doc: Add the Antenna Tuning on Thingy:91 X

Add the Antenna Tuning on Thingy:91 X

Signed-off-by: divya pillai <divya.pillai@nordicsemi.no>

Author: divipillai

README.md

@@ -15,4 +15,4 @@ This project is based on the
 
 ## Getting started
 
-To get started with hello-nrfcloud firmware for the Thingy:91 X, follow [documentation](https://hello-nrfcloud.github.io/firmware/html/index.html).
+To get started with hello-nrfcloud firmware for the Thingy:91 X, follow [documentation](https://docs.nordicsemi.com/bundle/addon-nrfcloud_firmware-latest/page/index.html).

docs/antennatuning.rst

@@ -0,0 +1,26 @@
+.. _hello_nrfcloud_antennatuning:
+
+Antenna Tuning
+##############
+
+The Thingy:91 X Hello nRF Cloud firmware uses the `Modem Antenna`_ library to configure the nRF9151’s MIPI RF Front-End Control Interface (RFFE) and the COEX pins.
+The Modem Antenna library uses the `%XMIPIRFFEDEV`_, `%XMIPIRFFECTRL`_, and `%COEXCONFIG`_ AT commands to send the configuration to the nRF9151 modem.
+The Thingy:91 X board files define the default AT commands that are sent to the modem using the following Kconfig options:
+
+* ``CONFIG_MODEM_ANTENNA_AT_MIPIRFFEDEV``
+* ``CONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_INIT``
+* ``CONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_ON``
+* ``CONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_OFF``
+* ``CONFIG_MODEM_ANTENNA_AT_MIPIRFFECTRL_PWROFF``
+* ``CONFIG_MODEM_ANTENNA_AT_COEX0``
+
+The default values for the Kconfig options used when building firmware for the Thingy:91 X target can be found in the `Thingy:91 X nRF9151 board configuration`_ file.
+
+You can modify the default values to optimize the antenna tuning of the Thingy:91 X for specific usage scenarios.
+Ignion, the manufacturer of the antenna used on the Thingy:91 X, explains in the `Ignion Antenna Technology Powering The-Nordic-Thingy 91 X`_ application note how the antenna tuning can be optimized for specific usage scenarios by adjusting the switching states of the antenna.
+
+The antenna switch states can be set in the :file:`prj.conf` file by changing the configuration of the ``%XMIPIRFFECTRL`` AT command or during runtime by issuing the ``AT%XMIPIRFFECTRL=<new_antenna_switch_states>`` AT command.
+
+.. important::
+   Modification of the default configuration for the RF Front-End of the Thingy:91 X may result in radiated emissions outside regulatory limits.
+   If you have a Thingy:91 X with a modified RF Front-End configuration, you must ensure that the operation of the modified Thingy:91 X complies with applicable regulatory requirements.

docs/index.rst

@@ -29,6 +29,7 @@ Read more about the various aspects of the firmware in the following sections.
    gsg_guide
    architecture
    led_indication
+   antennatuning
    troubleshooting
    known_issues
    release_notes

docs/links.txt

@@ -6,6 +6,7 @@
 
 .. _`nRF Cloud CoAP`: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/libraries/networking/nrf_cloud_coap.html
 .. _`Date-Time`: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/libraries/others/date_time.html
+.. _`Modem Antenna`: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/libraries/modem/modem_antenna.html
 .. _`connection manager`: https://docs.nordicsemi.com/bundle/ncs-latest/page/zephyr/connectivity/networking/conn_mgr/main.html
 .. _`Fuel Gauge`: https://docs.nordicsemi.com/bundle/ncs-latest/page/zephyr/hardware/peripherals/fuel_gauge.html
 .. _`BME68X IAQ driver`: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/drivers/bme68x_iaq.html
@@ -17,13 +18,18 @@
 .. _`Installing nRF Util`: https://docs.nordicsemi.com/bundle/nrfutil/page/guides/installing.html
 .. _`Connectivity Bridge`: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/applications/connectivity_bridge/README.html
 .. _`Thingy:91 X Recovery`: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/app_dev/device_guides/thingy91x/thingy91x_recover_to_factory_firmware.html
+.. _`%XMIPIRFFECTRL`: https://docs.nordicsemi.com/bundle/ref_at_commands_dect/page/REF/at_commands/sip_pin_configuration/xmipirffectrl.html
+.. _`%XMIPIRFFEDEV`: https://docs.nordicsemi.com/bundle/ref_at_commands_dect/page/REF/at_commands/sip_pin_configuration/xmipirffedev.html
+.. _`%COEXCONFIG`: https://docs.nordicsemi.com/bundle/ref_at_commands_dect/page/REF/at_commands/dect/coexconfig.html
+
 
 .. ### github.com
 
 .. _`zcbor`: https://github.com/NordicSemiconductor/zcbor
 .. _`NCS Example Application`: https://github.com/nrfconnect/ncs-example-application
 .. _`sdk-nrf PR #19024`: https://github.com/nrfconnect/sdk-nrf/pull/19024
 .. _`github_release`: https://github.com/hello-nrfcloud/firmware/releases
+.. _`Thingy:91 X nRF9151 board configuration`: https://github.com/nrfconnect/sdk-nrf/blob/6f02c434bada82fec5e26418d5cd1e6c091a46d1/boards/nordic/thingy91x/Kconfig.defconfig.nrf9151#L83
 
 
 .. ### other
@@ -34,6 +40,8 @@
 
 .. _`Interactive BOM PCA20065 1.0.0.`: https://htmlpreview.github.io/?https://github.com/hello-nrfcloud/firmware/blob/main/docs/pca20065_1_0_0.html
 
+.. _`Ignion Antenna Technology Powering The-Nordic-Thingy 91 X`: https://ignion.io/files/AN_Ignion-antenna-technology-powering-the-nordic-thingy91x
+
 .. _`nRF5340 application firmware`: https://github.com/hello-nrfcloud/firmware/releases/download/v2.0.1/connectivity-bridge-v2.0.1-thingy91x-nrf53-app.hex
 .. _`nRF5340 network firmware`: https://github.com/hello-nrfcloud/firmware/releases/download/v2.0.1/connectivity-bridge-v2.0.1-thingy91x-nrf53-net.hex
 .. _`nRF9151 firmware`: https://github.com/hello-nrfcloud/firmware/releases/download/v2.0.1/hello.nrfcloud.com-v2.0.1+debug-thingy91x-nrf91.hex