.. _faq_internal_rc_oscillator:

Using Internal RC Oscillator
############################

If an external crystal is not used to derive the low-frequency clock, internal RC oscillator can be used instead.

To use the internal RC oscillator, build applications with these additional configuration options:

.. code-block:: kconfig

   CONFIG_ATM_LPC_RCOS=y
   CONFIG_ATM_FORCE_LPC_RCOS=y

These additional configuration can be added to application's prj.conf file OR as command line build options or as extra_configs entry in sysbuild sample.yaml.

Here is a sample build reference:

.. code-block:: bash

   west build -p always -b ATMEVK-3430e-YQN-5 openair/samples/bluetooth/beacon --sysbuild -T samples.bluetooth.beacon.atm -DCONFIG_ATM_LPC_RCOS=y -DCONFIG_ATM_FORCE_LPC_RCOS=y