extruder: Allow an extruder object to be created without a stepper

This may be useful for dual hotend printers that have only one
stepper.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 9 insertions, 5 deletions

diff --git a/docs/Config_Reference.md b/docs/Config_Reference.md
index 223b576f..bc66b86a 100644
--- a/docs/Config_Reference.md
+++ b/docs/Config_Reference.md
@@ -638,10 +638,11 @@ max_accel: 1
 
 ### [extruder]
 
-The extruder section is used to describe both the stepper controlling
-the printer extruder and the heater parameters for the nozzle. See the
-[pressure advance guide](Pressure_Advance.md) for information on
-tuning pressure advance.
+The extruder section is used to describe the heater parameters for the
+nozzle hotend along with the stepper controlling the extruder. See the
+[command reference](G-Codes.md#extruder) for additional information.
+See the [pressure advance guide](Pressure_Advance.md) for information
+on tuning pressure advance.
 
 ```
 [extruder]
@@ -652,7 +653,10 @@ microsteps:
 rotation_distance:
 #full_steps_per_rotation:
 #gear_ratio:
-#   See the "stepper" section for a description of the above parameters.
+#   See the "stepper" section for a description of the above
+#   parameters. If none of the above parameters are specified then no
+#   stepper will be associated with the nozzle hotend (though a
+#   SYNC_EXTRUDER_MOTION command may associate one at run-time).
 nozzle_diameter:
 #   Diameter of the nozzle orifice (in mm). This parameter must be
 #   provided.