Low power aplication on 12F629

[El_AMPo]

I'm building a coin battery (CR2032) operated clock with a 12F629

The program uses TIMER1 interrupt configured to reload at 100hz and refresh variables each time.

On the main loop there is just a button push check loop to deliver time in case of pushing it.

For extending the battery life I tried to lower the cristal frequency (from 4M to 32K) but without luck in picbasic, I also disabled all hardware not in use (TMR0, WPU, VREF, COMP) and the pull-up on the button (GPIO3) is at 100K.

Right now the circuit is drawing 0,5mA and that is low but maybe i missing something else


My question is:
Did I miss something else to reduce power?

Also,
I was wondering if someone can point me up for some tips on how to proper design (software and hardware) for low power in timing aplications without using external RTCs
Because right now i'm guessing

Thanks

[Charlie]

Right now the circuit is drawing 0,5mA and that is low but maybe i missing something else


My question is:
Did I miss something else to reduce power?



A quick look at the datasheet suggests you could save considerable power by using sleep mode. Conceptually you set up the watchdog to wake you up after a certain number of clock cycles, then go to sleep and draw only nano-Amps until you are awakened. I believe you can set the watchdog, using the prescaler, to 128 clocks (or 64, or 32, etc.). If the processor has nothing to do, you can reset the watchdog, then go to sleep and get awakened after an exact number of clock cycles, increment your counters and display, and do anything else you need to do before resetting the watchdog and going back to sleep. If you can sleep 1/2 the time, you can save 1/2 the power - it's pretty linear.

[El_AMPo]

The problem with the watchdog is that it's not a reliable clock source for timing applications.
Maybe running the Timer1 counter from the main crystal while the pic processor is sleeping.
I know that can be done with an external (extra) oscillator, but I have no idea if it can be routed to the main one.

[ofuzzy1]

Try the 12f635 or the 12f683.

The 12F629 does not have the OSCCON @ [8F - hex] , register so you can't set the speed it is stuck at 4MHz.
You will need to read the DATA SHEET a bit more closely -- as always it is buried in the fineprint :)

some hints: * learned from observation, please let me know if I'm wrong : )

0. Set the 2007 Register BIT FIVE [5] to ZERO [0] *****************
----> I currently do this just before programming in the programmer configuration menu.
***** This disables the master reset and allows you a. to ignore it, b. use GPIO.3 as an input. ---> for the pros I have not figured out how to set this in PBasic. more rtf is in order.

1. SLEEP and NAP are not affected by the cpu speed [really helpful]
2. PAUSE will be affected by the timer speed, >> will shift the number
3. To save power turn off the outputs when you are not using them ie. TRISIO = $FF
--- You can use this instead of GPIO = XX to turn off your lamps

I also had trouble with setting PBasic to work on slow CPU

Here's my kludge on the 12f683 : )

This is blinking some lights in a special pattern
when off the cpu uses between 40-60 nano Amp!! Yes, NANO amps!
on a cr2016
[CODE]
-----------------------------------------------
The circuit is:
pin
1 - BATT+ not even a cap to pin.8 [ground] :)
2 - LED1 +
3 - LED2 +
4 - NC
5 - LED3 +
6 - LED4 +
7 - BUZZER.minus ---> *** this PIN is a SINK, shorts to ground so turn it to ZERO in GPIO.0 when you want it to work -- other end of the BUZZER TO to batt+, use GPIO.0
8- BATT -

LED1-4 - combined together then 100ohm to pin.8 [ground]



My typical header -- all commented on 12f683 for this program



'
' FOR LOW POWER DISABLE AS MANY FEATURES AS POSSIBLE.
' ** FOR 12F675 un-COMMENT CMCON=7, ANSEL=0, ADCON0=0
' ** FOR 12F629 COMMENT ALL
' CMCON = $07 'CMCON — COMPARATOR CONTROL REGISTER ALL DIGITAL
' TRISIO = %11111011 ' tristate mode 1=INPUT
' TRISA = %00001000 ' Set PORTA.0 to input A.3 input ONLY 1=in
' TRISA = %00001000 ' Set PORTA.3 input
' ADCON1 = %01100000 ' Set a2d convert at clk/6 [slowest]
' ADCON1 = %00000000 ' Set a2d convert at clk/2 [fastest]
' ANSEL = %00000000 ' AN0/RA0 as analog input 1=ANALOG
' ADCON0 = %00000001 ' .7=10bits left justify result!! / .0 1=a2d ON
' ADCON0 = %00000000 ' .7=10bits left justify result!! / .0 1=a2d ON
' WPUA = %00000000 ' TURN ON WEAK PULLUP 1=ON VALID=.5.4.2.1.0





' lifted right from the data sheet : )
'
'low speed osccon 31khz
''bit 6-4 IRCF<2:0>: Internal Oscillator Frequency Select bits
' correction
' by shifting
' |
' v
' 111 =8MHz
' 110 =4MHz (default) 0
' 101 =2MHz 1 2
' 100 =1MHz 2 4
' 011 =500kHz 3 8
' 010 =250kHz 4 16
' 001 =125kHz 5 32
' 000 =31kHz (LFINTOSC) 7 128

OSCCON.6 = 0
OSCCON.5 = 0
OSCCON.4 = 0
speed_shift CON 7 ' use 0-7 : oscillator / delay correction by shifting


' BYTES
led VAR byte ' lower 6 bits only for GPIO

' WORDS
X var word


' TEST ALL LAMPS GPIO.1.2.4 3=INPUT ONLY

' Delay for ~3 seconds
X= 3000 ' START UP DELAY TIME
'
' could of done this as a short gosub
'
led = $02
TRISIO = $FE - led
GPIO = led
Pause X >> speed_shift ' Delay for on time in milliseconds
led = $04
TRISIO = $FF - led
GPIO = led
Pause X >> speed_shift ' Delay for on time in milliseconds
led = $10
TRISIO = $FE - led
GPIO = led
Pause X >> speed_shift ' Delay for on time in milliseconds
led = $20
TRISIO = $FF - led
GPIO = led
Pause X >> speed_shift ' Delay for on time in milliseconds


....


LED = %00110110 ' GPIO.1.2.4.5

TRISIO = $FF ' TURN OFF OUTPUTS TO SAVE POWER
GPIO= led ' Chose which LED to Turn ON


' LED ON fast blink # led
TRISIO = $FF - led ' Enable output - fast blink # led
Pause 128 >> speed_shift

' LED OFF
TRISIO = $FF ' TURN OFF OUTPUTS TO SAVE POWER
Pause 256 >> speed_shift 'time in mS

end

[ofuzzy1]

Want to use pin4?
It will only be an INPUT.

' WHEN PROGRAMMING PROGRAM $2007.5 TO LOW THIS WILL ENABLE GPIO.3 / RA3 AS AN INPUT
'
' Set the 2007 Register BIT FIVE [5] to ZERO [0] *****************
----> I currently do this just before programming in the programmer configuration menu.
'
'OR
see: http://www.picbasic.co.uk/forum/showthread.php?t=14421

' change the config file
' OR IN THE C:\PBP\chip.INC
' i.e. C:\PBP\12F683.INC


change this line to:
device pic12F683, intrc_osc_noclkout, wdt_on, mclr_off, protect_off

and this line to:
__config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _CP_OFF



;************************************************* ***************
;* 12F683.INC *
;* *
;* By : Leonard Zerman, Jeff Schmoyer *
;* Notice : Copyright (c) 2005 microEngineering Labs, Inc. *
;* All Rights Reserved *
;* Date : 08/31/05 *
;* Version : 2.46a *
;* Notes : *
;************************************************* ***************
NOLIST
ifdef PM_USED
LIST
include 'M12F683.INC' ; PM header
device pic12F683, intrc_osc_noclkout, wdt_on, mclr_off, protect_off
; device pic12F683, intrc_osc_noclkout, wdt_on, mclr_on, protect_off

XALL
NOLIST
else
LIST
LIST p = 12F683, r = dec, w = -302
INCLUDE "P12F683.INC" ; MPASM Header
__config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _CP_OFF
; __config _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_ON & _CP_OFF

NOLIST
endif
LIST

[El_AMPo]

Try the 12f635 or the 12f683.

The 12F629 does not have the OSCCON @ [8F - hex] , register so you can't set the speed it is stuck at 4MHz.
You will need to read the DATA SHEET a bit more closely -- as always it is buried in the fineprint :)



It's quite similar your chip configs to what i'm using. 12F683 seems like a nice little chip, but still for timing applications you need an external Xtal, INTRC its not enough after some days running.

What would be handy is how to configure the 12f629 to run in LP xtal mode AND make it work in picbasic. No problem if the pause periods run slower you can always compensate for that, but the chip refuses to work in LP

[cncmachineguy]

but still for timing applications you need an external Xtal, INTRC its not enough after some days running

Sounds like a test is in order. Are you saying that after a few days the clock is no longer at said speed? by how much? I can see a test such as this:




main:
toggle port pin
goto main

this will give some freq out. so if we let it run a few days, we can see the new freq out.

[El_AMPo]

Sounds like a test is in order. Are you saying that after a few days the clock is no longer at said speed? by how much? I can see a test such as this:




main:
toggle port pin
goto main

this will give some freq out. so if we let it run a few days, we can see the new freq out.

It's a clock keeping code so you work "accumulating cycles", if you use an RC source, even if you calibrate it to a perfect frequency within a few days you will have noticeable drift because of temperature changes during the day and voltage drop from the battery. Crystals also suffer from drift but much less noticeable, and if you want better than that you will need temperature compensated RTCs or OCXO (oven controled crystal oscillators) both an overkill for my clock.

Talking about INTRC 4mhz clock... anyone was able to calibrate the value at 5 volts via oscal value?.
The factory default is calibrated at 4mhz 1% BUT at 3.5V 20ºC if I remember well. So at 5V it's like 1.1Mhz per instruction actually (measured), that means goodbye serial comms and reasonable good timing.

[cncmachineguy]

1.1Mhz per instruction actually (measured)


WOW, thats 10%!!!!