Max output power in BLE direct test mode

RE: Max output power in BLE direct test mode

JONATHAN LL — Mon, 04 Aug 2025 22:34:21 GMT

You can use the following nrfutil command:

nrfutil device x-read --address <address> --direct --core Network

Base address network RADIO
0x41008000
TXPOWER
0x50C

-----------------------

Base address network VREQCTRL
0x41004000
VREGRADIO.VREQH
0x500
VREGRADIO.VREQHREADY
0x508


nrfutil device x-read --address <address> --direct --core Network

So example:

C:\>nrfutil device x-read --address 0x4100850C --direct --core Network
1050053641
0x4100850C: 00000000

So did test and if you set the TX power to more then 3 dBm in the DTM app then it actually sets the power to -8dBm. So dont do that.

Regards,
Jonathan

RE: Max output power in BLE direct test mode

Rantanplan — Mon, 04 Aug 2025 15:25:13 GMT

Hi,
I can confirm that higher TXPOWER values than +3 dBm in the GUI are simply ignored (the old setting persists).

To get the highest output power with the nRF5340, + 3dBm must be selected, which results in:

TXPOWER = 0x0 and

VREQCTRL = 0x1.

Just to explain:
VREQCTRL = 0x1 enables +3 dBm output

TXPOWER is typically interpreted as negative value.

So, e.g. -2 dBm can be achieved with

VREQCTRL = 0x1 (3 dBm)

and

TXPOWER = 0xFF (-1)

Kind regards,

Christian

PS: Unfortunately, the ignoring of unsupported high power values is not reflected in the GUI. The GUI shows a bar with 8 dBm for the nRF5340 if the slider is set to 8 dBm. A error message would be highly appreciated here.

RE: Max output power in BLE direct test mode

Rantanplan — Fri, 01 Aug 2025 11:06:44 GMT

Hi,

sorry for the stupid question, but how to access the TXPOWER and VREQCTRL correctly from the application or network core of the nRF5340?

Many thanks and kind regards,

Christian

RE: Max output power in BLE direct test mode

JONATHAN LL — Fri, 01 Aug 2025 09:11:58 GMT

Hi,

Max TX power is +3dBm so set the UI to +3 dBm, adjusting the slider higher should still leave the TX power at largest possible value, but I have not tested this so can not confirm.

What you can do is read the TXPOWER register to see what value it has.

Regards,
Jonathan