Building scripts and tools for RTEMS RTOS.

Building process is completely automated with the script build_rtems.sh. This chapter describes how to use this script in a custom application.

Note that first time build requires Internet connection and takes around 40 minutes to complete.

• --cpu
  • Argument: CPU family name.
  • Description: Defines RTEMS target architecture.
  • Required: Yes
  • Example: --cpu=arm
• --bsp
  • Argument: Name of the board support package (BSP).
  • Description: Defines RTEMS BSP to use with the application.
  • Required: Yes
  • Example: --bsp=stm32f4
• --overwrite-bsp-dir
  • Argument: Absolute path to an external BSP directory.
  • Description: Allows to use an external board support package (BSP) sources. If directory name of the custom BSP conflicts with directory name of a standard BSP, the latter will be removed. Use this option if your application needs custom BSP.
  • Required: No
  • Example: --overwrite-bsp-dir=src/my-custom-bsp
• --amend-bsp-dir
  • Argument: Absolute path to an external BSP directory.
  • Description: Allows to overwrite some files of an existing BSP using cp -rf. Use this option if your application only needs to make some minor changes to a standard BSP.
  • Required: No
  • Example: --amend-bsp-dir=src/stm32f4
• --remove-unused-bsp
  • Description: Instructs the builder to remove all architectures and BSP that are unused in this build. This can speed up the build significantly.
  • Required: No
  • Example: --remove-unused-bsp

This variable allows the application to pass additional options to the RTEMS configure script. Please refer to the RTEMS documentation to learn more about available options, or just execute rtems/configure --help to see the list.

Example:

export RTEMS_CONFIGURE_EXTRA_OPTIONS="\
--disable-itron \
--disable-networking \
--disable-multiprocessing \
USE_TICKS_FOR_STATISTICS=1 \
CXXFLAGS_FOR_TARGET=-fno-exceptions \
"

This variable allows the application to pass additional options to RTEMS source builder (RSB). Please refer to the RSB documentation to learn more about available options.

Example:

export RTEMS_RSB_EXTRA_OPTIONS="--targetcxxflags=-fno-exceptions --libstdcxxflags=-fno-exceptions"

When build_rtems.sh completes successfully, the following outputs are generated:

• RTEMS GCC toolchain under zubax_rtems/toolchain
• RTEMS libraries under zubax_rtems/bsps
• Environment configuration file zubax_rtems/env.sh

The file env.sh is the main product of the build process. The application needs to source this file before invoking make. When sourced, this file alters the PATH variable so it contains references to the RTEMS toolchain, and also it sets the variable RTEMS_MAKEFILE_PATH which is required for the RTEMS build system.

When env.sh is sourced, the application can use make as shown in the RTEMS example applications. However, it may be beneficial to use application.mk instead of relying on the raw RTEMS build system, as it provides a few convenient abstractions. Since there's no user manual available for application.mk, the reader is advised to read the source to learn how to use it.

This example shows a possible way to build RTEMS for STM32.

# Complete list of BSP-specific options can be found in "<bsp-dir>/configure.ac".
export STM32F4_HSE_OSCILLATOR=8000000
export STM32F4_SYSCLK=8000000
export STM32F4_HCLK=$STM32F4_SYSCLK
export STM32F4_PCLK1=8000000
export STM32F4_PCLK2=$STM32F4_SYSCLK
export STM32F4_USART_BAUD=115200
export STM32F4_ENABLE_USART_1=""
export STM32F4_ENABLE_USART_2="1"
export STM32F4_ENABLE_USART_3="1"
export STM32F4_ENABLE_UART_4=""
export STM32F4_ENABLE_UART_5=""
export STM32F4_ENABLE_USART_6=""
export STM32F4_ENABLE_I2C1=""
export STM32F4_ENABLE_I2C2=""
export BSP_PRINT_EXCEPTION_CONTEXT="1"

# Optimizing for size - see https://devel.rtems.org/wiki/Projects/TinyRTEMS
export RTEMS_CONFIGURE_EXTRA_OPTIONS="\
--disable-itron \
--disable-networking \
--disable-multiprocessing \
USE_TICKS_FOR_STATISTICS=1 \
CXXFLAGS_FOR_TARGET='-fno-exceptions -fno-rtti' \
"

export RTEMS_RSB_EXTRA_OPTIONS="--targetcxxflags=-fno-exceptions --libstdcxxflags=-fno-exceptions"

zubax_rtems/build_rtems.sh --cpu=arm --bsp=stm32f105rc

The Eclipse plugin can be installed as described on the RTEMS wiki. When the plugin is installed, create a new project with RTEMS toolchain, then configure the RTEMS installation path on the RTEMS properties page at Project → Properties → C/C++ Build → RTEMS. For example, RTEMS installation path for architecture ARM and BSP stm32f105rc should be configured as follows:

• Base path: zubax_rtems/bsps
• BSP path: zubax_rtems/bsps/arm-rtems4.11/stm32f105rc

Note that these directories will be created when RTEMS is built. The example above shows relative pathes, but it is preferred to use absolute pathes instead.

If a make wrapper script is used, the default build command needs to be overriden. Go to Project → Properties → C/C++ Build, untick Use default build command, and set the field Build command to bash make.sh (assuming that the wrapper script is named make.sh).

These instructions are valid for ARM architecture and Black Magic Probe as a debugger.

• Go Window → Preferences → Run/Debug → Launching → Default Launchers:
  • Select GDB Hardware Debugging → [Debug], then tick only Legacy GDB Hardware Debugging Launcher, and make sure that the option for GDB (DSF) is disabled.
• Go Run → Debug Configurations:
  • Invoke the context menu for GDB Hardware Debugging, select New.
  • Tab Debugger:
    • Set the field GDB Command to the absolute path to your GDB executable arm-rtems4.11-gdb. To find out the absolute path, source the file env.sh and execute which arm-rtems4.11-gdb.
    • Untick Use remote target.
  • Tab Startup:
    • If a boot loader is used, make sure that Image offset is configured correctly.
    • Enter the following in the field Initialization commands:

target extended /dev/ttyACM0      # Update the serial port name according to your setup

monitor swdp_scan                 # Use jtag_scan instead if necessary
attach 1
monitor vector_catch disable hard

set mem inaccessible-by-default off
monitor option erase
set print pretty