly speaking, 256k of Flash
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(or even 128k for the integer-only version) and 64k of RAM should be enough for
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a 32-bit platform. As usual, the more, the better (this is especially true for
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the RAM memory).
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Next, check if a GCC/Newlib toolchain is available for the platform. TO be more
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precise, the compiler doesn't really matter, as long as you're able to compile
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Newlib with it. If you don't, you won't be able to compile eLua. This limitation
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might be eliminated in future versions, but it's not a priority of the project,
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so don't count on it happening too soon.
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After this, you need to make sure that you have a basic understanding of the
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platform, or at least of its initialization sequence. Most platforms require
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specific sequences for initializing the clock subsystem, or for disabling the
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watchdog timer, or for remapping the internal memory, and many others.
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Fortunately the vast majority of chips manufacturers provide support packages
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for their CPUs, so once you download the support package and understand the
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initialization code, you should be safe. At the very least, you'll need:
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- a "startup" sequence, generally written in assembler, that does very low level
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intialization, sets the stack pointer, zeroes the BSS section, copies ROM to
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RAM for the DATA section, and then jumps to main.
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- a linker command file for GNU LD.
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- the "high-level" initialization code (for example peripheral initialization).
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Let's suppose that your new platform is called "foo". In order to compile eLua
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for foo, follow these steps:
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1. create the src/platform/foo directory
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2. change the main build script (SConstruct) to include your new platform:
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(BEGIN SConstruct)
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..........................
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# Sanity check
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if platform not in [ 'at91sam7x', 'i386', 'foo' ]:
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print "Invalid platform", platform
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sys.exit( -1 )
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..........................
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(END SConstruct)
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3. you need at least 3 files (besides your platform specific files) in the
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src/platform/foo directory:
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- conf.py: this is read by SConstruct and describes how to build files for
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the platform, as well as the platform specific files. Start from an existent
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conf.py file and modify it to suit your needs, it's easier this way.
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- type.h: data types used by eLua, declared in a platform independent way.
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Again, start from an existent type.h file and modify it if needed.
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- platform_libs.h: see "platform modules.txt" for details.
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4. implement the platform interface functions (see "platform interface.txt"). By
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convention, they should be implemented in a file called "platform.c".
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5. That's it! Build (see "building.txt") and enjoy!
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