feat: add device firmware with USB API, StrixFPGA library and API check tools

tools/stream_entropy.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+"""Writes STRIX entropy to stdout continuously, for piping into test suites
+(e.g. `python3 tools/stream_entropy.py | qngmeter`). Uses the firmware's `entropy <n> bin`
+command (arduino/strix/API.md)."""
+
+import argparse
+import sys
+import time
+
+import serial
+
+CHUNK = 65536
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--port", default="/dev/ttyACM0")
+    parser.add_argument("--bytes", type=int, default=0, help="stop after this many bytes (0 = run until killed)")
+    args = parser.parse_args()
+
+    device = serial.Serial(args.port, 115200, timeout=5)
+    time.sleep(0.5)
+    device.reset_input_buffer()
+    out = sys.stdout.buffer
+    sent = 0
+    try:
+        while args.bytes == 0 or sent < args.bytes:
+            count = CHUNK if args.bytes == 0 else min(CHUNK, args.bytes - sent)
+            device.write(f"entropy {count} bin\n".encode())
+            header = device.readline().decode(errors="replace").strip()
+            if header != f"BIN {count}":
+                sys.exit(f"device: {header or 'timeout'}")
+            data = device.read(count)
+            if len(data) != count:
+                sys.exit(f"short read: {len(data)} of {count} bytes")
+            out.write(data)
+            out.flush()
+            sent += count
+    except (BrokenPipeError, KeyboardInterrupt):
+        pass
+
+
+if __name__ == "__main__":
+    main()