presence of multiple tags

[eoved]

Posted on March 05, 2014 at 21:04

Hi.

I am using CR95HF. I need to identify the presence of multiple  iso15693 tags ( placed on the same time ). I need to know how the amount of tags only. Is ther a command or algorithm ?. Please Advise. Ephraim Oved #cr95hf-iso15693 #m24lr #cr95hf #multi-tag #collision

[Anais GALLIGANI · Accepted solution]

Posted on March 06, 2014 at 13:08

Hello,

Are you using our software in order to control CR95HF?The inventory algorithm 16 slots is implemented inside.If not, inventory command is serving this aim; it is needed to control it.  In order to detect presence of many tags , it is needed to send an inventory 1 slot with a zero  masklength value.

• see also AN3375 http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/DM00025202.pdf
• And also AN3985  http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/DM00039049.pdf

If there is a collision

• Start an  inventory  16 slots with masklength at value 0, so no maskvalue.
• Many use cases possible for each slot 

1.  No answer, go to next slot (send EOF only)
2. Answer without any collision, recover UID
3. Answer with collision, recover slot number Sni
4. Complete or not the evaluation of the other slots
5. Put in quiet the other already identified tags
6. Start an inventory 16 slots with masklength = previous masklength+4 (0 + 4 from the first iteration) and maskvalue=previous maskvalue||SNi (Sni from first iteration)
7. Recover first step
8. If no more collision detected,end algo

Have a nice day,

Best regards,ST NFC/RFID Dynamic tag online support