# 1024hz to milliseconds **URL:** \ **Category:** Programming\ **Created:** [September 1, 2014, 9:42am UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169 "2014-09-01T09:42:51Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![jcarruthers](https://avatars.discourse-cdn.com/v4/letter/j/c68b51/32.png) [@jcarruthers](https://forum.arduino.cc/u/jcarruthers)\ **Post date:** [September 1, 2014, 9:42am UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/1 "2014-09-01T09:42:51Z")
I need accurate time for my project — specifically milliseconds. I plan to use a DS3231 RTC and it's 1024hz output. I can keep count of the output but of course I am stuck with a "millisecond" of 1024 every second. What's the most elegant way of converting a range of 0 to 1024 to 0 to 1000? My plan is to keep a count (that rolls from 1023 to 0) and then whenever I request a millisecond do the maths to convert it from 0-999 I can either do the obvious "hzCount \* (hz/1000)" or I could keep a look up table in memory and just do "msLUT[hzCount]" The truth is that I'll probably be calling a getMillis() every loop. Anything I'm missing? I'm really keen to learn about how to do these things as efficiently as possible. James ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [September 1, 2014, 10:53am UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/2 "2014-09-01T10:53:51Z")
Have you looked at the way Arduino tackles this problem? ---
**Author:** ![AJITnayak](https://avatars.discourse-cdn.com/v4/letter/a/f4b2a3/32.png) [@AJITnayak](https://forum.arduino.cc/u/AJITnayak)\ **Post date:** [September 1, 2014, 10:54am UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/3 "2014-09-01T10:54:38Z")
Why didn't used DS1307. You get accurate.problem need to use external crystal oscillator. I think it should work with library. Instead of conversion. [GitHub - JChristensen/DS3232RTC: Arduino Library for Maxim Integrated DS3232 and DS3231 Real-Time Clocks](https://github.com/JChristensen/DS3232RTC) library avialble here, Let me know if any problem in output. share your code and snapshot of the output window ---
**Author:** ![jcarruthers](https://avatars.discourse-cdn.com/v4/letter/j/c68b51/32.png) [@jcarruthers](https://forum.arduino.cc/u/jcarruthers)\ **Post date:** [September 1, 2014, 12:08pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/4 "2014-09-01T12:08:35Z")
So something like this: ```cpp ms += 1 fracms += 1 if (fracms == 42) { fracms = 0 ms -= 1 } if (ms == 1000) { ms = 0 } ``` Every 42 beats it corrects itself. Seems fair enough. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [September 1, 2014, 12:52pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/5 "2014-09-01T12:52:53Z")
> AMPS-N: > Why didn't used DS1307. You get accurate.problem need to use external crystal oscillator. I think it should work with library. Instead of conversion. > > [GitHub - JChristensen/DS3232RTC: Arduino Library for Maxim Integrated DS3232 and DS3231 Real-Time Clocks](https://github.com/JChristensen/DS3232RTC) library avialble here, Let me know if any problem in output. share your code and snapshot of the output window I think you've misunderstood the question. The DS1307 doesn't have a 1.024kHz output, only 4.096, 8.192 and 32.768kHz and 1Hz. ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [September 1, 2014, 1:06pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/6 "2014-09-01T13:06:11Z")
> JamesCarruthers: > I need accurate time for my project — specifically milliseconds. > ...SNIP.... Sorry, but I can't understand your post - even after having a quick look at the DS3231 datahsheet. I have no idea what you want to achieve or even how you think you might do it. What is your project? What amount of error in timing is acceptable? ( +/- how many microseconds or parts-per-million ) ...R ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [September 1, 2014, 1:09pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/7 "2014-09-01T13:09:26Z")
I read it as "I want to be able to timestamp to (roughly) millisecond accuracy" ---
**Author:** ![jcarruthers](https://avatars.discourse-cdn.com/v4/letter/j/c68b51/32.png) [@jcarruthers](https://forum.arduino.cc/u/jcarruthers)\ **Post date:** [September 1, 2014, 1:48pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/8 "2014-09-01T13:48:59Z")
> AWOL: > I read it as "I want to be able to timestamp to (roughly) millisecond accuracy" Yup, exactly. I'm trying to work out if using a higher hz would give me a more accurate millisecond by using the same technique. I guess it's a case of how accurate do I need... ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [September 1, 2014, 3:25pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/9 "2014-09-01T15:25:53Z")
> JamesCarruthers: > > > AWOL: > > I read it as "I want to be able to timestamp to (roughly) millisecond accuracy" > > Yup, exactly. You are still not expressing your requirement clearly. It sounds like you are content with an accuracy of +/- 1 msec, but you don't say how long that must be maintained for. If you want accuracy over a longer period than the Arduino can naturally maintain I would read millis() and the RTC periodically and keep a correction factor variable that represents how much has to be added or subtracted to/from the value for millis() to stay in step with the RTC. In other words if I wanted to record the time of an event I would save it as eventTime = millis() + correction; Would it not be easier just to read the RTC when the event occurs and ignore millis() altogether? ...R ---
**Author:** ![jcarruthers](https://avatars.discourse-cdn.com/v4/letter/j/c68b51/32.png) [@jcarruthers](https://forum.arduino.cc/u/jcarruthers)\ **Post date:** [September 1, 2014, 4:23pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/10 "2014-09-01T16:23:32Z")
In the same way I can get seconds() I'd like to be able to get milliseconds() Accurate as possible within reason. I'm using them to drive a strip of LEDs — at the moment I'm using only 60 and slight variances are noticeable. It's surprising how the eye can pick up on tiny millisecond differences. So at the moment I only need 1/60 accuracy. I'd like a solution that is scalable to a large number of LEDs ---
**Author:** ![Robin2](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/robin2/32/216045_2.png) [@Robin2](https://forum.arduino.cc/u/Robin2)\ **Post date:** [September 1, 2014, 6:09pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/11 "2014-09-01T18:09:26Z")
> JamesCarruthers: > I'm using them to drive a strip of LEDs If you just want to flash LEDs in a pattern and you are driving all the LEDs from a single Arduino then just use millis(). If they are not staying in sync with each other the way you want that is because you are not using millis() properly - not because of a deficiency in millis(). This demo[several things at a time](http://forum.arduino.cc/index.php?topic=223286.0) illustrates how to use millis(). ...R ---
**Author:** ![nilton61](https://avatars.discourse-cdn.com/v4/letter/n/ebca7d/32.png) [@nilton61](https://forum.arduino.cc/u/nilton61)\ **Post date:** [September 1, 2014, 8:03pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/12 "2014-09-01T20:03:42Z")
Why not implement a bresenham algrithm with a ratio of 125/128? ---
**Author:** ![jcarruthers](https://avatars.discourse-cdn.com/v4/letter/j/c68b51/32.png) [@jcarruthers](https://forum.arduino.cc/u/jcarruthers)\ **Post date:** [September 1, 2014, 8:09pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/13 "2014-09-01T20:09:42Z")
> AMPS-N: > Why didn't used DS1307. You get accurate.problem need to use external crystal oscillator. I think it should work with library. Instead of conversion. > > [GitHub - JChristensen/DS3232RTC: Arduino Library for Maxim Integrated DS3232 and DS3231 Real-Time Clocks](https://github.com/JChristensen/DS3232RTC) library avialble here, Let me know if any problem in output. share your code and snapshot of the output window Hi Jack, I have your library working — many thanks — saved me some time. I have set my squarewave to 1024Hz — but am unsure how to test it's actually working. I have it attached to a pin and attachInterrupt running a counter function on RISING. But no luck. ---
**Author:** ![Jiggy-Ninja](https://avatars.discourse-cdn.com/v4/letter/j/8edcca/32.png) [@Jiggy-Ninja](https://forum.arduino.cc/u/Jiggy-Ninja)\ **Post date:** [September 1, 2014, 8:24pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/14 "2014-09-01T20:24:45Z")
> JamesCarruthers: > In the same way I can get seconds() I'd like to be able to get milliseconds() > > Accurate as possible within reason. > > I'm using them to drive a strip of LEDs — at the moment I'm using only 60 and slight variances are noticeable. It's surprising how the eye can pick up on tiny millisecond differences. So at the moment I only need 1/60 accuracy. > > I'd like a solution that is scalable to a large number of LEDs I'm with Robin on this, if your timing errors are noticeable to the human eye, you're probably _way_ beyond millisecond error. What kind of LED strips are these? ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [May 5, 2021, 8:51pm UTC](https://forum.arduino.cc/t/1024hz-to-milliseconds/255169/15 "2021-05-05T20:51:05Z")