comedi_get_softcal_converter — get converter for software-calibrated subdevice


#include <comedilib.h>
int comedi_get_softcal_converter(unsigned subdevice,
 unsigned channel,
 unsigned range,
 enum comedi_conversion_direction direction,
 const comedi_calibration_t * parsed_calibration,
 comedi_polynomial_t * converter);




The function comedi_get_softcal_converter initializes the comedi_polynomial_t pointed to by converter so it can be passed to either comedi_to_physical or comedi_from_physical. The comedi_polynomial_t pointed to by converter can then be used to convert data for the specified subdevice, channel, and range. The direction parameter specifies whether converter will be passed to comedi_to_physical or comedi_from_physical. The parsed_calibration parameter points to the software calibration values for your device, and may be obtained by calling comedi_parse_calibration_file on a calibration file generated by the comedi_soft_calibrate program.

This function is only useful for boards that perform their calibrations in software on the host computer. A subdevice will advertise the fact that it depends on a software calibration with the SDF_SOFT_CALIBRATED subdevice flag.

Whether or not the result of this function actually depends on the channel parameter is hardware dependent. For example, the calibration of a multiplexed analog input will typically not depend on the channel, only the range. Analog outputs will typically use different calibrations for each output channel.

Software calibrations are implemented as polynomials (up to third order). Since the inverse of a polynomial of order higher than one can't be represented exactly as another polynomial, you may not be able to get converters for the reverse direction. For example, you may be able to get a converter for an analog input in the COMEDI_TO_PHYSICAL direction, but not in the COMEDI_FROM_PHYSICAL direction.

Return value

Returns 0 on success, -1 on failure.