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78 lines
3.4 KiB
Text
78 lines
3.4 KiB
Text
Samples of GNU Tools for ARM Embedded Processors v4.7+
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* Directory structure *
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samples/startup - Startup code needed by samples
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/ldscripts - Shared linker script pieces needed by samples
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/src - Sample source code and Makefile, each sub-dir is a case
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* Build *
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For Windows, linux-like tools is required to run command like make and rm.
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These samples are tested with cygwin.
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To build all samples, set arm-none-eabi-gcc in path, cd src and make.
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The makefile is configured to use newlib-nano by default. To disable it,
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pass USE_NANO= to make command line like:
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$ make USE_NANO=
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The makefile is configured to build for Cortex-M0 by default. To build for
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M3 or M4, pass CORTEX_M=3/4 respectively:
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$ make CORTEX_M=3
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* Porting *
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These samples are written in a way that easily porting to variant Cortex-M
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boards. Usually there are only two files you need modify for your boards.
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ldscripts/mem.ld defines address ranges for flash and RAM. Modify them to
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reflect start address and length of flash/RAM banks in your board, by
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following the embedded comments.
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src/retarget/retarget.c implements how to initialize UART, send/receive
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strings via UART. Since UART is configured and operated differently in
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different boards, you need put your board specific code in retarget.c
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to make UART work.
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Recommend to make clean after modifying mem.ld.
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* Sample cases introduction *
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** minimum - A minimum skeleton to start a C program with limited features.
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This case has a empty main. Code size built from it is only about 150 bytes,
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since it has almost no "fat" for a Cortex-M C program. Be noticed that this
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case doesn't support semihosting or C++ global constructor/destructor.
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** semihost - Show how to use semihosting for file IO.
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This case uses printf to output a string. Here printf is backup by
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semihosting, which does the real print job to a host machine.
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** retarget - Show how to use retarget (UART) for standard IO.
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This case uses printf to output a string. Here printf is backup by retarget.
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There is a retarget.c showing which libc interfaces need overloading to
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re-direct file IO operations to on-board devices (usually UART). This case
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isn't complete, real board specific code need adding to make UART work.
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This case also doesn't support semihosting or C++ global
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constructor/destructor.
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** fpout - Show how to print floating point.
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This case uses printf from newlib-nano to print floating point values. Since
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newlib-nano by default doesn't link code needed by floating point IO, this
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case demonstrates how to use this function in command line options. It also
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uses semihosting.
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** fpin - Show how to input/output floating point.
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This case uses sscanf from newlib-nano to input floating point values. Since
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newlib-nano by default doesn't link code needed by floating point IO, this
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case demonstrates how to use this function in command line options. It also
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uses semihosting.
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** qemu - Show how to build a Cortex-M bare-metal program running on qemu.
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This case builds a simple application that can run on qemu for ARM. It uses
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semihosting for file IO, which qemu supports.
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** cpp - How to setup a C++ project
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This case builds a simple C++ application using memory allocator, integer IO
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and global constructor/destructor.
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** multiram - How to use multiple RAM banks
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This case works with system with two RAM banks. It include startup and linker
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scripts that initializing multiple data sections and bss sections.
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