Book: Section 2: Blinking your first LED (draft)

[japaric]

From @jamesmunns on July 10, 2018 9:32

This section covers the equivalent of getting "Hello World" working for an embedded target. Examples should start high level, and build back up towards that point.

Copied from original issue: rust-embedded/wg#117

[japaric]

Triage: Tthis section has no instructions. @jamesmunns could you add some? IIRC, we agreed on using cortex-m-rt as a base and covering how to write a program in two different ways: using a high level api (e.g. f3) crate and w/o external dependencies.

[japaric]

I think it would be good to start this section with instructions on how to build and debug a Cortex-M program running on QEMU since everyone should be able to run that without external hardware. Then we can move onto the discovery board.

[WojciechMigda]

@japaric , would this be of any help?
https://github.com/WojciechMigda/how-to-qemu-arm-gdb-gtest

[japaric]

@WojciechMigda Unfortunately, no. That's using QEMU userspace emulation (qemu-arm) and that can only run programs compiled for hosted environments like the arm-unknown-linux-gnueabi target; that can't execute (or won't properly execute) bare metal programs compiled for ARM Cortex-M.

What we have to use in this section is QEMU full system emulation (qemu-system-arm). That can emulate a Cortex-M3 core (the LM3S6965) so we can run programs compiled for the thumbv7m-none-eabi target on it. I have done some initial experiments with that in this repo and have recently confirmed that semihosting works so we can cover hello world (see examples/hello.rs in the cortex-m-quickstart repo) in this chapter.

[frafra]

Just wanted to thank you for your great work. I am still learning Rust, I ordered the board you suggest, and I am eager to follow your tutorials. I hope I will be able to give something back to the community in the future. Thank you! 😃

[japaric]

This is pretty much done.