lsylvestre / O2B

A port of the OMicroB OCaml virtual machine dedicated for soft-core CPUs running on FPGAs

OCaml on FPGA Boards

O2B is a specific port of the OMicroB OCaml virtual machine dedicated to run on micro-processors implemented as soft-cores on FPGAs (such as the Nios2 processor on Intel/Altera FPGAs)

Requirements

For compiling the virtual machine :

• OPAM2 + OCaml (>= 4.10)
• obytelib (on OPAM)
• ocamlclean (on OPAM)
• ocamlbuild (on OPAM)
• gcc (for simulation)

For configuring and programming FPGAs :

• QuartusII (>= 17.1) suite of tools (to be downloaded from Intel FPGA website).

O2B currently supports Nios2 platforms on Intel/Altera FPGAs.

Using

The concept of physical target in OMicroB is replaced by that of platform in O2B.

A platform is a combination of

• a board (device type + peripherals)
• a system configuration (Softcore CPU type and configuration, memory, interfaces, custom components/instructions, ...)
• a board support package (BSP)

Each application, written in OCaml, and compiled to C code is intended to be run on a given platform.

Predefined platforms are provided in the distribution.

Instructions to design and implement new platforms for Altera/Intel boards are given in the directory ./platforms/quartus/Reeadme.md.

When targeting a FPGA, the OMicroB compiler is only used to generate the main C file from the bytecode representation of the program. This C file is then compiled using the Nios-specific C compiler to generate an .elf file which is then uploaded to the softcore processor which has been instanciated on the FPGA. The latter steps are carried out using the vendor-specific suite of tools (Quartus2 for Nios processors running on Intel FPGAs).

To configure and build the platform-independent tools

1. Configure

   • ./configure

   This will write several configuration files in ./etc

2. Build the OMicroB tools. From the top directory run

   • make

   This will build ./omicrob/bin/{bc2c,omicrob} and ./omicrob/lib.

To build / run an application

1. Go to the corresponding platform directory

   • cd platforms/<family>/<platform>

2. Build the OMicroB interfaces

   • make omicrob

3. For Intel/FPGA platforms, run the nios2_command_shell script (located in <altera>/nios2eds directory, where <altera> is the root of the Intel/Altera software installation)

   • <altera>/nios2eds/nios_command_shell.sh

4. Build the BSP

   • make bsp

5. Connect the target board and upload the hardware configuration :

   • make hw

   The platform is now ready to receive and execute the application code

6. Go to the associated application directory and generate the required Makefiles :

   • cd apps/<app>
   • ./make_makefiles

7. Generate the target C code

   • make code

   This will generate the file main.c from the source in main.ml. This file can be executed on the host machine (without using the target platform physical IOs of course !) by running

   • make sim

8. Build, compile and upload the softcore code on the target board

   • make build
   • make run