Arduino – Tips and tricks


Tips-n-tricks for the Arduino

I have put together some useful snippets of information from experiments and crawling the web for ideas and solutions to problems I have encountered on various projects.. enjoy!

 

Checking Memory usage

Including the following code above the void setup() method allows you to get back the free memory available. I usually use a Serial.println() command to dump it out so I can see whats happening memory wise as things are running.

The Code:

extern int __bss_end;
extern void *__brkval;

int memoryFree()
{
int freeValue;
if((int)__brkval == 0)
freeValue = ((int)&freeValue) – ((int)&__bss_end);
else
freeValue = ((int)&freeValue) – ((int)__brkval);
return freeValue;
}

Using It:

void setup()
{
Serial.begin(9600);
Serial.print(“MEM (before): “);
Serial.print(memoryFree()); // print the free memory
Serial.println(” bytes”);
….
}

Four useful links for the nRF24L01+

The nRF24L01+ is a versatile RF transceiver operating in the ISM band, here are 4 useful links to sites with information from beginner  to advanced.

 

DF-Robot LCD Initialization

I found that the standard LCD initialization code does not work on my DF robot LCD. The correct constructor is:

LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

 

Selective header file import based on IDE version

Simple MACRO to include correct header:

#if defined(ARDUINO) && ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#endif

Basic Input de-bouncing

Simple digital input de-bounce code, locks the program into a loop during debounce so its useable in simple apps only. A better version would be to enter on a 1ms timer, check and inc counters and then recheck on next 1ms entry. 15-20ms of stable state would be considered a correct and stable switch state. Also, ditch the boolean return and make it void, use a getState() method to give you the current state (not raw state from the switch).

const int inputPin = 2;	  // the number of the input pin
const int debounceDelay = 20;  // milliseconds to wait until stable

// debounce returns the stable switch state
boolean debounce(int pin)
{
  boolean state;
  boolean previousState;

  previousState = digitalRead(pin);	    // store switch state
  for(int counter=0; counter < debounceDelay; counter++)
  {
	delay(1);			// wait for 1 millisecond
	state = digitalRead(pin);  // read the pin
	if( state != previousState)
	{
	   counter = 0; // reset the counter if the state changes
	   previousState = state;  // and save the current state
	}
  }    
  return state;  
}

Input de-bounce using interupt

User submitted code to do it via an interrupt, could have more checks and a stable counter logic but the concept of using an ISR and entering on an interrupt should be expanded on.

/*
 * ISR Debounce
 */

// use 2ms debounce time
#define DEBOUNCE_TICKS (word)microsecondsToClockCycles(2000)

extern volatile unsigned long timer0_overflow_count;
word keytick;  // record time of keypress

void setup()
{                
  attachInterrupt(0,KeyPress,FALLING);
}

void KeyPress()
{
  keytick=(word)timer0_overflow_count;
}

// returns true if key pressed

boolean KeyCheck()
{
  if(keytick!=0)
  {
    if (((word)timer0_overflow_count-keytick)>DEBOUNCE_TICKS)
    {
      keytick=0;
      return true;
    }
  }
  return false;
}

// TEST CODE
void loop()                    
{
  if (KeyCheck())
  {
    // do something useful
  }
}

Enjoy!

-oOo-

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