Chapter 4. Software framework
4.1.26 How can I modify the transmit power for ESP32 Bluetooth®？
The Bluetooth transmit power can be congured via function esp_ble_tx_power_set();. Please refer to
esp_bt.h.
4.1.27 How is the networking compatibility of ESP32 Bluetooth® LE? Is it open-
sourced?
• ESP32 Bluetooth networking, BluFi networking for short, has a good compatibility as Bluetooth LE and is
compatible with many mainstream mobile phones such as Apple, HUAWEI, Mi, OPPO, MEIZU, OnePlus,
ZTE and etc.
• Currently, the BluFi protocol and phone application code is open-sourced.
4.1.28 When I execute example bt_spp_acceptor on ESP32, the IOS device cannot nd
the ESP32 device during scanning. What could be the reasons?
• Apple has opened Bluetooth® as: A2DP, HID’s keyboard, avrcp, SPP (need MFI), high-level Bluetooth LE
and ANCS for Bluetooth LE.
• If the IOS device expects to communicate with the end device via SPP, the SPP of the end device should have
the MFI certicate. However, ESP32 SPP does not have the MFI certicate, thus the IOS device cannot nd
ESP32 during scanning.
4.1.29 How is the security of ESP32 Bluetooth® LE/Bluetooth® Secure Simple Pairing
(SSP) compared to legacy pairing?
• Secure Simple Pairing (SSP) is more secure than legacy pairing.
• The legacy pairing uses symmetric encryption algorithm, while Secure Simple Pairing (SSP) uses asymmetric
cryptography algorithm.
4.1.30 How can I conrm the MTU size of ESP32 Bluetooth® LE?
• By default, the MTU size of ESP32 Bluetooth LE is 23 bytes, and can be congured to reach 517 bytes.
• For phones, the MTU size can be self-dened. Then, the end device with a smaller MTU will be chosen for
communication.
4.1.31 When advertising in ESP32 Bluetooth® LE mode, an error occurred as “W
(17370) BT_BTM: data exceed max adv packet length”. How can I resolve such
issue?
• This is because the advertising data has exceeded the maximum advertising packet length.
• The maximum data length of advertising payload is 31 bytes. If the actual data length exceeds 31 bytes, the
Bluetooth protocol stack will drop some data and generate an error warning.
• If the data to be advertised exceeds the maximum packet length, the extra data can be put in the scan response
packet.
Espressif Systems 48
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