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NAME move_info() - returns what would happen on a
move
DESCRIPTION
The move_info() function returns information
about what would happen on a subsequent move_all
command given the current motor positions and current values in
the A[] array. Such a function might be called, for
example, within the user_premove macro to determine
which motors will be moved to allow extra limit checking can be
performed involving the relative postion of motors.
If called with no arguments, returns a two-dimensional
associative array containing the move information. The array is
indexed by motor number and information keyword. The keywords
are
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"to_move" - nonzero if motor will move
"error" - reason the motor will not move
"commanded" - the commanded position
"magnitude" - magnitude of the move in user units
"current" - current position in user units
"current_dial" - current position in dial units
"target" - target position in user units
"target_dial" - target position in dial units
"backlash" - backlash for this move in user units
"leftover" - reminder due to motor resolution
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If called with a single argument that is one of the above
keywords, the function returns a one-dimensional associative
array indexed by motor number containing values for that keyword
for each motor. If called with a motor number or mnemonic as a
single argument, the function returns a one-dimensional
associative array, indexed by the above keywords containing
values for the one motor. If called with two arguments, motor
number and keyword, the function returns the corresponding single
value.
No matter how the function is called, the internal code will
calculate values for all motors. Thus, if multiple values are
needed, it is most efficient and recommended to call the function
once selecting arguments that will return all the needed values.
The "to_move" element will be 1 or 0, indicating
whether the motor would move or not. If there is condition that
prevents the move, the "error" element will contain
one of these strings:
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"low limit" - move exceeds low limit
"high limit" - move exceeds high limit
"busy" - motor is busy
"read only" - motor is configured as read only
"protected" - motor configuration does not allow moving
"disabled" - motor has been disabled
"externally disabled" - shared motor has been disabled
"unusable" - motor did not respond to presence test
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Otherwise, there will be no "error" array element.
The "target" and "target_dial"
values are the final position after backlash. The
"magnitude" value contains the distance to the
target position and does not include the magnitude of the
backlash.
The "leftover" value is the fractional value
that is the difference between the requested position and the
achievable position given the finite resolution of the motor.
For example, if a motor has 1000 steps per degree, each step
corresponds to 0.001 degrees. If one asks to move the motor to a
position of 1.0004 degrees, the motor will move to 1 degree and
the leftover value will be 0.0004 degrees.
The "commanded" value is the target position in
user units to the full precision requested. The other postion-
related values are rounded to the motor resolution. The
"commanded" position is saved after a move and is
available using special arguments to the built-in
read_motors() functions.
As mentioned above, if multiple values are needed, it is
better to make a single call of move_info() saving the return
values in an array, rather than making multiple calls, as each
call involves calculations for all the motor positions and
values, even if only selected values are returned. For example,
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{
local i, m[]
m = move_info()
for (i = 0; i < MOTORS; i++)
if (m[i]["to_move"]) {
...
}
}
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For the most part, the move_info() function will
reflect what will happen on the next move_all
command. However, for shared motors that can be moved by other
processes or for motors that have positions that drift or have
jitter, the status and position may change between the
move_info() call and the move_all call.
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Last Formatted May 12, 2012
Last Updated 06/08/11
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