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on_data_length_update_request_evt

joe.ker

Hi,

upon connection I get these messages via RTT:

nrf_ble_gatt:DEBUG:Peer on connection 0x0 requested an ATT MTU of 185 bytes. nrf_ble_gatt:DEBUG:Updating ATT MTU to 23 bytes (desired: 23) on connection 0x0.

Does anybody know what they mean?

Many thanks, Josef

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  • 0

    This probably means that one peer performed Exchange MTU Request on ATTribute Protocol layer and the other peer responded with Exchange MTU Response which resulted into automatic ATT_MTU alignment to minimum of numbers indicated by both sides. One said it can go up to 185 bytes but second indicated it can handle only 23 bytes (default size mandated by BT SIG spec for ATT layer on LE) so ATT_MTU settled on default size 23.

  • 0 in reply to endnode

    iOS devices are doing ATT_MTU extension by default, Android can do it but it's up to the app to ask for it through dedicated API function call. However it should work regardless if this procedure is done by master/client or not. If you have issues with connection to iOS devices then there can be many reasons. Provide more details, logs and preferably traces from the radio showing when connection broke (then you usually also see why;).

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  • 0 in reply to endnode

    iOS devices are doing ATT_MTU extension by default, Android can do it but it's up to the app to ask for it through dedicated API function call. However it should work regardless if this procedure is done by master/client or not. If you have issues with connection to iOS devices then there can be many reasons. Provide more details, logs and preferably traces from the radio showing when connection broke (then you usually also see why;).

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