rmptxf / nRF9160-google_iot_mqtt

This is an adaptation of Zephyr's Google Cloud IoT Core MQTT sample samples/net/cloud/google_iot_mqtt for the nRF9160-DK, using modem features to offload certificate storage, TLS and JWT calculation.

Google IOT MQTT Sample

Overview

Based on the Zephyr sample, and adapted for nRF9160, leveraging modem features.

This sample application demonstrates a "full stack" application. This currently is able to:

• Establish a TLS connection with the Google IOT Cloud servers
• Publish data to the Google IOT Cloud
• Send/Receive keep alive / pings from cloud server

Requirements

• Entropy source
• Google IOT Cloud account
• Google IOT Cloud credentials and required information
• Cellular connectivity

Building and Running

This application has been built and tested on the Nordic nRF9160-DK. ECDSA keys are required to authenticate to the Google IOT Cloud. The application includes a key creation script.

Run bash create_keys.sh <device-id> in the samples/net/cloud/google_iot_mqtt/src/private_info/ directory.

Clone the cred utility for programming credentials to the modem.

Program the client private key:

python3 cred.py \
  --client_private_key <device-id>-ec_private.pem \
  --sec_tag 10

Download cloud-side certs (primary and backup)

• primary
• backup

Convert cloud-side certs from binary to text

openssl x509 -inform DER -outform PEM -in gtsltsr.crt -out gtsltsr.pem
openssl x509 -inform DER -outform PEM -in GSR4.crt -out GSR4.pem

NOTE: It is not necessary to change the certs to to "C-Style\n" formatting.

Program the cloud-side certs:

python3 cred.py \
  --CA_cert gtsltsr.pem \
  --sec_tag 202
python3 cred.py \
  --CA_cert GSR4.pem \
  --sec_tag 203

Assign keys on Google Cloud IoT Core

• Device Details -> Assign Public Key
• Input Method: Enter Manually
• Public key format: ES256
• Public key value: content of <device-id>-ec_public.pem

Users will also be required to configure the following Kconfig options based on their Google Cloud IOT project. The following values come from the Google Cloud Platform itself:

• PROJECT_ID: When you select your project at the top of the UI, it should have a "name", and there should be an ID field as well. This seems to be two words and a number, separated by hyphens.
• REGION: The Region shows in the list of registries for your registry. And example is "us-central1".
• REGISTRY_ID: Each registry has an id. This is a string given when creating the registry.
• DEVICE_ID: A name given for each device. When viewing the table of devices, this will be shown.

From these values, the config values can be set using the following template:

CLOUD_CLIENT_ID="projects/PROJECT_ID/locations/REGION/registries/REGISTRY_ID/devices/DEVICE_ID"
CLOUD_AUDIENCE="PROJECT_ID"
CLOUD_SUBSCRIBE_CONFIG="/devices/DEVICE_ID/config"
CLOUD_PUBLISH_TOPIC="/devices/DEVICE_ID/state"

See Google Cloud MQTT Documentation.