Does the nRF51822 RTC or some clock function continue to run between power cycles?

[brianreinhold]

I need to create a health device that sends time stamps of the measurement. For that to work I would need the counter to continue between power cycles. Some devices have a CMOS to handle that but I am guessing that's part of the board design and not the chip. Not being an embedded systems expert playing with these chips is new to me. I am comfortable with the Bluetooth but that's about it.

I can deal with this if I send only live measurements by having the gateway set the time each connection but that wont work if I want to measurements off line (while not connected to a peer) and store them with time stamps.

I take it there is some type of CMOS RTC on the DK....

So in the end what I need is for the device to keep a tick count that never stops; it must keep ticking when the device is turned off so next time the device is powered up and I take a measurement I can record the time stamp of that measurement, connected to the peer or not.

I have looked at a lot of FORUM posts and as much documentation as I can find but they create more questions than they answer. I am trying to solve a problem that many Bluetooth Health Devices on the market have been able to solve.

1. There is a factory-set default initial time
2. Either the user or a peer device synchronizes the device time clock to a known time line.
3. Physiological measurements are time stamped based upon the device's synchronized time line
4. A time stamp is provided to measurements taken even if the device is not connected to any peer

The above means that there is some way that the device 'keeps' the internal time clock ticking so the device does not need to keep having its time initialized every time, allowing measurements to be taken 'offline', such as a person carrying a glucose monitor.

So I need to have a means of getting a clock tick WITH SoftDevice running

I need a means to keep the clock alive between power cycles.

[Vidar Berg]

Hello,

The peripherals, including the RTC, will be fully reset on boot (Reset behaviour). Only data in persistent memory (FLASH, UICR) is preserved after  a Power on reset (POR). So accurate time-keeping may be challenging if your device is expected to get power cycled frequently. 

External RTC modules such as this Maxim RTC module are commonly implemented with separate power supply (e.g. from a coin cell battery)  to allow the clock to run while the main system is powered down.

[brianreinhold]

It has become clear to me that the hardware I was given does not support a means of powering the RTC when the device powers down (though it runs on batteries)., So I cannot report time stamps (which by spec - not Bluetooth spec) says I cannot store measurements, they must be taken while connected and immediately transferred to the peer.