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[Bluetooth] MTU, Data_length, PHY setting in prj.conf

seongmincho

Hello,

I am programming BLE with the nRF52840-DK. [Toolchain Manager: v1.3.0, IDE: Visual Studio Code (VSCode), SDK: ncs v2.6.0 ]

My goal is to achieve a data throughput of 1.3Mbps in BLE. Therefore, I want to set 2M PHY, ATT_MTU = 247, and Data_length = 251.

However, I get an error when building the central. What could be the problem?

Parsing C:/ncs/v2.6.0/zephyr/Kconfig
Loaded configuration 'C:/ncs/v2.6.0/zephyr/boards/arm/nrf52840dk_nrf52840/nrf52840dk_nrf52840_defconfig'
Merged configuration 'C:/ncs/Myproject/240703_scan_adv_central/prj.conf'

warning: the value '251 #buffers for the data length max.' is invalid for BT_BUF_ACL_TX_SIZE (defined at C:/ncs/v2.6.0/nrf\samples\common\mcumgr_bt_ota_dfu/Kconfig:125, C:/ncs/v2.6.0/nrf\subsys\bluetooth\services\fast_pair/Kconfig.fast_pair:91, C:/ncs/v2.6.0/zephyr/subsys/bluetooth/common/Kconfig:9, subsys/bluetooth\common/Kconfig:9), which has type int -- assignment ignored

error: Aborting due to Kconfig warnings

Below is the prj.conf code for both the peripheral and central.

- Central prj.conf:

# BLE 
# Enable the BLE stack with GATT Client configuration
CONFIG_BT=y
CONFIG_BT_CENTRAL=y
CONFIG_BT_SMP=y

CONFIG_BT_SCAN=y
CONFIG_BT_SCAN_FILTER_ENABLE=y
CONFIG_BT_SCAN_UUID_CNT=1
CONFIG_BT_GATT_DM=y
CONFIG_HEAP_MEM_POOL_SIZE=2048
CONFIG_BT_SCAN_NAME_CNT=5
CONFIG_BT_SCAN_NAME_MAX_LEN=20


CONFIG_BT_NUS_CLIENT=y
CONFIG_BT_ATT_PREPARE_COUNT=2
CONFIG_BT_CONN_TX_MAX=10
CONFIG_BT_L2CAP_TX_BUF_COUNT=10

CONFIG_BT_BUF_ACL_TX_COUNT=10

CONFIG_BT_GATT_CLIENT=y
#For PHY
CONFIG_BT_USER_PHY_UPDATE=y
CONFIG_BT_CTLR_PHY_2M=y
#For data length
CONFIG_BT_USER_DATA_LEN_UPDATE=y
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251
CONFIG_BT_BUF_ACL_TX_SIZE=251 #buffers for the data length max.
CONFIG_BT_BUF_ACL_RX_SIZE=251
# For MTU : 251-4 = 247
CONFIG_BT_L2CAP_TX_MTU=247

- peripheral prj.conf:

#BLE
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y

CONFIG_BT_DEVICE_NAME="SEONGMIN"

CONFIG_BT_NUS=y

CONFIG_BT_MAX_CONN=1
CONFIG_BT_MAX_PAIRED=1

CONFIG_BT_ATT_PREPARE_COUNT=2
CONFIG_BT_L2CAP_TX_BUF_COUNT=10
CONFIG_BT_CTLR_PHY_2M=y
CONFIG_BT_BUF_ACL_TX_COUNT=10

# For PHY
CONFIG_BT_USER_PHY_UPDATE=y
# For data length 
CONFIG_BT_USER_DATA_LEN_UPDATE=y
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251
CONFIG_BT_BUF_ACL_TX_SIZE=251
CONFIG_BT_BUF_ACL_RX_SIZE=251
# For MTU : 251-4 = 247
CONFIG_BT_L2CAP_TX_MTU=247

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