This example demonstrates how you can create an application that updates its firmware Over The Air (OTA) using the MQTT protocol. This application uses OTA Firmware Upgrade via MQTT and follows the recommended versioning principles.

Based on ENABLE_OTA_ADVANCED the firmware data can be either without any encoding or be signed and encrypted.


There are two tools that facilitate the packiging and deployment of a new firmware.

For more information read Firmware packaging in the documentation of the OTA Firmware Upgrade via MQTT component.


Depending on ENABLE_SSL a standard SSL/TLS can be enabled. This way

  1. The communication between the application and the server will be encrypted using standard SSL.

  2. To prove that the server is the correct one: The MQTT clients should pin the public key fingerprint on the server. OR have a list of public key fingerprints that are allowed.

  3. Depending on ENABLE_CLIENT_CERTIFICATE the application can send a client certificate that is signed by the server.



Default: “test”

This variable contains the unique application name.


Default: not set

Contains the application major and minor versions separated by comma. Example “4.2”. If not set will use the current major and minor version from Sming.


Default: not set

Contains the application patch version as integer. For stable versions you can use 0 until 255. For unstable versions the current timestamp can be used as a patch version.


Default: 1 (enabled)

If set to 1 the OTA upgrade mechanism and application will use a varint encoding for the patch version. Thus allowing unlimited number of patch versions. Useful for enumerating unstable/nightly releases. A bit more difficult to read and write but allows for unlimited versions.

If set to 0 the OTA upgrade mechanism and application will use one byte for the patch version which will limit it to 256 possible patch versions. Useful for enumarating stable releases. Easier to write and read but limited to 256 versions only.


Default: 0 (disabled)

If set to 1 the library will work with OtaUpgradeStream which supports signature and encryption of the firmware data itself. See Over-the-Air Firmware Upgrade for details.


Default: unset (disable)

If set to 1 (highly recommended), OTA upgrade files will be trasnferred securely over TLS/SSL.


Default: 0 (disabled)

Used in combination with ENABLE_SSL. Set to 1 if the remote server requires the application to authenticate via client certficate.


Default: depends on ENABLE_SSL and ENABLE_CLIENT_CERTIFICATE values

Url containing the location of the firmware update MQTT server.


Environment Variables