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DS1307 SQW/OUT pin generate pulses at 1 second intervals

 
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bolubeyi



Joined: 27 Apr 2012
Posts: 15
Location: TURKEY

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DS1307 SQW/OUT pin generate pulses at 1 second intervals
PostPosted: Wed Sep 05, 2012 9:14 am     Reply with quote
Hi, I use ds1307 and ccs c. I want to generate pulses at 1 second intervals from ds1307 SQW/OUT - Square Wave/Output pins. How can I do this? How do I set ds1307?
temtronic



Joined: 01 Jul 2010
Posts: 9208
Location: Greensville,Ontario

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PostPosted: Wed Sep 05, 2012 10:20 am     Reply with quote
Here's the way I do it...
Sorry I don't know where this function came from but it does work...
Code:

void ds1307_init(void)
{
BYTE seconds = 0;

i2c_start();
i2c_write(0xD0); // WR to RTC
i2c_write(0x00); // REG 0
i2c_start();
i2c_write(0xD1); // RD from RTC
seconds = bcd2bin(i2c_read(0)); // Read current "seconds" in DS1307
i2c_stop();
seconds &= 0x7F;

delay_us(3);

i2c_start();
i2c_write(0xD0); // WR to RTC
i2c_write(0x00); // REG 0
i2c_write(bin2bcd(seconds)); // Start oscillator with current "seconds value
i2c_start();
i2c_write(0xD0); // WR to RTC
i2c_write(0x07); // point to Control Register
i2c_write(0x10); // Enable squarewave output pin
i2c_stop();
}

The second last line does the job. If you read the DS1307 datasheet, it'll also explain how to set for other interrupt rates.

hth
jay
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