AVR Freaks

(note that I've just given you 1 clue on how the problem can be subdivided)

I cannot tell from that code which of the channels 0 or 1 is the critical one but I guess you are going to want something like:

if ((channel == CRITICAL_CHANNEL) && (tempC > SOME_THRESHOLD) && (buzzing_not_already_started)) {
  // start the buzzing process
}

On the whole you can design your software like this. Write down in "broad brushstrokes" what you want to achieve. Worry about the details like "SOME_THRESHOLD" and how you are going to handle "buzzer_not_already_started" later.

It may be better to do this design on paper rather than in you C editor. When you have the overall plan you can implement the specifics of the detail in C.

EDIT: just learning the fundamentals of the English language ;-)

Too specific - broad brushstrokes first - as I say think, then design what it is you want to achieve first. Worry about the specifics of implementation when you have worked out the design.

Personally I don't know why you'd wait 500ms before reporting the alarm condition so I don't know why you wouldn't place such a check just immediately after taking the reading that matters - but details like this will come out when you THINK and DESIGN this thing. It seems to be a tragic deficiency in the modern education of potential engineers that they are taught the specifics of the syntax of C and how a device such as an ADC or timer or LCD works but no one seems to be teaching engineers to spend some time up front reading, thinking, designing, specifying before they rush into an implementation. It is utterly vital. The final solutions will be all the poorer for the lack of it.

The computer works step by step. Read an input. Is it hi or lo? Set a variable true or false to save the result. Turn an output on or off depending on the state of a variable. If you can express the program as a sequence of steps needed to get the result you want, and can write the steps or describe it to someone, you are about at the point to start the implementation. Transitioning from the design phase.

Electronics is purely my passion.

I'd have thought that gave all the more reason to try and learn to do it properly?

It isn't just about knowing the syntax of "int main(int argc, char * argv[])", "unsigned char number;", for(), while() and so on.

Engineering is about a process - the coding is just one step in that process.

I wish there were a way to implement delay in seconds.

As for delays. A lesson you will learn fairly early on in embedded engineering is that almost no one ever purposefully sits in a pointless delay in the real world. If nothing else you actually probably want to sleep() while you are delaying but usually that's going to mean an interrupt. Talking of interrupts almost all embedded apps employ some kind of housekeeping timer interrupt that maybe "ticks" once every 1/10/20/50ms or similar. (In Windows and Linux it used to be 10ms. These days it is 1ms or sometimes less). You can use this single source of "ticking" for all sorts of things. Say you want to delay for 30ms you might take a look at the current timer count then do something when that timer count is now+30ms. Such a universal timer is so common that almost all modern ARM processors even have a timer called SYSTICK for the very purpose. So if I were you I'd take a first look at timer interrupts and using one of the AVR timers to count up some global "system tick" that you cal use for various time measurement purposes. A second is then just now+1000 of a 1ms rate timer (or now+100 on 10ms).

Bob,

Only you would be perverse enough to run a systick at some speed that wasn't an obvious factor of "human time" like 35ms or whatever. I guess you count 28 ticks then wait the additional 20ms in some other way to make it up to 1000ms ?

example code for interrupts for topic above 

<

/*
 * main.c

 */

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>

volatile uint8_t ms2=0;
volatile uint8_t flaga1s=0;
volatile uint8_t sekundy=0;

int main (void)
{
TCCR1B|=(1<<WGM12);        //mode CTC
TCCR1A|=(1<<CS11)|(1<<CS10);  //divide  64 for 8MHZ;this is 125kHz or 8us
OCR1A=249;        //interrupts after 250 imp. clock, this is  2ms

 sei ();

if (flaga1s=1)
    {

    }
}

//-------------------------------------interrupts-------------------------------------------------------------

ISR ( TIMER1_COMPA_vect)
{
ms2++;
if (ms2>500)
    {
    flaga1s=1;
    sekundy++;
    }
}

>

Perverse? Have any avrfreaks ever had someone at work tell them they were perverse? Time for a forced vacation?