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Using RTC chip as an alarm to wake up PIC

 
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MILMAN
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Using RTC chip as an alarm to wake up PIC
PostPosted: Thu Jul 02, 2009 4:14 am     Reply with quote
Hello,

I am building a circuit that can be programmed to 'wake up' at certain times through out the day, collect data and then go to sleep mode.

I am having a lot of trouble even setting the RTC chip to tell the correct time, and I don't really know how to deal with different months/leap years etc. I have got hold of the code below from someone who has now left the department I work in (so can't ask for help) and have modified it a bit, but to be honest I don't understand much or any of what it is really doing?

If anyone could provide a brief explanation of this or another approach to implementing the time-based data collection idea I would be very grateful. Sorry this is a bit of a vague request,

any help much appreciated,

Cheers Smile

Code:
byte   day,month,year,hours,minutes,seconds;

void init_rtc()
{
    

   i2c_start();
   i2c_write(0xa0 | RTC_chip_add<<1);
   i2c_write(0x00);
   i2c_write(0x00);
   i2c_stop();
   delay_ms(11);
   
}

unsigned int get_low_bcd(unsigned int in_char)   // char lower nibble to bcd
   {
      return((in_char&0x7f)-48);
   }


separate

void set_time_and_date()
{
   byte   unitday,tenday,unitmonth,tenmonth,tenyear,unityear;
   byte   unithours,tenhours,unitminutes;
   byte   tenminutes,unitseconds,tenseconds;

   unitseconds=get_low_bcd(rtc_buffer[16]);
   tenseconds=get_low_bcd(rtc_buffer[15]);
   unitminutes=get_low_bcd(rtc_buffer[13]);
   tenminutes=get_low_bcd(rtc_buffer[12]);
   unithours=get_low_bcd(rtc_buffer[10]);
   tenhours=get_low_bcd(rtc_buffer[9]);
   unityear=get_low_bcd(rtc_buffer[7]);
   tenyear=get_low_bcd(rtc_buffer[6]);
   unitmonth=get_low_bcd(rtc_buffer[4]);
   tenmonth=get_low_bcd(rtc_buffer[3]);
   unitday=get_low_bcd(rtc_buffer[1]);
   tenday=get_low_bcd(rtc_buffer[0]);

   i2c_start();
   i2c_write(0xa0 | RTC_chip_add<<1);
   i2c_write(0x02);
   i2c_write((tenseconds * 16) + unitseconds);
   i2c_write((tenminutes * 16) + unitminutes);
   i2c_write((tenhours * 16) + unithours);
   i2c_write((unityear * 64) + (tenday * 16) + unitday);
   i2c_write((tenmonth * 16) + unitmonth);
   i2c_stop();
   delay_ms(11);

   fprintf(PC,"\f RTC written ...");
   lcd_init();
   printf(lcd_putc, "\n RTC written ...");
   
}

separate
void read_time_and_date()
{
   byte   dummy;

   fprintf(PC,"reading RTC from hardware...\n\r");

   i2c_start();
   i2c_write(0xa0 | RTC_chip_add<<1);
   i2c_write(0x02);
   i2c_start();
   i2c_write(0xa1 | RTC_chip_add<<1);
   seconds = i2c_read();
   minutes = i2c_read();
   hours = i2c_read();
   day = i2c_read();
   month = i2c_read();
   for(i=0;i<5;i++)
      dummy = i2c_read();
   i2c_stop();
   delay_ms(11);

   delay_ms(200);
   year = ((day&0xc0)/64)&0x03;
   day = (((day / 16) & 0x03) * 10) + (day & 0x0f);
   month = (((month / 16) & 0x01) * 10) + (month & 0x0f);
   hours = (((hours / 16) & 0x03) * 10) + (hours & 0x0f);
   minutes = (((minutes / 16) & 0x0f) * 10) + (minutes & 0x0f);
   seconds = (((seconds / 16) & 0x0f) * 10) + (seconds & 0x0f);

   fprintf(PC,"writing RTC to monitor ...\n\r");
   fprintf(PC,"year .. %3u\n\r",year);
   fprintf(PC,"month .. %3u\n\r",month);
   fprintf(PC,"day .. %3u\n\r",day);
   fprintf(PC,"hours .. %3u\n\r",hours);
   fprintf(PC,"minutes .. %3u\n\r",minutes);
   fprintf(PC,"seconds .. %3u\n\r",seconds);

   
}
MILMAN
Guest
PostPosted: Thu Jul 02, 2009 4:22 am     Reply with quote
Also the RTC chip I am using is PCF8583 and using PIC16F76. Thanks.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Jul 02, 2009 10:35 am     Reply with quote
There is a pcf8583 driver here, though it doesn't include alarm functions:
http://www.ccsinfo.com/forum/viewtopic.php?t=27988
It has a test program, and links to schematics.

If you have any questions about the driver, ask them here in this thread
(not in the driver thread).
MILMAN
Guest
PostPosted: Fri Jul 03, 2009 8:39 am     Reply with quote
Thank you so much. That has helped me loads!

I stupidly overlooked the fact that I had set the PCF8583 i2c address to 0xA2 as well so thanks for the note. It has also highlighted that it would have been a lot better if I had used the DS1307 chip, but o well, will know in the future!

Thanks again.
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