The nrf52x “RTC” is probably the worst-named peripheral I have come across in my 25+ years of writing firmware :-) It is not a RTC. It is just a timer that runs off a 32KHz crystal so is not what you are looking for. You will certainly need to use a timer to help keep track of “real-time” but you will have to do that in firmware (if you see what I am getting at here). Unless someone else has a better idea, you will have to do something like this:
1) Start up a timer (you can use the RTC timer for this as it is low power). 2) When your device receives “real-time” you read the current RTC counter and remember it 3) When you want time in the future you need to read the current RTC counter and subtract it from the stored value. You then calculate the amount of time that has passed and update real-time accordingly. Will PS You have to be careful about timer roll-over and dealing with that but that should be easy. > On Dec 27, 2018, at 8:57 AM, Christopher Collins <ch...@runtime.io> wrote: > > Hi Rohit, > > On Wed, Dec 26, 2018 at 11:55:56PM +0530, Rohit Gujarathi wrote: >> Hi Everyone, >> >> I wanted to make a desktop clock using mynewt and am stuck at setting the >> time. I read the os_timeval part but How do i set time in mynewt and >> display it human form? I am using the nrf52840 which has a RTC, how can i >> use that? has anyone used the __DATE__ and __TIME__ macro? > > The __DATE__ and __TIME__ macros are useful when you need to know when a > program was built. Since you are interested in the actual real time > (independent of the build time), these macros won't help you. > > I would look at the following two functions: > > os_gettimeofday() > > (http://mynewt.apache.org/latest/os/core_os/time/os_time.html#c.os_gettimeofday) > > os_settimeofday() > > (http://mynewt.apache.org/latest/os/core_os/time/os_time.html#c.os_settimeofday) > > When the device boots up, set its time using `os_settimeofday()`. To > display the current time, call `os_gettimeofday()` and convert the > result to a human readable format. > > These functions deal in UNIX time, i.e., seconds since 1970/01/01. > I'm afraid converting this number to a human readable format is not > trivial due to pesky human factors such as time zones, leap years, etc. > Luckily, these functions use the POSIX time data structures, so there > should be a lot of free code avialable online that does this conversion. > > I am not very familiar with the nRF52 RTC. Maybe others who are more > knowledgable can chime in. > > Chris
