getting started: NCS: add samples guide

Show how to compile and run the Hello sample on the nRF9160dk, with mention that
this approach may be used with other boards.

Signed-off-by: Mike Szczys <mike@golioth.io>

docs/getting-started/3-device-examples/2-compile-example-code/2-zephyr-ncs/02-zephyr-samples.md

@@ -0,0 +1,166 @@
+---
+title: Flashing with samples
+---
+
+import Tabs from '@theme/Tabs';
+import TabItem from '@theme/TabItem';
+
+The Golioth Firmware SDK includes [a number of Zephyr example
+applications](https://github.com/golioth/golioth-firmware-sdk/tree/main/examples/zephyr)
+to demonstrate each of our services. In this section we'll build the `hello`
+sample which connects to Golioth and sends "Hello Golioth! n" messages to our
+remote logging service.
+
+This same configure→build→flash process may be applied to all of the
+other Golioth Zephyr example apps.
+
+## Hardware choices
+
+These examples can be built for any hardware supported by Zephyr. However, each
+will need some device-specific configuration. Golioth maintains an NCS
+configuration for the [Nordic nRF9160
+DK](https://www.nordicsemi.com/Products/Development-hardware/nrf9160-dk)
+cellular development board as part of our continuous integration (CI).
+
+This page includes build commands for this board. You may model configuration
+for your own target hardware on the configuration and overlay files found in the
+`boards` directory of each example application.
+
+## Build the `hello` code example
+
+Navigate to the workspace installed in the previous section to ensure your
+virtual environment is activated before moving to the Golioth Firmware SDK
+folder:
+
+<Tabs
+groupId="os"
+defaultValue="linux"
+values={[
+{label: 'Linux', value: 'linux'},
+{label: 'MacOS', value: 'macos'},
+{label: 'Windows', value: 'windows'},
+]}>
+
+<TabItem value="linux">
+
+```console
+cd ~/golioth-ncs-workspace
+source .venv/bin/activate
+cd modules/lib/golioth-firmware-sdk
+```
+
+</TabItem>
+
+<TabItem value="macos">
+
+```console
+cd ~/golioth-ncs-workspace
+source .venv/bin/activate
+cd modules/lib/golioth-firmware-sdk
+```
+
+</TabItem>
+
+<TabItem value="windows">
+
+```console
+cd c:\golioth-ncs-workspace
+.venv\Scripts\activate.bat
+cd modules\lib\golioth-firmware-sdk
+```
+
+</TabItem>
+</Tabs>
+
+### Use hardcoded credentials
+
+Edit the `examples/zephyr/hello/prj.conf` file. Add the following lines,
+replacing the placeholder text with your credentials:
+
+```config title="examples/zephyr/hello/prj.conf"
+CONFIG_GOLIOTH_SAMPLE_PSK_ID="my-psk-id"
+CONFIG_GOLIOTH_SAMPLE_PSK="my-psk"
+```
+
+<details>
+  <summary>How to find credentials</summary>
+
+You must set Golioth credentials for the example to authenticate with Golioth.
+For these granular examples we will use hardcoded credentials.
+
+![Golioth Console device
+credentials](../../../assets/gettingstarted-console-deviceview-credentialspanel.png)
+
+* Golioth credentials are available in the `Credentials` tab for your device
+    * Open the Golioth Console
+    * Select `Devices` on  the left sidebar and choose your device from the
+      resulting list
+    * Click on the `Credentials` tab and copy your `PSK-ID` and `PSK`
+</details>
+
+
+:::info Not recommended for production
+
+We use hardcoded credentials for this example because they are the easiest to
+set up quickly. However, in production you should plan to use certificate
+authentication and store credentials outside of the firmware binary itself.
+
+:::
+
+### Build the firmware and flashing the device
+
+```console
+west build -b nrf9160dk_nrf9160_ns examples/zephyr/hello
+west flash
+```
+
+### Example Output
+
+View output from your device by opening a serial terminal (115200 8N1). The
+result should be a successful connection to Golioth.
+
+```console
+*** Booting nRF Connect SDK v2.5.0 ***
+[00:00:00.459,167] <dbg> hello_zephyr: main: start hello sample
+[00:00:00.459,197] <inf> golioth_samples: Waiting to obtain IP address
+[00:00:01.502,960] <inf> lte_monitor: Network: Searching
+[00:00:01.570,312] <inf> lte_monitor: RRC: Connected
+[00:00:04.557,617] <inf> lte_monitor: Network: Registered (roaming)
+[00:00:04.558,593] <inf> golioth_mbox: Mbox created, bufsize: 1144, num_items: 10, item_size: 104
+[00:00:04.866,027] <inf> golioth_coap_client: Start CoAP session with host: coaps://coap.golioth.io
+[00:00:04.866,058] <inf> golioth_coap_client: Session PSK-ID: devboard-one-id@ttgo-demo
+[00:00:04.867,492] <inf> golioth_coap_client: Entering CoAP I/O loop
+[00:00:07.450,653] <inf> golioth_coap_client: Golioth CoAP client connected
+[00:00:07.450,866] <inf> hello_zephyr: Sending hello! 0
+[00:00:07.450,897] <inf> hello_zephyr: Golioth client connected
+[00:00:12.450,927] <inf> hello_zephyr: Sending hello! 1
+[00:00:13.819,091] <inf> lte_monitor: RRC: Idle
+[00:00:13.955,017] <inf> lte_monitor: RRC: Connected
+[00:00:17.451,049] <inf> hello_zephyr: Sending hello! 2
+[00:00:19.182,403] <inf> lte_monitor: RRC: Idle
+[00:00:19.315,307] <inf> lte_monitor: RRC: Connected
+[00:00:22.451,171] <inf> hello_zephyr: Sending hello! 3
+```
+
+You can confirm this connection by viewing the Status section of the summary
+page for your device in the Golioth web console. You will also see the hello
+messages listed in the Log tab:
+
+![Golioth web console log messages](../assets/golioth-console-hello-log-messages.png)
+
+## Additional Golioth Example Code
+
+Congratulations on running the Hello app! The same process may be used to run
+[other Golioth example
+applications](https://github.com/golioth/golioth-firmware-sdk/tree/main/examples/zephyr).
+Be sure to reference the README file for each for detailed configuration and
+usage information.
+
+* **certificate_provisioning:** Use certificate authentication
+* **firmware_update:** Use Golioth over-the-air (OTA) firmware update
+* **hello:** Connect and send hello logging messages
+* **lightdb:** Set, get, and observe stateful data between device and cloud
+* **lightdb_stream:** Send time-series data from device to cloud
+* **logging:** Demonstrate logging messages of each different log level
+* **rpc:** Issue a remote procedure call (rpc) and received data back from device
+* **settings:** Demonstrate fleet-wide device settings service