A bit of a laugh..

time for a giggle..

helps now that the tension's eased up - aside from results, of course..

All over bar the groaning..

Well, that's that for another year (academically speaking), but this blog will continue..

Last two projects were a bit of a frost - got most of the Minor Project posted, but i suspect hardware & programming logic problems, as i couldn't get it to do what i thought it should - it kept doing what i actually had told it to do.

As a poster i once saw says:

*                   I Know You Believe You Understood

*                 What It Was That You Though I Said,

*                          But I'm Not Sure You Realise

*                  That What You Thought You Heard

*                             Was NOT What I Meant!!

i can hear my Arduino chortling away at that thought, since it seems to me that what i thought i'd told it to do was something other than what i wanted {sigh}..

Always assuming the hardware works as expected, of course..

Projects -- Interrupts: Mark II

/*
 * Project:      Project_interrupt
 * Author:      Jane-Maree Howard
 * Date:         Monday 21/11/2011
 * Platform:    Arduino 22
 * Purpose:    To demonstrate an interrupt on Digital pin 3
 * Operation:  Description: Connect a 20kilOhm resistor from
 *                          digital pin3 to digital pin13!
 *                          Earlier problem solved as we now have a hardware feedback
 *                          from OUTPUT digi-pin13 to INPUT digi-pin3,
 *                          to which the interrupt is attached.
 *                          The digital flip-flop occurs every second, is fed to digi-pin3,
 *                          which registers the change & triggers the interrupt,
 *                          which, in turn, calls blink() where the pin state variable is flipped.
 *                          This state change is fed back via digi-pin13 to digi-pin3, triggering
 *                          the interrupt once again.                 
 */
int           iPin13   = 13;
int            iPin3   = 3;
volatile int  iState   = LOW;

void setup()
{
  // open Serial port
  Serial.begin(9600); 
  // set pin13, pin3 as OUTPUTs
  pinMode(iPin13, OUTPUT);
  pinMode(iPin3, INPUT);
  // interrupt1 calls blink() when pin13 flip-flops
  attachInterrupt(1, blink, CHANGE);
  digitalWrite(iPin3, iState);
  Serial.println("\nStart\n");
}//setup()

void loop()
{
  // delay 1 second
  delay(1000);
  // in effect, flip pin13
  Serial.println(iState);
  digitalWrite(iPin13, iState);
  digitalWrite(iPin3, iState);
}//loop()

void blink()
{
  // flip value to trigger interrupt
  iState = !iState;
}//blink()
//END

i finally cracked it!

most annoying though..
..but when i wondered about which pin the interrupt operated on, i went back to the appropriate page.. 

..where i saw that interrupt-0 can be attached to digital pin 2, & interrupt-1 to digital pin 3.

after that, it was pretty much plain sailing - the feedback resistor instead of some weird software, & as can be seen at left, it works beeootifly-thank-yew!

on to my next problem: how can i use LDR hardware to trigger an interrupt (for my "fridge door open" stuff!

{sigh of relief!}.

Projects -- Interrupts

/* example of interrupt function using Arduino 22 */

int                 iPin   = 13;
volatile int  iState = LOW;

void setup()
{
  // open Serial
  Serial.begin(9600); 
  // set pin13 as OUTPUT
  pinMode(iPin, OUTPUT);
  // interrupt1 calls blink() when pin13 flip-flops
  attachInterrupt(1, blink, CHANGE);
  digitalWrite(iPin, 1);
  Serial.println("\nStart\n");
}//setup()

void loop()
{
  // delay 1 second
  delay(1000);
  // in effect, flip pin13
  Serial.println(iState);
  digitalWrite(iPin, iState);
}//loop()

void blink()
{
  // flip value to trigger interrupt
  iState = !iState;
}//blink()
//END

i have been trying to get this interrupt program to work - it doesn't alternate the way i think/assume it should.


it just changes at random, sometimes acting like a touch or proximity switch!

i'm baffled :-?



here's where the example code came from - i've modified it to produce a serial monitor output, & inserted another digitalWrite() statement in the setup to try to get the thing triggering regularly..

..but it doesn't {sigh}..

Test Schedule

Well, to start with, here's some test information. Bit scary.. i had the erroneous impression it'd be next week, but it isn't!

Here's some hardware pics & the ATmega328 datasheet..
..& the pin-mapping between the ATmega328 & the Arduino..

We're getting lotsa questions on this.
Here's a schematic of the Duemilanove..
..& the Uno schematic.
 .

Project 4 -- Major Project: initial survey..

Since this project involves THERMISTORS, i've gone to my other tech blog to see what i've done there.

And this entry has a handy data-table ^..^ .

The idea is to make a strip of about 4 or 5 thermistors to hang inside the door of my fridge; i want to see how much colder it is at the bottom compared to the top.

I know it is colder at the bottom, because meat keeps longer there, & sometimes starts to freeze, whereas it never does  that nearer the top.

I need some of that ribbon cable to 'insert' the thermistors into, & also to transmit data to the analog pins on my Arduino.  i also have a USB power supply, so i could actually do some data-logging over an extended period & save the data to EEPROM for later retrieval & display (& just by chance i've found a LED-strip with about 10 LEDs on it that i'd forgotten i had!).

I'd like to add TWI to a 24LCxx if i can, as that would allow more data to be stored.

A photo-cell (these entries) could tell me when the fridge door was opened.

Another little wrinkle would be to average all the thermistor readings at any one time, &  switch on a motor, say, if the average temperature rises above a preset value.

First things first, however: i need to set up the thermistor strip, write the basic software, & get that part working;  i can add bells & whistles later.

PROGMEM - some interesting stuff from Peter B

PROGMEM example

/*

 * Project:    PROGMEM_example
 * Author:     Peter Brook, tidied by Jane-Maree Howard
 * Date:       Tuesday 01/11/2011
 * Platform:   Arduino 22
 * Purpose:    To demonstrate storing data in Arduino's flash memory
 * Operation:  Description: Stores 10x10 matrix (int) in Flash memory
 *                          using the PROGMREM keywords & library
 *             Declare:     formatting buffer (char); word counter (int);
 *                          10X10 data matrix - myData[10][10] (int)
               Setup():     Serial@38400baud:TAKE CARE TO SET SM CORRECTLY         
               Loop():      Print to SM by ROWS, then by COLUMNS; 

 *                          setup() again & loop()
 */
#include {avr/pgmspace.h}      // PROGMEM library
 char chBuffer [5];            // Serial output formatting buffer
 word serialCount;             // word count (2 Bytes)
void setup(void)
{
    Serial.begin(38400);       // Serial connection @ 38400 baud!!
    Serial.println("\nPress space bar .");
//    while (Serial.read() != 32)   delay(1); // Wait for space 
}//setup()

// this is the data to be stored
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;      // loop counters
    byte n;       // Byte output vble
    
    // print heading for ROWS
    Serial.println("\nData by Rows.");
    for (i=0; i < 100;i++) 
    {
       // some formatting conditions
       if ((i %8)==0) 
          Serial.print("|");
       if ((i %16)==0) 
          Serial.println("");
       // now read a Byte from Flash memory
       n = pgm_read_byte_near(i);
       Serial.print(" ");
       // format output to Serial
       sprintf(chBuffer, "%02x", n);
       // print output 
       Serial.print(chBuffer);
       // next word (= 2 Bytes)
       serialCount++; 
     }//for (i)
    
    // print heading for COLUMNS
    Serial.println(" ");
    Serial.println("\nData by Columns.");
    for (i=0; i < 10; i++) 
    {
      Serial.println(" ");
      for (j=0; j < 10; j++) 
      {
        // print each column entry in BYTE format
        n = pgm_read_word_near(&myData[j][i]);
        Serial.print(n, BYTE);   
      }//for(j)
    }//for (i)
    
    // now set up to go round again
    Serial.println(" ");
    delay(3000);   
    setup();    
    Serial.println(" ");  //start over
}//loop()
/* END */
 

See the following links to find out how some of this stuff works.. 

PROGMEM      printf