BLE

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mongoose-os-libs/bt-common mgos_bt.h    

Currently contains only GATT server implmenetation for ESP32.

Configuration section

bt-common library adds a bt configuration section with the following settings:

"bt": {
  "enable": true,             // Enabled by default. Disabled on first reboot with WiFi on
  "dev_name": "",             // Device name. If empty, value equals to device.id
  "adv_enable": true,         // Advertise our Bluetooth services
  "keep_enabled": true,       // Keep enabled after successful boot with WiFi on
  "scan_rsp_data_hex": "",    // Custom scan response data, as hex string (e.g. `48656c6c6f` for `Hello`)
  "allow_pairing": true,      // Allow pairingbonding with other devices
  "max_paired_devices": 10,   // Allow pairing with up to this many devices; -1 - no limit
  "gatts": {
    "min_sec_level": 0,       // Minimum security level for all attributes of all services.
                              // 0 - no auth required, 1 - encryption reqd, 2 - encryption + MITM reqd
    "require_pairing": false  // Require taht device is paired before accessing services
  }
}

Security

Default settings allow for unrestricted access: anyone can pair with a device and access the services. A better idea is to set bt.gatts.require_pairing to true, bt.allow_pairing to false and only enable it for a limited time via mgos_bt_gap_set_pairing_enable when user performs some action, e.g. presses a button. Raising bt.gatts.min_sec_level to at least 1 is also advisable. Note: At present, level 2 (MITM protection) is not usable as it requires device to have at least output capability during pairing, and there's no API for displaying the pairing code yet.


(sizeof

#define MGOS_BT_ADDR_STR_LEN (sizeof(struct mgos_bt_addr) * 3 + 2 /* type */)
#define MGOS_BT_UUID_STR_LEN (sizeof(struct mgos_bt_uuid) * 3)
#define MGOS_BT_DEV_NAME_LEN 32

Each byte is transformed into 3 bytes: "XX:", and last byte into "XX\0"

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