OTA

OTA package notification

To indicate it's current software/firmware version, the device publishes Firmware and Device Info message. The server then evaluates whether an update is necessary and, if so, publishes a message on the downlink/ota/json topic:

{
    "url": "https://blynk.cloud/static/file.tar.gz?token=jOuWQWu_bOANvBPzz4LllPDMk7sYAAQMa",
    "size": 20082,
    "type": "TMPLabcd1234",
    "ver": "0.5.0",
    "build": "Mar 05 2024 18:29:27"
}

This message can also be delivered at any time during the device operation, i.e. when Blynk.Air shipment is created or when the Preferred Time condition is met.

The device must verify whether the update is feasible and then download the OTA package using HTTP/HTTPS. Additionally, the HTTP Response Headers provide valuable information:

• x-sha256 - Base64-encoded SHA256 digest of the OTA package

• x-md5- HEX-encoded MD5 digest of the OTA package

• x-fw-type - The firmware type

• x-fw-ver - The firmware version string

• x-fw-build - The firmware build time

type, ver, build fields are available only if Blynk.Cloud can extract this information (stored as a binary info tag) from the uploaded OTA package file.

After installing the update, the device re-connects to Blynk.Cloud and publishes the updated Firmware and Device Info message.

mosquitto_sub -h blynk.cloud -p 8883 -u device -P '{DEVICE_TOKEN}' -t 'downlink/ota/json'