CC1352P: Tx power for advertisement set #2

Shuyang Zhong

Part Number: CC1352P
Other Parts Discussed in Thread: SYSCONFIG,

In simple_peripheral example there are 2 advertisement sets, one is legacy using 1M PHY and the other is extended using Coded PHY.

When enabling 20dBm Tx power from sysconfig and using a spectrum analyzer to measure the Tx power, I found that when the 2 advertisement sets are both enabled, the Tx power for the coded PHY is 14dBm, while the 1M PHY can reach 20dBm on channel 37 and 38 (as described in TX Power Backoff Table for CC13x2P Devices section of BLE user's guide).

I tested with only 1 advertisement set and both 1M PHY and Coded PHY can output 20dBm as expected. Why the Coded PHY is limited to 14dBm when 2 advertisement sets are enabled at the same time?

BR,

Shuyang

over 4 years ago

0 Arthur R☑️ over 4 years ago

TI__Mastermind 28317 points

Hi,

I assume that you are using the LAUNCHXL-CC1352P-2, is that correct?

Also, what SDK version are you using?

Regards,

Arthur

0 Shuyang Zhong over 4 years ago in reply to Arthur R☑️

TI__Expert 5115 points

Yes, LAUNCHXL-CC1352P-2 with SDK6.10

0 Arthur R☑️ over 4 years ago in reply to Shuyang Zhong

TI__Mastermind 28317 points

I am checking with other team members to find an explanation.

0 Jan over 4 years ago in reply to Shuyang Zhong

TI__Mastermind 44780 points

Hi Shuyang,

Can you try using two 1M PHY advertising sets and measuring the tx power? Do you see 20dBm on both or 14dBm on one and 20dBm in the other like you see when you do one coded and one 1M advertising set?

Best Regards,

Jan

0 Shuyang Zhong over 4 years ago in reply to Jan

TI__Expert 5115 points

Hi Jan,

I've tried with two 1M PHY advertising sets, the result was the same as using coded PHY, 14dBm on one and 20dBm on another (on channel 37 and 38).

On channel 39 both advertising were 14dBm.

Best regards,

Shuyang

0 Jan over 4 years ago in reply to Shuyang Zhong

TI__Mastermind 44780 points

Hi Shuygang,

Can you try using the HCI_EXT_SetTxPowerCmd() function to change the tx transmit power? The following thread provides some useful information on how to do this: https://e2e.ti.com/support/wireless-connectivity/bluetooth-group/bluetooth/f/bluetooth-forum/990571/cc2642r-how-to-change-transmit-power-of-advertisment

Let me know if the function is able to change the observed txPower on the second advertisement set.

Best Regards,

Jan

0 Shuyang Zhong over 4 years ago in reply to Jan

TI__Expert 5115 points

Hi Jan,

Using HCI_EXT_SetTxPowerCmd() made no difference.

I have found some clues about this issue:

1. When only 1 legacy advertisement set is used, Tx power is normal (20dBm on channel 37 and 38, 14dBm on channel 39).

2. When only 1 extended advertisement set is used, Tx power on channel 37/38/39 is all 20dBm.

20dBm on channel 39 when using extended advertisement:

3. When 1 legacy + 1 extended advertisement sets are used, Tx power of the extended advertisement becomes 14dBm on all channels(37/38/39).

14dBm on channel 37 when using two advertisement sets:

Based on this observation, my guess is that the TxPowerBackoffTable is not applied to extended advertisement set, so after a legacy advertisement is sent on channel 39 with 14dBm, the Tx power is not changed back when the next extended advertisement is sent.

If I am understanding right, the Tx power backoff value should be 14dBm on channel 39 when using 1M PHY, no matter legacy or extended advertisement is used, is that right? If yes I think the behavior of the stack does not meet the spec.

Can you please confirm with our R&D team for the logic behind this behavior? Thanks very much!

Best regards,

Shuyang

0 Jan over 4 years ago in reply to Shuyang Zhong

TI__Mastermind 44780 points

Hi Shuyang,

I will look into this and get back to you.

Best Regards,

Jan

0 Jan over 4 years ago in reply to Jan

TI__Mastermind 44780 points

Hi Shuyang,

We are still looking into this and I will update you as soon as I have some additional information to share.

Best Regards,

Jan

0 Jan over 4 years ago in reply to Jan

TI__Mastermind 44780 points

Hi Shuyang,

We have been able to schedule some testing in the lab for early next week. In the meantime, could you provide us with the projects you used for your tests?

Best Regards,

Jan

0 Shuyang Zhong over 4 years ago in reply to Jan

TI__Expert 5115 points

Hi Jan,

Please find the projects used as attached, all projects are based on SDK 6.20 and CC1352P-2 LaunchPad.

simple_peripheral_CC1352P_2_LAUNCHXL_tirtos7_ticlang_one_legacy_adv: 1 legacy advertisement, 1M PHY, 20dBm

simple_peripheral_CC1352P_2_LAUNCHXL_tirtos7_ticlang_one_ext_adv: 1 extended advertisement, 1M PHY, 20dBm

simple_peripheral_CC1352P_2_LAUNCHXL_tirtos7_ticlang_two_adv_20dBm: 2 advertisements (1 legacy + 1 extended), both use 1M PHY, 20dBm

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/538/Adv_5F00_Tx_5F00_Power_5F00_Test.7z

Regards,

Shuyang

+1 Jan over 4 years ago in reply to Shuyang Zhong

TI__Mastermind 44780 points

Hi Shuyang,

We were able to reproduce the behavior observed locally. I have filed a ticket with all of the provided information. The ticket should be addressed by R&D soon and afterwards a plan to investigate and work on the issue will be formulated. In the meantime, is this behavior causing issues for the customer? Is the customer able to work around this issue or are they blocked because of it?

Best Regards,

Jan

0 Shuyang Zhong over 4 years ago in reply to Jan

TI__Expert 5115 points

Hi Jan,

Thanks for the support!

The customer has been able to work around this by just enabling one advertisement set, but it is good to know that this issue will be fixed in the future SDK to avoid similar issues from other customers.

Best regards,

Shuyang

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CC1352P: Tx power for advertisement set #2