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[on:]

i  use ultrasonic sensor arduino and  atmega328p  ,when i upload the arduino example ping code , the result will be normal,stable.but when i write my c code in atmel studio upload it, everything is fine except the distance stable,like this: 968,968...968, 138,968.....968,138. i don't know how it come out ? i just know after i send a pulse message and wait for the echo, the power will be  low,high,low(for the distance 968) , i think the situation 138 is just high low, could anyone tell me why? thank you!

  if someone need the code , i will upload it .

[Reply #1 on:]

Are you using the Arduino pulseIn() function in Atmel Studio?

[Reply #2 on:]

yes i rewrite the code by myself.      

Code:

int getPulseWidth(int pingID) {
int timecount = 0;
int val = 0 ;
if(pingID == 7) {
val = PIND>>pingID; // Append signal value to val
 
while(val ==0) { // Loop until pin reads a high value

val = PIND>>pingID;
// USART_putint(val);
}


while(val == 1)
{
// USART_send('b');
  val = PIND>>pingID;
//  USART_putint(val);
++timecount;  // Count echo pulse time
}
}

[Reply #3 on:]

pulseIn() returns an unsigned long.  Perhaps you are overflowing your 16-bit integer.

Do you not care what the actual time is?  It looks like your pulse width is returned in arbitrary units.

[Reply #4 on:]

pulseIn() returns an unsigned long.  Perhaps you are overflowing your 16-bit integer.

Do you not care what the actual time is?  It looks like your pulse width is returned in arbitrary units.

I think so. That might be the reason.

[Reply #5 on:]

because i want detect the number of people who come through the door, so i don't need the accurate distance , i just set a distance , when someone come in or out the data will be small than the distance what i set. i'm sorry i forget to show all of the program , it should return timecount  .