Google Nest Thermostat Driver for Crestron Home

Visit console.nest.google.com/device-access and accept the Sandbox terms. Requires a personal @gmail.com account; Google Workspace accounts are not supported. The $5 fee is charged once per Google account and grants lifetime API access.

From the Device Access Console click Create Project. Give the project a name (e.g. Crestron Home). When prompted for an OAuth Client ID, skip for now — you'll create it in step 6 and link it here. Leave Enable Events set to Disabled for now — you'll turn it on in step 10 once you have a Pub/Sub topic to point it at. On the project page, copy the Project ID (a UUID) into a notepad — you'll need it in several later steps and again in Crestron Home in step 11.

Open console.cloud.google.com/projectcreate and create a new project (any name; e.g. Zentura Nest). Copy the Project ID Google assigns — this is your Google Cloud Project ID, distinct from the Device Access Project ID you copied in step 2. If you already have a personal Cloud project you'd like to reuse, you can pick that instead.

In your Google Cloud project, open APIs & Services → Library and enable BOTH of the following (search by name, then click Enable on each):

• Smart Device Management API — lets the driver read and control your thermostats.
• Cloud Pub/Sub API — lets the driver receive real-time mode / setpoint / humidity updates within ~1 second of a change.

Open APIs & Services → OAuth consent screen.

• User type: External (the only option for personal Gmail accounts).
• App name: any (e.g. Crestron Home Nest); User support email and Developer contact: your own email.
• Add the scopes: https://www.googleapis.com/auth/sdm.service AND https://www.googleapis.com/auth/pubsub
• Publishing status → In production. This is critical — if you leave it as Testing, Google expires the refresh token after 7 days and the driver stops working. Personal-use apps with only SDM + Pub/Sub scopes are not subject to Google's brand-review process.

In APIs & Services → Credentials, click Create Credentials → OAuth client ID.

• Application type: Web application
• Authorized redirect URIs: add exactly https://zenturahome.com/oauth/nest/callback.html

Click Create. Copy the Client ID and Client Secret (treat the secret like a password).

Now return to the Device Access Console, open your project, and paste the new Client ID into the OAuth Client ID field on the project page. (If you skipped this earlier in step 2, this is where you wire it up.)

Open zenturahome.com/oauth/nest/callback.html in a new tab. Paste your SDM Project ID (step 2) and OAuth Client ID (step 6), then click Authorize with Google. Sign in with the Google account that owns your Nest devices, tick the box next to each thermostat Crestron Home should control, then click Next → Allow. The page always requests both the sdm.service and pubsub scopes so you can enable real-time updates later just by setting GCP Project ID in the driver. Google redirects you back to the same callback page.

On the callback page, a single-use Authorization Code appears. Click Copy within 5 minutes — codes expire quickly. If you see an error banner instead, return to step 7 and try again.

⚠️ Verify the consent screen showed BOTH scopes during sign-in: "See and/or control the devices that you selected" AND "View and manage Pub/Sub topics and subscriptions". If you only saw the SDM permission, the pubsub scope is not registered on your OAuth Consent Screen (step 5) — add it there and repeat steps 7–8, otherwise the driver will hit 403 insufficient scope errors on every Pub/Sub pull.

The Zentura Nest driver auto-creates the Pub/Sub topic and subscription on first start — you just need to give it your Google Cloud Project ID.

Your Google Cloud Project ID is the alphanumeric identifier shown in the top banner of the Cloud Console or in the project selector (e.g. my-home-nest-123456) — not the alphanumeric identifier shown in the top banner of the Cloud Console or in the project selector (e.g. my-home-nest-123456) — not the Device Access Project ID from step 2. Copy it; you'll paste it into the driver's GCP Project ID field in step 11.

The driver will automatically create:

• Topic projects/{your-gcp-project-id}/topics/nest-events
• Pull subscription projects/{your-gcp-project-id}/subscriptions/nest-events-sub

You only need to register the topic name in the Device Access Console (next step).

Prefer to create them yourself? You still can — open Pub/Sub → Topics → Create Topic with the names above (leave "Add a default subscription" checked), then paste the subscription path into the driver's optional Pub/Sub Subscription Path field instead of GCP Project ID.

Return to the Device Access Console and open your project. Set:

• Enable Events: Enabled
• Pub/Sub topic: paste the topic name from step 9, e.g. projects/{your-gcp-project-id}/topics/nest-events

Click Add & Validate (or Save). The console verifies that Google's SDM publisher group can publish to your topic and, if the topic doesn't yet grant that group access, attempts to grant it automatically.

If validation fails with a permissions error: open the topic in Cloud Console → Pub/Sub → Topics, click the topic, go to the Permissions tab → Grant Access, paste sdm-publisher@googlegroups.com as the principal (this is a Google-managed group, not a service account), choose role Pub/Sub Publisher, click Save, then retry Add & Validate.

If you skip this step the driver still works in polling-only mode — trait changes appear within one polling interval (default 60s) instead of within 1s.

In the Crestron Home setup app go to Settings → Drivers → Add Driver, choose Nest Thermostat (by Zentura Home). The pair wizard begins with four read-only licensing pages (License info, License Status, Processor MAC, then click Next on each) and then presents these connection fields:

• Device Access Project ID — step 2
• OAuth Client ID — step 6
• OAuth Client Secret — step 6
• Authorization Code — step 8

Tap Apply. The driver exchanges the code for a long-lived refresh token, discovers your thermostats, and adds a native Climate tile for each one. The Authorization Code field clears itself afterwards.

Enable real-time updates (recommended): after pairing, open the driver settings tab and set GCP Project ID (from step 9). The driver auto-provisions nest-events + nest-events-sub in your GCP project on the next reload and pushes thermostat changes within ~1 second. Leave blank to run in polling-only mode.

Verify it's working: enable Enable Debug Log on the driver and watch for a periodic PubSub: heartbeat state=RUNNING pulls=N events=N … line (every 5 minutes). state=DISABLED means you intentionally left GCP Project ID blank (polling-only). state=SCOPE_MISSING means the OAuth token is missing the pubsub scope — re-pair via the callback page.

From this point forward the driver runs unattended; if you ever revoke access in Google or change OAuth credentials, repeat steps 7 → 11.