Mousefood – Build embedded terminal UIs for microcontrollers

Text based graphics with fancy or custom fonts is just crazy efficient. That is exactly how we got the amazing graphics of The Last Ninja or Turrican on machines with less than 64KiB useable RAM.

Same for more modern embedded devices. If you constrain yourself to text you increase both runtime performance and your developer productivity.

Rust on embedded uses a HAL layer, which is vendor independent (and resolved at compile time, like templates would be in C++). It doesnt cover everything yet, but basics like GPIO, SPI, I2C etc are covered. This avoids the issue of N drivers times M vendor SDKs: I2C drivers can just be written against the HAL, and you instantiate with a specific HAL in your application. Also reduces vendor lock-in. The setup process still requires some chip specific code to select which pins to use etc, but once you are past that you can be vendor neutral.

Speaking of which, the API uses some clever patterns (called typestate) to ensure at compile time that your peripheral config is valid: if you "take" GPIO2 you can do that again, so you can't give the same pin to two different pieces of code by mistake. And if the driver expects a pin configured as output you can't give an input pin (you can convert a pin to "dynamic at runtime" if you really need to, so there is an escape hatch).

Then there is the embassy framework. This is an alternative to RTOSes (there are some Rust RTOSes as well, haven't tried them). It makes use of async/await tasks in Rust that are statically allocated and scheduled. You can have several priority levels of schedulers (even though internally the schedulers are cooperative for the tasks inside, but they are preempting between schedulers by using interrupts).

Async actually makes many things on embedded easier, such as waiting for a GPIO. No longer do you need to write your own interrupt handler, or figure out when to put the chip on a low power state, the scheduler and HAL futures do it for you.

All that said: C++ still is a larger ecosystem with more tutorials, drivers and better chip support. But that is advancing rapidly in the Rust world. ESP32 series has official vendor support in Rust for example, as does at least one or two other vendors (or they are in the process of adding it). Popular chips like the RP2040 etc have support, and I have seen HALs for NRF and ST around (but never played with them). Drivers for common chips exist.

So I would say it is worth experimenting with at least, but you should check up front what HALs and drivers exist for what you want to use and check how complete those are. Two years ago I wanted to do I2S things on the ESP32, but that was still missing. A year ago it had support, but some of the DMA things were clunky still. I should check again some time.

I first learned about password hashing when I tried to make the actually most secure door lock program. I first used raw SHA-256, but then someone on the forum introduced me to PBKDF2...

Sometimes I miss those days.