bring back request_tip_len_on_channel

pylabrobot/liquid_handling/backends/hamilton/STAR.py

@@ -7317,6 +7317,54 @@ async def clld_probe_z_height_using_channel(
 
     return result_in_mm
 
+  async def request_tip_len_on_channel(
+    self,
+    channel_idx: int,  # 0-based indexing of channels!
+  ) -> float:
+    """
+    Measures the length of the tip attached to the specified pipetting channel.
+    Checks if a tip is present on the given channel. If present, moves all channels
+    to THE safe Z position, 334.3 mm, measures the tip bottom Z-coordinate, and calculates
+    the total tip length. Supports tips of lengths 50.4 mm, 59.9 mm, and 95.1 mm.
+    Raises an error if the tip length is unsupported or if no tip is present.
+    Parameters:
+      channel_idx: Index of the pipetting channel (0-based).
+    Returns:
+      The measured tip length in millimeters.
+    Raises:
+      ValueError: If no tip is present on the channel or if the tip length is unsupported.
+    """
+
+    # Check there is a tip on the channel
+    all_channel_occupancy = await self.request_tip_presence()
+    if not all_channel_occupancy[channel_idx]:
+      raise ValueError(f"No tip present on channel {channel_idx}")
+
+    # Level all channels
+    await self.move_all_channels_in_z_safety()
+    known_top_position_channel_head = 334.3  # mm
+    fitting_depth_of_all_standard_channel_tips = 8  # mm
+    unknown_offset_for_all_tips = 0.4  # mm
+
+    # Request z-coordinate of channel+tip bottom
+    tip_bottom_z_coordinate = await self.request_z_pos_channel_n(
+      pipetting_channel_index=channel_idx
+    )
+
+    total_tip_len = round(
+      known_top_position_channel_head
+      - (
+        tip_bottom_z_coordinate
+        - fitting_depth_of_all_standard_channel_tips
+        - unknown_offset_for_all_tips
+      ),
+      1,
+    )
+
+    if total_tip_len in [50.4, 59.9, 95.1]:  # 50ul, 300ul, 1000ul
+      return total_tip_len
+    raise ValueError(f"Tip of length {total_tip_len} not yet supported")
+
   async def ztouch_probe_z_height_using_channel(
     self,
     channel_idx: int,  # 0-based indexing of channels!