Change advertising TX power on NRF53

[Samuel Escobar]

Greetings,

I am using the NRF53 DK along with the Zephyr/Beacon (nRF Connect SDK v1.91) example for an ultra-low power application. I would like to know how I can change the default TX power used during advertisement. Or which is the proper way of doing it?

I appreciate any input or directions towards the required information.

Thanks beforehand.

Samuel.  

[Hung Bui]

Hi Samuel, 

You can have a look at this example: https://docs.zephyrproject.org/latest/samples/bluetooth/hci_pwr_ctrl/README.html

You can find the code to change TXPower in set_tx_power() function. 

[Samuel Escobar]

Der Hung, thanks for your reply. I've seen the example that you mentioned and I've taken the set_tx_power() function and implemented it on my code. I added the required libraries and copied the CONFIGS found on the "hci_power_ctrl" example.

Now I am getting one error message and one warning once this function runs.

The error is thrown from this part of the set_tx_power() function:

and the warning I really dont know what to make of it. 

Would you happen to know what might be happening?

Thanks in advance.

Samuel

[Hung Bui]

Hi Samuel, 

You would need to make sure you have added this CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y

Into the network core application which is the hci_rpmsg. 
To do that (if you don't want to modify the hci_rmpsg directly)  you need to create an overlay file named hci_rpmsg.conf inside  child_image folder in your project. 
And you add CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y in that file, the same as in the hci_pwr_ctrl example. 

Also make sure you only set the tx power to what available in the datasheet of the nRF5340: 

0dBm 0x0 0 dBm
Neg1dBm 0xFF -1 dBm
Neg2dBm 0xFE -2 dBm
Neg3dBm 0xFD -3 dBm
Neg4dBm 0xFC -4 dBm
Neg5dBm 0xFB -5 dBm
Neg6dBm 0xFA -6 dBm
Neg7dBm 0xF9 -7 dBm
Neg8dBm 0xF8 -8 dBm
Neg12dBm 0xF4 -12 dBm
Neg16dBm 0xF0 -16 dBm
Neg20dBm 0xEC -20 dBm

Neg40dBm 0xD8 -40 dBm

..

[Samuel Escobar]

Dear Hung,

Thanks for your help eventually I managed to get it to work with the information you provided.

One additional thing I had to figure out was that the set_tx_power() function must be called after the advertising payload was set. Just in case someone runs into the same issue.