What is PIND?

[gilperon]

I have a code that reads the value of a sensor and because it needs to be very fast it does not use digitalRead but a strange form of reading. In the top of the code it shows:

#define IRSENSOR PIND
int irpin = 2;
I have no idea why this PIND referes to my arduino pin 2, but it only work if my sensor is in pin 2. If I want to change to pin 9 and only change the irpin varialbe it does not work. Why?

To read the sensor I use this code:

while (IRSENSOR & (1 << irpin )) {
Have no idea why this work. Does anyone know this kind of programming with arduino?

[pylon]

That's called direct port manipulation and is used to achieve much higher speed in operating the digital inputs/outputs. The drawback is that it's very processor dependent and changing the pins is not easy for the casual Arduino programmer.

PIND is the input register of port D (pins 0 to 7 on the UNO). That means you can use pins 2 to 7 on the UNO for your IR sensor, otherwise you have to change the port.

To use pin 9, change PIND to PINB and irpin to 1.

[system]

PORTD is a memory-mapped port, so it can't be a byte. It isn't surprising it doesn't work.

[system]

I'm not sure I understand what you want.
PIND is a macro which dereferences a pointer.
It cannot be a constant.

[LarryD]

while (irport & (1 << irpin )) {
IS
while (PORTD & (1 << 1 )) {
IS
while (PORTD & 0b00000010) {

//You are reading D1
// PIND
// D0=0x01 D1=0x02 D2=0x04 D3=0x08 D4=0x10 D5=0x20 D6=0x40 D7=0x80

[jboyton]

This is a more easily maintained way to do it. The macros do the work of converting pin number to port register and mask. So you can change the pin without worrying about the rest of the code.

int irPin = 1;

volatile uint8_t *irPort = portInputRegister(digitalPinToPort(irPin));
uint8_t irBitMask = digitalPinToBitMask(irPin);

while (*irPort & irBitMask) {
  // your code here
}

[LarryD]

Prove your hypothesis
What do you get when you try this?

void setup()
{
  Serial.begin(9600); 
  pinMode(2,INPUT_PULLUP);
}

void loop()
{
  //mask off bit 2
  byte x= PIND & 0b00000100;  //read D2
  Serial.print( "PIND = " );      
  Serial.println( x );
  delay(100);
}

[LarryD]

Well, that would print 4 if the pin was HIGH and 0 if it were low.
YES

However, treating it as a boolean and changing the if line to :

if( x ){

will cause it to print PIND == HIGH when the pin is HIGH and PIND == LOW when the pin is LOW.

It would

[LarryD]

You could obviously use:

if( x == 4){ //a bit cryptic though

However, true/false is the norm

I was just showing gilperon what was actually happening.

[LarryD]

while (PINB & (1 << B00100000)
No

[LarryD]

while (PINB & (1 << B00100000)) //B00100000 = 32 decimal

try

while (PINB & (1 << 5))

or try

while (PINB & B00100000))

[LarryD]

//               DDDDDD
//               111100  
//               321098   
while (PINB & B00100000))

[LarryD]

Re attach the sketch that you have.

[LarryD]

This is what I get

[LarryD]

Is you serial monitor set to 9600?
Is you switch/ultrasonic wired properly?

void setup() {
  Serial.begin(9600);
  //         DDDDDD
  //         111100 
  //         321098
  DDRB  = B00010000; //0=input 1=output
  PORTB = B00000000;
}

void loop() {
  //         DDDDDD
  //         111100 
  //         321098
  PORTB = B00010000;  //12 HIGH
  delayMicroseconds(10);
  PORTB = B00000000;  //12 LOW
  long start_time = micros();
  //               DDDDDD
  //               111100 
  //               321098
  while (PINB & B00100000) 
  {
    Serial.println("sh_t show up");
  }

  Serial.println(micros() - start_time);
  delay(1000);

}

[LarryD]

1<<5
says
Shift the 1 to the left 5 places resulting in B00100000

1<<B00100000 note B00100000 is a binary number which is 32 decimal
says
Shift the 1 to the left 32 places resulting in ? ? ? ?, cannot do more than 7 shifts on a byte

EDIT:
Have you tried using a simple switch instead of your ultrasonic?

[LarryD]

Try the code in reply 28 with the !
from pin 13 to switch connected to ground
from pin 13 a 1K resistor to +5V

What do you get?

!(PINB & B00100000) just inverts the test logic

This is what I get if I push the switch

[LarryD]

But the code I provided you is showing me 4, 4, 4... many times at every 1000 ms. Any suggestion what I may doing wrong?

Looks like the ultrasonic is not give you an output

[LarryD]

This is with the ! and me pushing a switch as described

[LarryD]

Did you say you confirmed the ultrasonic sensor is giving a pulse to the Arduino?

I haven't hook up a sensor yet I just used a switch as mentioned.

Using a switch does display the time in uS when the switch is let go as seen in the image below