ST25R3911B reception fast mode not working

[mdesc]

Hello.

I'm currently working on a RFID research project using 2 ST RFID chip : ST25R3911B and ST25DV64K. The reader is the discovery kit with a home-made antenna to suit to the project constraint. The external filter has been redesigned and transferred power to the tag is all good.

The tag is based on the ST25DV64K plugged to a specific antenna as well. There's a parallel circuit that provides power (harvesting with diodes) to a MCU and sensors. The energy harvesting feature of the ST25DV wasn't enough for our needs.

Even without consumming power on the tag (only the RFID chip and diodes bride), i can't manage to suceed a FAst Read BLock command. I have 50% of error i'd say. Normal read work well, even with a 30 mW consumption after the diode bridge. But I can't manage to make the fast mode working.

I've tried to change filters parameters (register in the ST25R3911) but no success.

Could it be the specific antenna bandwidth ?

Is there any tricks in the ST25R3911B to achieve fast mode ?

(i've spied all the configuration sent on SPI, i've the same)

Thanks for your help

best regards

[Ulysses HERNIOSUS]

Hi mdesc,

are you using our RFAL?

There is one subtle difference from ST25R3911B perspective for ISO15693 fast vs normal speed: For fast mode you need to decrease the MRT value a bit. RFAL is built to cope with this but maybe you have it too aggressive for fast mode.

Regards, Ulysses

[mdesc]

Hello,

Yes i'm using your RFAL in the firmware for the STM32 connected to the ST25R3911B. I use the following function :

rfalST25xVPollerFastReadSingleBlock

I've checked all it was doing regarding reception stage filters and it was OK.

Register 0x08 stream mode def :

scp1 scp0 = 10 (4 pulses)

Register 0x1A Reciever configuration :

Recommended for 424/484 kHz subcarrier (page 9/116 on datasheet)

I havent, myself, change any configuration as it seems to be OK and chosen by RFAL.

I read in the datasheet that MRT value is the mask receive time. I wasn't aware of that parameter.

I don't know the value set by the RFAL .

Is it the same that RFAL set for normal and fast mode ?

SHouldn't the RFAL set it properly ?

Which value for the register I should try for the fast mode ?

Thanks a lot for your reply.

Fast mode is mandatory to achieve our system bitrate and we are, at the moment, in a deadlock.

Thanks again

[Ulysses HERNIOSUS]

Hi mdesc,

I tried issuing Fast Read Single Block on our ST25R3911B-DISCO GUI as per attached screenshot and I get a 100% success with an ST25TV02K. Is it the same for you when using our demo? And your issue only happens with your system/antenna?

If so, then can you share your antenna parameters?

Beneficial could also be to look into the signals in the field using a spy coils and using the receiver observation modes of ST25R3911B to do signal integrity.

As far as I know we have relaxed the MRT in RFAL for both speeds. The resulting MRT value should be 0x40.

Best Regards, Ulysses

[mdesc]

Hello Ulysses,

Indeed, If I use the disco kit and a ST25DV kit, it works.

It's probably due to antennas bandwidth, i'll send you parameters. (im working from home today)

Normal mode is all success even while transferring 30 mW power to my tag electronics.

Fast mode works only 50% of time, even without transferring power.

You've written that there are observation modes of ST25R3911B ? How can I use them ? Is there something written in the datasheet ?

Best regards,

melanie

[Ulysses HERNIOSUS]

Hi melanie,

please see Table 13. Test Access Register - tana signal selection of CSI and CSO pins in the DS.

I recommend to use tana = 0x01 and observe with a scope or logic analyzer capable of recording analog channels. To improve signal quality you can additionally cut the capacitive plates close to the UFL connector pads.

In software you can call rfalSetObsvMode(0x0a,0x01); to have also a nice TX signal and not flood the lines with noise when no reception is expected.

Best Regards, Ulysses