Elapsed Timer Demo

[lil_mark]

Hi Darrel,
first of all compliments for this excellent job.
I would use "DEFINE OSC 48", because I need to compile for PIC18F4550 using USB.
And using USB in PBP we must set "DEFINE OSC 48" due to PLL...
When I try, I always receive the error "Symbol not previously defined (TimerConst)".
So I tried setting the right TimerConst in the "Elapsed_INT-18.bas" file...
I read all in this thread, and tried using the TimerCalc form, but it seem is impossible getting: 10,000 "Ticks", 100 Freq and 48 OSC all together.
So it means it's impossible using USB and Elapsed Timer at the same time ?
Is there a TimerConst that work with osc @ 48 MHZ ?
Mark

[Darrel Taylor]

Hi Mark, and thanks!

Is there a TimerConst that work with osc @ 48 MHZ ?

Yes there is.
In 2003 I hadn't heard of a 48mhz pic

Hmmm, let's see here,
pulling up mister_e's PicMultiCalc ... (Timer Helper page)
http://www.picbasic.co.uk/forum/atta...achmentid=2957

and ... uht oh, with the existing timer load routine, the best we can do is 99.999hz. Not so good for a long-term timer.

But not a problem, increasing the timer reload time to 10 instructions (add 3 nop's), with a Timer1 prescaler of 2, the reload value is 5541.

I'm sure that will elicit more questions, but I'll let you give it a go first.
<br>

[hackableFM]

I have given this a good reading over but some of it has gone straight over my head.
I intend to built a control unit based around a 16F877 which will include menu's to control output pins on the PIC, Obviously within the menu there will likely be instructions which will keep the processor busy for a few Ms at a time. My project ideas originally were to include an external clock device such as the DS1307 or the DS1603 to keep track of time whilst the rest of the program (Menu's etc etc) is running and keeping the processor busy.
I was advised on this forum to look at this thread and if this is what I think it is then it will be truly fantastic for my project.

My problem is that when the PIC returns from a menu I want it to display the time on the LCD. Am I right in what I have read in thinking (Besides setting LCD pins & oscillator etc) I can simply include all of the attached files in post number 1 of this thread but modify the 'loop' subroutine within "Test_Elapsed_LCD.pbp" file, to include my menu software?

I understand that this thread creates a time elasped counter and not a clock, but I do have in mind ideas to include buttons with which I can set the hours, minutes & seconds. I will also miss out the displaying of 'Days' when it comes to print on the LCD.

Apologies for what might seem to be a simple question to you guys but I have only been playing for a couple of months with PIC's and I am trying to learn from other people's examples.

Thanks.

hackableFM.

[Darrel Taylor]

I intend to built a control unit based around a 16F877 which will include menu's to control output pins on the PIC, Obviously within the menu there will likely be instructions which will keep the processor busy for a few Ms at a time. My project ideas originally were to include an external clock device such as the DS1307 or the DS1603 to keep track of time whilst the rest of the program (Menu's etc etc) is running and keeping the processor busy.
I was advised on this forum to look at this thread and if this is what I think it is then it will be truly fantastic for my project. ...

It can do the things you are suggesting.

But it's not a replacement for a battery backed-up RTC chip.
Any RESET will lose the accumulated time.

I have used it as a clock running on-chip, but on power-up it reads the time from an RTC. That way it doesn't have to continuously read the time via I2C and it's always available from the internal time clock.
<br>

[hackableFM]

Thank you, This sounds good so I'll have a bit more of a read up on it, I'll try to understand more about how it works before I go building anything.

Battery backed is not an issue, this will be connected to a permanent 12v system within a caravan and therefore never likely to loose the accumulated time.

hackableFM...

[jmgelba]

Hi Darrel,

I'm trying to create a timer - a run time timer that will turn off an output after 30 minutes. Would this code work for such a task?

Thanks

[Darrel Taylor]

Sure, it'll do that really easy.

IF MinutesChanged THEN
    MinutesChanged = 0
    IF Minutes = 30 THEN
        ; turn off whatever it is here
        GOSUB ResetTime
    ENDIF
ENDIF