defmt is a highly efficient logging framework that targets resource-constrained devices, like microcontrollers.defmt stands for "deferred formatting".

Rather than performing formatting input like255u8 into"The temperature is 255°C" on the embedded device, the formatting is deferred to the host that will output the logs. This way, only the relevant data needs to be sent to the host instead of the entire format string. Additionally the transmitted data is compressed, for example bycompressing several booleans into one byte.

This means thatdefmt:

• reduces compiled binary size, since it only has to contain indices to log strings saved by the host instead of the string itself
• reduces computation efforts on the target, because the formatting of e.g.255u8 to"255" happens on the host that displays the logging output, not the target
• reduces delays and log buffer usage, since there is less data sent from the embedded device to the host

For more details on how it works, check out thedefmt book.

flip-link adds zero-cost stack overflow protection for your embedded programs – no MPU or stack probe support needed!

It does this byflipping the standard memory layout of ARM Cortex-M programs.

With this inverted memory layout, the stack "overflows" instead of corrupting memory when it hits the boundary of the RAM region. This boundary collision raises a hardware exception (usually the "hard fault" exception), which by default halts the program.

For more details, check out ourblog post introducingflip-link.

Theapp-template is a Cargo project template, so you can hit the ground running withprobe-run,defmt andflip-link. Using the knurlingapp-template, andcargo-generate, you can start your embedded project by just running

$cargo generate \    --git https://github.com/knurling-rs/app-template \    --branch main \    --name my-app

and specifying your desired HAL and compilation target.

defmt-test is an embedded test harness that lets you write and rununit tests as if you were using the built-in#[test] attribute, but they'll run on your embedded target.

Of course,defmt-test also gives you an#[init] attribute for initialization functions needed to set up your peripherals etc.

For more details, check out ourblog post introducingdefmt-test. Also check ourblog post series on testing embedded Rust code.

nrdfdu is a CLI tool for loading firmware onto an nRF52840 microcontroller running Nordic Semi's USB DFU bootloader.

derive-mmio is a macro for auto-generating MMIO access methods for a structure. You can see an example of how to use it in theFerrous Systems training material.