Companion code for the book Real-Time C++

This is the companion code for the book C.M. Kormanyos, Real-Time C++: Efficient Object-Oriented and Template Microcontroller Programming, Fourth Edition (Springer, Heidelberg, 2021). ISBN 9783662629956

This repository has three main parts.

• Reference Application ref_app located in ./ref_app
• Examples from the book
• Code Snippets from the book

GNU/GCC cross compilers and various additional tools running on Win*, optionally needed for certain builds as described below, can be found in the related ckormanyos/real-time-cpp-toolchains repository.

Details on the Reference Application

The reference application boots via a small startup code and subsequently initializes a skinny microcontroller abstraction layer (MCAL). Control is then passed to a simple multitasking scheduler that schedules the LED application, calls a cyclic a benchmark task, and services the watchdog.

The LED application toggles a user-LED with a frequency of 1/2 Hz The result is LED on for one second, LED off for one second --- cyclically and perpetually without break or pause.

Portability

The application software is implemented once and used uniformly on each supported target in the reference application. Differences among the individual targets arise only in the lower software layers pertaining to chip-specific and board-specific startup/MCAL details.

In this way the application software exhibits a high level of portability.

Supported Targets in the Reference Application

The reference application supports the following targets:

Target name (as used in build command)	Target Description
avr	MICROCHIP(R) [former ATMEL(R)] AVR(R) ATmega328P
atmega2560	MICROCHIP(R) [former ATMEL(R)] AVR(R) ATmega2560
atmega4809	MICROCHIP(R) [former ATMEL(R)] AVR(R) ATmegax4809
am335x	BeagleBone with Texas Instruments(R) AM335x ARM(R) A8
bcm2835_raspi_b	RaspberryPi(R) Zero with ARM1176-JZFS(TM)
Debug/Release	PC on Win* via MSVC x64 compiler Debug/Release
host	PC/Workstation on Win*/mingw64/*nix via host compiler
lpc11c24	NXP(R) OM13093 LPC11C24 board ARM(R) Cortex(TM)-M0
rl78	Renesas(R) RL78/G13
rx63n	Renesas(R) RX630/RX631
stm32f100	ST Microelectronics(R) STM32F100 ARM(R) Cortex(R)-M3
stm32l100c	ST Microelectronics(R) STM32L100 ARM(R) Cortex(R)-M3
stm32l152	ST Microelectronics(R) STM32L152 ARM(R) Cortex(R)-M3
stm32f407	ST Microelectronics(R) STM32F407 ARM(R) Cortex(R)-M4
stm32f429	ST Microelectronics(R) STM32F429 ARM(R) Cortex(R)-M4
stm32f446	ST Microelectronics(R) STM32F446 ARM(R) Cortex(R)-M4
v850es_fx2	Renesas(R) Electronics V850es/Fx2 upd703231
x86_64-w64-mingw32	PC on Win*/mingw64 via GNU/GCC x86_x64 compiler
xtensa32	Espressif (XTENSA) NodeMCU ESP32

Getting Started with the Reference Application

It is easiest to get started with the reference application using one of the supported boards, such as Arduino or RaspberryPi ZERO or BeagleBone, etc. The reference application can be found in the directory ./ref_app and its subdirectories.

The reference application uses cross-development based on *nix-like make tools in combination with either Bash/GNUmake, Microsoft(R) Visual Studio(R) via External Makefile, or platform-independent CMake.

Upon successful completion of the build, the resulting build artifacts, including HEX-files (such as ref_app.hex), map files, size reports, etc., are available in the bin directory.

Build with Bash Shell Script and GNU make

To get started with the reference application on *nix

• Open a terminal in the directory ./ref_app.
• The terminal should be located directly in ./ref_app for the paths to work out (be found by the upcoming build).
• Identify the Bash shell script ./ref_app/target/build/build.sh.
• Consider which configuration (such as target avr) you would like to build.
• Execute build.sh with the command: ./target/build/build.sh avr rebuild.
• This shell script calls GNU make with parameters avr rebuild which subsequently rebuilds the entire solution for target avr.
• If you're missing AVR GCC tools and need to get them on *nix, run sudo apt install gcc-avr avr-libc.

Example build on *nix for target avr

We will now exemplify how to build the reference application on a command shell in *nix for target avr. This target system includes essentially any ARDUINO(R)-compatible board. This is also the board compatibility actually used with the homemade boards in the book.

Install gcc-avr if needed.

sudo apt install gcc-avr avr-libc

Clone or get the ckormanyos/real-time-cpp repository. Then build with:

cd real-time-cpp
cd ref_app
./target/build/build.sh avr rebuild

Example build on *nix for target stm32f446

We will now exemplify how to build the reference application on a command shell in *nix for an ARM(R) target. Consider, for example, the build variant target stm32f446. The NUCLEO-F446RE board from STMicroelectronics(R) can conveniently be used for this.

Install gcc-arm-none-eabi if needed.

sudo apt install gcc-arm-none-eabi

Clone or get the ckormanyos/real-time-cpp repository. Then build with:

cd real-time-cpp
cd ref_app
./target/build/build.sh stm32f446 rebuild

Build with VisualStudio(R) Project and CMD Batch

To get started with the reference application on Win*

• Clone or get the ckormanyos/real-time-cpp repository.
• Get and setup (from the ckormanyos/real-time-cpp-toolchains repository) any needed GNU/GCC cross compilers running on Win*, as described in detail a few paragraphs below.
• Start Visual Studio(R) 2019 (or later, Community Edition is OK)
• Open the solution ref_app.sln in the ./ref_app directory.
• Select the desired configuration.
• Then rebuild the entire solution.

The ref_app build in Microsoft(R) VisualStudio(R) makes heavy use of cross development using a project workspace of type External Makefile. GNUmake is invoked via batch file in the build process. It subsequently runs in combination with several Makefiles.

To build any ref_app target other than Debug or Release for Win32, a cross-compiler (GNU/GCC cross compiler) is required. See the text below for additional details.

GNU/GCC cross compilers running on Win* intended for the reference application on VisualStudio(R) can be found in the toolchains repository, ckormanyos/real-time-cpp-toolchains. The toolchains repository contains detailed instructions on installing, moving and using these ported GNU/GCC compilers.

Note on GNUmake for Win*: A GNUmake capable of being used on Win* can be found in the make-4.2.1-msvc-build repository. If desired, clone or get the code of this repository. Build make-4.2.1 in its x64 Release configuration with MSVC (i.e., VC 14.2 or later, Community Edition is OK).

Build with Cross-Environment CMake

Cross-Environment CMake can build the reference application. For this purpose, CMake files have also been created for each supported target.

Consider, for instance, building the reference application for the avr target with CMake. The pattern is shown below.

cd real-time-cpp
mkdir build
cd build
cmake ../ref_app -DTRIPLE=avr -DTARGET=avr -DCMAKE_TOOLCHAIN_FILE=../ref_app/cmake/gcc-toolchain.cmake
make -j ref_app

Switch from avr to, for instance, bcm2835_raspi_b or stm32f446 to build for one of the supported ARM(R) targets such as RaspberryPi(R) Zero with ARM(R) 1176-JZF-S or ST Microelectronics(R) STM32F446 ARM(R) featuring Cortex(TM)-M4.

Following the standard *nix pattern to build with x86_64-w64-mingw32 or host from the MSYS or Cygwin console should work too.

Build with ATMEL(R) AtmelStudio(R)

There is also a workspace solution for ATMEL(R) AtmelStudio(R) 7. It is called ref_app.atsln and is also located in the ./ref_app directory.

Target Details

Target details including startup code and linker definition files can be found in the ./ref_app/target directory and its subdirectories. There are individual subdirectories for each supported target microcontroller system.

The MICROCHIP(R) [former ATMEL(R)] AVR(R) configuration called target avr runs on a classic ARDUINO(R) compatible board. The program toggles the yellow LED on portb.5.

The MICROCHIP(R) [former ATMEL(R)] ATmega4809 configuration called target atmega4809 runs on an ARDUINO(R) EVERY compatible board clocked with the internal resonator at 20MHz. The program toggles the yellow LED on porte.2 (i.e., D5).

The Espressif (XTENSA) NodeMCU ESP32 implementation uses a subset of the Espressif SDK to run the reference application with a single OS task exclusively on 1 of its cores.

The NXP(R) OM13093 LPC11C24 board ARM(R) Cortex(TM)-M0 configuration called "target lpc11c24" toggles the LED on port0.8.

The ARM(R) Cortex(TM)-M3 configuration (called target stm32f100) runs on the STM32VLDISCOVERY board commercially available from ST Microelectronics(R). The program toggles the blue LED on portc.8.

The second ARM(R) Cortex(TM)-M3 configuration (called target stm32l100c) runs on the STM32L100 DISCOVERY board commercially available from ST Microelectronics(R). The program toggles the blue LED on portc.8.

The third ARM(R) Cortex(TM)-M3 configuration (called target stm32l152) runs on the STM32L152C-DISCO board commercially available from ST Microelectronics(R). The program toggles the blue LED on portb.6.

The first ARM(R) Cortex(TM)-M4 configuration (called target stm32f407) runs on the STM32F4DISCOVERY board commercially available from ST Microelectronics(R). The program toggles the blue LED on portd.15.

Another ARM(R) Cortex(TM)-M4 configuration (called target stm32f446) runs on the STM32F446 Nucleo-64 board commercially available from ST Microelectronics(R). The program toggles the green LED on porta.5.

The ARM(R) A8 configuration (called target am335x) runs on the BeagleBone board (black edition). For the white edition, the CPU clock needs to be reduced from 900MHz to something like 600MHz. This project creates a bare-metal program for the BeagleBone that runs independently from any kind of *nix distro on the board. Our program is designed to boot the BeagleBone from a raw binary file called MLO stored on a FAT32 SDHC microcard. The binary file includes a special boot header comprised of two 32-bit integers. The program is loaded from SD-card into RAM memory and subsequently executed. When switching on the BeagleBone black, the boot button (S2) must be pressed while powering up the board. The program toggles the first user LED (LED1 on port1.21).

The ARM(R) 1176-JZF-S configuration (called target bcm2835_raspi_b) runs on the RaspberryPi(R) Zero (PiZero) single core controller. This project creates a bare-metal program for the PiZero. This program runs independently from any kind of *nix distro on the board. Our program is designed to boot the PiZero from a raw binary file. The raw binary file is called kernel.img and it is stored on a FAT32 SDHC microcard. The program objcopy can be used to extract raw binary from a ELF-file using the output flags -O binary. The kernel.img file is stored on the SD card together with three other files: bootcode.bin, start.elf and (an optional) config.txt, all described on internet. A complete set of PiZero boot contents for an SD card running the bare-metal reference application are included in this repo. The program toggles the GPIO status LED at GPIO index 0x47.

Target v850es_fx2 uses a classic Renesas(R) V850es/Fx2 core. The upd703231 microcontroller derivative on an F-Line Drive It starter kit is used.

For other compatible boards, feel free contact me directly or submit an issue requesting support for your desired target system.

Benchmarks

Benchmarks provide scalable, portable C++11 means for identifying the performance and the performance class of the microcontroller. For more information, see the detailed information on the benchmarks pages.

All Bare-Metal

Projects in this repo are programmed OS-less in naked, bare-metal mode making use of self-written startup code. No external libraries other than native C++ and its own standard libraries are used.

Consider, for instance, the BeagleBone Black Edition (BBB, also known as target am335x) --- one of several popular target systems supported in this repository. The projects on this board boot from the binary image file MLO on the SD card. Like all other projects in this repository, the BBB projects perform their own static initialization and chip initialization (i.e., in this particular case chip initialization of the ARM(R) 8 AM335x processor). The BBB projects, following initialization, subsequently jump to main() which initializes the am335x MCAL and starts our self-written multitasking scheduler.

The image below depicts the bare-metal BeagleBone Black Edition in action. In this bare-metal operation mode, there is no running *nix OS on the BBB, no keyboard, no mouse, no monitor, no debug interface and no emulator. See also the corresponding pdf image.

The microcontroller on the board is cyclically performing one of the benchmarks mentioned above. The first user LED is toggled on port1.21 in multitasking operation and the oscilloscope captures a real-time measurement of the benchmark's time signal on digital I/O port1.15, header pin P8.15 of the BBB.

Continuous Integration (CI)

Continuous integration uses GitHub Actions programmed in YAML. The CI script exercises various target builds, example builds and benchmark builds/runs on GitHub Actions' instances of ubuntu-latest, windows-latest and macos-latest using GNUmake, CMake or MSBuild depending on the particular OS/build/target-configuration.

Build Status

Here is the build status badge.

The build status badge represents the state of the nightly CI builds and tests.

GNU/GCC Compilers

The reference application and the examples (also the code snippets) can be built with GNU/GCC compilers and GNUmake on *nix. GNU/GCC cross compilers and GNUmake on *nix are assumed to be available in the standard executable path, such as after standard get-install practices.

Some ported GNU/GCC cross compilers for Win* are available in the toolchains repository, real-time-cpp-toolchains. These can be used with the microcontroller solution configurations in the reference application when developing/building within Microsoft(R) VisualStudio(R). Various other GNU tools such as GNUmake, SED, etc. have been ported and can be found there. These are used in the Makefiles When building cross embedded projects such as ref_app on Win*.

In the reference application on Win*, the Makefiles use a self-defined, default location for the respective tools and GNU/GCC toolchains. The toolchain default location on Win* is ./ref_app/tools/Util/msys64/usr/local. This particular toolchain location is inspired by the msys2/mingw64 system.

Toolchains intended for cross MSVC/GCC builds on Win* should be located there. These toolchains are not part of this repository and it is necessary to get these toolchains separately when using the supported Win* builds when optionally using VisualStudio(R) Projects with CMD Batch.

Detailed instructions on getting and using the toolchains for cross MSVC/GCC builds on Win* are available in the real-time-cpp-toolchains repository. These instructions provide guidance on using these toolchains when selecting the Microsoft(R) VisualStudio(R) project (via the usual, above-described MSVC/Win*-way) to build the reference application.

C++ Language Adherence

A GNU/GCC port (or other compiler) with a high level of C++11 awareness and adherence such as GCC 5 through 11 (higher generally being more advantageous) or MSVC 14 or higher is required for building the reference application (and the examples and code snippets).

Some of the code snippets demonstrate language elements not only from C++11, but also from C++14, 17, 20. A compiler with C++17 support (such as GCC 6, 7, or 8) or even C++20 support (such as GCC 10 or 11, clang 12 or MSVC 14.2) can, therefore, be beneficial for success with all of the code snippets.