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Simple Calculator


One of my math classes had a test recently, and the Professor only allowed "simple" calculators. I forgot all about that particular requirement, and was planning on taking my TI-89 until the test day rolls around and I was reminded. So I rushed out this little application in half an hour that does simple integer math (+,-,*,/,^). I think it shows the power of the Propeller that I was able to build this system so quickly and easily, and that it works the way it's supposed to. Another 15 minutes today (after the test) made the output and input a little nicer and more efficient.

The system has a keyboard and a LCD tv screen taped to a demo board and a 7.2V NiMH RC car battery. It uses the standard library objects for those, plus FDXP for the strToDec routine.
In the end there weren't any numbers on the test that would have required a calculator, so I didn't get to use it. Also, I was told that a simple calculator can't have a full QWERTY keyboard or a multi-line display. I took comfort, though, in the fact that the Propeller was always ready and able to do the job.


The Code:


{{

This is a fun little calculator program for the Demo Board.

March 2010, SRLM
}}


CON

  _xinfreq = 5_000_000
  _clkmode = xtal1 + pll16x

OBJ
  keyboard : "keyboard"
  tv : "Tv_Text"
  serial : "FullDuplexSerialPlus"

VAR
   byte num[20]
   byte input[20]
   long done
   long key
   long size
   long num1, num2
   long counter
   long answer
   long operator

PUB Main

  keyboard.start(26, 27)
  tv.start(12)
  serial.start(0,1,0, 57600)

  waitcnt(clkfreq + cnt)

  tv.str(string("SRLM Calc!", 13))

  done := size := 0

  repeat
    'Get input
    repeat counter from 0 to 20
      input[counter] := keyboard.getKey
      if(input[counter] == 13) 'Enter key
        input[counter] := 0
        quit
      tv.out(input[counter])

    'Parse first number
    repeat counter from 0 to 20
      if(input[counter] => "0" AND input[counter] =< "9")
        num[counter] := input[counter]
      else
        num[counter] := 0
        quit
    if(counter <> 0)
      num1 := serial.StrtoDec(@num)
    else
      num1 := answer

    'Parse operator
    operator := input[counter]
    counter++

    bytemove(@input, @input+counter, 20)
   
    'Parse second number
    repeat counter from 0 to 20
      if(input[counter] => "0" AND input[counter] =< "9")
        num[counter] := input[counter]
      else
        num[counter] := 0
        quit
    num2 := serial.StrtoDec(@num)   
 
    if operator == 42
      answer := num1 * num2
    elseif operator == 47
      answer := num1 / num2
    elseif operator == 43
      answer := num1 + num2
    elseif operator == "-"
      answer := num1 - num2
    elseif operator == "^"
      answer := 1
      repeat counter from 1 to num2
        answer *= num1
    else
      answer := 0

    tv.str(string(" = "))
    tv.dec(answer)
    tv.out(13)


Attachments
(Right click and "Save Link As...")

Calculator.spin
(c)2010 Cody Lewis
lewisc@cs.ucr.edu