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More cleanup
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Tido Klaassen
@@ -1,12 +1,16 @@
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# ARM Cortex-M Port
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Author: Tido Klaassen <tido@4gh.eu>
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License: BSD Revised. Needs libopencm3, which is LGPLv3.
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## Summary and Prerequisites
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This port should run on any Cortex-M0/3/4/4F (M0+ not tested).
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It uses RedHat's [newlib](https://sourceware.org/newlib/) and [libopencm3]
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(https://github.com/libopencm3/libopencm3). You will also need an ARM compiler
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toolchain. If you want to flash or debug your target, [openocd](http://openocd.org)
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is also a must. For STM32 targets [stlink](https://github.com/texane/stlink)
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might also be helpful.
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is also a must. For STM32 targets [stlink](https://github.com/texane/stlink)
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might be helpful.
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On Debian systems, compiler, newlib and openocd can easily be installed by the
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package manager (untested, not going to set up a new system just to test this):
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@@ -27,7 +31,7 @@ There are additional subdirectories:
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* **boards** contains subdirectories for specific hardware. Each
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board needs at least a Makefile fragment, which defines certain variables
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describing the hardware used, as well as a list of extra object files needed.
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There will usually be at least a ``board_setup.c``, which contains code to
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There will usually be at least a `board_setup.c`, which contains code to
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initialise the hardware properly (clocks, UART, systick timer, GPIOs, etc.).
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* **common** contains code needed by multiple boards, such as
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@@ -35,14 +39,14 @@ stub functions for newlib or routines shared by multiple boards using the
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same family of target MCUs.
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* **linker** contains linker script fragments for specific target MCUs. These
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just define the target's memory areas (RAM, Flash)and include libopencm3's
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main linker script for the appropriate chip family
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just define the target's memory areas (RAM, Flash) and include libopencm3's
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main linker script for the appropriate chip family.
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* **libopencm3** unless you compile and link against an external installation
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of libopencm3, this will be a Git submodule containing, surprise!, libopencm3
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of libopencm3, this will be a Git submodule containing, surprise!, libopencm3.
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* **build** this is a temporary directory where all object files end up in and
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which will be removed by ``make clean``
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which will be removed by `make clean`.
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## Build Preparation
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Unless you decide to use an external installation of libopencm3, you will have
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@@ -77,14 +81,14 @@ use it to flash the application image:
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```
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make BOARD=*yourboard* BINARY=*yourimage* flash
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```
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NB: with the ek-lm4f120xl board openocd will report an error after flashing.
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N.B.: with the ek-lm4f120xl board openocd will report an error after flashing.
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I think it is because it can not handle the changed core clock after the
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application starts, but I simply can't be bothered to further investigate this.
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The application gets flashed and you can ignore the error.
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## Adding New Boards
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To add support for a new board, you will have to provide at least two parts.
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First, a ``Makefile.include`` to be pulled in by the main Makefile. Second,
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First, a `Makefile.include` to be pulled in by the main Makefile. Second,
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some set-up code for your specific hardware. If there is no linker script for
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your MCU, you will have to add one, too.
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@@ -111,47 +115,47 @@ objs += board_setup.o
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objs += stubs.o stm32_con.o
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```
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**TARGET** is the name for the actual MCU used on your board. It will be used
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to locate the linker script file in the ``linker`` directory by appending
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``.ld`` to it.
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* **TARGET** is the name for the actual MCU used on your board. It will be used
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to locate the linker script file in the `linker` directory by appending
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`.ld` to it.
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**LIBNAME** is the name of the opencm3 library to link your object files
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* **LIBNAME** is the name of the opencm3 library to link your object files
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against.
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**DEFS** are flags that will be appended to the CPPFLAGS. You will at least
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* **DEFS** are flags that will be appended to the CPPFLAGS. You will at least
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have to define the opencm3 target family (STM32F1 here), so the build process
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will find the right header files to include. If you are using the stub and
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console functions provided in the common directory, you will also have to
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define the reserved main stack size (MST_SIZE) and which UART to use for stdio
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(STD_CON).
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**FP_FLAGS** which floating point format to use. For MCUs without hardware
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support for floating point (M0/3, sometimes 4), use ``-msoft-float``,
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otherwise use ``-mfloat-abi=hard -mfpu=fpv4-sp-d16``. You could add these
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directly to ``ARCH_FLAGS``, but this way it is easily overridden from the
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* **FP_FLAGS** which floating point format to use. For MCUs without hardware
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support for floating point (M0/3, sometimes 4), use `-msoft-float`,
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otherwise use `-mfloat-abi=hard -mfpu=fpv4-sp-d16`. You could add these
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directly to `ARCH_FLAGS`, but this way it is easily overridden from the
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make command line.
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**ARCH_FLAGS** specify the instruction (sub)set and CPU type to compile for,
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as well as any quirk tunings needed and the ``FP_FLAGS``. These flags are
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* **ARCH_FLAGS** specify the instruction (sub)set and CPU type to compile for,
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as well as any quirk tunings needed and the `FP_FLAGS`. These flags are
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handed to preprocessor, compiler, assembler and linker.
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The following flags are only used for flashing the target with openocd:
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**OOCD** binary to call. Give full path if it is not in your PATH environment
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* **OOCD** binary to call. Give full path if it is not in your PATH environment
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variable.
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**OOCD_INTERFACE** tells open which interface config to use
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* **OOCD_INTERFACE** tells open which interface config to use
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**OOCD_BOARD** tells openocd which board config file to use.
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* **OOCD_BOARD** tells openocd which board config file to use.
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**objs** here you __append__ object files to include into __all__ binaries
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* **objs** here you _append_ object files to include into _all_ binaries
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built for this board. The main Makefile will search for matching source files
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(*.c and *.S) in the main port directory, the board directory and the common
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directory. You will usually have at least a ``board_setup.c`` specific to
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directory. You will usually have at least a `board_setup.c` specific to
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your hardware and pull in the system and stdio stubs provided in the
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``common`` directory.
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`common` directory.
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As you will probably know, variables assigned with the ``?=`` operator are
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As you will probably know, variables assigned with the `?=` operator are
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only altered if they have not been already set. This way you can easily test
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different options for a build by providing the variables on the make command
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line.
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@@ -169,13 +173,13 @@ atomthread's kernel. At the very least you will have to
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interact with the outside world in any way...)
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The test suit programs expect your board set-up code to provide a function
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named ``int board_setup(void)`` to perform this tasks.
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named `int board_setup(void)` to perform this tasks.
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### Linker Script
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If you are using an hitherto unknown target MCU, you will have to provide a
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linker script for it in the ``linker`` directory. The script's name must
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be the same as given to the ``TARGET`` variable in your Makefile.include,
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with the extension ``.ld`` added. It is recommended that you just define
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linker script for it in the `linker` directory. The script's name must
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be the same as given to the `TARGET` variable in your Makefile.include,
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with the extension `.ld` added. It is recommended that you just define
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your MCU's memory regions and include libopencm3's linker file for your
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target's product family. Please look at the provided linker files for examples
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on how to do this.
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@@ -29,6 +29,9 @@
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.syntax unified
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/**
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* Create more readable defines for usable intruction set and FPU
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*/
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#undef THUMB_2
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#undef WITH_FPU
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@@ -40,10 +43,15 @@
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#define WITH_FPU
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#endif
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/**
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* Extern variables needed for context switching and first thread restore
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*/
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.extern CTX_SW_NFO
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.extern _stack
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.extern vector_table
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/**
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* Some bit masks and registers used
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*/
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.equ FPU_USED, 0x00000010
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.equ SCB_ICSR, 0xE000ED04
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.equ PENDSVCLR, 0x08000000
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@@ -56,7 +64,7 @@
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.thumb_func
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archFirstThreadRestore:
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/**
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* Disable interrupts. They should be disabled anyways, but just
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* Disable interrupts. They should be disabled anyway, but just
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* to make sure...
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*/
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movs r1, #1
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@@ -71,9 +79,9 @@ archFirstThreadRestore:
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msr MSP, r1
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/* Update ctx_switch_info, set this thread as both running and next */
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ldr r1, = CTX_SW_NFO
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ldr r1, = CTX_SW_NFO
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str r0, [r1, #0]
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str r0, [r1, #4]
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str r0, [r1, #4]
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/* Get thread stack pointer from tcb. Conveniently the first element */
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ldr r1, [r0, #0]
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@@ -83,9 +91,9 @@ archFirstThreadRestore:
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* Set bit #1 in CONTROL. Causes switch to PSP, so we can work directly
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* with SP now and use pop/push.
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*/
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movs r1, #2
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movs r1, #2
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mrs r2, CONTROL
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orrs r2, r2, r1
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orrs r2, r2, r1
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msr CONTROL, r2
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/**
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@@ -119,8 +127,8 @@ archFirstThreadRestore:
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* Move SP to position of r8 and restore high registers by loading
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* them to r4-r7 before moving them to r8-r11
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*/
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add SP, #16
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pop {r4-r7}
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add SP, #16
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pop {r4-r7}
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mov r8, r4
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mov r9, r5
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mov r10, r6
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