This is a sample project that works both on local etherned (with the external
CoAP interface for devices) or via a cellular IoT modem (with the CIoT CoAP
interface). The project uses PlatformIO but should build equally well for any
supported device in Zephyr. The file zephyr/prj.conf contains the required
configure flags for the build.
Run and deploy to the device with pio run --target=upload. Use
pio device monitor --raw to view the log.
The ethernet-connected devices uses DTLS with client certificates to authenticate and verify the client connection.
The CIoT devices may elect to use unencrypted UDP for the CoAP service. This makes deployments a bit easier and less resource hungry since they won't need a client certificate, DNS or DHCP support and everything can be configured via Span.
The project is developed on a STM32 F429zi board but it should be relatively easy to modify it to run on any board with ethernet/wifi connectivity or a cellular IoT modem (like the nRF91 from Nordic Semiconductor) as long as it has a rudimentary socket support.