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planmas
Joined: 18 Aug 2011
Posts: 8
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| 18F26K20 + int_rda + sleep problem |
 Posted: Thu Aug 18, 2011 3:07 pm |
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Hi,
I'm using compiler version 4.114 and a PIC18F26K20.
I have a small program with the objective of waking up the PIC from its sleep via serial interrupt (rda).
I have tried to use both sleep modes, idle and deep. I'm able to achieve success with idle mode, but I'm incapable of waking up the PIC once it gets into deep sleep.
I'm controlling the sleep mode by connecting pin C3 to logic 1 or 0 and using the hardware pins for the serial communication.
The code is the following:
| Code: |
#include "18F26K20.h"
#fuses HS, NOWDT, NOPROTECT, NOLVP
#use delay(clock=20000000)
#use rs232(uart1, baud=9600, stream = PC)
short sleep_mode;
void piscaLed(int pino, int atraso){
output_high(pino);
delay_ms(atraso);
output_low(pino);
delay_ms(atraso);
}
#int_rda
void serial_isr(){
char c;
c = fgetc(PC);
fprintf(PC,"%c",c);
if(input(pin_c3)==0)
sleep_mode = FALSE;
if(input(pin_c3)==1)
sleep_mode = TRUE;
}
void main()
{
sleep_mode=FALSE;
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
while(TRUE){
if(sleep_mode){
//sleep(SLEEP_IDLE); //It works well with this line instead of the bottom one
sleep(SLEEP_FULL);
}
delay_ms(1);
fprintf(PC,"\n\r");
fprintf(PC,"NOT SLEEPING");
fprintf(PC,"\n\r");
piscaLed(PIN_A4,500);
}
}
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Does anyone has any idea why serial interrupt cannot wake the PIC when it is in deep sleep?
Best wishes
planmas |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Aug 18, 2011 6:54 pm |
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It won't wake-up in sleep mode because the main oscillator is shut down
and the UART receiver needs a clock to run its internal circuits. It works
in Idle mode because in that mode the PIC's oscillator is still running.
More info:
http://www.ccsinfo.com/forum/viewtopic.php?t=31308
http://www.ccsinfo.com/forum/viewtopic.php?t=36125
http://www.ccsinfo.com/forum/viewtopic.php?t=36728
However, there is another way to do it. Read this section in the 18F26K20
data sheet. There are several more paragraphs besides this:
| Quote: |
18.3.3 AUTO-WAKE-UP ON BREAK
During Sleep mode, all clocks to the EUSART are
suspended. Because of this, the Baud Rate Generator
is inactive and a proper character reception cannot be
performed. The Auto-Wake-up feature allows the
controller to wake-up due to activity on the RX/DT line.
This feature is available only in Asynchronous mode.
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planmas
Joined: 18 Aug 2011
Posts: 8
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| Posted: Fri Aug 19, 2011 4:53 am |
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Thank you for the reply.
| Quote: | | It won't wake-up in sleep mode because the main oscillator is shut down |
It confirms what I was thinking.
I will explore the AUTO-WAKE-UP ON BREAK section of the datasheet and more paragraphs.
I will post my results in the next couple of days in order to try to help anyone with the same problem.
Thank you once again.
Planmas. |
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