chipmisc: Add support for configuring ad5206 digipots

Support an "ad5206" config section so that one can configure the
digipots found on Reprap "RAMBo" boards.

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

config/example-extras.cfg

@@ -81,3 +81,33 @@
 #   enabled, and then the 'value' parameter can be specified using the
 #   desired amperage for the stepper. The default is to not scale the
 #   'value' parameter.
+
+
+# Statically configured AD5206 digipots connected via SPI bus (one may
+# define any number of sections with an "ad5206" prefix).
+#[ad5206 my_digipot]
+#enable_pin:
+#   The pin corresponding to the AD5206 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.
+#channel_1:
+#channel_2:
+#channel_3:
+#channel_4:
+#channel_5:
+#channel_6:
+#   The value to statically set the given AD5206 channel to. This is
+#   typically set to a number between 0.0 and 1.0 with 1.0 being the
+#   highest resistance and 0.0 being the lowest resistance. However,
+#   the range may be changed with the 'scale' parameter (see
+#   below). If a channel is not specified then it is left
+#   unconfigured.
+#scale:
+#   This parameter can be used to alter how the 'channel_x' parameters
+#   are interpreted. If provided, then the 'channel_x' parameters
+#   should be between 0.0 and 'scale'. This may be useful when the
+#   AD5206 is used to set stepper voltage references. The 'scale' can
+#   be set to the equivalent stepper amperage if the AD5206 were at
+#   its highest resistance, and then the 'channel_x' parameters can be
+#   specified using the desired amperage value for the stepper. The
+#   default is to not scale the 'channel_x' parameters.

config/generic-rambo.cfg

@@ -76,13 +76,6 @@ pin: PH5
 
 [mcu]
 serial: /dev/ttyACM0
-custom:
-  # Initialize digipot
-  send_spi_message pin=PD7 msg=0487 # X = ~0.75A
-  send_spi_message pin=PD7 msg=0587 # Y = ~0.75A
-  send_spi_message pin=PD7 msg=0387 # Z = ~0.75A
-  send_spi_message pin=PD7 msg=00A5 # E0
-  send_spi_message pin=PD7 msg=017D # E1
 
 [printer]
 kinematics: cartesian
@@ -91,6 +84,18 @@ max_accel: 3000
 max_z_velocity: 5
 max_z_accel: 100
 
+[ad5206 stepper_digipot]
+enable_pin: PD7
+# Scale the config so that the channel value can be specified in amps.
+# (For Rambo v1.0d boards, use 1.56 instead.)
+scale: 2.08
+# Channel 1 is E0, 2 is E1, 3 is unused, 4 is Z, 5 is X, 6 is Y
+channel_1: 1.34
+channel_2: 1.0
+channel_4: 1.1
+channel_5: 1.1
+channel_6: 1.1
+
 # Enable 16 micro-steps on steppers X, Y, Z, E0, E1
 [static_digital_output stepper_config]
 pins:

config/makergear-m2-2012.cfg

@@ -76,13 +76,6 @@ hard_pwm: 1
 
 [mcu]
 serial: /dev/ttyACM0
-custom:
-  # Initialize digipot
-  send_spi_message pin=PD7 msg=0487 # X = ~0.75A
-  send_spi_message pin=PD7 msg=0587 # Y = ~0.75A
-  send_spi_message pin=PD7 msg=0387 # Z = ~0.75A
-  send_spi_message pin=PD7 msg=00A5 # E0
-  send_spi_message pin=PD7 msg=017D # E1
 
 [printer]
 kinematics: cartesian
@@ -91,6 +84,17 @@ max_accel: 3000
 max_z_velocity: 25
 max_z_accel: 30
 
+[ad5206 stepper_digipot]
+enable_pin: PD7
+# Scale the config so that the channel value can be specified in amps
+scale: 1.56
+# Channel 1 is E0, 2 is E1, 3 is unused, 4 is Z, 5 is X, 6 is Y
+channel_1: 1.0
+channel_2: 0.75
+channel_4: 0.82
+channel_5: 0.82
+channel_6: 0.82
+
 # Enable 8 micro-steps on steppers X, Y, Z, E0
 [static_digital_output stepper_config]
 pins: