CC1352P7: Adding BLE Observer affects RAT in prop mode

DenisY

Part Number: CC1352P7

I am using Prop mode, BLE advertisements (and several profiles), and DMM to keep them together.

And it works perfectly. My Prop mode implementation based on RAT timer, and the syncronisation precision is excellent, usually less than 1 us / second with accounting to drift. I can do Prop search, enable and disable BLE advertisement, transfer data with OAD -- everything I do does not affect RAT, it is always extremely precise.

But I recently added BLE Observer role into the code, and RAT timer goes wild.

Scanning for BLE tags around just for 1 second causes RAT timer to be off for -200 us. Running the scan every few seconds changes the average RAT drift for 20 ppm.

Hardware engineer said that difference cannot be explained by temperature. Can you please help finding the issue.

CC1352P7

SDK 5.10.00.48

over 2 years ago

0 Arthur R☑️ over 2 years ago

TI__Mastermind 25896 points

Hi Denis,

Are you using an external crystal in your application?

Could this be related to the following?: https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/1068369/cc1352p7-rat-not-accurate-without-external-32khz-crystal/3964275#3964275

Regards,

Arthur

0 DenisY over 2 years ago in reply to Arthur R☑️

Prodigy 60 points

Arthur

Thank you. Unfortunately no, we are using both 48MHz and 32KHz crystals in the design. And both are correctly assigned in the device configuration.

This is very strange issue, because I used to think RAT as extremely precise point of reference, and apparently BLE scan manipulating it in some unclear way.

I am thinking to manually RF_yield() after Prop mode operations, just to check if sleep mode somehow connected to the issue. But even then... 200us leap equal to 7 ticks of LF crystal, it just does not sound plausible.

0 Arthur R☑️ over 2 years ago in reply to DenisY

TI__Mastermind 25896 points

Hi Denis,

It does seems like the scanner command makes use of the channel 1 of the radio timer.

It uses it to setup a time base when executing the command.

Do you have the option to use of of the other channels?

Regards,

Arthur

0 DenisY over 2 years ago in reply to Arthur R☑️

Prodigy 60 points

Interesting. I can see the gag start delayed. Where I can read about the other channels?

0 Arthur R☑️ over 2 years ago in reply to DenisY

TI__Mastermind 25896 points

Hi Denis,

They are documented in the RF driver code (RFCC26X2_multiMode.c:172), as well as in the technical reference manual, chapter 25.11 (RFC_RAT register docs).

In the radio driver, it actually states that your application should only be using channel 5,6 and 7.

Regards,

Arthur

Sub-1 GHz

Sub-1 GHz forum

CC1352P7: Adding BLE Observer affects RAT in prop mode