Dealing with microcontrollers involves using several different tools as we'll be dealing with an architecture different than your laptop's and we'll have to run and debug programs on a remote device.

We'll use all the tools listed below. Any recent version should work when a minimum version is not specified, but we have listed the versions we have tested.

  • Rust 1.31, 1.31-beta, or a newer toolchain PLUS ARM Cortex-M compilation support.
  • cargo-binutils ~0.1.4
  • qemu-system-arm. Tested versions: 3.0.0
  • OpenOCD >=0.8. Tested versions: v0.9.0 and v0.10.0
  • GDB with ARM support. Version 7.12 or newer highly recommended. Tested versions: 7.10, 7.11, 7.12 and 8.1
  • [OPTIONAL] git OR cargo-generate. If you have neither installed then don't worry about installing either.

The text below explains why we are using these tools. Installation instructions can be found on the next page.

cargo-generate OR git

Bare metal programs are non-standard (no_std) Rust programs that require some fiddling with the linking process to get the memory layout of the program right. All this requires unusual files (like linker scripts) and unusual settings (like linker flags). We have packaged all that for you in a template so that you only need to fill in the blanks such as the project name and the characteristics of your target hardware.

Our template is compatible with cargo-generate: a Cargo subcommand for creating new Cargo projects from templates. You can also download the template using git, curl, wget, or your web browser.


cargo-binutils is a collection of Cargo subcommands that make it easy to use the LLVM tools that are shipped with the Rust toolchain. These tools include the LLVM versions of objdump, nm and size and are used for inspecting binaries.

The advantage of using these tools over GNU binutils is that (a) installing the LLVM tools is the same one-command installation (rustup component add llvm-tools-preview) regardless of your OS and (b) tools like objdump support all the architectures that rustc supports -- from ARM to x86_64 -- because they both share the same LLVM backend.


QEMU is an emulator. In this case we use the variant that can fully emulate ARM systems. We use QEMU to run embedded programs on the host. Thanks to this you can follow some parts of this book even if you don't have any hardware with you!


A debugger is a very important component of embedded development as you may not always have the luxury to log stuff to the host console. In some cases, you may not have LEDs to blink on your hardware!

In general, LLDB works as well as GDB when it comes to debugging but we haven't found an LLDB counterpart to GDB's load command, which uploads the program to the target hardware, so currently we recommend that you use GDB.


GDB isn't able to communicate directly with the ST-Link debugging hardware on your STM32F3DISCOVERY development board. It needs a translator and the Open On-Chip Debugger, OpenOCD, is that translator. OpenOCD is a program that runs on your laptop/PC and translates between GDB's TCP/IP based remote debug protocol and ST-Link's USB based protocol.

OpenOCD also performs other important work as part of its translation for the debugging of the ARM Cortex-M based microcontroller on your STM32F3DISCOVERY development board:

  • It knows how to interact with the memory mapped registers used by the ARM CoreSight debug peripheral. It is these CoreSight registers that allow for:
    • Breakpoint/Watchpoint manipulation
    • Reading and writing of the CPU registers
    • Detecting when the CPU has been halted for a debug event
    • Continuing CPU execution after a debug event has been encountered
    • etc.
  • It also knows how to erase and write to the microcontroller's FLASH