Handling large number of inputs in PIC microcontroller

Question

I am interfacing PIC32 MCU with 24 inputs and UART. When any inputs comes, this data is transferred to PC via uart. I am using multiple if condition like

if(input1==high)
{
  putsUART("input 1 ON\n");
}
if(input2==high)
{
  putsUART("input 2 ON\n");
}

What this if condition is doing is whenever an input comes, it keep on printing the data like

input 1 ON
input 1 ON
input 1 ON

and it goes on. I want it to be displayed once only. For example, if I applied input1, input 1 ON should be printed once and if remove the input input 1 OFF should be displayed once. I don't know how can I run this if condition only once. Please help. Thanks.!

CODE(just for 3 inputs):

 int main()
 {
  TRISAbits.TRISA6 = 1;
  TRISAbits.TRISA7 = 1;
  TRISGbits.TRISG13 = 1;
  while(1)
  {
   if(PORTAbits.RA6 == 0)         //INPUT 1
  {
   putsUART2("Input: 1 ON\n");
   Delayms(1000);
  }
  if(PORTAbits.RA7 == 0)          //INPUT 2
   {
   putsUART2("Input: 2 ON\n");
   Delayms(1000);
  }
  if(PORTAbits.RG13 == 0)          //INPUT 3
  {
   putsUART2("Input: 3 ON\n");
   Delayms(1000);
  }
 }
}

Answer 1

You need to remember the state of each input, and only output to the UART if it changes.

Something like this, just for one input so you get the idea :

// NB - put these lines outside your loop
uint8_t uLastRA6State = 0;                // last known state of RA6
uint8_t uLastRA7State = 0;                // last known state of RA7
// ... etc. 
// use one variable for each input, or if memory is tight, you could
// alternatively use one byte per 8 pins, but this more "wasteful"
// version is easier to understand the principle

while (1)
{
    // ...

    // NB - put this code inside your loop
    if (PORTAbits.RA6 != uLastRA6State)
    {
        // save current state
        uLastRA6State = uLastRA6State ? 0 : 1;

        // output change
        if (uLastRA6State)
            putsUART2("Input: 1 ON\n");
        else
            putsUART2("Input: 1 OFF\n");
    }

    // ... do the same for other inputs, e.g.
    if (PORTAbits.RA7 != uLastRA7State)
    {
        // ... similar to above, for RA7
    }
}