I am getting wrong parity bits from RFID tag

Hordeus · Aug 6, 2019

Hello everyone! I am working on a project making RFID reader by myself. I follow this circuit and check the output using oscilloscope. Data must have a framed like this. But i am getting wrong parity bits. Look at following pictures. Scope screen shifted by half resolution (3 is first display 2 is second display). From first 2 pictures I see:
1 1 1 1 1 1 1 1 1
1 1 0 1 0
1 1 1 1 0
last zeros must be even parity bits of first 4 bits in every row. Its a wrong parity bit. Help me please!

rjenkinsgb · Aug 6, 2019

I agree, based on the visible waveforms - though the data appears inverted, with "1" bits having high to low transitions.

I think you are missing the actual start of the data & seeing a block of zeros, not the real data run-in.

Photo 5 - 6 shows a nine-ones pattern then sets of five bits with even parity to the end of the display, with low to high as "1"

Data
00011
11110

00000
00000
1010?

That is: $1 F 0 0 A

The card number is stored as eight hexadecimal digits. The decimal number on the card face translates to 00A2 969D

The first two fit the card version number positions, then 0 0 A fit with the start of the card serial number...

I am getting wrong parity bits from RFID tag

Hordeus

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rjenkinsgb

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I am getting wrong parity bits from RFID tag

Hordeus

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