My project: I am developing a system consisting of a central and up to 20 peripherals based on the Multi-NUS protocol. Toolchain and SDK : NCS v2.6.1. Development target: custom boards with BT840XE (central) and BT840F (peripherals) from Fanstel.
Problem Statement: When one of the devices is at the limit of radio range, we observe successive disconnections/connections which always result in a blocking of the central unit.
For example :
[00:01:21.354,614] \033[0m<inf> central_uart: Disconnected: CE:29:79:93:DE:21 (random) (reason 8)\033[0m
[00:01:21.573,913] \033[0m<inf> central_uart: Filters matched. Address: CE:29:79:93:DE:21 (random) connectable: 0 RSSI: -88\033[0m
[00:01:21.885,498] \033[0m<inf> central_uart: Connected: CE:29:79:93:DE:21 (random)\033[0m
[00:01:21.885,528] \033[0m<inf> central_uart: NUS Client module initialized\033[0m
[00:01:35.036,956] \033[1;31m<err> bt_gatt_dm: Characteristic discover failed, error: -128.\033[0m
[00:01:35.036,987] \033[1;33m<wrn> central_uart: Error while discovering GATT database: (-128)\033[0m
[00:01:35.037,353] \033[0m<inf> central_uart: Disconnected: CE:29:79:93:DE:21 (random) (reason 8)\033[0m .=> Blocking
Or :
[00:01:00.829,559] \033[0m<inf> central_uart: Filters matched. Address: CE:29:79:93:DE:21 (random) connectable: 0 RSSI: -89\033[0m
[00:01:01.146,209] \033[0m<inf> central_uart: Connected: CE:29:79:93:DE:21 (random)\033[0m
[00:01:01.146,240] \033[0m<inf> central_uart: NUS Client module initialized\033[0m
[00:01:01.397,949] \033[0m<inf> central_uart: Service not found\033[0m
[00:01:01.398,254] \033[0m<inf> central_uart: Disconnected: CE:29:79:93:DE:21 (random) (reason 62)\033[0m => Blocking
Solution suggestion : in the scanning process only accept connections with an RSSI greater than a certain value. For example like what is done in the zephyr/bluetooth/central_multilink example.
Could someone suggest me how to add this feature to the Multi-NUS app? Or any other solution to this problem !!!
Thank you in advance for your help