Unable to build sample "Bluetooth: Direction Finding Connectionless Locator" for nRF54L15

[idbj]

Hi! I am trying to get the samples "Bluetooth: Direction finding connectionless locator" and "Bluetooth: Direction finding connectionless beacon" to work on nRF54L15dk. I want to only use the pcb antenna on both the locator and beacon for IQ sampling. I got the beacon to work by altering the `prj.conf` to this:

CONFIG_BT=y
CONFIG_BT_DEVICE_NAME="Test beacon"
CONFIG_BT_CTLR=y
CONFIG_BT_DF=y
 
CONFIG_BT_CTLR_DF=y
CONFIG_BT_EXT_ADV=y
CONFIG_BT_PER_ADV=y
CONFIG_BT_BROADCASTER=y
CONFIG_BT_CTLR_DF_CTE_TX=y
CONFIG_BT_DF_CONNECTIONLESS_CTE_TX=y
CONFIG_BT_CTLR_DF_ADV_CTE_TX=y
CONFIG_BT_CTLR_DF_ANT_SWITCH_TX=n
CONFIG_BT_DF_CTE_TX_AOD=n
 
CONFIG_BT_CTLR_ADVANCED_FEATURES=y
CONFIG_BT_CTLR_ADV_SYNC_PDU_BACK2BACK=y
CONFIG_BT_CTLR_DF_PER_ADV_CTE_NUM_MAX=16

CONFIG_BT_CTLR_ADV_EXT=y
CONFIG_BT_CTLR_ADV_PERIODIC=y

CONFIG_BT_CTLR_DF_ANT_SWITCH_RX=n
CONFIG_BT_CTLR_DF_SCAN_CTE_RX=n


I now struggle to build the locator example, here is my current config. The errors are:

1. BT_LL_SW_SPLIT - causes assertion error with "Missing antenna pattern used to select antenna for PDU Tx during the DFE Idle state. Set the dfe-pdu-antenna devicetree property."
2. CONFIG_BT_CTLR_DF_SUPPORT - not able to enable this

CONFIG_BT=y
CONFIG_BT_DEVICE_NAME="DF Connectionless Locator App"
CONFIG_BT_CTLR=y
CONFIG_BT_DF=y
CONFIG_BT_HCI=y

CONFIG_BT_CTLR_DF=y

# This line causes assertion error with error:
# static assertion failed: "Missing antenna pattern
# used to select antenna for PDU Tx during the DFE Idle
# state. Set the dfe-pdu-antenna devicetree property."

CONFIG_BT_LL_SW_SPLIT=y
CONFIG_BT_CTLR_DF_ANT_SWITCH_RX=n
CONFIG_BT_EXT_ADV=y
CONFIG_BT_PER_ADV_SYNC=y
CONFIG_BT_OBSERVER=y
#CONFIG_BT_CTLR_DF_SUPPORT=y The build stops at this, but is not possible to enable manually
#CONFIG_BT_CTLR_DF_CTE_RX_SUPPORT=y
CONFIG_BT_CTLR_DF_CTE_RX=y
CONFIG_BT_DF_CONNECTIONLESS_CTE_RX=y
CONFIG_BT_CTLR_DF_SCAN_CTE_RX=y
CONFIG_BT_DF_CTE_RX_AOA=y
 
CONFIG_BT_CTLR_SYNC_PERIODIC=y
CONFIG_BT_CTLR_DF_PER_SCAN_CTE_NUM_MAX=16

[PaKa]

Direction Finding is not supported with the nRF54L15. The platform to use for Direction Finding is the nRF52833. For AoA you will need to have an antenna array for the receiver side.

[Filip Zawadiak]

Just to make it clear, it is not supported in SoftDevice or not supported by the hardware? Registers for it seems to be present and documented?

I would like to add location information to large number of simple devices moving in a space and it does not need to be super precise but should be constantly available. AoD signal from few points could be possibly a solution. CS seems to slow and complicated to track 50+ devices...

[PaKa]

Not supported in SW. 

That said, without an antenna array you won't be able to get any direction data out of the IQ data so wouldn't yield any location support either. 

Direction finding requires an antenna array on one side to work. Channel Sounding can work with single antennas on each side.

[Filip Zawadiak]

Thanks for clarification. Yes, understand the need for antenna on one side.
Are there any plans to add DF to SoftDevice stacks?
Were there any tests done of usage of IQ data from CTE sent over multiple channels to estimate distance from AoD device - one of few ideas I want to try?