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 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 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
>
