Totalizer Batch Volume functionality (#113)

Add functions to get and set the totalizer batch volume on controllers.

---------

Co-authored-by: Alex Ruddick <[email protected]>

alicat/driver.py

@@ -377,6 +377,51 @@ async def set_pressure(self, pressure: float) -> None:
             await self._set_control_point('abs pressure')
         await self._set_setpoint(pressure)
 
+    async def get_totalizer_batch(self, batch: int = 1) -> str:
+        """Get the totalizer batch volume.
+
+        Args:
+            batch: Which of the two totalizer batches to query.
+                Default is 1; some devices have 2
+
+        Returns:
+            line: Current value of totalizer batch
+        """
+        command = f'{self.unit}$$TB {batch}'
+        line = await self._write_and_read(command)
+
+        if line == '?':
+            raise OSError("Unable to read totalizer batch volume.")
+        else:
+            values = line.split(" ")  # type: ignore[union-attr]
+            return f'{values[2]} {values[4]}' # returns 'batch vol' 'units'
+
+    async def set_totalizer_batch(self, batch_volume: float, batch: int = 1, units: str = 'default') -> None:
+        """Set the totalizer batch volume.
+
+        Args:
+            batch: Which of the two totalizer batches to set.
+                Default is 1; some devices have 2
+            batch_volume: Target batch volume, in same units as units
+                on device
+            units: Units of the volume being provided. Default
+                is 0, so device returns default engineering units.
+        """
+        engineering_units_table = {"default":0, "SμL":2, "SmL":3, "SL":4, \
+                    "Scm3":6, "Sm3":7, "Sin3":8, "Sft3":9, "kSft3":10, "NμL":32, \
+                    "NmL":33, "NL":34, "Ncm3":36, "Nm3":37}
+
+        if units in engineering_units_table:
+            units_no = engineering_units_table[units]
+        else:
+            raise ValueError("Units not in unit list. Please consult Appendix B-3 of the Alicat Serial Primer.")
+
+        command = f'{self.unit}$$TB {batch} {batch_volume} {units_no}'
+        line = await self._write_and_read(command)
+
+        if line == '?':
+            raise OSError("Unable to set totalizer batch volume. Check if volume is out of range for device.")
+
     async def hold(self) -> None:
         """Override command to issue a valve hold.