Fix ATT descriptor discovery handle range and response parsing

[thematrix999]

Problem

ATTClass::discoverDescriptors() currently has two issues.

First, the descriptor discovery range ends at the value handle of the next characteristic. This includes the next characteristic declaration and value in the descriptor range of the current characteristic.

Second, byte 1 of an ATT Find Information Response is a Format field, not a length multiplier. Format 0x01 contains 4-byte entries (2-byte handle + 2-byte UUID), while format 0x02 contains 18-byte entries (2-byte handle + 16-byte UUID).

The current implementation calculates an 8-byte entry length for format 0x02 and always parses UUIDs as 16-bit.

This can cause discoverAttributes() to fail or time out when a service contains multiple 128-bit characteristics.

Related to #277.

Changes

• End descriptor discovery immediately before the next characteristic declaration.
• Parse both ATT Find Information Response formats correctly.
• Reject unsupported response format values.

Hardware test

Tested using two Arduino Nano 33 BLE boards, one configured as central and the other as peripheral, with ArduinoBLE 1.5.0.

The peripheral exposes a 128-bit service containing multiple 128-bit characteristics, including a notify characteristic with a CCCD.

Before the change:

• The BLE connection succeeds.
• discoverAttributes() does not complete.
• The central reports HCI receive-buffer overflows.
• The connection eventually terminates.

After the change:

• Attribute discovery completes successfully.
• The expected characteristics are found.
• CCCD subscription succeeds.
• The central receives 16-byte notifications correctly.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 15.24%. Comparing base (281377b) to head (0aeeb27).

Files with missing lines	Patch %	Lines
src/utility/ATT.cpp	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #435      +/-   ##
==========================================
- Coverage   15.25%   15.24%   -0.02%     
==========================================
  Files          29       29              
  Lines        3684     3687       +3     
==========================================
  Hits          562      562              
- Misses       3122     3125       +3     

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[github-actions]

Memory usage change @ 0aeeb27

Board	flash	%	RAM for global variables	%
arduino:esp32:nano_nora	🔺 +36 - +36	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_giga:giga	🔺 0 - +64	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nano:nano33ble	🔺 0 - +64	0.0 - +0.01	0 - 0	0.0 - 0.0
arduino:mbed_nano:nanorp2040connect	🔺 +26 - +26	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nicla:nicla_vision	🔺 0 - +64	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_opta:opta	🔺 0 - +64	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A
arduino:renesas_portenta:portenta_c33	🔺 +32 - +32	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:renesas_uno:unor4wifi	🔺 +32 - +32	+0.01 - +0.01	0 - 0	0.0 - 0.0
arduino:samd:mkrwifi1010	🔺 +24 - +24	+0.01 - +0.01	0 - 0	0.0 - 0.0
arduino:samd:nano_33_iot	🔺 +24 - +24	+0.01 - +0.01	0 - 0	0.0 - 0.0
arduino:zephyr:unoq	🔺 +116 - +128	+0.01 - +0.02	🔺 +36 - +36	+0.01 - +0.01
arduino:zephyr_main:giga	🔺 +120 - +124	+0.01 - +0.01	🔺 +36 - +36	+0.01 - +0.01
arduino:zephyr_main:nano33ble	🔺 +120 - +124	+0.02 - +0.02	🔺 +36 - +36	+0.03 - +0.03
arduino:zephyr_main:opta	🔺 +120 - +124	+0.01 - +0.01	🔺 +36 - +36	+0.01 - +0.01
arduino:zephyr_main:portentac33	🔺 +120 - +124	+0.01 - +0.01	🔺 +36 - +36	+0.03 - +0.03
arduino:zephyr_main:portentah7	🔺 +120 - +124	+0.01 - +0.01	🔺 +36 - +36	+0.01 - +0.01

Click for full report table

Board	examples/Central/LedControl flash	%	examples/Central/LedControl RAM for global variables	%	examples/Central/PeripheralExplorer flash	%	examples/Central/PeripheralExplorer RAM for global variables	%	examples/Central/Scan flash	%	examples/Central/Scan RAM for global variables	%	examples/Central/ScanCallback flash	%	examples/Central/ScanCallback RAM for global variables	%	examples/Central/SensorTagButton flash	%	examples/Central/SensorTagButton RAM for global variables	%	examples/Peripheral/Advertising/EnhancedAdvertising flash	%	examples/Peripheral/Advertising/EnhancedAdvertising RAM for global variables	%	examples/Peripheral/Advertising/RawDataAdvertising flash	%	examples/Peripheral/Advertising/RawDataAdvertising RAM for global variables	%	examples/Peripheral/BatteryMonitor flash	%	examples/Peripheral/BatteryMonitor RAM for global variables	%	examples/Peripheral/ButtonLED flash	%	examples/Peripheral/ButtonLED RAM for global variables	%	examples/Peripheral/CallbackLED flash	%	examples/Peripheral/CallbackLED RAM for global variables	%	examples/Peripheral/EncryptedBatteryMonitor flash	%	examples/Peripheral/EncryptedBatteryMonitor RAM for global variables	%	examples/Peripheral/LED flash	%	examples/Peripheral/LED RAM for global variables	%
arduino:esp32:nano_nora	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0	36	0.0	0	0.0
arduino:mbed_giga:giga	0	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	0	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed_nano:nano33ble	64	0.01	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	64	0.01	0	0.0	64	0.01	0	0.0	0	0.0	0	0.0	64	0.01	0	0.0	64	0.01	0	0.0	64	0.01	0	0.0	64	0.01	0	0.0	64	0.01	0	0.0
arduino:mbed_nano:nanorp2040connect	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0	26	0.0	0	0.0
arduino:mbed_nicla:nicla_vision	0	0.0	0	0.0	0	0.0	0	0.0	64	0.0	0	0.0	0	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	0	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0
arduino:mbed_opta:opta	0	0.0	0	0.0	0	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	0	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0	64	0.0	0	0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
arduino:renesas_portenta:portenta_c33	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0	32	0.0	0	0.0
arduino:renesas_uno:unor4wifi	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0	32	0.01	0	0.0
arduino:samd:mkrwifi1010	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0
arduino:samd:nano_33_iot	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0	24	0.01	0	0.0
arduino:zephyr:unoq	116	0.01	36	0.01	124	0.02	36	0.01	124	0.02	36	0.01	124	0.02	36	0.01	128	0.02	36	0.01	124	0.02	36	0.01	124	0.02	36	0.01	120	0.02	36	0.01	124	0.02	36	0.01	128	0.02	36	0.01	116	0.01	36	0.01	116	0.01	36	0.01
arduino:zephyr_main:giga	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01
arduino:zephyr_main:nano33ble	120	0.02	36	0.03	120	0.02	36	0.03	124	0.02	36	0.03	124	0.02	36	0.03	120	0.02	36	0.03	124	0.02	36	0.03	120	0.02	36	0.03	124	0.02	36	0.03	124	0.02	36	0.03	120	0.02	36	0.03	124	0.02	36	0.03	120	0.02	36	0.03
arduino:zephyr_main:opta	124	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01
arduino:zephyr_main:portentac33	120	0.01	36	0.03	120	0.01	36	0.03	120	0.01	36	0.03	120	0.01	36	0.03	124	0.01	36	0.03	120	0.01	36	0.03	124	0.01	36	0.03	120	0.01	36	0.03	120	0.01	36	0.03	120	0.01	36	0.03	120	0.01	36	0.03	124	0.01	36	0.03
arduino:zephyr_main:portentah7	120	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	124	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01	120	0.01	36	0.01

Click for full report CSV

Board,examples/Central/LedControl<br>flash,%,examples/Central/LedControl<br>RAM for global variables,%,examples/Central/PeripheralExplorer<br>flash,%,examples/Central/PeripheralExplorer<br>RAM for global variables,%,examples/Central/Scan<br>flash,%,examples/Central/Scan<br>RAM for global variables,%,examples/Central/ScanCallback<br>flash,%,examples/Central/ScanCallback<br>RAM for global variables,%,examples/Central/SensorTagButton<br>flash,%,examples/Central/SensorTagButton<br>RAM for global variables,%,examples/Peripheral/Advertising/EnhancedAdvertising<br>flash,%,examples/Peripheral/Advertising/EnhancedAdvertising<br>RAM for global variables,%,examples/Peripheral/Advertising/RawDataAdvertising<br>flash,%,examples/Peripheral/Advertising/RawDataAdvertising<br>RAM for global variables,%,examples/Peripheral/BatteryMonitor<br>flash,%,examples/Peripheral/BatteryMonitor<br>RAM for global variables,%,examples/Peripheral/ButtonLED<br>flash,%,examples/Peripheral/ButtonLED<br>RAM for global variables,%,examples/Peripheral/CallbackLED<br>flash,%,examples/Peripheral/CallbackLED<br>RAM for global variables,%,examples/Peripheral/EncryptedBatteryMonitor<br>flash,%,examples/Peripheral/EncryptedBatteryMonitor<br>RAM for global variables,%,examples/Peripheral/LED<br>flash,%,examples/Peripheral/LED<br>RAM for global variables,%
arduino:esp32:nano_nora,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0,36,0.0,0,0.0
arduino:mbed_giga:giga,0,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,0,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed_nano:nano33ble,64,0.01,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,64,0.01,0,0.0,64,0.01,0,0.0,0,0.0,0,0.0,64,0.01,0,0.0,64,0.01,0,0.0,64,0.01,0,0.0,64,0.01,0,0.0,64,0.01,0,0.0
arduino:mbed_nano:nanorp2040connect,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0,26,0.0,0,0.0
arduino:mbed_nicla:nicla_vision,0,0.0,0,0.0,0,0.0,0,0.0,64,0.0,0,0.0,0,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,0,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0
arduino:mbed_opta:opta,0,0.0,0,0.0,0,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,0,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0,64,0.0,0,0.0
arduino:mbed_portenta:envie_m7,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A
arduino:renesas_portenta:portenta_c33,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0,32,0.0,0,0.0
arduino:renesas_uno:unor4wifi,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0,32,0.01,0,0.0
arduino:samd:mkrwifi1010,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0
arduino:samd:nano_33_iot,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0,24,0.01,0,0.0
arduino:zephyr:unoq,116,0.01,36,0.01,124,0.02,36,0.01,124,0.02,36,0.01,124,0.02,36,0.01,128,0.02,36,0.01,124,0.02,36,0.01,124,0.02,36,0.01,120,0.02,36,0.01,124,0.02,36,0.01,128,0.02,36,0.01,116,0.01,36,0.01,116,0.01,36,0.01
arduino:zephyr_main:giga,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01
arduino:zephyr_main:nano33ble,120,0.02,36,0.03,120,0.02,36,0.03,124,0.02,36,0.03,124,0.02,36,0.03,120,0.02,36,0.03,124,0.02,36,0.03,120,0.02,36,0.03,124,0.02,36,0.03,124,0.02,36,0.03,120,0.02,36,0.03,124,0.02,36,0.03,120,0.02,36,0.03
arduino:zephyr_main:opta,124,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01
arduino:zephyr_main:portentac33,120,0.01,36,0.03,120,0.01,36,0.03,120,0.01,36,0.03,120,0.01,36,0.03,124,0.01,36,0.03,120,0.01,36,0.03,124,0.01,36,0.03,120,0.01,36,0.03,120,0.01,36,0.03,120,0.01,36,0.03,120,0.01,36,0.03,124,0.01,36,0.03
arduino:zephyr_main:portentah7,120,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,124,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01,120,0.01,36,0.01

[thematrix999]

For context, the four failing compile jobs also fail on the latest scheduled workflow run from the current master branch:

https://github.com/arduino-libraries/ArduinoBLE/actions/runs/30351039055

The failing targets are the same:

• arduino:megaavr:uno2018:mode=on
• arduino:zephyr_main:nicla_sense
• esp32:esp32:esp32c6
• esp32:esp32:esp32h2

The Nano 33 BLE compilation, unit tests, and spell check pass.

Codecov reports no patch coverage because the existing unit test suite does not currently exercise ATTClass::discoverDescriptors(). The change has been tested on hardware using two Nano 33 BLE boards, as
described in the PR.