nRF52840 Radio receiving with CRC

RE: nRF52840 Radio receiving with CRC

TigerD — Tue, 19 Oct 2021 12:33:32 GMT

Hi Vidar,

Thank you for your valuable knowledge. I will try to use EVENTS_ADDRESS and compensate T.

Best Regards,

David

RE: nRF52840 Radio receiving with CRC

Vidar Berg — Tue, 19 Oct 2021 09:13:45 GMT

Hi David,

I think the RSSI will be more accurate if you start the sampling after receiving the EVENTS_ADDRESS so that the sample is taken while receiving the packet payload. Also note that - 99dBm is outside the valid RSSI range between -90 to -20 dB.

For even better accuracy you should consider including temperature compensation with the internal TEMP sensor: [153] RADIO: RSSI parameter adjustment

Best regards,

Vidar

RE: nRF52840 Radio receiving with CRC

TigerD — Mon, 18 Oct 2021 15:44:54 GMT

Hi Vidar,

Thank you for debugging my code. I made a mistake in frc_tx code by setting

NRF_RADIO_CRC_ADDR_SKIP instead of NRF_RADIO_CRC_ADDR_INCLUDE.

Now I set CRCCNF to

nrf_radio_crc_configure(RADIO_CRCCNF_LEN_Disabled, NRF_RADIO_CRC_ADDR_INCLUDE, 0x18E);

on both projects, and I still got:

Was the above setup for CRC not enough?

EDIT1 : the CRCPOLY is 0x18D not 0x18E passed in.

Is one byte CRC not enough?

EDIT -2 : made mistake again: It shall be configured as :

nrf_radio_crc_configure(RADIO_CRCCNF_LEN_One, NRF_RADIO_CRC_ADDR_SKIP, 0x18D);

Then it works. Thank you again.

Could you please review RSSI value reading :

    nrf_radio_shorts_enable(NRF_RADIO_SHORT_READY_START_MASK | NRF_RADIO_SHORT_END_START_MASK
      | RADIO_SHORTS_ADDRESS_RSSISTART_Msk | RADIO_SHORTS_DISABLED_RSSISTOP_Msk
      );

if (nrf_radio_event_check(NRF_RADIO_EVENT_RSSIEND)) {
rssi = (volatile uint8_t )NRF_RADIO->RSSISAMPLE;
}

Is that correct?

I have noticed that under -85dBm rssi, it starts having receiving problem (skipped or rejected by CRCOK). But in some other applications, -99 dBm is still capable of receiving. I am not so sure that is there anything wrong with my code (radio test and frc_tx).

Thank you,

David Zhou

RE: nRF52840 Radio receiving with CRC

Vidar Berg — Mon, 18 Oct 2021 15:12:41 GMT

Hi David,

Thanks. I ran you code here and noticed the same problem you've been describing. However, when I look at the RADIO registers I see that CRC has not been enabled. CRCCNF is '0'.

RE: nRF52840 Radio receiving with CRC

TigerD — Fri, 15 Oct 2021 13:55:36 GMT

Hi Vidar,

I have attached two projects source code. Global Macros:

SDK7=SDK7=F:\_Develop\nRFSDK\nRF5_SDK_17.0.2_d674dde

EDIT1:

Project folder structure:

local_root:

nRF5_SDK_17.0.2_d674dde
_Project\nRF_17\frc_tx
\radio_test

Load radio_test, and type print_rx on UART terminal, it will receive packages from frc_tx project running from a second nRF52840 DK.

I calculated checksum, printed on the second and third bytes, if not equal. (EF BA), Fourth byte [03], is the number of packages with checksum error. (But all packages are received when CRCOK event triggered). (Radio channel is fixed at 10).

20 EF BA 03 24 05 06 07 08 09 0A 0B 0C 0D 09 BF
10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F

At the same time, could you please review my code for reading RSSI values? I noticed that RSSI >|(-85)|, it is likely to have checksum errors. But for Beacon examples, RSSI at -99 or less (more negative), is still receiving packets ok. I am wondering I did anything wrong in reading RSSI, or something else.

Appreciate your help!

David Zhou

devzone.nordicsemi.com/.../frc_5F00_tx.zip

devzone.nordicsemi.com/.../radio_5F00_test.zip

RE: nRF52840 Radio receiving with CRC

Vidar Berg — Fri, 15 Oct 2021 11:58:52 GMT

Hi David,

The RADIO should only report packets with a valid checksum, and I think it should be unlikely to have a CRC collision here. Seems more likely that there is a FW bug causing the log buffer to become invalid, etc.

Could you provide the code you use to test this?

Best regards,

Vidar