I tried every configuration options one by one to change the MTU size, but it doesn't work.
I connect to nRF52840 with Raspbery Pi and when I subscribe to a notification, I receive the following error:
<wrn> bt_att: No ATT channel for MTU 30 <wrn> bt_gatt: No buffer available to send notification <err> app: Couldn't send notificaton. (err: -12)
#CONFIG_BT_CTLR_DATA_LENGTH_MAX=128 #CONFIG_BT_BUF_ACL_RX_SIZE=128 #CONFIG_BT_BUF_ACL_TX_SIZE=128 CONFIG_BT_L2CAP_TX_MTU=128