I'm inquiring about the "CRC Failed" error.

[hee910224]

Hello, I'm asking because I haven't solved the problem in a few days.
I used a translator because I was not good at English.

I'm trying to do "ni USRP 2900" ads-b communication in window 10.

I installed gnuradio directly from Windows 10 and USRP from ni, so I use it without Cmake or any other build work you uploaded.

When I used the code you posted on the git, the message below appeared and overflow continued.
"Ousrp_source :error: In the last 758 ms, 3 overflows occurred."
Then, I changed the sample rate and several values, and when I first run the program, I get the data as shown below.

[INFO] [UHD] Win32; Microsoft Visual C++ version 14.2; Boost_107800; UHD_4.4.0.0-release [INFO] [B200] Detected Device: B200 [INFO] [B200] Operating over USB 3. [INFO] [B200] Initialize CODEC control... [INFO] [B200] Initialize Radio control... [INFO] [B200] Performing register loopback test... [INFO] [B200] Register loopback test passed [INFO] [B200] Setting master clock rate selection to 'automatic'. [INFO] [B200] Asking for clock rate 16.000000 MHz... [INFO] [B200] Actually got clock rate 16.000000 MHz. [INFO] [B200] Asking for clock rate 40.000000 MHz... [INFO] [B200] Actually got clock rate 40.000000 MHz. [INFO] ---------------------------------------------------------------------- [INFO] �[1m�[35mDatetime�[0m: �[22m2023-11-10 02:17:34.567997 UTC�[0m�[0m [INFO] �[1m�[35mSNR�[0m: �[22m15.80 dB�[0m�[0m [INFO] �[1m�[35mDownlink Format (DF)�[0m: �[22m26�[0m �[2mReserved�[0m�[0m [DEBUG] �[1m�[32mDF�[0m: �[22m26�[0m �[2mUnknown DF�[0m�[0m [INFO] ---------------------------------------------------------------------- [INFO] �[1m�[35mDatetime�[0m: �[22m2023-11-10 02:17:34.568097 UTC�[0m�[0m [INFO] �[1m�[35mSNR�[0m: �[22m11.22 dB�[0m�[0m [INFO] �[1m�[35mDownlink Format (DF)�[0m: �[22m25�[0m �[2mReserved�[0m�[0m [DEBUG] �[1m�[32mDF�[0m: �[22m25�[0m �[2mUnknown DF�[0m�[0m [INFO] ---------------------------------------------------------------------- [INFO] �[1m�[35mDatetime�[0m: �[22m2023-11-10 02:17:34.571209 UTC�[0m�[0m [INFO] �[1m�[35mSNR�[0m: �[22m13.69 dB�[0m�[0m [INFO] �[1m�[35mDownlink Format (DF)�[0m: �[22m16�[0m �[2mLong Air-Air Surveillance (ACAS)�[0m�[0m [INFO] �[1m�[35mCRC�[0m: �[22m�[31mFailed�[0m �[2mUnrecognized AA from AP�[0m�[0m [INFO] �[1m�[35mAddress Announced (AA)�[0m: �[22m40ced8�[0m�[0m [DEBUG] �[1m�[32mFEC�[0m: �[22mConservative error correction lookup failed to get syndrome�[0m�[0m Ousrp_source :error: In the last 1129 ms, 1 overflows occurred. [INFO] ---------------------------------------------------------------------- [INFO] �[1m�[35mDatetime�[0m: �[22m2023-11-10 02:17:34.575103 UTC�[0m�[0m [INFO] �[1m�[35mSNR�[0m: �[22m16.10 dB�[0m�[0m [INFO] �[1m�[35mDownlink Format (DF)�[0m: �[22m6�[0m �[2mReserved�[0m�[0m [DEBUG] �[1m�[32mDF�[0m: �[22m6�[0m �[2mUnknown DF�[0m�[0m

As this data appears, the message CRC Failed continues to appear.

If you change the parameter value, the message below appears.

"
[DEBUG] DF: 8 Unknown DF
[DEBUG] DF: 3 Unknown DF
[DEBUG] DF: 0 Unknown DF
Ousrp_source :error: In the last 758 ms, 3 overflows occurred.
[DEBUG] DF: 11 Unknown DF
O[INFO] ----------------------------------------------------------------------
[INFO] Datetime: 2023-11-08 08:06:59.909242 UTC
[INFO] SNR: 11.04 dB
[INFO] Downlink Format (DF): 18 Extended Squitter/Non-Transponder
[INFO] CRC: Failed PI^CRC = 16553477
[DEBUG] DF: 25 Unknown DF
[DEBUG] DF: 3 Unknown DF
O[INFO] ----------------------------------------------------------------------
[INFO] Datetime: 2023-11-08 08:07:00.077605 UTC
[INFO] SNR: 8.57 dB
[INFO] Downlink Format (DF): 19 Military Extended Squitter
[INFO] CRC: Failed PI^CRC = 14293493
[DEBUG] DF: 28 Unknown DF
[DEBUG] DF: 27 Unknown DF
[INFO] ----------------------------------------------------------------------
[INFO] Datetime: 2023-11-08 08:07:00.147801 UTC
[INFO] SNR: 5.91 dB
[INFO] Downlink Format (DF): 17 Extended Squitter
[INFO] CRC: Failed PI^CRC = 13570376
[DEBUG] DF: 0 Unknown DF
[DEBUG] DF: 31 Unknown DF
[INFO] ----------------------------------------------------------------------
[INFO] Datetime: 2023-11-08 08:07:00.222440 UTC
[INFO] SNR: 10.50 dB
[INFO] Downlink Format (DF): 18 Extended Squitter/Non-Transponder
[INFO] CRC: Failed PI^CRC = 178647
OOusrp_source :error: In the last 841 ms, 4 overflows occurred.
[DEBUG] DF: 8 Unknown DF
OOO[DEBUG] DF: 23 Unknown DF
[DEBUG] DF: 27 Unknown DF
O[DEBUG] DF: 27 Unknown DF
[DEBUG] DF: 11 Unknown DF
Ousrp_source :error: In the last 832 ms, 5 overflows occurred.
O[DEBUG] DF: 22 Unknown DF
OO[DEBUG] DF: 14 Unknown DF
[DEBUG] DF: 10 Unknown DF
[DEBUG] DF: 16 Unknown DF
O[DEBUG] DF: 11 Unknown DF
"
gnu adsb.zip

I don't know if this is a problem because the plane doesn't pass in my area or if it's an error in the code.

I can't find an answer when I Google "CRC error" from gnuradio.

Have you experienced any of the same problems with implementing ads-b?

I really want to solve it. Please help me!

[mhostetter]

You need to lower the sample rate to reduce the overflows. The overflows will drop samples, which can corrupt packets and lead to CRC failures.