[ntp:questions] ntp & system without a rtc

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Sat May 11 00:40:31 UTC 2013


John Hasler wrote:
> E-Mail writes:
>> The uC likely has a RTC, its just not battery backed up?
>
> The Raspberry Pi has no rtc.

Raspberry Pi has a Broadcom BCM2835 SoC (700 MHz ARM11 ARM1176JZF-S)
  Broadcom seems to want to hold their full datasheet from public view.
 Perhaps it doesn't have an internal RTC peripheral.


Many ARM SoCs have an internal RTC peripheral.
 If the product manufacturer doesn't supply an easy
  way to connect a battery on their PCB,
  the RTC is still in the chip.


> There is no point in having one without a battery.

Or a "SuperCap", depending how long it is typically off.

Just like e.g. the PPS input on a Pi,
 if the chip package has a RTC, and the pin/trace is
  accessible, you could hook up a Batt/CAP.

 ... or e.g. hook up a RTC chip on the I2C, ...

I noticed someone make a RTC with batt for the Pi
<http://www.hobbytronics.co.uk/raspberry-pi-real-time-clock>

 Likely several others do too, {Seems so}.
 <http://www.instructables.com/id/How-to-add-a-Real-time-clock-to-the-Raspberry-Pi-o/>
 <https://www.modmypi.com/rasclock-raspberry-pi-real-time-clock-module>
 <http://learn.adafruit.com/adding-a-real-time-clock-to-raspberry-pi/overview>


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