处理来自键盘的用户输入时出现逻辑错误

Question

First of all this is homework. I am trying to do the following:

The user should be be able to input one or two digit number solution with the proper sign.

I am programming a Freescale HCS12 micro controller. So, I cannot use any of the C libraries.

I created the following function to grab user input from a keypad one at a time. Then, my goal is to print it to the LCD, and wait for the user to press the next key, if any. If the user presses another number, then I concatenate it to the previous number. I don't have to do error checking, so I can expect that the user will not input more than two numbers.

In the code, if the user presses 14, I return a negative number.

My problem is that for the number I finally save in the 'numberEntered' variable is not what the user pressed.

Below you will find my code:

 //this method will take user input and display it to LED
  int processAnswer(void)
  {
    int sign;  //if sign remains zero, then number entered by user is positive
    int counter;
    int negFlag;
    numberEntered = 0;
    sign = 0;  //if sign remains zero, then number entered by user is positive
    counter = 0;
    negFlag =0;
   //Program will continue to query for a key until someting is pressed
   //The number 0x1F is a number assigned in getKey() routine if no key is pressed
      inKey = 0;
      while(1){
        inKey = getkey();
        keyrelease(); //checks if key is released
        if(inKey == 15){
          break;
        }
        if(inKey == 0x1F){
          continue;
        }

        if(inKey != 14 && inKey != 0x1F ){
          counter++;

        }
        if(inKey != 14 && counter == 2 ){  
          numberEntered = numberEntered * 10;
          numberEntered = numberEntered + inKey;
          displayNumber(numberEntered);

        }

        if(inKey != 14 && numberEntered < 10){
          numberEntered = inKey;
          displayNumber(numberEntered);
        }
        if(inKey == 14 ){

          if(negFlag==0){

          Command(0x86);
          Print('-');
          sign = 1;
          negFlag = 1;
          }

          continue;
        }

      }//end of while loop


           //if user pressed key 'C', then delete input
        // if(inKey == 12) //if the user wants to delete latest input
        // {

        //  //Command(0x85); //sets cursor to address 0x05 of first line
        //  //Print(0x00);  //will clear previous input
        //  //Command(0x84);
        //  //Print(0x00);
        //  numberEntered=backspace(numberEntered);

        // }


  //return final answer from user
      if(sign == 1)
      {
        numberEntered = -numberEntered;
      }
      return numberEntered;
  }//end of processAnswer function

Answer 1

You need to structure into one loop, I'm sure there are bugs but you can work them out - something like:

sign = 0;
number = 0;
while (inKey == 0x0F) {
   inkey = getKey();
   keyRelease();

   if (inKey == 15)
      break;
   if (inKey == 14)
      sign = 1;
   else {
       number += inKey;
       displayNumber(number);
       number = number*10;
   }
 }
 if (sign && number) {
    number = ~number +1;