Changing tx power has no effect under Zephyr

RE: Changing tx power has no effect under Zephyr

tesc — Wed, 12 Oct 2022 16:05:20 GMT

Hi,

I am happy to see you solved the main issue, through addressing both advertising sets.

When it comes to Bluetooth Controller, the SoftDevice Controller (SDC) is our proprietary BLE controller based on the link layer of our SoftDevice BLE stack. The SoftDevice Controller is the preferred controller to use with nRF Connect SDK. It is specially tailored for nRF SoCs, and this is also the controller we qualify with the Bluetooth SIG for use with our SDK, resulting in a QDID you can use for the qualification of your product. If using the Zephyr Controller then you must do the corresponding qualification yourself or rely on a third party having already done so. Regardless of which controller you use, the host layer will be the Zephyr BLE host which we also qualify for nRF Connect SDK releases.

Regards,
Terje

RE: Changing tx power has no effect under Zephyr

AndyM — Tue, 11 Oct 2022 18:27:26 GMT

UPDATE
The issue was due to the fact that my application has

CONFIG_BT_EXT_ADV_MAX_ADV_SET=2 as it needs 2 adv sets - one for mesh and one for beacon advertising

However the code that set the tx power only updated tx power in the first adv set

struct bt_hci_cp_vs_write_tx_power_level *cp;

cp->handle = sys_cpu_to_le16(0);

So the second adv set ( which is used for beacon advertising ) was never updated.

cp->handle = sys_cpu_to_le16(1); does the trick

Thanks for help!

RE: Changing tx power has no effect under Zephyr

AndyM — Tue, 11 Oct 2022 15:14:02 GMT

The sample does work.

NOTE

The sample proj.conf has

CONFIG_BT_CTLR_ADVANCED_FEATURES enabled. That gives a warning that a

CONFIG_BT_LL_SW_SPLIT dependency is missing

But it builds and works with and without CONFIG_BT_LL_SW_SPLIT
The problem is somewhere else. Our program uses mesh. I'll investigate and update.

If you have any pointers that would be appreciated.

Question

What's the advantage of using ( or not using ) SoftDevice Controller vs Zephyr BT stack ( CONFIG_BT_LL_SW_SPLIT =y)?

Thanks

RE: Changing tx power has no effect under Zephyr

tesc — Tue, 11 Oct 2022 11:50:39 GMT

Hi,

The HCI Power Control example already uses the SoftDevice Controller. Does the unchanged example as delivered through nRF Connect SDK also not work?

Testing the example here, on an nRF52 DK, I confirm both through power measurement (Power Profiler Kit II) and thorugh nRF Connect on Android, that TX power decreases step-wise (5 seconds on each step) then repeating that pattern indefinitely.

Regards,
Terje

RE: Changing tx power has no effect under Zephyr

AndyM — Mon, 10 Oct 2022 14:23:18 GMT

Our code is based on that sample. No errors are returned but the RSSI levels do not change. Verified that in the nRF connect mobile app on Android

What are the alternatives?

I could disable Zephyr BT stack and use the SDK SoftDevice controller -if I'm not mistaken, CONFIG_BT_LL_SW_SPLIT controls that

Is this a possibility? If so - could you point me to the API to set TX power using SoftDevice controller?

Thanks

RE: Changing tx power has no effect under Zephyr

tesc — Mon, 10 Oct 2022 12:01:40 GMT

Hi,

TX power can be set dynamically using the HCI, yes.

Setting it dynamically is also the workaround prior to nRF Connect SDK 2.1.0, if you want a fixed TX power setting other than the default, since fixed TX power setting does not work for the SoftDevice Controller prior to SDK 2.1.0. Hence the note.

I recommend having a look at the Bluetooth: HCI Power Control example, as it does exactly what you want; it changes TX power dynamically. In main.c you will find set_tx_power() and get_tx_power() functions, that are called from other functions inside main.c. I see that in that example, the CONFIG_BT_CTLR_ADVANCED_FEATURES is also enabled, although I am not sure which exact features used depend on this setting.

Regards,
Terje

RE: Changing tx power has no effect under Zephyr

AndyM — Thu, 06 Oct 2022 14:28:04 GMT

CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL is enabled

Please clarify your last statement about nRF Connect SDK and a CONFIG_BT_CTLR_TX_PWR_PLUS_8 setting
Does this mean that the TX power cannot be set dynamically?

I found a function
radio_tx_power_set() in subsys\bluetooth\controller\ll_sw\nordic\hal\nrf5\radio\radio.c

It sets the TX power register directly
Can I use that instead of the HAL API ? Or is this a private function?

RE: Changing tx power has no effect under Zephyr

tesc — Thu, 06 Oct 2022 13:02:13 GMT

Hi,

In order for the HCI commands to control the TX power, you also need to set the config:

CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y

Please note that from nRF Connect SDK v2.1.0, the SoftDevice Controller will use the CONFIG_BT_CTLR_TX_PWR_* settings, e.g. CONFIG_BT_CTLR_TX_PWR_PLUS_8 for +8 dBm.

Regards,
Terje