Raspberry Pi 3+ Baremetal with Rust

This project is my first project published on GitHub.

I started with this after seeing a YouTube video of lowlevellearning.

Credits:

Credits go to:

lowlevellearning for:

• Getting me interested in the first place;
• Giving clear instructions on how to start;
• Sharing knowledge/code.

Paul Simon as I took some of his remarks in the comments of the YouTube video.

Source

I took some source files from

Linker script

As base, I took the linker script from lowlevellearning: https://github.com/lowlevellearning/raspberry-pi-baremetal-c

Achievements

1. Have a blinking LED by running baremetal on a RPI3+ (2023-03-13);
2. Have code stored in GitHub (2023-03-14).

Next Steps

In random order, I'd like to add the following features to my code:

1. Sent data from UART to the world;
2. Receive data from the world on the UART;
3. I.S.O. loop-s with nop instructions, use timers.
   1. Investigate using interrupts?
4. Interrupts
   1. Enabling/Disabling interrupts;
   2. Interrupt Service Routine;
   3. Interrupt Vector table;

Setup

Hardware:

• PC, running Debian (Bullseye);
• Raspberry Pi 3+, as I had one available at the time of starting;
• Power supply;
• 16GB SD card, formatted as FAT32, as storage device;
• USB-SD convertor to write files to SD.

Software:

• Debian Bullseye;
• Rust compiler, toolchain etc. etc.;
• Microsoft Visual Studio Code;
• GIT.

OS

I'm using a Debian (Bullseye) distribution with Rust installed using:

curl https://sh.rustup.rs -sSf | sh

Install Rust toolchain for RPI:

rustup toolchain add armv7a-none-eabi

Install binutils for Cargo

cargo install cargo-binutils

rustup component add llvm-tools-preview

Download RPi files

Some extra files are needed, next to kernel7.img to run the code on the RPI.

From: https://github.com/raspberrypi/firmware/tree/master/boot

Download: bootcode.bin, start.elf and fixup.dat

These are placed in the folder to_put_on_sd.

Build

To build the code:

cargo build

Make the RPI kernel image

cargo objcopy -- -O binary ./to_put_on_sd/kernel7.img

Run

Mount SD card.

Copy the files in ./to_put_on_sd/ in the root of the SDCard:

• kernel7.img
• bootcode.bin
• start.elf
• fixup.dat
• config.txt

Unmount SD card.

Place SD in Raspberry Pi.

Power Raspberry Pi.

Useful commands

To check if the addresses (for example the start of the code) is correct:

arm-none-eabi-objdump -D target/armv7a-none-eabi/debug/my-rusty-pi|less

To disassemble a 'release' binary:

cargo objdump --release -- --disassemble --no-show-raw-insn