Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

I am getting wrong parity bits from RFID tag

Status
Not open for further replies.

Hordeus

New Member
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!
 

Attachments

  • 1.jpg
    1.jpg
    33 KB · Views: 234
  • 3.jpg
    3.jpg
    88.1 KB · Views: 232
  • 2.jpg
    2.jpg
    81.1 KB · Views: 231
  • 4.jpg
    4.jpg
    91.1 KB · Views: 230
  • 5.jpg
    5.jpg
    92.9 KB · Views: 231
  • 6.jpg
    6.jpg
    91 KB · Views: 234
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...
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top