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Over-the-Air (OTA) Updates ​

Client firmware is updated over-the-air without physical access. The OTA URL is provisioned to the device by the Controller during provisioning and is not configured directly on the client.

The config partition (WiFi credentials, MQTT settings, CA certificate) is never touched by OTA. Configuration survives all firmware updates.

No filesystem OTA on ESP8266

The OTA manifest may include a littlefs field, but ESP8266 Client firmware intentionally ignores it. Only the application (sketch) slot is updated via OTA. Filesystem updates are not supported over the air on ESP8266 — this is by design. Future ESP32-based client variants may handle filesystem OTA differently.

Update Schedule ​

The client checks for a firmware update:

  • 30 seconds after boot
  • Every 24 hours thereafter

How It Works ​

The client calls GET {otaUrl}?current_version={VERSION} using the URL provisioned in its configuration. The server returns the next available version; see the OTA Update Flow for server-side behavior, response codes, and version sequencing details.

The client reads only two fields from the response:

FieldRequiredDescription
versionYesVersion string of the available firmware
urlYesDirect URL to the firmware binary

If version matches the running firmware or url is empty, no update is performed.

TLS Certificate Handling ​

If a CA certificate was provisioned to the device, that certificate is used to validate the OTA server. If no certificate is present, TLS validation is skipped.

Update Process ​

When a newer version is found:

  1. The device publishes its current and available versions to its MQTT update state topic.
  2. ESPhttpUpdate downloads and flashes the firmware binary to the application OTA slot.
  3. On success, the device reboots automatically into the new firmware.
  4. On failure, the error count is incremented.

Triggering an Immediate Check ​

An OTA check can be triggered on demand by publishing do-update to the device's MQTT update command topic.

Home Assistant Integration ​

On each MQTT connection, the client publishes a Home Assistant MQTT discovery payload for an update entity. This exposes the installed and available firmware versions in Home Assistant and allows updates to be triggered from the HA UI.