Hi David,
I used to think it was strange too and always included the clock
functionality in the microcontroller. However, I was always fine-tuning
the accuracy. I believe that someone was posting to this list a little
while back about his own Atmel microcontroller clock-code accuracy issues.
Later, I needed to build a clock that knew what day it was. I started
putting thought into adding that to the microcontroller, how to account
for leap-years, which months have how many days, etc. It was all more
than doable, but I decided to use the opportunity to try using an RTC.
Another driving factor was battery-backup. The RTC I was using (another
from Maxim, can't remember the name but it is a 8-pin DIP) made battery
backup a complete breeze. Real battery backup, a CR2032 or similar, with
a total of months/years of battery life driving the RTC & TCXO.
The RTC I used was I2C and it also provided an opportunity to learn how
to interface with I2C parts. :)
In the future, I'll probably use an RTC when I feel like it, on more
complex clocks that have a smidge of extra space on the board and maybe
could also use some reduction in microcontroller software size.
It is important to note that these builds are strictly for a hobby and
not sale, so 'price is no object' provided that I can sample the parts
for free. An RTC, TCXO and max6921 might total $25-$30 if I was doing
this for sale, so that would be a non-starter. Of course, I've used
those above parts as well as tons of other Maxim IC parts at work on
larger projects. Maxim IC gets their money's worth out of me, I think. :)
-Adam
On 11/21/2013 2:09 PM, David Forbes wrote:
On 11/21/2013 3:03 PM, Gideon Wackers wrote:
I will
also add a RTC because for what they cost it seems like they make
things a
lot easier.
I have always thought it strange when people do that. After all, the
job of a microcontroller that runs a clock is to keep track of the
time and make it show up on the display. Why add a second chip to keep
track of the time when the micro is perfectly capable of doing that job?
Especially if someone has already written the code for you, unless
they did a bad job of it.
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