NRF 5340DK CONFIG_BT_MAX_CONN cannot go above 5

[DamoMul]

Project based on NUS Central example.

Application is to connect to multiple peripherals concurrently running a custom service and subscribe to Notifications on a characteristic.

This i have working.

This is for an environmental measuring application, and ideally, the Central could support more than 40 concurrent connections.

No Pairing is required. connection is completed against a list of MAC Addresses

I have an issue where if i set CONFIG_BT_MAX_CONN to > 5 then there is a compiliation error

C:/ncs/v2.8.0/zephyr/include/zephyr/toolchain/gcc.h:87:36: error: static assertion failed: ""
   87 | #define BUILD_ASSERT(EXPR, MSG...) _Static_assert((EXPR), "" MSG)
      |                                    ^~~~~~~~~~~~~~
C:/ncs/v2.8.0/zephyr/subsys/bluetooth/common/dummy.c:75:1: note: in expansion of macro 'BUILD_ASSERT'
   75 | BUILD_ASSERT(CONFIG_BT_BUF_ACL_RX_COUNT > CONFIG_BT_MAX_CONN);

How can i Increase the number of connections?
I have tried to search for CONFIG_BT_BUF_ACL_RX_COUNT in the prj.conf

if I try to set CONFIG_BT_BUF_ACL_RX_COUNT it shows up as undefined.

using SDK vers 2.8.0

[Kazi Afroza Sultana]

Hello,

The error seems related to the requirement that CONFIG_BT_BUF_ACL_RX_COUNT must be greater than CONFIG_BT_MAX_CONN.

It is a known issue which is mentioned here Known issues. For Bluetooth multilink with nRF5340 where you only use central can try to set this in prj.conf file

# For application core
CONFIG_BT_MAX_CONN=10 (for example maximum connection 10)
CONFIG_BT_BUF_ACL_RX_COUNT=11 ( this must be greater than the CONFIG_BT_MAX_CONN)

# For network core (if using nRF5340)
CONFIG_BT_CTLR_SDC_PERIPHERAL_COUNT=0  # If you're only using central role

regarding central connection you can read this ticket (+) Central connection two two or more peripherals - Nordic Q&A - Nordic DevZone - Nordic DevZone

Thanks.

BR

kaz

[DamoMul]

Many thanks
I will review this information and try the suggestions and reply back

[DamoMul]

Looping back to update.
I tried the steps above with no success, however, following the link provided i was able to use the Central_Multilink example as a base for my application
Having ported over my application code this is proving successful.

Many Thanks