Read Captured Position Return

Usage

status = flex_read_cap_pos_rtn(u8 boardID, u8 axisOrEncoder, i32* capturedPosition);

Purpose

Reads a captured position value from an axis or encoder.

Tip  Refer to the Remarks section for information about how the behavior of this function differs between controllers.

Parameters

Parameter Discussion

axisOrEncoder is the axis or encoder to read. Valid values are NIMC_AXIS1 through NIMC_AXIS30 or NIMC_ENCODER1 through NIMC_ENCODER30. On motion controllers that support fewer than thirty axes, reading non-existent axes or encoders returns error –70006 (NIMC_badResourceIDOrAxisError). Refer to Axes and Encoders for axis and encoder resource IDs.

capturedPosition is the position value captured when the corresponding high-speed capture input went active.

Using This Function

This function returns the value in the single high-speed capture register of the axis or encoder selected. This value was captured when an enabled high-speed capture input went active.

For buffered high-speed capture, the captured positions are stored in a buffer. Use Read Buffer to read the captured positions.

High-speed capture functionality is performed by the encoder resources themselves. When this function is sent to an axis, the value returned is actually from the mapped encoder resource.

Refer to the Enable High-Speed Capture and Read High-Speed Capture Status functions for more information about the high-speed capture inputs and typical applications.

Note  For closed-loop stepper motion systems in which the encoder counts per revolution differs from the steps per revolution, the captured position is in encoder counts.

Remarks

This section includes information about how the behavior of this function differs among the controllers that support it.

NI 73xx Controller Considerations

The following list includes considerations you must make when you are using this function with a 73xx motion controller:

• NI 73xx controllers do not support multiple simultaneous high-speed captures per axis. NIMC_SECOND_HS_CAPTURE is not supported.

NI SoftMotion Controller Considerations

The following list includes considerations you must make when you are using this function with the NI SoftMotion Controller:

• The NI SoftMotion Controller supports multiple simultaneous high-speed captures per axis

  To read the captured position on an axis, use the constant for that axis. For example, if the first high-speed capture is on axis 1, the function call appears as

  status = flex_read_cap_pos_rtn (boardID, NIMC_AXIS1, &capturedPosition);

  To read the captured position on the secondary high-speed capture line, use the second high-speed capture constants NIMC_SECOND_HS_CAPTURE1 through NIMC_SECOND_HS_CAPTURE30. For example, if the second high-speed capture is on axis 1, the function call appears as

  status = flex_read_cap_pos_rtn (boardID, NIMC_SECOND_HS_CAPTURE1, &capturedPosition);

• The NI SoftMotion Controller for Copley Controls' Accelnet and Xenus CANopen drives does not support multiple simultaneous high-speed captures per axis. NIMC_SECOND_HS_CAPTURE is not supported.