CC1310: RSSI value differentiation analysis

Rain Wang

Part Number: CC1310

Hi TI

Test environment: The customer uses his own board, uses the RF studio transceiver automatic test function, sets the RF parameters such as the transmit power, exports the. C and. H configuration files, loads them into his own CCS project, compiles them and downloads them to his own board.

After reading the RSSI value, it is found that the RSSI value in the original message received by the customer is inconsistent with the one read by RF Studio, and the difference is about 15dBm each time.

1. Can you help me analyze the reason? I think it is caused by the customer's own software, but the RF configuration used is the same as that of RFstudio, so I don't know how to solve this problem, thank you.

2. Can RFstudio save the original packet receiving RSSI to analyze the correspondence between the RSSI value on the interface and the actual data frame? Can you explain the data source of the RSSI value in RF studio?

over 2 years ago

0 Arthur R☑️ over 2 years ago

TI__Mastermind 25906 points

Hi Rain,

I think this might have to do with the RSSI_OFFSET inside of the chip. This depends of the PHY being used. SmartRFStudio uses a different RSSI calculation method also.

Please look at the following threads:

https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/793208/cc1310-rx-rssi-offset

https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/978699/cc1310-cant-take-good-rssi-value-using-cc1310-without-cc1190/3615587#3615587

https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/694138/ccs-cc1310-rssi-offset-setting-for-hsm-without-cc1190/2557786#2557786

https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz-group/sub-1-ghz/f/sub-1-ghz-forum/856174/ccs-launchxl-cc1350-rssi-to-dbm-equation-after-reading-from-register-0x4004-517c/3171796#3171796

I hope that helps,

Regards,

Arthur

0 Rain Wang over 2 years ago in reply to Arthur R☑️

Expert 1400 points

Hi Arthur

Thank you for your timely reply. After reading your link, the following questions are not very clear. I hope you can help explain or share documents:

1. Why do I need to add RSSI offset? Would like to explain it in more detail

2. Is this offset added by the data sender device? The above phenomenon is caused by the different settings of the offset value in the client program and the RFstudio program? How to confirm the offset value added in RFstudio?

0 Siri over 2 years ago in reply to Rain Wang

TI__Guru* 86731 points

The RSSI offset will vary with different PHYs and with different HW.

What you need to do is to adjust the offset on your HW so that you will have the correct RSSI reported.

To do this, you should have a signal with a known signal strength from a signal generator input to your board (via a cable).

The offset is set by an override, and you need to change this override on your board to make the RSSI reading correct.

If you look at the override list for different PHYs/settings you will see something like this:

// Rx: Set RSSI offset to adjust reported RSSI by +5 dB (default: 0), trimmed for external bias and differential configuration
(uint32_t)0x00FB88A3,

// override_phy_rx_rssi_offset_neg2db.xml
// Rx: Set RSSI offset to adjust reported RSSI by -2 dB (default: 0), trimmed for external bias and differential configuration
(uint32_t)0x000288A3,

where the FB and 02 are the offset.

Siri

0 Rain Wang over 2 years ago in reply to Siri

Expert 1400 points

Hi Siri

Thank you for your answer.

Why is the RSSI value in the RFstudio at 470MHz and the RSSI value read by the customer's own software not much different under the same hardware condition, but the RSSI value read at 868MHz is quite different? How should we position the cause of this gap?

0 Siri over 2 years ago in reply to Rain Wang

TI__Guru* 86731 points

Not sure I understand what/how you are testing.

Are they using the same HW with both Studio and own SW, and if yes, what HW are you using?

Do you have two different boards since you are testing both 433 MHz and 868 MHz?

You cannot use a 433 MHz board for operation in the 868 MHz band, or vice versa.

How are they reading the RSSI in their customer code? Do they look at the appended RSSI in a packet or are they just reading the rssi value when in RX?

Siri

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CC1310: RSSI value differentiation analysis