Deafult Tx Power changed to 0dBm in DTM library since SDK10

[endnode]

Dear Nordic team,

Beside other persistent issues with your proprietary DTM command for setting Tx Power (see here and here) I've found that default Tx Power in ble_dtm module was changed from max (+4dBm) to 0dBm in SDK10 (and kept in SDK11). See line #30 of /components/ble/ble_dtm/ble_dtm.h

#define DEFAULT_TX_POWER                RADIO_TXPOWER_TXPOWER_0dBm      /**< Default Transmission power using in the DTM module. */

Isn't it in contradiction with BT Core spec (at least with v4.0) where it is required to run DTM at maximum output power? This is my understanding from BT SIG Core 4.0 Volume 6 (Core System Package [Low Energy Controller Volume]) Part F (Direct Test Mode) Section 2.1 (Test Sequences) that DTM commands issued over "DTM Uart" and "HCI" are equal. Then Host Control Interface Functional Specification (Volume 2 Part E Section 7) says that commands should be performed at maximum transmit power, e.g. see this example in paragraph 7.8.29:

What was rationale behind this change (and could it be reverted back?;).

Thanks Jan

[Hung Bui]

Hi again Jan,

I understand that the command is from the host to the controller. But in the end, the DTM is to verifiy of the functionalities of a product. I don't see the point of testing something that the product doesn't offer. I just double checked with one of our hardware guys and he said we changed it to 0dBm not by accident and don't think we will change it back to 4dBm.

But as mentioned, you can easy change it back to 4dBm if you like.

[endnode]

Hi Hung Bui,

Thanks for the effort, good to know that Nordic at least did it on purpose not by mistake;) I've changed in our code as well as fixing vendor specific commands for actual setting of TXPOWER register during DTM. Still would be better to keep our code in-line with Nordic SDK (because all manual merging during each SDK migration is time consuming) but that's life.

Cheers Jan