Testing Bare Metal Rust, written to be run from the U-Boot bootloader on the ARM Cortex-A9. Target platform is the Terasic DE-10 Nano.
Read the The Embedded Rust Book. Watch BAREMETAL RUST Runs on EVERYTHING by Low Level Learning.
For peripherals refer to the Cyclone V Hard Processor System Technical Reference Manual and also the Cyclone V HPS Register Address Map and Definitions which can both be found online.
To build the tool you need:
- Host PC with Rust and Cargo installed
- A cross compiler
rustup target add armv7a-none-eabi - A device with an ARM Cortex-A9 (or similar) running U-Boot (tested with SPL 2023.04)
Run the build.sh script to build the tool using the linker.ld file. It will also convert the elf file to a raw binary file bin.
./build.sh
If you need to make changes to the linker.ld file, be sure to delete the target folder, otherwise the compiler might skip recompiling.
You need a way to copy the built raw binary file bin from your host PC to the ARM. Options include JTAG, TFTP, serial UART custom protocols or using the SD card.
In my case I am using SSH to copy the file on the target device SD card when it runs buildroot Linux. After that I am rebooting the ARM to get back into the U-boot. Not exactly sensible considering the final product is not supposed to have a Linux running but o well. The easiest but also most annoying alternative is to simply copy the file over manually with an SD card reader.
Modify and then run the cp_to_arm.sh script.
./cp_to_arm.sh
Boot into the U-Boot. To copy the binary from the SD card into the RAM at address 0x0100_0000, and then run from this address, run the following commands:
fatload mmc 0:1 0x01000000 bin
go 0x01000000
It should say something like:
## Starting application at 0x01000000 ...
## Application terminated