Converting Bytes from hex to Dec

[Melanie]

>> "The DS1307 returns the seconds in hex so 59secs = 3B"

No it doesn't! The DS1307 gives you Binary Coded Decimal (BCD), so 59 seconds is %01011001 = $59

If RTCSeconds is $59 then...

UnitSeconds=RTCSeconds & $0F ' will get you your lower 4 bits = $09
TensSeconds=RTCSeconds >> 4 ' will get you your upper four bits = $05

[Rob Martin]

Mel

That works perfectly!
I understand the basis of BCD but need to do somemore reading.
I assume I just reverse the formula to convert the other way? Or is that to simplistic

Thanks as always for your invaluable help.

ROb

[Melanie]

>> "I assume I just reverse the formula to convert the other way? "

Basically Yes...

If you want to Save 27 minutes into the Minutes Register, then you save $27. The 2 is the twenty out of the twenty minutes and the "7" is the seven.

Remember, that when reading or writing you should never have an 'alphabetic' character... there are exceptions, some of the registers have the 7th bit as a special bit... just strip it out if it's not needed. The seconds register especially.... if the 7th bit is set to '1' then the clock isn't running - which is a way you can tell if the DS1307 is initialised or not.