Nim Template for Embive

A simple program that runs inside the Embive interpreter.

Requirements (to build)

• GCC (riscv32-unknown-elf)
  • Download the RISC-V toolchain
  • Install the dependencies from the README
  • Compile and install it:
    • $ ./configure --prefix=/opt/riscv --with-arch=rv32imaczicsr_zifencei --with-abi=ilp32
    • $ make -j8
  • Add /opt/riscv/bin to your PATH
• Nim (v2.2.2 or greater)
  • Install latest stable release:
    • curl https://nim-lang.org/choosenim/init.sh -sSf | sh

How to build

• Compile the project
  • $ nim build project

How to run

• Create a new project
  • $ cargo new embive-project && cd embive-project
• Add Embive as a dependency
  • $ cargo add embive
• Copy the example from Embive's docs/readme.
• Change the code to: const ELF_FILE: &[u8] = include_bytes!("../app.elf");
• Copy the generated app.elf (inside out folder) to your project
• Run it:
  • $ cargo run --release

Stack

By default, the stack size is set to 2048 bytes (0x800).
You can change this by modifying the STACK_SIZE variable in the linker script.

Heap

The heap is set at the end of the memory space allocated by the application (after data and stack).
As such, the heap size doesn't need to be known at link time, instead being able to grow as large as the maximum memory available.

RAM calculation

You can calculate the minimum amount of RAM needed by you application with the following equation:

• total_ram = data + bss

To get the data and bss sizes, you can run:

• $ riscv32-unknown-elf-size out/app.elf
  • The stack and heap will be reported as part of the bss

The result should be something like this:

   text    data     bss     dec     hex filename
    348       8    2060    2416     970 out/app.elf

For this result, our minimum RAM size would be:

• total_ram = 8 + 2060 = 2068 bytes