ArduinoBLE Allow valueSize changes after initialization to adjust to MTU size

When trying to implement a BLE MIDI wrapper on top of ArduinoBLE I was losing data because the MTU negotiated with the server (in this case Apple Mac or iOS devices) was not matching the valueSize / buffer. Normally this might not be an issue but in the particular case of MIDI over BLE, the official spec and parsing of the data requires that packets are handled discreetly, so if the server thinks the packet size is X and we (the client) think it's Y then messages are sent incorrectly.

I suspect there are also other situations where matching the buffer size in the BLE parsing code and the MTU is better, more efficient and/or the only way to be accurate.

This implementation adds the methods necessary to resize, check the MTU size and be notified of MTU negotiation changes, but leaves the decision to resize up to the user of the library.

Apr 09 '25 16:04 matpowel

All committers have signed the CLA.

Apr 09 '25 16:04 CLAassistant

Codecov Report

Attention: Patch coverage is 0% with 23 lines in your changes missing coverage. Please review.

Project coverage is 9.56%. Comparing base (c91c02c) to head (d22a91c). Report is 21 commits behind head on master.

Files with missing lines	Patch %	Lines
src/local/BLELocalCharacteristic.cpp	0.00%	8 Missing :warning:
src/local/BLELocalDevice.cpp	0.00%	6 Missing :warning:
src/BLECharacteristic.cpp	0.00%	5 Missing :warning:
src/BLEDevice.cpp	0.00%	2 Missing :warning:
src/utility/ATT.cpp	0.00%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #391      +/-   ##
=========================================
- Coverage    9.62%   9.56%   -0.07%     
=========================================
  Files          28      28              
  Lines        3656    3679      +23     
=========================================
  Hits          352     352              
- Misses       3304    3327      +23

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Apr 09 '25 16:04 codecov[bot]

Memory usage change @ d22a91cde773155bb31a1dda033841a9f8c5640d

Board	flash	%	RAM for global variables	%
`arduino:mbed_nano:nano33ble`	:small_red_triangle: +136 - +136	+0.01 - +0.01	:small_red_triangle: +8 - +8	0.0 - 0.0
`arduino:mbed_nano:nanorp2040connect`	:small_red_triangle: +140 - +140	0.0 - 0.0	:small_red_triangle: +8 - +8	0.0 - 0.0
`arduino:megaavr:uno2018:mode=on`	:small_red_triangle: +180 - +180	+0.37 - +0.37	:small_red_triangle: +4 - +4	+0.07 - +0.07
`arduino:renesas_uno:unor4wifi`	:small_red_triangle: +120 - +136	+0.05 - +0.05	:small_red_triangle: +8 - +8	+0.02 - +0.02
`arduino:samd:mkrwifi1010`	:small_red_triangle: +136 - +144	+0.05 - +0.05	:small_red_triangle: +8 - +8	+0.02 - +0.02
`arduino:samd:nano_33_iot`	:small_red_triangle: +136 - +144	+0.05 - +0.05	:small_red_triangle: +8 - +8	+0.02 - +0.02

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:mbed_nano:nano33ble`	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0	136	0.01	8	0.0
`arduino:mbed_nano:nanorp2040connect`	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0	140	0.0	8	0.0
`arduino:megaavr:uno2018:mode=on`	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07	180	0.37	4	0.07
`arduino:renesas_uno:unor4wifi`	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	120	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02
`arduino:samd:mkrwifi1010`	136	0.05	8	0.02	144	0.05	8	0.02	144	0.05	8	0.02	144	0.05	8	0.02	136	0.05	8	0.02	144	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	144	0.05	8	0.02	144	0.05	8	0.02
`arduino:samd:nano_33_iot`	136	0.05	8	0.02	144	0.05	8	0.02	144	0.05	8	0.02	144	0.05	8	0.02	136	0.05	8	0.02	144	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	136	0.05	8	0.02	144	0.05	8	0.02	144	0.05	8	0.02

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:mbed_nano:nano33ble,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0,136,0.01,8,0.0
arduino:mbed_nano:nanorp2040connect,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0,140,0.0,8,0.0
arduino:megaavr:uno2018:mode=on,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07,180,0.37,4,0.07
arduino:renesas_uno:unor4wifi,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,120,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02
arduino:samd:mkrwifi1010,136,0.05,8,0.02,144,0.05,8,0.02,144,0.05,8,0.02,144,0.05,8,0.02,136,0.05,8,0.02,144,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,144,0.05,8,0.02,144,0.05,8,0.02
arduino:samd:nano_33_iot,136,0.05,8,0.02,144,0.05,8,0.02,144,0.05,8,0.02,144,0.05,8,0.02,136,0.05,8,0.02,144,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,136,0.05,8,0.02,144,0.05,8,0.02,144,0.05,8,0.02

Apr 09 '25 16:04 github-actions[bot]