BLE decode advertising header packet incorrect

I have been decoding a BLE advertising packet, I am getting correct preamble and access address but once I try to decode the PDU starting with the header it is incorrect. The preamble and access address are simply decoded through GFSK , with the endian swapped on the access address. Is there typically some form of encoding used in the PDU header that could explain why I cannot decode the correct header?

for example I am decoding the header to be 0x6F5B but using a BLE sig tester I can confirm the header is 0x201F, I know my decoding is working well before the header so I do not expect such drastic differences,

Thanks for your help in advance.

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0 user109878 over 3 years ago

Hi Terje,

Yes thats correct i am decoding directly from the radio peripheral,

Thanks,

William
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0 user8164 over 3 years ago in reply to user109878

Hi,

In that case I think you are basically down to consulting the Bluetooth Core Specification, as well as checking you do have the correct buffer sizes, etc., for correctly receiving the package. Please note also that depending on interference, you could receive erroneous messages (which checksums in the BLE protocol should detect.)

Are you consistently decoding the same wrong value?

Regards,
Terje
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0 user8164 over 3 years ago in reply to user109878

Hi,

In that case I think you are basically down to consulting the Bluetooth Core Specification, as well as checking you do have the correct buffer sizes, etc., for correctly receiving the package. Please note also that depending on interference, you could receive erroneous messages (which checksums in the BLE protocol should detect.)

Are you consistently decoding the same wrong value?

Regards,
Terje
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0 user109878 over 3 years ago in reply to user8164

Hi,

Thanks for your help, i dont think I'm having any buffer problems, I am consistently receiving the same value for the advertising packet header 0x6F5B, using another device I know it is really 0x201F. The preamble and access address are all correct, I think I may be missing some step in decoding the header of the advertising packet PDU, do you know if there is some encoding in place in the header?

Regards,

William
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