Intro

This tool takes a bitmap, and outputs a GDS and LEF file that can be used in an sky130 / OpenLANE flow. Furthermore, the necessary files are included that allow this to be directly used as a submission for the (excellent) https://www.zerotoasiccourse.com/.

Note: Since we can only use metals 1-4, metal 5 will still have PDN wires going over our art. If someone can solve that, I’m all ears.
Note2: Depending on your bitmap, you can still cause DRC issues. Use caravel’s make precheck to figure them out. I’ve seen BEOL checks fail because of pixels that diagonally ‘touch corners’ but are otherwise unconnected, so make sure to avoid those in your input image.

Installation

You’ll need to have the Magic VLSI tool installed. I’ve tested it within OpenLANE (https://github.com/The-OpenROAD-Project/OpenLane) docker (run make mount).

Running

make clean && make GDS_WIDTH=50 IMAGE=chip_art.png

The GDS_WIDTH specifies how wide (in um) you want the image to render in the GDS.

Output

It will create GDS/LEF files in gds/ folder.

Hacking

Check the chip_art.py script for a bunch of stuff that’s hardcoded and only tested on sky130 / OpenLANE.

How does it work?

It maps supported bitmaps to gray scale images, and the pixel values get then mapped to metal layers in the GDS. The Python script outputs a Magic file, and the Makefile uses Magic to generate GDS and LEF.

In order to satisfy DRC and LVS, the GDS also contains a power and ground rail!