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low current consumption problem

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lboghy

Joined: 04 Jun 2008
Posts: 23

low current consumption problem

Posted: Tue Sep 27, 2011 1:35 pm

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Hello!
I tried to reduce the power consumption on 16f1939 microcontroller.
First I tried to use sleep function and wake-up using interrupt on change on falling edge:

Code:

#BYTE INTCON = 0x00B
#BIT GIE = INTCON.7
#BIT IOCIE = INTCON.3
#BIT IOCIF = INTCON.0

#BYTE IOCBN = 0x395
#BIT IOCBN3 = IOCBN.3
#BIT IOCBN2 = IOCBN.2
#BIT IOCBN1 = IOCBN.1
#BIT IOCBN0 = IOCBN.0

#BYTE IOCBF = 0x396
#BIT IOCBF3 = IOCBF.3
#BIT IOCBF2 = IOCBF.2
#BIT IOCBF1 = IOCBF.1
#BIT IOCBF0 = IOCBF.0

#define ROW1 PORTB0 //digital input
#define ROW2 PORTB1 //digital input
#define ROW3 PORTB2 //digital input
#define ROW4 PORTB3 //digital input

IOCBN3 = 1;IOCBN2 = 1;IOCBN1 = 1;IOCBN0 = 1;//activate falling //edge

the program was:
while(1)
{
if (timer_unpressed == 100)
{
sleep_flag = 1;
IOCIE = 1;//activate interrupt on change
sleep();
}
if (sleep_flag)
if((!ROW1) || (!ROW2) || (!ROW3) || (!ROW4))
{
unpressed_tmr = 0;
sleep_flag = 0;//go out of sleep
}
if(!sleep_flag)
{
//.... program functions - writing to a I2c rheostat
}

After entering on sleep if I press a key of row1..4 is doing reset.

-----------------------------------------------------------------------------
A second way was to reduce the internal clock speed from 4 MHz to 32KHz:

Code:

if(sleep_flag)
{
if((!ROW1) || (!ROW2) || (!ROW3) || (!ROW4))
{
#use delay(int=4000000)
}
}
if (unpressed_tmr > 100 && (!sleep_flag)) //
{
sleep_flag = 1;
#use delay(int=32000)
}

but the consumption is not decrease. I think that is not go to low speed clock.

Can anyone help me?

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Tue Sep 27, 2011 2:06 pm

Reply with quote

Quote:

A second way was to reduce the internal clock speed from 4 MHz to 32KHz:

if(sleep_flag)
{
if((!ROW1) || (!ROW2) || (!ROW3) || (!ROW4))
{
#use delay(int=4000000)
}
}
if (unpressed_tmr > 100 && (!sleep_flag)) //
{
sleep_flag = 1;
#use delay(int=32000)
}

but the consumption is not decrease. I think that is not go to low speed clock.

Putting #use delay() statements in the middle of the program does not
generate code to change the internal oscillator frequency. You need to
use the setup_oscillator() function to do that.

The #use delay() statement only tells the CCS compiler what the current
oscillator frequency is.

Also, #use delay() only affects code that occurs after the #use delay()
statement in the file. (Going from top to bottom in the file).
If your program jumps back up to an earlier line in the file, then it delays
such as delay_us(), will run at the rate of the previous #use delay()
statement.

This thread has sample code for switching oscillator frequencies and
setting #use delay():
http://www.ccsinfo.com/forum/viewtopic.php?t=32758

lboghy

Joined: 04 Jun 2008
Posts: 23

Problem solved
Posted: Wed Sep 28, 2011 2:26 pm

Dear PCM, Thank you for your prompt response. Is working, the power consumption is less 40 times using low oscillator frequnecy.

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