TX Power Level Setting nrf5340 nrf Connect SDK

[kpreiss]

We are using the Softdevice controller from the nRF Connect SDK on the nrf5340 processor and have implemented the commands to read and set the tx power level in the controller.  Do you know if passing a tx power level of 3 with the HCI BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL command will set the tx power level to +3dBm in the nrf5340 radio?  There's a note in the datasheet stating +3dBm power is possible if the VREQCTRL.VREQH is set.  What happens if we try to set a power level greater than 3 dBm?  Does the get TX power command (BT_HCI_OP_VS_READ_TX_POWER_LEVEL ) return a truncated power level to be reflective of the actual setting?

Thanks!

[Marte Myrvold]

Hi,

Do you know if passing a tx power level of 3 with the HCI BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL command will set the tx power level to +3dBm in the nrf5340 radio?

Yes, if you are using the SoftDevice controller then you can set the tx power to +3 dBm with the BT_HCI_OP_VS_WRITE_TX_POWER_LEVEL command. The Zephyr controller does not support +3 dBm on the nRF5340.

What happens if we try to set a power level greater than 3 dBm?

Then it will be set to +3 dBm instead.

Does the get TX power command (BT_HCI_OP_VS_READ_TX_POWER_LEVEL ) return a truncated power level to be reflective of the actual setting?

BT_HCI_OP_VS_READ_TX_POWER_LEVEL returns the actual tx power.

If you are curious and want to test this out you can use the Bluetooth: HCI Power Control sample. This sample will change the tx power to the values in the array txp, so you can change the values in txp to test with 3 dBm and above 3 dBm. The sample also reads the tx power with BT_HCI_OP_VS_READ_TX_POWER_LEVEL and prints it. Just add the following to prj.conf:

CONFIG_BT_LL_SOFTDEVICE=y

CONFIG_BT_LL_SW_SPLIT=y

Then build the sample for the net core and build the empty app core sample for the app core to test it out.

Best regards,

Marte