CODEWITHSUNDEEP
c++carduino
kingcobra1986
kingcobra1986

Reputation: 971

Get pin input without the Arduino Library

I am not allowed to use the Arduino Library (or any Library) for this program. How would I check the input of a pin?

I found two different functions:

In Arduino.h:

#define bitRead(value, bit) (((value) >> (bit)) & 0x01)

Following digitalRead back to pgmspace.h:

#define __LPM_enhanced__(addr)  \
(__extension__({                \
    uint16_t __addr16 = (uint16_t)(addr); \
    uint8_t __result;           \
    __asm__ __volatile__        \
    (                           \
        "lpm %0, Z" "\n\t"      \
        : "=r" (__result)       \
        : "z" (__addr16)        \
    );                          \
    __result;                   \
}))

For the first one, I don't know where bit and value come from and I just don't understand the second one at all.

Upvotes: 0

Views: 685

Answers (2)

mactro
mactro

Reputation: 518

I will assume that you use Arduino Uno, however, general rule applies to any Arduino.

First, you need to check Arduino pin mapping:

Then, let's assume you want to use digital pin 2, so PD2 on Atmega168/328. (PD2 is short for PORTD pin 2). To use it as an input you need to do:

DDRD &= ~(1 << PD2);

DDRD is data direction register for port D. Whole operation sets bit corresponding to pin 2 to 0. Then to read this pin:

if (PIND & (1<<PD2)) {
  // do something
}

Also, please check, how to manipulate single bits: How do you set, clear, and toggle a single bit?

Upvotes: 0

Sanu - Open Maker
Sanu - Open Maker

Reputation: 34

There is no need to go to these implementations. It pretty simple as follows.

LED13 will turn on when Pin 0 is high. I tested this code on arduino 

#include <avr/io.h>                                      // Includes all the definition of register port etc  
#ifndef F_CPU

#define F_CPU 16000000UL      //Need to include it before <util/delay.h>

#endif                                       //Change 16000000 with your crystal freq. In my case its 16 MHz

#include <util/delay.h>    //includes delay functions delay_ms and delay_us

void setup() {
  // put your setup code here, to run once:
  DDRB |= 0xFF; //Configured Port B as OP
  DDRD &= 0x00; //Configured Port D as IP
}

void loop() {
  // put your main code here, to run repeatedly:
  
  if (PIND&(0x01)) //to check pin0 of portD (which is Pin 0 of arduino)
    PORTB |= 0xFF;
  else
    PORTB &= 0x00;

}

Upvotes: 1

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