Config over BLE GATT

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mongoose-os-libs/bt-service-config

Overview

This library provides a way to examine and change configuration over Generic Attribute Service (GATT) Bluetooth Low-Energy (BLE) service.

The service is designed to be usable with any generic BLE mobile app that supports GATT, e.g. BLE Scanner (Android, iOS).

Note: Default BT configuration is permissive. See https://github.com/mongoose-os-libs/bt-common#security for a better idea.

Attribute description

The service UUID is 5f6d4f53-5f43-4647-5f53-56435f49445f, which is a representation of a 16-byte string _mOS_CFG_SVC_ID_.

The service defines 3 characteristics (attributes):

• 306d4f53-5f43-4647-5f6b-65795f5f5f30 (0mOS_CFG_key___0) - a write-only attribute that selects the configuration key to be operated on. The key is a string of components separated by period, e.g. wifi.sta.ssid or debug.level.
• 316d4f53-5f43-4647-5f76-616c75655f31 (1mOS_CFG_value_1) - a read-write attribute that returns value of the selected key when read or accepts the value to be set. Note that value is not applied immediately after writing. Instead, consecutive writes to this key are appended to form the value to be set (this is due to small value of the default MTU and differences in how clients handle writes exceeding the MTU). For easy manual entry, attribute values are returned as strings and expected as strings as well. So, to enter value of 123, one should submit string 123, not hex value 0x7b. Boolean values should be entered as strings true or false.
• 326d4f53-5f43-4647-5f73-6176655f5f32 (2mOS_CFG_save__2) - a write-only attribute that applies value submitted to the value attribute to the key selected via the key attribute. The value written to this key can be one of:
  • 0 - just set the value, change will not be persisted
  • 1 - set and save the config
  • 2 - set, save and reboot

Example - configuring WiFi

Here is an example of the configuration provisioning a device - configuring WiFi station settings (we'll use key, value and save to abbreviate long UUIDs):

• Set the SSID, do not save the config yet
  • wifi.sta.ssid -> key
  • MyNetwork -> value
  • 0 -> save
• Set the password, do not save the config yet
  • wifi.sta.pass -> key
  • MyPassword -> value
  • 0 -> save
• Enable the station, save and reboot
  • wifi.sta.enable -> key
  • true -> value
  • 2 -> save

Once device is confirmed to have successfully connected to WiFi, BT config can be disabled:

• bt.config_enable -> key # Or bt.enable to disable Bluetooth entirely.
• false -> value
• 2 -> save # Save and reboot with BT configuration disabled.

See Also

See rpc-gatts library, which provides a GATT service that acts as an RPC channel. It accepts incoming RPC frames and can send them as well - or rather, makes them available for collection.

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