Using internal 128kHZ Oscillator vs. external oscillator

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Anonymous
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Per this thread: Re: clock reference/RTC during deep sleep?

We do not have an external 32kHz crystal on our board.  Is there a simple example of how to setup the rtc_sample application to run off of the internal 128kHz oscillator?  What simple modifications are required?

Thanks in advance,

    Aaron

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MichaelF_56
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aneedles

I'm pretty sure that the rtc_sample in the SDK covers both the on-chip RTC and the external 32 KHz LPO.

* RTC Sample

*

* This application provides the sample code for interfacing with

* the on-chip RTC clock. It is highly recommended that an external 32K

* xtal be used when accurate time is to be maintained. The accuracy

* of the time maintained with the an external LPO is an order of magnitude

* better than the internal LPO.

*

*

* Features demonstrated

*  - Use of the on-chip RTC interface.

*  - Use of the external 32 KHz LPO for sleep and deep sleep.

*  - Entering deep sleep on demand.

*  - Using the external LPO (32KHz xtal) for timed wake from deep sleep.

*

* To demonstrate the app, work through the following steps.

* 0. Enable the external 32KHz oscillator on the TAG board (see Quick Start Guide -

*    make sure that R102 and R103 on BCM920737TAG_Q32 are populated

*    with a 0 Ohm resistor, else the the behavior is undefined).

* 1. Plug the WICED eval board into your computer

* 2. Build and download the application (to the WICED board)

* 3. Application initializes and RTC and prints time every second.

* 3.a Application programs and enters deepsleep, optionally configuring for a timed wake.

*/

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