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Due: Friday,
February 16 by 4:00 p.m.
Create a reverse polish notation (RPN) calculator using
LabVIEW. In RPN arithmetic the operators follow the arguments that
they operate on. For example to write the expression A sin (k
x - w t) in RPN one would
write
k x * w
t * - sin A *
Notice that in RPN no parenthesis are needed. To
implement this type of arithmetic on a calculator one uses a stack.
Values are pushed onto the stack from the top and then removed from the top
of the stack as needed. This would be a LIFO (Last In First Out) type
stack. We will use an array to serve as the stack. In the above
example, the value of k would be placed on the stack and then
the value of x placed on the stack. The *
operator would remove the k and the x and
replace these two values with the single value equal to the product k
x. Notice that some operators (like sin above for
example) will only take one value from the stack and replace it with an
altered value.
A working version of a LabVIEW RPN Calculator VI is
available in the RPN Calculator (DEMO).llb LabVIEW Library which is
stored in the G:\PLAB\Physics 418\ directory. I've saved this VI
without its block diagram to make it more fun for you to figure out how to
implement the various features of the calculator. The front panel is
depicted below.
Your version is to implement at a minimum the following:
- A QUIT button that will turn off the calculator (by
exiting the LabVIEW VI).
- A register to enter a new value onto the stack and an
ENTER button that will place the contents of this register onto the
stack. Notice that the example will also place the value in the
register on the stack if the Enter key on the PC KEYBOARD is
depressed. Also you do not have to click the mouse inside the
register to begin typing numbers into it. See if you can figure
out how to add these features for the praise and admiration of your peers
(in other words it is not required for the grade).
- At least three of the stack operations buttons:
- DROP - Removes the top value from the stack (if it
exists).
- DUP - Pushes a duplicate copy of the top value onto the
stack.
- CLEAR - Clears the entire stack contents.
- SWAP - Swaps the two top values on the stack.
- At least three of the one argument operators:
SIN, COS, TAN, ASIN, ACOS, ATAN, SQRT, LN, 1/x, x^2, e^x and +/-
(changes sign of top of stack).
- The four arithmetic operators that require two
arguments (+, -, * and /). Others could be added like y^x for
example.
- The stack contents should be displayed on the front
panel.
Here are some hints to help get you started. You
should use the state machine concept discussed in class to make this VI much
easier to implement. The stack will be stored in a shift register so
that its contents will be available each time through the loop and you can
write the new contents to the shift register before finishing the
iteration. A snippet of code that will perform the DUP operation (as
well as check to make sure that the stack actually contains something to
duplicate) is shown below. In the False case (not shown) the contents
of the stack are simply wired through the case statement.
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