Decreased TX power and RSSI

RE: Decreased TX power and RSSI

runsiv — Tue, 21 May 2024 09:02:20 GMT

Thanks for the patience. Its been holidays here in Norway so we have not been in the office since Thursday. Glad to hear you wear able to figure it out

Regards

Runar

RE: Decreased TX power and RSSI

AndyM — Thu, 16 May 2024 21:14:28 GMT

Update

I found the root of the problem

The advertising set handle I passed to set_tx_power was wrong.
I use extended advertising set and assumed that its handle value is always 1
That is not the case in SDK 2.5 so my code broke
So the solution is to use bt_hci_get_adv_handle() and set the TX for the adv set I'm interested in.

Looks like I'm good 🙂

Thank you
Andy

RE: Decreased TX power and RSSI

AndyM — Wed, 15 May 2024 23:07:17 GMT

Did some more testing
Same application code with different SDK's at ~5 m distance between central and peripheral

3.2.99-ncs2

TX RSSI
0 -76
8 -65
-8 -80
-20 -87
-40 -90

SDK 2.4.0 and SDK 2.5.0

TX RSSI
0 -71
8 -71
-8 -70
-20 -71
-40 -70

RE: Decreased TX power and RSSI

AndyM — Wed, 15 May 2024 13:39:53 GMT

My code uses exact same function to get the power level so I'm pretty confident it changes

My application requires dynamic TX power adjustment in some cases. It used to work in SDK's prior to 2.5.0 that I'm using now.
I went back to v3.2.99-ncs2 ( not sure what SDK it maps to ) and at -40 TX the packets from the peripheral do not reach central - as expected. But with SDK 2.5.0 the central continues to receive them at -64 dBM from 5.5 m

RE: Decreased TX power and RSSI

runsiv — Wed, 15 May 2024 06:37:30 GMT

I will need to check. Normally if I have the need to adjust TX power I do with Kconfig option CONFIG_BT_CTLR_TX_PWR_ or CONFIG_BT_CTLR_TX_PWR_ANTENNA can be used.

Could you try to add the get_tx_power function from here to see if it actually changes the tx power?

Regards

Runar