Skip to content

Latest commit

 

History

History
77 lines (46 loc) · 2.52 KB

README.md

File metadata and controls

77 lines (46 loc) · 2.52 KB
Raw

RiscyD2

RiscyD2 is a tiny RISC-V based microcontroller/softcore running on a Digilent Arty A7-35T board.

Project structure

  • chip: RTL code for a RISC-V CPU core implementing the RV32I base instruction set, with M standard extension support.
  • binutils: Contains an assembler that emits RISC-V flat binary.
  • emulation: A RISC-V RV32IM emulator written in Python.
  • test: Simple unit tests for arithemtic, load/store and csr instructions.

The project is mainly educational, and is inspired by From the Transistor to the Web Browser.

Prerequisites

  • Icarus Verilog
  • Python3
  • PySerial

Running on an FPGA

RiscyD2 currently only supports Arty A7-35T, but the plan is to add support for more boards.

To set it up:

  • Compile the bootrom:

python3 binutils/asm/asm.py -i os/bootrom.asm -o code.o

  • Save the code.mem file you got from the previous step
  • Create a Vivado project
  • Add the content of chip/rtl as design sources
  • Add code.mem as a Memory file
  • Add constraints located under chip/fpga/arty_a7/arty_a7_35t.xdc as constraint file
  • Synthesize, implement and generate bitstream
  • Load the bitstream to the board

At this point the chip is deployed to the board, and the bootrom is running. It continously checks the UART port for incoming exe files.

Programming RiscyD2

To compile programs for the board you can either use the assembler in the repository (recommended to run the programs in the sample folder), or use a real compiler, like GCC.

Toy examples

Compile an example program located under sample:

python3 binutils/asm/asm.py -i sample/switches.asm -o exe.o

Real-world examples

For a relatively complex example program, see the porting of TinyMaix to RiscyD2.

To compile C programs, the following toolchain is recommended:

Send the exe through UART:

python3 tools/talk2d2.py -i path/to/exe

The binary format is fairly simple: the first 4 bytes encode the size of the exe, followed by the exe. That's it.

To listen to incoming data from the board, run:

python3 tools/listen2d2.py

(NOTE: to get the ID of your board run ls /dev/tty.* in your terminal.)

License

MIT