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02-esp32_bme280_ciotc_arduino.ino
README.md
ciotc_config.h
esp32-mqtt.h

README.md

ESP32 BME280 Google Cloud IoT Core (Arduino)

ESP32 Arduino code that sends BME280 sensor data to Google Cloud IoT Core

Dependencies

You'll need to install from the Arduino IDE those dependencies:

  • BME280:
    • Adafruit BME280 Library by Adafruit (more info)
    • Adafruit Unified Sensor by Adafruit (more info)
  • Cloud IoT Core:
    • Google Cloud IoT Core JWT by Vladimir Korukov (more info)
    • rBase64 by Abhijit Bose (more info)
  • MQTT bridge:

Setup Cloud IoT Core

Install the gcloud command-line tool, and run the following:

export PROJECT_ID="<project-id>"
export PUBSUB_TOPIC="iotcore-topic"
export PUBSUB_SUBSCRIPTION="iotcore-subscription"
export REGISTRY_NAME="iotcore-registry"
export DEVICE_NAME="esp32"

# Choose your region: https://cloud.google.com/compute/docs/regions-zones/
# Valid cloud regions are {asia-east1,europe-west1,us-central1}
export REGION_NAME="us-central1"

# Authorize gcloud to access the Cloud Platform with Google user credentials
gcloud auth login

# Create a new project
gcloud projects create $PROJECT_ID

# Set default project
gcloud config set project $PROJECT_ID

# Enable Cloud Pub/Sub
gcloud services enable pubsub.googleapis.com

# Enable billing (required for Cloud IoT. You can also use the `gcloud beta billing` CLI)
open https://console.cloud.google.com/iot/api?project=$PROJECT_ID

# Enable Cloud IoT
gcloud services enable cloudiot.googleapis.com

# Give permission to Cloud IoT Core to publish messages on Cloud Pub/Sub
gcloud projects add-iam-policy-binding $PROJECT_ID --member=serviceAccount:cloud-iot@system.gserviceaccount.com --role=roles/pubsub.publisher

# Create Cloud Pub/Sub topic for event notifications
gcloud pubsub topics create $PUBSUB_TOPIC

# Create Cloud Pub/Sub subscription
gcloud pubsub subscriptions create $PUBSUB_SUBSCRIPTION --topic $PUBSUB_TOPIC

# Create Cloud IoT registry specifying Cloud Pub/Sub topic name
gcloud iot registries create $REGISTRY_NAME \
  --region=$REGION_NAME \
  --event-notification-config=topic=$PUBSUB_TOPIC \
  --enable-mqtt-config --enable-http-config

# Generate an Elliptic Curve (EC) ES256 private / public key pair
openssl ecparam -genkey -name prime256v1 -noout -out ec_private.pem
openssl ec -in ec_private.pem -pubout -out ec_public.pem

# Create a new Cloud IoT device
gcloud iot devices create $DEVICE_NAME --region=$REGION_NAME --registry=$REGISTRY_NAME --public-key="path=./ec_public.pem,type=es256"

ciotc_config.h

  • Update the ciotc_config.h files with your Wi-Fi and Cloud IoT details.
  • Set the private_key_str constant using data from the following command:
$ openssl ec -in ec_private.pem -noout -text

Wiring

The BME280 sensor should be connected to the ESP32 over I2C.
If the BME280 I2C address is not 0x76, you'll need to modify the BME280_ADDRESS constant.
Depending on your board, you'll also need to modify the SDA and SCL pin names in the Wire.begin(SDA, SCL); call.

Wemos Lolin D32 Pro

  • SDA: 21
  • SCL: 22

Wemos Lolin32 Lite

  • SDA: 15
  • SCL: 2

DOIT Esp32 DevKit v1

  • SDA: 21
  • SCL: 22

Verify that it works

After flashing the ESP32, you can verify that it sends data to Google Cloud, by pulling Cloud/PubSub messages from the subscription:

$ gcloud pubsub subscriptions pull --auto-ack $PUBSUB_SUBSCRIPTION --limit=1
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