If loop triggers even when the condition fails.

Projects Programming
1 
#include <SPI.h>
char buff [50];
volatile byte indx;
volatile boolean process_it;
int i = 0;
void setup (void) {

   Serial.begin (115200);
   pinMode(MISO, OUTPUT); // have to send on master in so it set as output
   SPCR |= _BV(SPE); // turn on SPI in slave mode
   indx = 0; // buffer empty
   process_it = false;
   Serial.println("The Program is Executing");
   Serial.println(true);
   SPI.attachInterrupt(); // turn on interrupt _BV(SPE)
}
 
ISR (SPI_STC_vect) // SPI interrupt routine SPI_STC_vect transfer complete handler.
{ 
   byte c = SPDR; // read byte from SPI Data Register
   if (indx < sizeof buff) {
      buff [indx++] = c; // save data in the next index in the array buff
      if (c == '\n') //check for the end of the word
      Serial.println("Inside \r If condition");
      process_it = true;
   }
}
 
void loop (void) {
   //Serial.println(process);
   if (process_it == true) {
      process_it = false; //reset the process
      Serial.println("Bow");
      Serial.println (buff); //print the array on serial monitor
      indx= 0; //reset button to zero
   }
   }

I have attached the screenshot of the output. Actually I am send Hello World throught SPI. The if loop should get executed only when process is true. and the correct output should be HELLO WORLD.

Screenshot from 2019-09-29 15-16-25.png
Screenshot from 2019-09-29 15-16-25.png1366×768 68.9 KB

2

Don't do serial I/O in interrupt context.

3 
      if (c == '\n') //check for the end of the word
            Serial.println("Inside \r If condition");
      process_it = true;

It looks like you meant that to be:

      if (c == '\n') //check for the end of the word
      {
            Serial.println("Inside \\n If condition");
            process_it = true;
      }
4

johnwasser:

      if (c == '\n') //check for the end of the word

        Serial.println("Inside \r If condition");
  process_it = true;




It looks like you meant that to be:



  if (c == '\n') //check for the end of the word

  {
        Serial.println("Inside \\n If condition");
        process_it = true;
  }

...apart from the serial I/O in interrupt context, obviously.