The GNU ARM Embedded Toolchain is a complete open-source toolchain for ARM Cortex-M and Cortex-R family microcontrollers. It includes the GNU compiler (GCC), GNU debugger (GDB), and other tools like GNU Binutils for working with binary and object files. The toolchain allows developers to build applications for ARM-based microcontrollers and design custom boards using ARM CPUs. With the GNU ARM toolchain, developers can write, compile, and debug ARM applications on Linux, Windows, and macOS hosts.
Overview
The GNU ARM Embedded Toolchain contains pre-built cross compilers and other tools for creating firmware for ARM Cortex-M and Cortex-R processors. The toolchain supports major ARM architectures like Cortex-M0, Cortex-M3, Cortex-M4, Cortex-R4, and Cortex-R5. It enables compiling code on a PC and deploying it to an ARM target. The toolchain is open source and offered under the GPL license.
The key components and tools included in the ARM Embedded GNU Toolchain are:
- GCC – the GNU Compiler Collection including C and C++ compilers
- GDB – the GNU Debugger
- Binutils – utilities like assembler, linker, archive manager
- Newlib – the C standard library implementation
- GDBServer – allows debugging ARM programs remotely
By integrating these components, the toolchain provides everything required to build ARM applications. Developers can write code in C/C++, assemble it, link it, debug it, all targeting the ARM architecture. The toolchain supports ARM’s Thumb instruction set in addition to traditional 32-bit ARM instructions.
Benefits
Here are some of the major benefits of using the GNU ARM Embedded Toolchain:
- Completely open source – developers can inspect, modify and enhance all components.
- Supports major ARM architectures like Cortex-M and Cortex-R series.
- Works across Linux, Windows and macOS hosts for ARM application development.
- Includes Newlib C library tailored for embedded use.
- Integrated debugging and profiling using GDB and logging utilities.
- Regular updates with latest GCC, GDB improvements and bug fixes.
- Binutils provides ARM-specific assembler, linker and object file utilities.
- Allows mixing high-level C/C++ code with low-level ARM assembly.
- No vendor lock-in, companies can customize and enhance the toolchain.
By using the GNU ARM toolchain, developers avoid vendor-specific proprietary toolchains. They can take advantage of continual open source improvements. The toolchain is trusted by many companies building products with ARM chips.
Components
Here is a more detailed overview of the key components that make up the GNU ARM Embedded Toolchain:
GCC Compiler
This is the GNU Compiler Collection which includes C and C++ compilers for the ARM architecture. GCC contains front-ends for various languages and back-ends for many CPU architectures. For ARM, it can generate either 32-bit or 16-bit Thumb instruction set code. GCC supports ARM and Thumb-2 instruction sets used in Cortex-M and Cortex-R series chips.
GCC enables compiling C/C++ code into ARM assembly language. It includes optimizations for code size, speed and supports many compile-time checks and warnings. GCC is continually updated to generate better ARM code. It supports the latest C++17, C11 and GNU C standards.
GDB Debugger
GDB is the GNU debugger that allows debugging ARM programs. Developers can set breakpoints, examine variables, stack traces, disassemble code and perform many other debugging tasks. GDB has a command line interface and also GUIs like Nemiver and IDE integration. GDB can debug optimised ARM code like尾 call elimination and inlined functions.
For embedded ARM development, GDB is often used remotely with GDBServer running on the target hardware and GDB on the host computer. Developers can debug even before the hardware is fully operational.
GNU Binutils
Binutils provides ARM-specific tools for binary file manipulation required when building firmware. This includes:
- ar – archive manager for creating ARM libraries
- as – assembler for converting ARM assembly to object files
- ld – linker for combining objects into ARM executables
- strip – removes debug symbols from ARM binaries
- objdump/objcopy – display and modify ARM object files
These lower level tools work at the binary and object code level. They provide the foundation for compiling, linking and debugging ARM applications using the toolchain.
Newlib C Library
Newlib is a C standard library implementation targeted at embedded systems. It provides common functions for string handling, mathematical operations, input/output etc. Newlib is designed for microcontrollers with limited RAM and code space. It avoids bloat common in desktop C libraries.
Newlib is highly configurable to only include required functionality. It can be tailored for the specific ARM chip being used. Newlib supports ARM architectural features like interworking between Thumb and ARM code.
GDBServer
GDBServer runs on the remote ARM device and allows the GDB debugger to connect to it from a host PC. This enables remote debugging over JTAG or a serial port connection. GDBServer forwards GDB commands to the device being debugged. It transmits memory, register and breakpoint information back to GDB.
GDBServer helps with debugging ARM programs even when hardware like JTAG debug probes is not fully implemented. It requires just a minimal implementation on the device side.
Getting the Toolchain
There are a few ways to get the GNU ARM Embedded Toolchain:
- Download Pre-built Binary – Binary builds for Windows, Linux and macOS can be downloaded from the GNU ARM Embedded Toolchain project page. These come packaged with GCC, GDB, Newlib etc pre-built.
- Install using Package Manager – On Linux, tools like apt, yum, pacman, brew can often directly install the latest GNU ARM Embedded toolchain packages.
- Build from Source – Developers can build the GCC, Binutils, GDB components from source for more customization and control.
The pre-built binaries offer the quickest way to start ARM development on supported hosts. Building from source takes more time but allows tweaking the configuration.
Using the Toolchain
Once installed, the toolchain is ready to build ARM applications. Here is an overview of a typical embedded workflow:
- Developers write C/C++ code on their host Linux/Windows/macOS machine.
- The arm-none-eabi-gcc compiler compiles C/C++ code into ARM binaries targeting a particular microarchitecture.
- The generated object files are linked into an executable using arm-none-eabi-ld.
- This ARM binary can then be deployed to the target hardware.
- arm-none-eabi-gdb allows debugging ARM code remotely often using a JTAG probe.
- Additional utilities like objdump, size can inspect binaries.
The toolchain is usually invoked from the command line but can also be used from within IDEs like Eclipse, Visual Studio Code etc. Many IDEs support launching the GNU ARM tools for building and debugging.
The toolchain abstracts developers from ARM hardware details. Same compiled ARM code often runs on different microcontrollers with only minor retargeting.
Conclusion
The GNU toolchain provides a complete open-source solution for developing on the ARM architecture. It is trusted by both hobbyists and companies building ARM-powered products. The toolchain leverages active development in the GCC, GDB and Binutils open source projects to benefit ARM developers.
Using the GNU ARM Embedded Toolchain allows creating firmware for ARM Cortex-M and Cortex-R series chips from Linux, Windows and macOS desktops. Companies avoid vendor lock-in and can enhance the toolchain for their specific needs. With continual improvements to the gcc compiler and gdb debugger, ARM developers reap the benefits through this toolchain.
