70 lines
2.2 KiB
Python
70 lines
2.2 KiB
Python
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#!/usr/bin/env python3
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"""Turn a Quartus .ttf bitstream into the app image embedded in a MKR Vidor 4000 sketch.
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The Vidor bootloader expects the bitstream bytes bit-reversed relative to Quartus' .ttf
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output, written as a C initializer list (bitstream.h), plus a signature block (signature.h)
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describing where the image goes in the FPGA's flash. The app image slot starts at 512 KB.
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"""
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import argparse
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import hashlib
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from pathlib import Path
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APP_OFFSET_KB = 512
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IMAGE_TYPE_APP = 1
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def reverse_bits(byte: int) -> int:
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return int(f"{byte:08b}"[::-1], 2)
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def read_ttf(path: Path) -> bytes:
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values = (field.strip() for field in path.read_text().split(","))
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return bytes(reverse_bits(int(v)) for v in values if v)
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def format_initializer(data: bytes) -> str:
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lines = []
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for start in range(0, len(data), 16):
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chunk = data[start:start + 16]
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if len(chunk) == 16:
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lines.append(", ".join(f"{b:3d}" for b in chunk) + ",")
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else:
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lines.append("".join(f"{b:3d}, " for b in chunk))
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return "\n".join(lines) + "\n"
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def hex_bytes(data: bytes) -> str:
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return ", ".join(f"0x{b:02x}" for b in data) + ","
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def format_signature(image_text: str, length: int) -> str:
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digest = hashlib.sha256(image_text.encode()).digest()
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return "\n".join([
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"NO_BOOTLOADER,",
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hex_bytes((APP_OFFSET_KB * 1024).to_bytes(4, "little")),
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hex_bytes(length.to_bytes(4, "little")),
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hex_bytes(digest),
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hex_bytes(IMAGE_TYPE_APP.to_bytes(4, "little")),
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"0x00, 0x00, 0x00, 0x00, // force flag",
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"NO_USER_DATA,",
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]) + "\n"
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def main() -> None:
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parser = argparse.ArgumentParser(description=__doc__)
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parser.add_argument("ttf", type=Path, help="Quartus .ttf bitstream")
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parser.add_argument("out_dir", type=Path, help="directory for bitstream.h and signature.h")
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args = parser.parse_args()
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data = read_ttf(args.ttf)
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image_text = format_initializer(data)
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args.out_dir.mkdir(parents=True, exist_ok=True)
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(args.out_dir / "bitstream.h").write_text(image_text)
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(args.out_dir / "signature.h").write_text(format_signature(image_text, len(data)))
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print(f"{len(data)} bytes -> {args.out_dir}/bitstream.h, signature.h")
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if __name__ == "__main__":
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main()
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