RE: Rom size occupied for NCS v3.0.2 with bluetooth stack.

Kazi Afroza Sultana — Fri, 04 Jul 2025 13:17:05 GMT

Hello,

I can see both peripheral and central are enabled in the prj.conf file.

Enabling both central and peripheral roles, extended advertising, GATT client, scanning, and other advanced features (like PHY coded, dynamic TX power, etc.) significantly increases the flash footprint.

You also need dual band DFU; this requires two application slots of equal size, also space for MCUboot and settings partitions. You can read this case Smaller flash size BLE DFU with NCS possible?

You can reduce flash usage by disabling unused features, using minimal configurations, and optimizing buffer sizes. For example, based on the prj_minimal.con files from the samples peripheral_lbs and peripheral_uart , there is a config file with minimal configurations

CONFIG_BT_DEBUG_NONE=y
CONFIG_BT_ASSERT=n
CONFIG_BT_DATA_LEN_UPDATE=n
CONFIG_BT_PHY_UPDATE=n
CONFIG_BT_GATT_CACHING=n
CONFIG_BT_GATT_SERVICE_CHANGED=n
CONFIG_BT_GAP_PERIPHERAL_PREF_PARAMS=n
CONFIG_BT_SETTINGS_CCC_LAZY_LOADING=y
CONFIG_BT_HCI_VS_EXT=n
CONFIG_BT_CTLR_PRIVACY=n
CONFIG_BT_CTLR_PHY_2M=n
CONFIG_BT_BUF_EVT_DISCARDABLE_COUNT=1
CONFIG_BT_BUF_EVT_DISCARDABLE_SIZE=43
CONFIG_BT_BUF_EVT_RX_COUNT=2
CONFIG_BT_CONN_TX_MAX=2
CONFIG_BT_L2CAP_TX_BUF_COUNT=2
CONFIG_BT_CTLR_RX_BUFFERS=1
CONFIG_BT_BUF_ACL_TX_COUNT=3
CONFIG_BT_BUF_ACL_TX_SIZE=27

however you may need some of the configs for your application; so, 512 KB may not be enough for your application.

RE: Rom size occupied for NCS v3.0.2 with bluetooth stack.

Turbo J — Fri, 04 Jul 2025 05:49:22 GMT

No. Once you enable both central and peripherial BTLE mode, you will need a ton of flash ROM space for the supporting code base.

Consider a bigger chip variant or external flash.