Does anyone actually use the DS1307's square wave output? (And if so, what for?)

e.g. suppose you have a RTC connected to the sketch and you want to keep time up to date without reading the RTC over and over, you can get a pulse every second to update the time (seconds/minutes/hours/etc). That has probably less overhead than reading the RTC over I2C.

So now to my supplementary question: how to make it work? Using the registers as explained in the data sheet is a bit above me. As far as I can see there's no simple way provided by the library. edit.... I'm thinking a byte write of some kind, to adress 68's register 7, a value that sets bit 4 and…

Jimbo, I have a DS1307 library that gives full access to all the functionality of the IC. Link from my Code libraries (below).

Thanks Marco- I'll have a look.

Jim-- It is very easy to set the control register 07h (bits 4,1,0) in the DS1307 to enable and set the SQW with out any library except Wire.h. The data sheet http://datasheets.maximintegrated.com/en/ds/DS1307.pdf You use a simple function void writeRTC(byte location, byte data) // writes data to …

Take a look at the DS3231 http://datasheets.maximintegrated.com/en/ds/DS3231.pdf In the control register 0Eh for the square wave, bit 6 is Battery Backed Square Wave Enable/Disable, and the square wave can be turned off when Vcc is taken over by Vbat. The DS3231 is more accurate than the DS1307, h…

@cattledog , could you please clarify a bit more as how to set interval for SQW? Is there an example you could share with us? Thank you,

Write to the appropriate bits of the control register: Bit 7: Output Control (OUT). This bit controls the output level of the SQW/OUT pin when the square-wave output is disabled. If SQWE = 0, the logic level on the SQW/OUT pin is 1 if OUT = 1 and is 0 if OUT = 0. On initial application of power to …

@cattledog , could you please clarify a bit more as how to set interval for SQW? Is there an example you could share with us? You add the register writing function to your code. You call it with the values given. If you can please explain what you don't understand about what was given in reply #5,…

Practical use of DS1307 SQW output?

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JimboZA December 31, 2014, 6:15am 7

Thanks Guys, that was easy.

It's a bit disconcerting that it keeps the wave going when the main power is off: that's a sure way to kill your backup battery.

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Practical use of DS1307 SQW output?

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