tmc2660: Implementation of TMC2660 extra (#621)

Signed-off-by: Florian Heilmann <Florian.Heilmann@gmx.net>

config/example-extras.cfg

@@ -662,6 +662,86 @@
 #   above list.
 
 
+# Configure a TMC2660 stepper motor driver via SPI bus. To use this
+# feature, define a config section with a tmc2660 prefix followed by
+# the name of the corresponding stepper config section (for example,
+# "[tmc2660 stepper_x]"). The current of the TMC2660 stepper driver
+# is adjustable at run-time using
+# "SET_TMC_CURRENT STEPPER=stepper_x CURRENT=.1" type extended g-code
+# commands.
+#[tmc2660 stepper_x]
+#cs_pin:
+#   The pin corresponding to the TMC2660 chip select line. This pin
+#   will be set to low at the start of SPI messages and raised to high
+#   after the message completes. This parameter must be provided.
+#bus:
+#   Select the SPI bus the TMC2660 stepper driver is connected to. This
+#   depends on the physical connections on your board, as well as the
+#   SPI implementation of your particular microcontroller. This parameter
+#   must be provided.
+#freq: 2000000
+#   SPI bus frequency used to communicate with the TMC2660 stepper
+#   driver. the default is 2000000.
+#microsteps:
+#   The number of microsteps to configure the driver to use. Valid
+#   values are 1, 2, 4, 8, 16, 32, 64, 128, 256. This parameter must
+#   be provided.
+#interpolate: True
+#   If true, enable step interpolation (the driver will internally
+#   step at a rate of 256 micro-steps). This only works if microsteps
+#   is set to 16. The default is True.
+#run_current:
+#   The amount of current (in amps) to configure the driver to use
+#   during stepper movement. This parameter must be provided.
+#idle_timeout: 0
+#   The amount of time in seconds after which the run_current of the
+#   stepper driver will be lowered to this percentage of run_current.
+#   Set to 0 to disable the idle timeout. The default is 0.
+#idle_current_percent: 30
+#   The percentage of the run_current the stepper driver will be
+#   lowered to after the idle_timeout has expired. The current will
+#   be raised again once the stepper has to move again. Make sure to
+#   set this to a high enough value such that the steppers do not lose
+#   their position. There is also a delay of up to 100 ms until the
+#   current is raised again, so take this into account commanding fast
+#   moves when the stepper is idling. The default is 30.
+#driver_DEDGE: False
+#driver_TBL: 36
+#   Valid values are 16, 24, 36, 54.
+#driver_CHM: spreadcycle
+#   Valid values are 'spreadcycle' and 'constant_toff'
+#driver_RNDTF: False
+#driver_HDEC: False
+#driver_HEND: 7 if spreadcycle is used, 3 otherwise
+#driver_HSTRT: 5 if spreadcycle is used, 4 otherwise
+#driver_TOFF: 7 if spreadcycle is used, 4 otherwise
+#driver_SEIMIN: half
+#   Valid values are 'quarter' and 'half'.
+#driver_SEDN: 32
+#   Valid values are 1, 2, 8, 32.
+#driver_SEMAX: 0
+#driver_SEUP: 1
+#   Valid values are 1, 2, 4, 8.
+#driver_SEMIN: 0
+#driver_SFILT: True
+#driver_SGT: -64
+#driver_SLPH: min
+#   Valid values are 'min', 'min_tc', 'med_tc', 'max'
+#driver_SLPL: min
+#   Valid values are 'min', 'med', 'max'
+#driver_DISS2G: False
+#driver_TS2G: 0.8
+#   Valid values are 0.8, 1.2, 1.6, 3.2.
+#driver_VSENSE: high
+#   Valid values are 'high' and 'low'
+#
+#   Set the given register during the configuration of the TMC2660
+#   chip. This may be used to set custom motor parameters. The
+#   defaults for each parameter are next to the parameter name in the
+#   above list. See the TMC2660 datasheet about what each parameter
+#   does and what the restrictions on parameter combinations are.
+
+
 # Homing override. One may use this mechanism to run a series of
 # g-code commands in place of a G28 found in the normal g-code input.
 # This may be useful on printers that require a specific procedure to