h2zero
ACL buffer cannot be changed; and enables broken MTUs as client
/** @brief ACL Buffer size */
#define CONFIG_BT_NIMBLE_TRANSPORT_ACL_SIZE 255
In nimconfig.h this variable is not guarded, so it cannot be redefined in compile flags. I would like to understand why?
I have a problem with esp32dev and esp32-s3 platforms working as BLE clients: By setting
#define CONFIG_BT_NIMBLE_ATT_PREFERRED_MTU 512
and calling
NimBLEDevice::setMTU(CONFIG_BT_NIMBLE_ATT_PREFERRED_MTU)
I enable receiving notifications longer than the default 255, but the bytes in the notifications are nonsense beyond 255 (mostly nulls).
NimBLE version is 2.3.6, also tested 1.4.3.
I manually hacked #define CONFIG_BT_NIMBLE_TRANSPORT_ACL_SIZE 512 in the nimconfig.h and the packets seem to come through correctly.
Interestingly these issues do not exist on server side: I have another esp32-s3 communicating with the MTU==512, and at least Android platforms receive all data without issue.
The fix is in the master branch, though it should be made automatic, which I will add later. https://github.com/h2zero/NimBLE-Arduino/blob/5dad8939fbea864857a009b6a4936028a7179057/src/syscfg/syscfg.h#L1394
