Add min_slope_ratio argument to AFM.move_just_onto_surface.

To match the following calibcant commit:

  commit 7c934e1f5f0838a42a7a0b1d5a392e3f0686e1c4
  Author: W. Trevor King <wking@drexel.edu>
  Date:   Mon Jan 23 14:41:10 2012 -0500

    Add min-slope-ratio option to BumpConfig.

diff --git a/pyafm/afm.py b/pyafm/afm.py
index d99835eb0f31cbed9c6aa9aef392e420965e6fa6..92c0679071b7dc8add4a7aca27088d0cc634f27b 100644 (file)
--- a/pyafm/afm.py
+++ b/pyafm/afm.py
@@ -62,7 +62,8 @@ class AFM (object):
         if hasattr(self.temperature, 'get_temperature'):
             return self.temperature.get_temperature()
 
-    def move_just_onto_surface(self, depth=-50e-9, setpoint=2, far=200):
+    def move_just_onto_surface(self, depth=-50e-9, setpoint=2,
+                               min_slope_ratio=10, far=200):
         """Position the AFM tip close to the surface.
 
         Uses `.piezo.get_surface_position()` to pinpoint the position
@@ -92,15 +93,18 @@ class AFM (object):
         _LOG.debug("see if we're starting near the surface")
         try:
             pos = self.piezo.get_surface_position(
-                axis_name=self.axis_name, max_deflection=target_def)
+                axis_name=self.axis_name, max_deflection=target_def,
+                min_slope_ratio=min_slope_ratio)
         except _FlatFit, e:
             _LOG.info(e)
             pos = self._stepper_approach_again(
-                target_deflection=target_def, far=far)
+                target_deflection=target_def, min_slope_ratio=min_slope_ratio,
+                far=far)
         except _SurfaceError, e:
             _LOG.info(e)
             pos = self._stepper_approach_again(
-                target_deflection=target_def, far=far)
+                target_deflection=target_def, min_slope_ratio=min_slope_ratio,
+                far=far)
 
         pos_m = _convert_bits_to_meters(axis.config, pos)
         _LOG.debug('located surface at stepper %d, piezo %d (%g m)'
@@ -112,7 +116,8 @@ class AFM (object):
             self.stepper.step_relative(-1, backlash_safe=True)
             try:
                 pos = self.piezo.get_surface_position(
-                    axis_name=self.axis_name, max_deflection=target_def)
+                    axis_name=self.axis_name, max_deflection=target_def,
+                    min_slope_ratio=min_slope_ratio)
             except _FlatFit, e:
                 _LOG.debug(e)
                 continue
@@ -124,7 +129,8 @@ class AFM (object):
             self.stepper.step_relative(1)
             try:
                 pos = self.piezo.get_surface_position(
-                    axis_name=self.axis_name, max_deflection=target_def)
+                    axis_name=self.axis_name, max_deflection=target_def,
+                    min_slope_ratio=min_slope_ratio)
             except _FlatFit, e:
                 _LOG.debug(e)
                 continue
@@ -143,7 +149,7 @@ class AFM (object):
             % (depth, self.stepper.position, target, target_m))
 
 
-    def _stepper_approach_again(self, target_deflection, far):
+    def _stepper_approach_again(self, target_deflection, min_slope_ratio, far):
         _LOG.info('back off %d half steps and approach until deflection > %g'
                  % (far, target_deflection))
         # back away
@@ -154,7 +160,8 @@ class AFM (object):
                 'additional surface location attempt (stepping backwards)')
             try:
                 pos = self.piezo.get_surface_position(
-                    axis_name=self.axis_name, max_deflection=target_deflection)
+                    axis_name=self.axis_name, max_deflection=target_deflection,
+                    min_slope_position=min_slope_postion)
                 return pos
             except _SurfaceError, e:
                 _LOG.info(e)