Arduino int problem

Question

I made a counter to count pulses:

int count = 0 ;
.
.
.
setup()
{ 
} 
while (count <= 35000)
{ 
 digitalWrite(9, HIGH);
 delayMicroseconds(500);
 digitalWrite(9, LOW);
 count = count + 1;
}

But when I try while(count <= 40000), it does not stop counting.

Answer 1

int in AVR GCC is 16 bits. All possible int values are less than 32767.

• Nick Gammon: To be precise, the maximum value of int on this platform is 32767. If you add 1 to 32767 you get -32768 which then counts back up to 0, then up to 32767 and so on.
• Nick Gammon: If you made it unsigned int then the maximum value is 65535 which would work for counting up to 40000.

Answer 2

You have reached the maximum number that an int can represent. That is 32767.

int is a variable type that is made up of 16 bits. It is signed, meaning that it can represent positive and negative numbers.

Out of the 65536 (ie. 2^16) possible numbers from the 16 bits, half of them represent negative numbers and the remaining half represents positive numbers (including zero). Or in other words, -32768 to 32767.

If you don't need negative numbers, then you can change your variable type to unsigned int which will use numbers up to a maximum of 65535. So it becomes:

unsigned int count = 0;

Answer 3

But when I try while(count <= 40000), it does not stop counting.

"int" has a range from -32k to +32k-1. so "count <= 40000" will always be true as count is "int".