tmc2130: Add initial support for TMC2130 stepper motor drivers

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

config/example-extras.cfg

@@ -402,6 +402,44 @@
 #   default is to not scale the 'channel_x' parameters.
 
 
+# Configure a TMC2130 stepper motor driver (one may define any number
+# of sections with a "tmc2130" prefix).
+#[tmc2130 my_name]
+#cs_pin:
+#   The pin corresponding to the TMC2130 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.
+#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 TMC2130 step interpolation (the driver will
+#   interally step at a rate of 256 micro-steps). 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.
+#hold_current:
+#   The amount of current (in amps) to configure the driver to use
+#   when the stepper is not moving. The default is to use the same
+#   value as run_current.
+#sense_resistor: 0.110
+#   The resistance (in ohms) of the motor sense resistor. The default
+#   is 0.110 ohms.
+#stealthchop: False
+#   Enable "stealthChop" mode. The default is False.
+#driver_IHOLDDELAY: 8
+#driver_TPOWERDOWN: 0
+#driver_BLANK_TIME_SELECT: 1
+#driver_TOFF: 1
+#driver_HEND: 7
+#driver_HSTRT: 0
+#   Set the given register during the configuration of the TMC2130
+#   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.
+
+
 # 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