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Thingy:91 X: Hello nRF Cloud: Firmware Architecture

This is the firmware that is programmed on the nRF9151 of the Thingy:91 X in factory. It's goal is to showcase the device's functionality and to spur interest into trying out the device. nRF Cloud CoAP is used as the cloud solution.

The architecture is based on ZBUS. Rather than having a main.c file to tie the application together, 12 modules communicate via ZBUS channels. This enables us to keep the modules relatively small and reusable by separation of concerns.

Cloud to device communication is done with runtime settings. Device to cloud communication uses CBOR encoded LwM2M objects. Each module encodes its own data using ZCBOR. The format is specified in CDDL files and encoding functions are automatically generated. The encoded data is sent to the payload channel, which takes care of forwarding it to cloud.

Trigger module

  • beating heart of the application: send triggers to control other modules
  • handles the different states the application is in

Transport module

  • manage connection to nRF Cloud CoAP, notify about cloud connection status
  • forward payloads to cloud

Network module

FOTA module

  • FOTA handling using nRF Cloud CoAP, notifies about FOTA status

App module

  • manages runtime settings
  • wrap date_time library, notify when time is available

Memfault module

  • upload runtime stats and coredumps to Memfault for easier debugging

Battery module

  • wrap fuel_gauge subsystem and publish battery status as payload

Button module

  • notify other modules about button presses
  • publish button message as payload

Environment module

  • wrap bm68x_iaq driver and publish air quality, temperature, humidity data as payload

LED module

  • monitor various events and display sophisticated LED patterns

Location module

  • wrap location library, gather and send location data
  • note: data is sent directly using the library rather than being repackaged in the module

Shell module

  • test related shell functions
  • turn off UART for power saving when leaving polling mode

Overview of modules reading/writing ZBUS channels

Note: the ERROR channel and channels only used internally in modules were omitted.

CHANNEL battery environment location network trigger app button fota led memfault shell transport
CLOUD r r r r r w
CONFIG r r w
LOCATION w r r
BUTTON r w w
FOTA r w
TRIGGER r r r r w
TRIGGER_MODE w r
NETWORK r r w r r
PAYLOAD w w w w r
TIME r r r w r