Timer PIC16F57

[leonel]

Hello.
I´m trying to write a simple example that will make my led´s flash every 20s.
I understand timer´s in PIC16F872 because they have interrupts associated (TMR1), but i´m using PIC16F57 which only has one timer, TMR0, and no interrupts...
TMR0 timer is an 8-bit special function register with working range of 256. Assuming that 4MHz oscillator is used, TMR0 can measure 0-255 microseconds range (at 4MHz, TMR0 increments by one microsecond), but how do i measure 20s with TMR0?
Regards

[Dwayne]

Hello Leonel,

I´m trying to write a simple example that will make my led´s flash every 20s.
I understand timer´s in PIC16F872 because they have interrupts associated (TMR1), but i´m using PIC16F57 which only has one timer, TMR0, and no interrupts...

I don't know what you want to do... but how complicated do you want to get????

psuedo code..(that just may work, but haven't tested it).

TRISB=%00000000
Loop:
Portb.0 = High
Pause 500
Portb.0=Low
Pause 20000 'pause 20 seconds.
goto loop
end

Dwayne

[Acetronics2]

Hi, leonel

At each interrupt, you increment ( or easier decrement !!! ) a counter ...which (inc) rements another counter if the first overflows ... which ( inc ) rements ...

etc. etc.

Permits to do something else during blinking ... ( isn't it Dwayne ??? )

can be done with PBP or directly with assembler ... ( No, ... i didn't tell it ... my doctor said: no shock on the head, ... )

Alain

PS : No interrupt ... so you poll for TMR0 overflow !!!

[Dwayne]

Hello Alain,

Alain >>Permits to do something else during blinking ... ( isn't it Dwayne ??? )<<

Don't know <smile>. Simple program to blink a light?

With change of Chips? With no info on the final project, With no intended purpose but to blink a light, and "Simple example"? I can only assume a Blinky Light...Hopefully He will have it running, and if the info we gave him doesn't pan out, He can give us more info, so that we can become a little more detailed <g>.

Like What Ralph posted on the FAQ...

Need chip #, Code, details, Projects purpose, and other things.
I rememeber a while back, a person asked to change a 4 (separate) byte Hex to Decimal...I gave him the code, then his example had 5 (separate) bytes coming in, and he wondered why it didn't give him the right answer<g>.

Dwayne

[leonel]

Using pause command i don´t see if any other input. What i want is put my output high during 20s but at the same time see if other input goes high. If it goes high i will start over again, my time goes to 0s, and i will start counting 20s

[Acetronics2]

Hi, leonel ...

Don't shout at me but I did something like that with a resettable 555 and some CD4000 logic ... it was in one of my prior lives.

Said honestly, the 16F57 is not really the best Choice here ...

Alain

[leonel]

Yes, i know that´s not the best choice, but it´s what i have i know that with some logic i can do that, but i have 8 inputs and mixing all together i will need "some CD4000" and i have space problems (in my box i have to put 8 relays, and all electronic...), that´s why i want to use a cheaper PIC...

[Acetronics2]

Your project looks like a quizz box ...

20 second to answer ... who's the quickest of 8 !!!

we REALLY need to know a lot more about your top secret weapon. ...

if you really want help, of course

Alain

[leonel]

Here´s my code to do what i said (with a little help of Dwayne).
Compiling my code there´s some warnings "Crossing page boundary -- ensure page bits are set." I read in PBP manual that i don´t have to worry because PBP take care of this for me. It´s true?

[Dwayne]

Hello Leonel,

Leonel

If it´is pressed i turn on the relay and stays on for 20s or 40s (depending the position of a switch). If one button is pressed while one relay is on the time goes to begin and the two relays stays on again 20s or 40s.

Hummm....I see a 40 second delay.... not a twenty second delay... thus a new variable has been added

Ok. let me get this straight...(correct me if I am wrong).

1. You have 8 LED's (or relays).
2. You have 1 switch that is connected to some kind of software relay that says 20 or 40 seconds. (I am going to assume you have this switch set to the 20 second position for this message)
3. If #1 button is pressed, it will turn on relay 1 for 20 seconds (or 40, depending upon if the HighLow software switch is on or off) If a second button is pressed BEFORE the first relay resets, Both the first Relay and the NEW relay (The one that you just got through pressing) stays on for at LEAST another 20 seconds.
4. If another button (lets say relay #3) is pressed BEFORE Button 1 and 2 go off in their allowed time, all 3 relays will be active for at least another 20 seconds..
5. But at ANY time, there is a 20 second interval of NO button pressing, all the relays will turn off....

Is this correct?

Dwayne

[Dwayne]

Hello Leonel,

I am going to assume what I posted was correct...Here is some code to look at...Using my code, I added just a few things to allow for all your switches.

Switching var byte;
Counter1 var word
  Counter2 Var word
  Loop:
  Counter1=0
  Counter2=0
  Loop2:
   if Counter1< 20
     if Counter2 <1000
     if switching=1 then Pause 1  'Pause 1/1000 of a second to make 20
     if switching=0 then Pause 2  'Pause 1/500 of a second to make 40

     if Portb.0=1 then 
            turn on switch.
            goto Loop
      endif

      if Portb.1=1 then 
            turn on switch.
            goto Loop
      endif

      if Portb.2=1 then 
            turn on switch.
            goto Loop
      endif

      ....
      ....    (for each of your eight switches)


        Counter2=Counter2+1;
     Endif
     
     if(Counter2>=1000)
       Counter1=Counter1+1;
       counter2=0;
     endif
   endif
   if Counter1<20 goto Loop2

  Portb=0;  'turn off ALL of the switches!
  Blink light = on
  Pause 200  'pause 1/5 of a second to light up the light.
  Blink Light = off
  goto Loop:

The above code will take care of your switches, but the problem comes with your Blinky light every 20 seconds. If a person keeps pressing switches, your light will not blink every 20 seconds. Thus some kind of internal timer is needed to take care of your blinky to have it blink every 20 seconds.

Dwayne

[leonel]

Yes... all your 5 points are correct. If you understand my code that´s a good beginning!
Thank you!

[Dwayne]

Hello Leonel,

Yes, I pretty much understood your code...

Just a couple of suggestions.

If and then statements...

If a "IF statement has only one statement, you do not need a "endif".


The if statement below NEEDS a endif

  If a > b then
       c=d
       d=f
       f=g
   endif

this does not need a endif statement;

  if  a=b then c=d
  ...
  ...
  if d=f then d=g
  ....

This will help you on your code space and readability...(Of course I must look whos speaking too <chuckle> I think my code is some of the hardest to read <g>)

Dwayne

[Dwayne]

Hello Leonel,,

just had a brain fart to take care of your blinky light...

Switching var byte;
  LightCount var Word
  Counter1 var word
  Counter2 Var word
  LightCount=0
  Loop:
  Counter1=0
  Counter2=0
  Loop2:
   if Counter1< 20
     if Counter2 <1000
     if switching=1 then Pause 1  'Pause 1/1000 of a second to make 20
     if switching=0 then Pause 2  'Pause 1/500 of a second to make 40

     LightCount=LightCount+1
     If LightCount=20000 then
       LightCount=0
       Blink light = on
       Pause 200  'pause 1/5 of a second to light up the light.
       Blink Light = off
     endif


     if Portb.0=1 then 
            turn on switch.
            goto Loop
      endif

      if Portb.1=1 then 
            turn on switch.
            goto Loop
      endif

      if Portb.2=1 then 
            turn on switch.
            goto Loop
      endif

      ....
      ....    (for each of your eight switches)


        Counter2=Counter2+1;
     Endif
     
     if(Counter2>=1000)
       Counter1=Counter1+1;
       counter2=0;
     endif
   endif
   if Counter1<20 goto Loop2

  Portb=0;  'turn off ALL of the switches!
  goto Loop:

I put a separate counter for the blinky... stuck the blinky in the routine so that it will be called all the time, removed it from the end of the routine and since you said it doesn't matter too much on the exact time.... well...

Dwayne