PROGMEM example

#include <avr/pgmspace.h>
 char buffer [5];
 word serialCount;
void setup(void)
{
    Serial.begin(38400);
    Serial.println("\nPress space bar .");
//    while (Serial.read() != 32)   delay(1); // Wait for space
 
}
const int mydata[10][10] PROGMEM = {
    '0', '1', '2', '3', '4', '5', '6', '7', '8', 'A',
    '1', '1', '2', '3', '4', '5', '6', '7', '8', 'B',
    '2', '1', '2', '3', '4', '5', '6', '7', '8', 'C',
    '3', '1', '2', '3', '4', '5', '6', '7', '8', 'D',
    '4', '1', '2', '3', '4', '5', '6', '7', '8', 'E',
    '5', '1', '2', '3', '4', '5', '6', '7', '8', 'F',
    '6', '1', '2', '3', '4', '5', '6', '7', '8', 'G',
    '7', '1', '2', '3', '4', '5', '6', '7', '8', 'H',
    '8', '1', '2', '3', '4', '5', '6', '7', '8', 'I',
    '9', '1', '2', '3', '4', '5', '6', '7', '8', 'Z' };

void loop(void) {
    int i,j;
    byte n;
    Serial.println("\nData by Rows.");
    for (i=0; i < 100;i++) {
  // Serial.println(" ");
        if ((i %8)==0) Serial.print("|");
        if ((i %16)==0) Serial.println("");
   n = pgm_read_byte_near(i);
 // Serial.print(n, HEX);
          Serial.print(" ");
          sprintf(buffer, "%02x", n);
          Serial.print(buffer);
          serialCount++;
          
         // Serial.print("\t"); 
     }
    
    Serial.println(" ");
    Serial.println("\nData by Columns.");
    for (i=0; i < 10; i++) {
   Serial.println(" ");
   for (j=0; j < 10; j++) {
  n = pgm_read_word_near(&mydata[j][i]);
  Serial.print(n, BYTE);
   }
    }
    Serial.println(" ");    setup();    Serial.println(" ");  //start over
}
 

Timer0 First Program- Polling

/*
  Timer 0 Experiment
 */
int state = 1;
byte ticks, tocks;
long loopCounter;
long popCounter;
unsigned long time;
void setup() {                
  // initialize the digital pin as an output.
  // Pin 13 has an LED connected on most Arduino boards:
  pinMode(13, OUTPUT); 
  TIMSK0 = 0;     //turn off Interrupt for Timer0
  TCCR0B = 5; //Prescaler divieds by 1024 
  Serial.begin(9600);
}

void loop() {

   while(byte(TIFR0 &0x01) ==0){}; // loop til flag goes up
    TIFR0 = 1;      //clear flag
    ticks++;
  
    if (ticks == 60) {
      ticks=0; 
      ToggleLED();
  //    Serial.print("TT ");
    }
}
void ToggleLED(){
  if (state==1) {
    digitalWrite(13,LOW);
    state = 0;
  }
  else {
    digitalWrite(13,HIGH);
    state=1;
 //   Serial.print("I've tohggled");
  } 
} 

IIC or I2C or TWI

The TWI bus

Good tutorial from DigiKey

other training modules of electronic parts from digikey

A good introduction to IIC with an Arduino Focus is here.


The Arduino library with functions that handle the TWI bus is the Wire Library

A good example of using IIC eeproms with Arduinos is here.

A typical IIC device is the eeprom below.

An Arduino setup

and you can join up two Arduinos using the IIC bus

And another good TWI link for eeprom

This code worked for me straight from the forum to the freetronics eleven at 24LC256.

And here's the data on the24LC256 eeprom.

ZigBee

This is the quickest way to get two Arduinos to talk to each other wirelessly

Accelerometers

How do we sense movement and store and display it? Study this IC and come up with a schematic and software to read and display outputs. See the associated task.

Pin outs

We found that the pins on the Arduino board did not correspond to the pins on the AVR Mega328. Here's a useful mapping of pins. Note the two hardware interrupt pins.

Interrupts

There are two hardware interrupt pins on our Arduino. Interrupt 0 and interrupt 1. These cut off what ever processing is going on and carry out the interrupt service routine that you indicate.