Problem of ST25R3911 ERR_RF_COLLISION

[HPARK.1]

I used ST25R3911 and ST25DV16K for nfc.

I frequently get an error message about ERR_RF_COLLISION from rfalST25xVPollerFastReadMessage.

What is the problem?

As far as I know that RF_COLLISION is happened when the NFC reader has multiple NFC Tags neraby.

But, I only used one tag(ST25DV16K).

[Brian TIDAL]

Hi,

can you provide some additional informations about your setup:

• HW:
  • X-NUCLEO-NFC05A1 or custom board or ST25R3911B-DISCO?
  • MCU: STM32? or other MCU?
• SW
  • X-CUBE-NFC5 or STSW-ST25RFAL001?
  • RFAL version (see RFAL_VERSION in rfal_rf.h)

Can you check the value of RFAL_FDT_LISTEN_V_ADJUSTMENT: is it 128U?

Do you have similar issue with rfalST25xVPollerReadMessage?

Rgds

BT

[HPARK.1]

Reader : Custom board(STM32F091 & ST25R3911) - one board

(Reader antenna is made very similar to the EV Kit.

Tag : Mother board(STM32F103) + ST25DV16K EV Ant(https://www.st.com/en/evaluation-tools/ant-1-6-st25dv.html)

X-CUBE-NFC5 / v2.0.10 

RFAL_FDT_LISTEN_V_ADJUSTMENT : 128

I don't know exactly about your question, because I only userfalST25xVPollerFastReadMessage.

I'll test that using rfalST25xVPollerReadMessage.

[HPARK.1]

Reader : Custom board(STM32F091 & ST25R3911) - one board

(Reader antenna is made very similar to the EV Kit.

Tag : Mother board(STM32F103) + ST25DV16K EV Ant(https://www.st.com/en/evaluation-tools/ant-1-6-st25dv.html)

X-CUBE-NFC5 / v2.0.10 

RFAL_FDT_LISTEN_V_ADJUSTMENT : 128

I don't know exactly about your question, because I only userfalST25xVPollerFastReadMessage.

I'll test that using rfalST25xVPollerReadMessage.

[Brian TIDAL]

Hi,

Our ISO 15693 decoder returns ERR_FRAMING when the Start of Frame is not detected and returns ERR_COLLISION for other errors (such as logic 0 or logic 1 not being properly received). This might be due to some reception errors (i.e. it might be a antenna issue on reader side). I would suggest to do some trials with rfalST25xVPollerFastReadMessage on X-NUCLEO-NFC05A1: if it properly works on X-NUCLEO-NFC05A1 and not on the custom board, the antenna should be checked (see AN4974 Antenna matching for ST25R3911B/ST25R391x devices).

Can you elaborate on "Reader antenna is made very similar to the EV Kit"? Do you mean similar to the ST25DV-Discovery kit antenna?

Rgds

BT

[HRYU.11]

Dear ST..

I am RYU, a Community Member's HW engineer.

​History is as follows. (From a H/W point of view...)

(1) Our NFC Antenna size is different from ISO(NFC Antenna size).

--> Antenna size 146mm * 86mm(Reader and Tag antenna size are the same size, FAE recommanded)

​(2) NFC Reader antenna matching --> see attached file("NFC Reader Module_RF matching.pdf")

(3) Test results

-.(Our products)NFC Reader + NFC Tag = V_EH(3.0V maintained distance) is 40mm.

-.(Our product)NFC Reader + EV-kit ST25DV C1 Tag = V_EH(3.0V maintained distance) is 90mm.

​ -.(Our product)NFC Reader + (Hand-made Antenna) 90mm*90mm Tag = V_EH(3.0V maintained distance) is 40mm.

-.(Our product)NFC Reader + (Hand-made Antenna) 40mm*30mm Tag = V_EH is not working.

Based on the Test results, I have the questions below.

Question#1 : When designing a TAG Antennam, should I consider the Reader Antenna size?

(If I want the same performance as EV-kit C1 Tag..)

Question#2 : When NFC communication, is it only good at a specific distance?

(40mm is works well, but 10mm is not work.)

Question#3 : When during NFC Reader operation, if there is a change in the distance between the Tag and the Reader,

The NFC Reader does not recognize the Tag. What's the reasen?

Please check it.

[Travis Palmer]

Hello,

Q#1: We generally see two use cases here:

1.) The reader should work with as many tags as possible. Different antenna sizes and different technologies should deliver the same performance. Such a device would be a multi-purpose reader. In this case reader and tag should comply with the standards. Like NFC Forum Analog defines tests and rules for such devices.

2.) The reader and a set of tags belong together. Other tags may not be read by the reader. The reader should still comply with the standards. For example the Hmin and Hmax of ISO14443 should be respected for safe operation. Other devices shall not be harmed or disturbed. But it is possible to change reader and tag geometries to maximize the power transfer between reader and tag. Typically these special applications like OTA-NFC FW/parameter upgrades of devices or wireless charging applications.

Q#2&3: Typically "slow" movement of tags inside the NFC operating area should not be a problem. I would recommend to define two points in the operating area like:

0,0,40 => Ok-Point

0,0,10 => Nok-Point

and compare electrical parameters of the reader between these two points.

Such parameters could be:

VDD ... supply voltage, different antenna loading can cause different load condition and therefore voltage drops in the supply

I_VDD ... supply current,

V_RFI ... Receiver input voltage, use measure amplitude command to measure the V_RFI, adjust V_RFI to max 2.7Vpp using the capacitive v-divider. In close distance it could get smaller due to detuning of the antenna. Anyhow it should stay between 0.5V and 2.7V.

Reader waveshape ... look at over-, undershoots or other strange differences between those two points in the OV.

tag backscatter ... does the backscatter of the tag change between those two points? Is it still there in both positions? If the backscatter is gone, the tag did not understand the reader.

Enable test access ... output analog and digital receiver signals to CSI and CSO and look at the difference between the signals in the two positions.

br Travis

[HRYU.11]

Hello,

 I have the Question & Answer below.

(1) I use the NFC, but I don't know about the NFC forum.

So, I want to know if the size of the NFC Antenna design I want is possible.

(2) 0,0,40 => Ok-Point & 0,0,10 => Nok-Point

--> Question : I don't know what it means.

(3) CSI & CSO are not designed.

​ --> Answer : It was not designed because there were no operational problems. (FAE recommand)

​(4) NFC is our sole model. It is not compatible with other products.

Please check it.

Thanks​

[Travis Palmer · Accepted solution]

​Hello,

(1): According to Antenna matching tool the self resonance is above 13.56MHz and a proper matching network can be done.

The Q-Factor is 19, which is quite ok for ISO14443 and most bit rates.

(2): sorry i was not entirely clear: 0,0,40 should mean x=0, y=0, z=40 => 40 mm above the center of the antenna.

BR Travis