nRF54L15 DKs cannot connect with each other

[Ziyao Zhou]

Hi

I have two DKs, previously they work well, however, after I add the nRF21540 FEM on each DK, I always receive this in my central device:

00> Connection (606) - Central Tx Power = 8
00> [00:10:15.344,398] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:15.594,660] <wrn> bt_conn: conn 0x20012e08 failed to establish. RF noise?
00> [00:10:15.594,956] <wrn> central_uart: Security failed: C9:94:E8:62:AE:97 (random) level 1 err 9 
00> [00:10:15.594,970] <err> bt_gatt_dm: Discover failed, error: -128.
00> [00:10:15.594,976] <err> central_uart: could not start the discovery procedure, error code: -128
00> [00:10:15.595,042] <wrn> central_uart: Pairing failed conn: C9:94:E8:62:AE:97 (random), reason 9 
00> [00:10:15.595,156] <wrn> central_uart: MTU exchange failed (err 14)
00> [00:10:15.595,253] <inf> central_uart: Disconnected: C9:94:E8:62:AE:97 (random), reason 0x3e 
00> [00:10:15.601,036] <inf> central_uart: Filters matched. Address: C9:94:E8:62:AE:97 (random) connectable: 1
00> [00:10:15.624,196] <inf> central_uart: Connected: C9:94:E8:62:AE:97 (random)
00> PHY update requested (2M)
00> Connection param update requested (interval=)
00> Actual Tx Power: 8
00> Connection (608) - Central Tx Power = 8
00> [00:10:15.625,359] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:15.875,622] <wrn> bt_conn: conn 0x20012e08 failed to establish. RF noise?
00> [00:10:15.875,918] <wrn> central_uart: Security failed: C9:94:E8:62:AE:97 (random) level 1 err 9 
00> [00:10:15.875,932] <err> bt_gatt_dm: Discover failed, error: -128.
00> [00:10:15.875,938] <err> central_uart: could not start the discovery procedure, error code: -128
00> [00:10:15.876,004] <wrn> central_uart: Pairing failed conn: C9:94:E8:62:AE:97 (random), reason 9 
00> [00:10:15.876,118] <wrn> central_uart: MTU exchange failed (err 14)
00> [00:10:15.876,216] <inf> central_uart: Disconnected: C9:94:E8:62:AE:97 (random), reason 0x3e 
00> [00:10:15.893,827] <inf> central_uart: Filters matched. Address: C9:94:E8:62:AE:97 (random) connectable: 1
00> [00:10:15.924,658] <inf> central_uart: Connected: C9:94:E8:62:AE:97 (random)
00> PHY update requested (2M)
00> Connection param update requested (interval=)
00> Actual Tx Power: 8
00> Connection (610) - Central Tx Power = 8
00> [00:10:15.925,820] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:16.176,084] <wrn> bt_conn: conn 0x20012e08 failed to establish. RF noise?
00> [00:10:16.176,380] <wrn> central_uart: Security failed: C9:94:E8:62:AE:97 (random) level 1 err 9 
00> [00:10:16.176,394] <err> bt_gatt_dm: Discover failed, error: -128.
00> [00:10:16.176,400] <err> central_uart: could not start the discovery procedure, error code: -128
00> [00:10:16.176,466] <wrn> central_uart: Pairing failed conn: C9:94:E8:62:AE:97 (random), reason 9 
00> [00:10:16.176,580] <wrn> central_uart: MTU exchange failed (err 14)
00> [00:10:16.176,677] <inf> central_uart: Disconnected: C9:94:E8:62:AE:97 (random), reason 0x3e 
00> [00:10:16.180,107] <inf> central_uart: Filters matched. Address: C9:94:E8:62:AE:97 (random) connectable: 1
00> [00:10:16.208,609] <inf> central_uart: Connected: C9:94:E8:62:AE:97 (random)
00> PHY update requested (2M)
00> Connection param update requested (interval=)
00> Actual Tx Power: 8
00> Connection (612) - Central Tx Power = 8
00> [00:10:16.209,771] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:16.215,729] <inf> central_uart: Data Rate: 0.00 bps (0.00 bytes/s)
00> [00:10:16.215,889] <inf> central_uart: avg_rate  = 0.000000
00> 
00> [00:10:16.215,897] <inf> central_uart: RXRX  = 127
00> 
00> Adaptive Tx power selected = 0
00> [00:10:16.460,035] <wrn> bt_conn: conn 0x20012e08 failed to establish. RF noise?
00> [00:10:16.460,331] <wrn> central_uart: Security failed: C9:94:E8:62:AE:97 (random) level 1 err 9 
00> [00:10:16.460,345] <err> bt_gatt_dm: Discover failed, error: -128.
00> [00:10:16.460,351] <err> central_uart: could not start the discovery procedure, error code: -128
00> [00:10:16.460,417] <wrn> central_uart: Pairing failed conn: C9:94:E8:62:AE:97 (random), reason 9 
00> [00:10:16.460,531] <wrn> central_uart: MTU exchange failed (err 14)
00> [00:10:16.460,547] <wrn> central_uart: ATT error code: 0x0E
00> [00:10:16.460,660] <inf> central_uart: Disconnected: C9:94:E8:62:AE:97 (random), reason 0x3e 
00> [00:10:16.483,252] <inf> central_uart: Filters matched. Address: C9:94:E8:62:AE:97 (random) connectable: 1
00> [00:10:16.550,006] <inf> central_uart: Connected: C9:94:E8:62:AE:97 (random)
00> PHY update requested (2M)
00> Connection param update requested (interval=)
00> Actual Tx Power: 8
00> Connection (614) - Central Tx Power = 8
00> [00:10:16.551,169] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:16.801,432] <wrn> bt_conn: conn 0x20012e08 failed to establish. RF noise?
00> [00:10:16.801,728] <wrn> central_uart: Security failed: C9:94:E8:62:AE:97 (random) level 1 err 9 
00> [00:10:16.801,742] <err> bt_gatt_dm: Discover failed, error: -128.
00> [00:10:16.801,748] <err> central_uart: could not start the discovery procedure, error code: -128
00> [00:10:16.801,814] <wrn> central_uart: Pairing failed conn: C9:94:E8:62:AE:97 (random), reason 9 
00> [00:10:16.801,928] <wrn> central_uart: MTU exchange failed (err 14)
00> [00:10:16.802,026] <inf> central_uart: Disconnected: C9:94:E8:62:AE:97 (random), reason 0x3e 
00> [00:10:16.809,402] <inf> central_uart: Filters matched. Address: C9:94:E8:62:AE:97 (random) connectable: 1
00> [00:10:16.834,703] <inf> central_uart: Connected: C9:94:E8:62:AE:97 (random)
00> PHY update requested (2M)
00> Connection param update requested (interval=)
00> Actual Tx Power: 8
00> Connection (616) - Central Tx Power = 8
00> [00:10:16.835,865] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:17.086,128] <wrn> bt_conn: conn 0x20012e08 failed to establish. RF noise?
00> [00:10:17.086,424] <wrn> central_uart: Security failed: C9:94:E8:62:AE:97 (random) level 1 err 9 
00> [00:10:17.086,438] <err> bt_gatt_dm: Discover failed, error: -128.
00> [00:10:17.086,444] <err> central_uart: could not start the discovery procedure, error code: -128
00> [00:10:17.086,510] <wrn> central_uart: Pairing failed conn: C9:94:E8:62:AE:97 (random), reason 9 
00> [00:10:17.086,624] <wrn> central_uart: MTU exchange failed (err 14)
00> [00:10:17.086,721] <inf> central_uart: Disconnected: C9:94:E8:62:AE:97 (random), reason 0x3e 
00> [00:10:17.104,005] <inf> central_uart: Filters matched. Address: C9:94:E8:62:AE:97 (random) connectable: 1
00> [00:10:17.131,498] <inf> central_uart: Connected: C9:94:E8:62:AE:97 (random)
00> PHY update requested (2M)
00> Connection param update requested (interval=)
00> Actual Tx Power: 8
00> Connection (618) - Central Tx Power = 8
00> [00:10:17.132,661] <err> central_uart: Stop LE scan failed (err 0)
00> [00:10:17.216,020] <inf> central_uart: Data Rate: 0.00 bps (0.00 bytes/s)
00> [00:10:17.216,177] <inf> central_uart: avg_rate  = 0.000000
00> 
00> [00:10:17.216,185] <inf> central_uart: RXRX  = 127

Whether the amplifier cause this problems? What is RF noise here? Could you give me some advice?

[Priyanka]

Hi,

Since you encounter these issues after incorporating the FEM, it is likely causing the issue. RF noise could be anything which causes a radio frequency interference, for eg, signal reflection, crosstalk, wrong antenna matching, or overamplification etc.

Make sure you have configured the nRF21540 properly. Both in the dts and config.

Also make sure that the antennas are properly connected, and the boards are a few meters apart etc.

Regards,

Priyanka

[Ziyao Zhou]

After I reconnect all the components, error gone, thank you!