Correction Via Mcbsp Interface - Scanlab RTC 5 PC Interface Board Installation And Operation Manual

Then, Processing-on-the-fly correction must be acti-
(1)
vated via set_fly_rot . The parameter Resolution
[in counts per revolution] must thereby be specified.
The inverse of this parameter defines the rotation [in
number of revolutions] of the current output position
in the image field corresponding to one counting unit
(see below).
The set_fly_rot command resets the encoder counter
Encoder0 to zero.
Thereafter, the output value is calculated from the
current output position via a linear transformation
(rotation around the specified rotation center, where
rotation angle / 360° = current Encoder0 counter
value / Resolution). This correction is performed
(2)
every 10 µs .
Determining the Resolution Parameter
If the angular position of the workpiece is to be regis-
tered via an incremental encoder, then a calibration
must be performed to determine a value for the
Resolution parameter:
 Read the counter start value (via get_encoder)
and begin the rotation (any desired number of
full rotations)
 Count the number of revolutions.
 Stop the rotation and read the counter end value
(3)
(via get_encoder) .
 The parameter Resolution [i.e. the counts per
revolution] can then be calculated as follows:
Resolution = (counter end value – counter start
value) / number of revolutions
Note that the number of counts per revolution is
equal to the number of encoder signal edges per
revolution i.e. four times the number of encoder
increments per revolution (see
If the workpiece rotates at a constant speed  [in
number of revolutions per second] and an encoder
simulation was activated via simulate_encoder, then
the Resolution parameter can be calculated as
follows:
Resolution = (1000000 counts/second) / 
It might be necessary to adjust the sign of
Resolution to the direction of rotary movement.
(2)
(1) See footnote on page 179.
(2) The encoder counters are 32-bit counters (for signed 32-bit
values). If the maximum (minimum) count is reached, then
counting will continue with the minimum (maximum) count.
(3) Alternatively, the counter start and end values can be stored in
®
a buffer on the RTC 5 via the list command
and then retrieved from there via the control command
read_encoder.
®
RTC 5 PC Interface Board
Rev. 1.9 e
8 Advanced Functions for Scan Head and Laser Control

Correction via McBSP Interface

If angle-position values for Processing-on-the-fly
correction of rotary movement are forwarded via the
McBSP interface, then Processing-on-the-fly
correction must be activated via set_fly_rot_pos.
Here, the required Resolution parameter has the
same meaning as with
larly determined (see above), with the difference that
McBSP input values are queried via
(while counter values are queried via get_encoder).
Notes
• As with using McBSP input values to compensate
page 216).
store_encoder
set_fly_rot
linear motions, McBSP input values get copied to
internal memory location 0 (see notes on
page 180).
and can be simi-
read_mcbsp
182