From efbc3201c4eff1bca1fbec0c7add386f6ee4a9fd Mon Sep 17 00:00:00 2001 From: "W. Trevor King" Date: Mon, 23 Jan 2012 15:41:52 -0500 Subject: [PATCH] Add AFM._check_target_deflection to avoid approaching forever. Also use the deflection channel config to convert `setpoint` to bits, instead of the output z channel config. --- pyafm/afm.py | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/pyafm/afm.py b/pyafm/afm.py index 0c89df9..a73b597 100644 --- a/pyafm/afm.py +++ b/pyafm/afm.py @@ -83,9 +83,11 @@ class AFM (object): stepper_tolerance = 2*self.stepper.step_size axis = self.piezo.axis_by_name(self.axis_name) + def = self._deflection_channel() zero = _convert_volts_to_bits(axis.config['channel'], 0) - target_def = _convert_volts_to_bits(axis.config['channel'], setpoint) + target_def = _convert_volts_to_bits(def.config, setpoint) + self._check_target_deflection(target_def) _LOG.debug('zero the %s piezo output' % self.axis_name) self.piezo.jump(axis_name=self.axis_name, position=zero) @@ -148,6 +150,14 @@ class AFM (object): 'positioned %g m into the surface at stepper %d, piezo %d (%g m)' % (depth, self.stepper.position, target, target_m)) + def _check_target_deflection(self, target_deflection): + def = self._deflection_channel() + max_def = def.get_maxdata(): + if target_deflection > max_def: + _LOG.error(('requested setpoint ({:g} V = {:d} bits) is larger ' + 'than the maximum deflection value of {:d} bits' + ).format(setpoint, target_deflection, max_def)) + raise ValueError(setpoint) def _stepper_approach_again(self, target_deflection, min_slope_ratio, far): _LOG.info('back off %d half steps and approach until deflection > %g' @@ -173,6 +183,7 @@ class AFM (object): def stepper_approach(self, target_deflection): _LOG.info('approach with stepper until deflection > {}'.format( target_deflection)) + self._check_target_deflection(deflection=target_deflection) cd = self.piezo.read_deflection() # cd = current deflection in bits _LOG.debug('single stepping approach') while cd < target_deflection: -- 2.26.2