Scanlab RTC6 PCIe Board - Correction Via Mcbsp Interface

RTC6 boards
Doc. Rev. 1.0.21 en-US
8 Advanced Functions for Scan Head Control and Laser Control
245
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Correction via McBSP Interface
To be able to pass position values via the
McBSP interface, the Processing-on-the-fly correction
must be activated by:
• set_fly_x_pos and/or set_fly_y_pos
• set_mcbsp_in for positional values in
2 spatial directions
• set_multi_mcbsp_in for positional values in all
3 spatial directions (requires no scaling factors)
Here, the scaling factor [in bits per bits] defines the
relation between the shift [in bits] of the current
output position in the Image Field and the input value
[in bits] at the McBSP interface. See also Section
”Determining the Scaling Factors”, page 245.
Thereafter, the output value is calculated from the
current output position by adding (for all
spatial directions) the product of the scaling factor
and the current input value at the McBSP interface.
This correction takes place every 10 µs.
At the McBSP interface, see Chapter 4.6.6
”McBSP/ANALOG Socket Connector”, page 84, there
are available:
• For 1D corrections –
signed 32-bit values
• For 2D corrections –
signed 16-bit values per axis
(the y value is in the lower 16 bits and the y value
in the upper 16 bits of the value at the
McBSP interface)
Notes
• After set_fly_x_pos and set_fly_y_pos, the input
values received at the McBSP interface
automatically get copied to internal memory
location 0. This still applies even after
Processing-on-the-fly correction gets switched off
by fly_return, set_fly_x_pos, set_fly_y_pos or
set_fly_rot_pos, as well as after
load_program_file. The current data at memory
location 0 can be queried by read_mcbsp(0) .
• In contrast, activation of Processing-on-the-fly
correction by set_mcbsp_in or
set_mcbsp_in_list also result in McBSP input
values being copied to internal memory locations
1, 2 and/or 3, see Section ”Correction via
McBSP Interface with Additional McBSP Input”,
page 246.
• After Processing-on-the-fly correction is activated
by set_multi_mcbsp_in or
set
_multi_mcbsp_in_list, t
he transmitted data
gets consecutively written to memory locations
0…3. From there, they can be read out unsorted
by read_mcbsp or sorted by read_multi_mcbsp.
Determining the Scaling Factors
The scaling factors can be determined
experimentally:
(1) Read out the start input value by read_mcbsp.
(2) Start the movement.
(3) Stop the movement.
(4) Read out the end input value by read_mcbsp.
(5) Measure the distance traveled in mm.
(6) Calculate the position increment i as follows:
(7) Calculate the scaling factors Scalex and Scaley
[in bits per bits] as follows:
Whereby K is the calibration factor [in bits per
mm], see Chapter 7.3.2 ”Image Field Size and
Image Field Calibration”, page 167 and i is the
encoder increment from Step 6.
i
end input value start input value–
distance travelled
--------------------------------------------------------------------------------------=
Scalex
K
i
x
----=
Scaley
K
i
y
----=