add minimal MNL100 bring-up script

mnl100.py

@@ -0,0 +1,48 @@
+import time
+import serial
+
+
+def main():
+    with serial.Serial("/dev/cuaU0", timeout=1., exclusive=True) as port:
+        def transact(rdu):
+            telegram = b"#!@" + rdu
+            telegram += bytes("{:02X}".format(sum(telegram)), "ascii")
+            telegram += b"\r"
+            port.write(telegram)
+            
+            telegram = port.read_until(expected=b"\r")
+            if not telegram or telegram[-1] != 0x0d:
+                raise TimeoutError
+            match telegram[0]:
+                case 0x0d:    # acknowledge
+                    return None
+                case 0x3c:    # reply
+                    return telegram[3:-3]
+                case 0x1b:    # error
+                    raise IOError("laser reported error")
+                case _:
+                    raise ValueError("invalid reply from laser")
+
+        transact(b"g")  # laser on
+        print("laser turning on...")
+        try:
+            while True:
+                short_status = transact(b"W")  # GetShortStatus
+                if short_status == b"W01":
+                    break
+                time.sleep(0.3)
+            print("laser is on")
+            transact(b"u")   # ExtTrigmode
+            print("laser is ready")
+            # keep the laser on (auto-shutdown if no comms for 30s)
+            while True:
+                transact(b"W")  # GetShortStatus
+                time.sleep(5.0)
+        finally:
+            transact(b"X")  # laser off
+            print("laser is off")
+
+
+if __name__ == "__main__":
+    main()
+