My reply was definitely a bit confusing based on Chris’s reply. He is correct and if you use those API to set/get time of day what I was saying you need to do in firmware is already done for you.
Hopefully that clears up any confusion. > On Dec 27, 2018, at 9:21 AM, will sanfilippo <wi...@runtime.io> wrote: > > 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 >
