fix(api): Allows floating-point temperatures to be set/read to/from t…

…emp-deck (#1798)

api/opentrons/drivers/temp_deck/driver.py

@@ -40,6 +40,10 @@
 TEMP_DECK_COMMAND_TERMINATOR = '\r\n\r\n'
 TEMP_DECK_ACK = 'ok\r\nok\r\n'
 
+# Number of digits after the decimal point for temperatures being sent
+# to/from Temp-Deck
+GCODE_ROUNDING_PRECISION = 3
+
 
 class TempDeckError(Exception):
     pass
@@ -64,7 +68,7 @@ def _parse_string_value_from_substring(substring) -> str:
                 substring))
 
 
-def _parse_number_from_substring(substring) -> int:
+def _parse_number_from_substring(substring) -> float:
     '''
     Returns the number in the expected string "N:12.3", where "N" is the
     key, and "12.3" is a floating point value
@@ -76,7 +80,7 @@ def _parse_number_from_substring(substring) -> int:
         value = substring.split(':')[1]
         if value.strip().lower() == 'none':
             return None
-        return int(value)
+        return round(float(value), GCODE_ROUNDING_PRECISION)
     except (ValueError, IndexError, TypeError, AttributeError):
         log.exception('Unexpected argument to _parse_number_from_substring:')
         raise ParseError(
@@ -202,8 +206,9 @@ def disengage(self) -> str:
     def set_temperature(self, celsius) -> str:
         self.run_flag.wait()
         try:
+            celsius = round(float(celsius), GCODE_ROUNDING_PRECISION)
             self._send_command(
-                '{0} S{1}'.format(GCODES['SET_TEMP'], int(celsius)))
+                '{0} S{1}'.format(GCODES['SET_TEMP'], celsius))
         except (TempDeckError, SerialException, SerialNoResponse) as e:
             return str(e)
         return ''

api/tests/opentrons/drivers/module_drivers/test_temp_deck_driver.py

@@ -90,10 +90,10 @@ def _mock_send_command(self, command, timeout=None):
     temp_deck._send_command = types.MethodType(_mock_send_command, temp_deck)
 
     temp_deck.set_temperature(99)
-    assert command_log[-1] == 'M104 S99'
+    assert command_log[-1] == 'M104 S99.0'
 
     temp_deck.set_temperature(-9)
-    assert command_log[-1] == 'M104 S-9'
+    assert command_log[-1] == 'M104 S-9.0'
 
 
 def test_fail_set_temp_deck_temperature(monkeypatch):