fix default vvp, some doc

README.md

@@ -1,2 +1,27 @@
 # In-Field Testing Using MISR
 
+## Setup
+
+After cloning this repository, run:
+
+```
+git submodule init
+git submodule update
+```
+
+This project uses [Nix](https://nixos.org) to manage reproducible programming environments.
+
+Run `nix develop` to enter a shell with all necessary software.
+
+If `nix` is not installed, follow this [guide](https://librelane.readthedocs.io/en/stable/installation/nix_installation/index.html). No need to clone `librelane` here, but it is good to set up the `extra-substituters` as described in the guide for using LibreLane in the future (for making layouts with SkyWater 130nm technology).
+
+## Usage
+
+Compile jpeg decoder core using `iverilog` and run RTL simulation of the jpeg decoder core using `vvp`:
+
+```
+nix develop
+make
+uv run jpeg_core_tb_run_plasma.py
+```
+

jpeg_core_tb_run_plasma.py

@@ -56,7 +56,6 @@ def run_simulation(jpeg_path, ppm_path, vvp_path):
     """
     Decode jpeg_path into ppm_path with vvp sim.vvp and return the result as a PIL Image.
     """
-    assert os.path.exists(vvp_path), "sim.vvp not found — run 'make sim.vvp' first"
     
     result = subprocess.run(
         ['vvp', vvp_path, f'+infile={jpeg_path}', f'+outfile={ppm_path}'],
@@ -112,14 +111,15 @@ def main():
                         help='Plasma coarsest feature size in pixels (default 32)')
     parser.add_argument('--save-input',  metavar='PATH', help='Save generated JPEG to this path')
     parser.add_argument('--save-output', metavar='PATH', help='Save RTL output PPM to this path')
-    parser.add_argument('--vvp-path', metavar='PATH', default='sim.vvp',
+    parser.add_argument('--vvp-path', metavar='PATH', default='jpeg_core_tb.vvp',
-                        help='Path to compiled simulation (default: sim.vvp)')
+                        help='Path to compiled simulation (default: jpeg_core_tb.vvp)')
     args = parser.parse_args()
 
     mcu, subsampling_str = (16, '4:2:0') if args.subsampling else (8, '4:4:4')
 
     assert args.width  % mcu == 0, f"width {args.width} must be a multiple of {mcu} for {subsampling_str}"
     assert args.height % mcu == 0, f"height {args.height} must be a multiple of {mcu} for {subsampling_str}"
+    assert os.path.exists(args.vvp_path), f"{args.vvp_path} not found - run 'make' first"
 
     print(f"input: width={args.width} height={args.height} YCbCr={subsampling_str} q={args.quality} seed={args.seed}")