diff --git a/mpf/devices/stepper.py b/mpf/devices/stepper.py
index f3a68c8cd..126f72b0b 100644
--- a/mpf/devices/stepper.py
+++ b/mpf/devices/stepper.py
@@ -92,7 +92,7 @@ def validate_and_parse_config(self, config, is_mode_config, debug_prefix: str =
             if cfg in config:
                 for pos, value in config[cfg].items():
                     if isinstance(value, str):
-                        config[cfg][pos] = { 'event': value }
+                        config[cfg][pos] = {'event': value}
         config = super().validate_and_parse_config(config, is_mode_config, debug_prefix)
         platform = self.machine.get_platform_sections(
             'stepper_controllers', getattr(config, "platform", None))
diff --git a/mpf/platforms/fast/communicators/exp.py b/mpf/platforms/fast/communicators/exp.py
index 8c6528693..f4d0e98c7 100644
--- a/mpf/platforms/fast/communicators/exp.py
+++ b/mpf/platforms/fast/communicators/exp.py
@@ -110,9 +110,10 @@ def set_led_fade_rate(self, board_address: str, rate: int) -> None:
         self.send_and_forget(f'RF@{board_address}:{Util.int_to_hex_string(rate, True)}')
 
     def register_processor(self, message_prefix, board_address, device_id, callback):
+        """Register an exp board processor to handle messages."""
         if message_prefix not in self.message_processors:
             self.message_processors[message_prefix] = partial(self._process_device_msg, message_prefix)
-            self._device_processors[message_prefix]= dict()
+            self._device_processors[message_prefix] = dict()
         if board_address not in self._device_processors[message_prefix]:
             self._device_processors[message_prefix][board_address] = dict()
         self._device_processors[message_prefix][board_address][device_id] = callback
diff --git a/mpf/platforms/fast/fast_stepper.py b/mpf/platforms/fast/fast_stepper.py
index 5935030c6..a10a4131c 100644
--- a/mpf/platforms/fast/fast_stepper.py
+++ b/mpf/platforms/fast/fast_stepper.py
@@ -10,6 +10,7 @@
 MIN_SPEED = 350
 MAX_SPEED = 1650
 
+
 class FastStepper(StepperPlatformInterface):
 
     """A stepper in the FAST platform connected to a FAST Expansion Board."""
@@ -31,6 +32,7 @@ def __init__(self, breakout_board, port, config):
         self._default_speed = Util.int_to_hex_string(self.config['default_speed'], True)
 
     def home(self, direction):
+        """Return the stepper to its home position."""
         if direction != 'counterclockwise':
             raise ConfigFileError("FAST Stepper only supports home in counter-clockwise direction. "
                                   "Please rewire your motor and set homing_direction: counterclockwise "
@@ -39,6 +41,7 @@ def home(self, direction):
         self._send_command("MH")
 
     async def wait_for_move_completed(self):
+        """Wait for the stepper to stop moving."""
         # If not moving, return immediately
         if not self._is_moving:
             return
@@ -73,7 +76,8 @@ def move_rel_pos(self, position, speed=None):
     def move_vel_mode(self, velocity):
         """Move the motor indefinitely in either direction.
 
-        FAST does not support this, so instead send the longest possible move time."""
+        FAST does not support this, so instead send the longest possible move time.
+        """
         base_command = "MR" if velocity < 0 else "MF"
         # The only place in MPF code that uses move_vel_mode is the software-based
         # homing, which sends 1/-1 as values. Interpret that as slowest possible
@@ -88,9 +92,10 @@ def stop(self):
         self._send_command("MC")
 
     def set_home_position(self):
+        """Not used."""
         pass
 
-    def _send_command(self, base_command, payload=[]):
+    def _send_command(self, base_command, payload=set()):
         self.exp_connection.send_and_forget(','.join([
             f'{base_command}@{self.base_address}:{self.stepper_index}', *payload]))
 
diff --git a/mpf/platforms/p_roc_devices.py b/mpf/platforms/p_roc_devices.py
index f68462b09..71ec625d0 100644
--- a/mpf/platforms/p_roc_devices.py
+++ b/mpf/platforms/p_roc_devices.py
@@ -487,7 +487,7 @@ def move_vel_mode(self, velocity):
         else:
             self.move_rel_pos(-16384)
 
-    def move_rel_pos(self, position):
+    def move_rel_pos(self, position, speed=None):
         """Move stepper by x steps."""
         if abs(position) > 16384:
             raise ValueError("Cannot move more than 16384 steps but tried {}".format(position))
diff --git a/mpf/platforms/pololu/pololu_tic.py b/mpf/platforms/pololu/pololu_tic.py
index 16b355678..ade5e15fe 100644
--- a/mpf/platforms/pololu/pololu_tic.py
+++ b/mpf/platforms/pololu/pololu_tic.py
@@ -189,7 +189,7 @@ def move_abs_pos(self, position):
         self._move_complete.clear()
         self.tic.rotate_to_position(self._position)
 
-    def move_rel_pos(self, position):
+    def move_rel_pos(self, position, speed=None):
         """Move axis to a relative position."""
         self._position += position
         self._move_complete.clear()
diff --git a/mpf/platforms/spike/spike.py b/mpf/platforms/spike/spike.py
index 00cb52334..d655270a1 100644
--- a/mpf/platforms/spike/spike.py
+++ b/mpf/platforms/spike/spike.py
@@ -420,10 +420,10 @@ async def is_move_complete(self) -> bool:
             return False
         return info['position'] == self._position
 
-    def move_rel_pos(self, position):
+    def move_rel_pos(self, position, speed=None):
         """Move relative to current position."""
         self._position += int(position)
-        self._move_to_absolute_position(self._position, self.config['speed'])
+        self._move_to_absolute_position(self._position, speed or self.config['speed'])
 
     def move_vel_mode(self, velocity):
         """Move stepper in a direction."""
diff --git a/mpf/platforms/step_stick.py b/mpf/platforms/step_stick.py
index 5e5ebee3c..b7d412259 100644
--- a/mpf/platforms/step_stick.py
+++ b/mpf/platforms/step_stick.py
@@ -35,7 +35,7 @@ def start_stepper(self, **kwargs):
         if self.enable_output:
             self.enable_output.enable()
 
-    def move_rel_pos(self, position):
+    def move_rel_pos(self, position, speed=None):
         """Move a number of steps in one direction."""
         if self._move_task and not self._move_task.done():
             raise AssertionError("Last move has not been completed. Calls stop first.")
diff --git a/mpf/platforms/trinamics_steprocker.py b/mpf/platforms/trinamics_steprocker.py
index a92c785c8..d7a5d312d 100644
--- a/mpf/platforms/trinamics_steprocker.py
+++ b/mpf/platforms/trinamics_steprocker.py
@@ -110,7 +110,7 @@ def move_abs_pos(self, position):
         microstep_pos = self._uu_to_microsteps(position)
         self.tmcl.mvp(self._mn, "ABS", microstep_pos)
 
-    def move_rel_pos(self, position):
+    def move_rel_pos(self, position, speed=None):
         """Move axis to a relative position."""
         microstep_rel = self._uu_to_microsteps(position)
         self.tmcl.mvp(self._mn, "REL", microstep_rel)
diff --git a/mpf/platforms/virtual.py b/mpf/platforms/virtual.py
index 7d8164a69..19cb95bb5 100644
--- a/mpf/platforms/virtual.py
+++ b/mpf/platforms/virtual.py
@@ -512,7 +512,7 @@ async def wait_for_move_completed(self):
         """Wait until move completed."""
         await asyncio.sleep(0.1)
 
-    def move_rel_pos(self, position):
+    def move_rel_pos(self, position, speed=None):
         """Move axis to a relative position."""
         self._current_position += position