TIMER 0 - [Solved]

Gabriel · Joined: 03 Aug 2009 Posts: 1067 Location: Panama

Hi,

PCM 4.132 + MPLAB 8.85
16F88

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Gabriel · Joined: 03 Aug 2009 Posts: 1067 Location: Panama

Hi PCM...

Thanks for the suggestion, however i think i need to further explain my intentions...
Its powering a sensor in a data logger... I'm trying to save power by disabling the module...

In your proposed solution, does the timer keep counting? (consuming energy)

I don't really get how you can turn it on but not off...
or is it always on? and I'm just using its output selectively as you mention?

Pardon my timer ignorance..

Edit: I see its off during sleep so thats good for my app... but still ... I want to turn it OFF.

Edit (again):... I believe the secret lies in T0CS on OPTION_REG indeed.... I shall test and share!

thanks!

G
_________________
CCS PCM 5.078 & CCS PCH 5.093

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Before worrying about this issue, I would check the current consumption
of Timer0 by connecting an Ammeter that reads in microamps or
Nanoamps to the PIC and measure it. You can easily do this with
Timer1 or Timer2, since they can be turned on and off.

Ttelmah · Joined: 11 Mar 2010 Posts: 19447

As a comment, setting it to the external pin, if this pin isn't driven, risks drawing significantly _more_ power, than just letting it run!....

If you look in the header file for the PIC, you will find (for instance), that Timer1, has a 'T1_DISABLED' option. Then that there is no similar option for Timer0. Look in the data sheet, and the reason 'why', is simply that there is no option to disable this timer. You will save a tiny fraction, by setting it to clock as slowly as possible (T0_DIV_256), but the amount is so incredibly small, that even having a single pin floating, will draw hundreds of times as much....

So, you can stop it by selecting:
SETUP_TIMER_0(T0_DIV_256|T0_EXT_L_TO_H);

but you _must_ then drive the RA4 pin either high or low.

The same applies to all input pins, these _must_ be driven to either Vss, or Vdd levels, or you risk power consumption that makes the timer look totally insignificant.

Worth perhaps putting it in perspective. The current drawn by not washing the PCB really thoroughly, or even breathing near the board, far exceeds what is drawn by this module....

Best Wishes

temtronic · Posted: Fri Jun 22, 2012 5:19 am

also....

you can always add a larger capacity battery to your project !
The amount of time spent on reducing current flow is HUGE compared to the cost of another battery.Realistically you'll have to tear your code apart line by line to see if it can be made smaller or more efficient,getting rid of excess code,dupicate functions,use fast_io() not stanard_io(), etc.

Unless you've got a LOT of time and like the 'exercise' of maximizing power consumption(who wnats to count electrons ?!), reality is that a bigger battery is easier,cheaper,faster and works a whole lot better.

I gave up on the 'smaller is better' idiom decades ago.My boards are 'man-sized' allowing easy upgrades or mods the customer wants(always AFTER the project is 'done'),battery option is always AA cells,with pins for external battery as well.Same with code.I use a large memory PIC so it's easy to add those 'features' the customer forgot...

yes, it cost a few pennies up front but the added R&D/code cutting time is next to nothing as there's room to fulfill the project without making new board, another PIC,etc.

Gabriel · Joined: 03 Aug 2009 Posts: 1067 Location: Panama

jeremiah · Joined: 20 Jul 2010 Posts: 1337

Gabriel · Joined: 03 Aug 2009 Posts: 1067 Location: Panama

Gabriel · Joined: 03 Aug 2009 Posts: 1067 Location: Panama

Jeremiah you are right..

so... what the hell is timer 0 doing if my code does _not_ use it?
(like in simple led blink program)

it has to be in a defined state:
ON
OFF
ALWAYS_ON (but "disconected")

EDIT:
So, further datasheet diving has convinced me its:
ALWAYS_ON (but "disconected")
In which case, as PCM Programmer suggested, the proper way to "turn it off" is to disable the interrupt... and as others suggested, its really not worth persuing as there are no tangible gains... however, when not using its better to leave it as a timer rather than a counter so that it does not pull any current from the external clock input pin...

i think that about sums it up. (might be old for you, but its new to me)

Thank you all..

G
_________________
CCS PCM 5.078 & CCS PCH 5.093