Dynamic Tx power control issue with FEM-enabled boards

RE: Dynamic Tx power control issue with FEM-enabled boards

Golovin Sergey — Mon, 18 Dec 2023 11:40:39 GMT

Thank you! It helps.

RE: Dynamic Tx power control issue with FEM-enabled boards

Kenneth — Sun, 17 Dec 2023 19:39:46 GMT

For the devicetree bindings I can see they are set to (default) 12 or 22 dB depending on the variant used, see:
https://github.com/nrfconnect/sdk-nrf/blob/v2.5.0/dts/bindings/radio_fem/skyworks%2Csky66407-11.yaml#L38
https://github.com/nrfconnect/sdk-nrf/blob/v2.5.0/dts/bindings/radio_fem/skyworks%2Csky66112-11.yaml#L47

The tx-gain-db can be modified in an overlay file if the output power is different from these values.

Kenneth

RE: Dynamic Tx power control issue with FEM-enabled boards

Golovin Sergey — Thu, 14 Dec 2023 16:12:49 GMT

Now I understand. Can I configure somehow the gain of FEM? As far as I understand I cannot set TX power to more than 18 dBm ( -4 dBm of nrf52832 + 22 dBm of Skyworks FEM ) because of the BLE specification.

RE: Dynamic Tx power control issue with FEM-enabled boards

Kenneth — Thu, 14 Dec 2023 15:31:20 GMT

Hello,

If I were to guess here the skyworks have fixed 22dB gain, and given that the supported output power of the nRF52832 radio:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/radio.html#register.TXPOWER

Then the closest step to 4dBm is -20 + 22 = 2

Then the closest step to 2dBm is -20 + 22 = 2

Then the closest step to 0dBm is -40 + 22 = -18

Then the closest step to -4dBm is -40 + 22 = -18

...

The radio don't have any configurable step between -40dBm and -20dBm.

Kenneth

RE: Dynamic Tx power control issue with FEM-enabled boards

Golovin Sergey — Wed, 13 Dec 2023 14:28:53 GMT

This is an output of hci_pwr_ctrl sample on my custom board:

▒*** Booting nRF Connect SDK v2.5.0 ***
Starting Dynamic Tx Power Beacon Demo
[00:00:00.000,579] <inf> bt_sdc_hci_driver: SoftDevice Controller build revision:
                                            c5 93 ba a9 14 4d 8d 05  30 4e 9b 92 d7 71 1e e8 |.....M.. 0N...q..
                                            aa 02 50 3c                                      |..P<
[00:00:00.003,021] <inf> bt_hci_core: HW Platform: Nordic Semiconductor (0x0002)
[00:00:00.003,051] <inf> bt_hci_core: HW Variant: nRF52x (0x0002)
[00:00:00.003,082] <inf> bt_hci_core: Firmware: Standard Bluetooth controller (0x00) Version 197.47763 Build 2370639017
[00:00:00.003,967] <inf> bt_hci_core: Identity: FA:2D:DF:9B:D8:3B (random)
[00:00:00.003,997] <inf> bt_hci_core: HCI: version 5.4 (0x0d) revision 0x1102, manufacturer 0x0059
[00:00:00.004,028] <inf> bt_hci_core: LMP: version 5.4 (0x0d) subver 0x1102
Bluetooth initialized
Dynamic Tx power Beacon started
Get Tx power level ->-> default TXP = 0
Set Tx power level to 4
Actual Tx Power: 2
Get Tx power level -> TXP = 2
Set Tx power level to 3
Actual Tx Power: 2
Get Tx power level -> TXP = 2
Set Tx power level to 0
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to -4
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to -8
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to -12
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to -16
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to -20
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to -40
Actual Tx Power: -18
Get Tx power level -> TXP = -18
Set Tx power level to 4
Actual Tx Power: 2
Get Tx power level -> TXP = 2
Set Tx power level to 3
Actual Tx Power: 2

This is output of hci_pwr_ctrl sample on nrf21540dk_nrf52840:

*** Booting nRF Connect SDK v2.5.0 ***
Starting Dynamic Tx Power Beacon Demo
[00:00:00.000,457] <inf> bt_sdc_hci_driver: SoftDevice Controller build revision:
                                            c5 93 ba a9 14 4d 8d 05  30 4e 9b 92 d7 71 1e e8 |.....M.. 0N...q..
                                            aa 02 50 3c                                      |..P<
[00:00:00.002,990] <inf> bt_hci_core: HW Platform: Nordic Semiconductor (0x0002)
[00:00:00.003,021] <inf> bt_hci_core: HW Variant: nRF52x (0x0002)
[00:00:00.003,051] <inf> bt_hci_core: Firmware: Standard Bluetooth controller (0x00) Version 197.47763 Build 2370639017
[00:00:00.003,906] <inf> bt_hci_core: Identity: E4:B6:79:75:A1:BD (random)
[00:00:00.003,936] <inf> bt_hci_core: HCI: version 5.4 (0x0d) revision 0x1102, manufacturer 0x0059
[00:00:00.003,967] <inf> bt_hci_core: LMP: version 5.4 (0x0d) subver 0x1102
Bluetooth initialized
Dynamic Tx power Beacon started
Get Tx power level ->-> default TXP = 0
Set Tx power level to 4
Actual Tx Power: 2
Get Tx power level -> TXP = 2
Set Tx power level to 3
Actual Tx Power: 2
Get Tx power level -> TXP = 2
Set Tx power level to 0
Actual Tx Power: -2
Get Tx power level -> TXP = -2
Set Tx power level to -4
Actual Tx Power: -6
Get Tx power level -> TXP = -6
Set Tx power level to -8
Actual Tx Power: -10
Get Tx power level -> TXP = -10
Set Tx power level to -12
Actual Tx Power: -30
Get Tx power level -> TXP = -30
Set Tx power level to -16
Actual Tx Power: -30
Get Tx power level -> TXP = -30
Set Tx power level to -20
Actual Tx Power: -30
Get Tx power level -> TXP = -30
Set Tx power level to -40
Actual Tx Power: -30

Similar behaviour, but not the same.

RE: Dynamic Tx power control issue with FEM-enabled boards

Kenneth — Wed, 13 Dec 2023 13:53:42 GMT

Hello,

Can you check this example:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/samples/bluetooth/hci_pwr_ctrl/README.html

Kenneth