Problem with NFC-ST25R95 tag detection

[Ashish_]

Hello,

I'm use ST25R95. I'm facing problem with Tag detection in WEF mode.

Its working fine with WEF from Time out and IRQ_In low pulse, But not get wake from sleep mode

when I configured it for a Tag detection.

Observation: I seen during Tag Calibration that there is no change appear in result of calibration Idle command with

Tag or Without Tag, all time the pattern of response even without Tag or with Tag calibration is same. Obvious that

calibration should be without Tag, but I tried with tag to check what changes happen in response from slave, but there is no change, I get always same response pattern.

I'm use these commands for calibration and to put in WEF mode respectively, 

{ST25R95_COMMAND_IDLE, 0x0E, 0x03, 0xA1, 0x00, 0xF8, 0x01, 0x18, 0x00, 0x00, 0x60, 0x60, 0x00, 0x00, 0x3F, 0x01};

{ST25R95_COMMAND_IDLE, 0x0E, 0x0A, 0x21, 0x00, 0x79, 0x01, 0x18, 0x00, 0x00, 0x60, 0x60, 0x74, 0x84, 0x3F, 0x08};

Also with value of gRFAL.wum.cfg.indAmp.delta = 4U, Its woke up without Tag and response is 02(Tag detection),

when I change this value from 4U to 8U, I don't get wake up event. 

 

Kindly help me out.

[Ashish_]

Observation: 

I always gets value of DacDataRef after calibration is 0x54

[Brian TIDAL]

Hi,

what is your HW setup: do you use ST board such as X-NUCLEO-NFC03A1 or a custom board?

Regarding the FW: do you use the RFAL? Which package is being used (X-CUBE-NFC3 or STSW-ST25R-LIB) and which version?

Do you use the st25r95CalibrateTagDetector that is called inside rfalInitialize or your own calibration procedure?

Regarding the command used for entering in Wait For Event mode, it seems different from the one provided inside the RFAL and the WU Control value is not inline with the Datasheet recommended value. I would suggest to use the one provided inside the RFAL and to use the RFAL wake up mode API.

On my side with a X-NUCLEO-NFC03A1, gRFAL.wum.CalTagDet is 0x80 in free air and 0x60 when a tag is on the antenna.

Rgds

BT

[Ashish_]

Hello,

I'm using it with a custom board.

Yes. Using RFAL lib files,   

/** PROJECT: ST25R95 firmware
* $Revision: $
* LANGUAGE: ISO C99
*/

Even Tag reading and all that functionality works fine.

I'm using Lib function st25r95CalibrateTagDetector that is called inside rfalInitialize for calibration. 

 

If I set WU Control value = 0x38 0x01 as per recommended, with that it is not woke up by even providing Low pulse on IRQ_IN pin as well as by Tag detection also not work. But if I set it by 0x79 0x00 recommended in Application note AN3433, it is wake up by providing Low pulse on IRQ_IN pin as well It woke up without Tag if value of gRFAL.wum.cfg.indAmp.delta = 4U as per Lib, but if I change it from 4U to 8U, It is not wake up by Tag detection even I tap Tag on antenna. 

On my side gRFAL.wum.CalTagDet is 0x54 in free air and with Tag also. Some time it returns 0x50 when a tag is on the antenna.

Thanks.

 

 

[Brian TIDAL]

Hi,

the value provided by RFAL is able to properly manage the wake up pulse on IRQ_IN. This is the WU source field and its value is 0A which means Low pulse on IRQ_IN and tag detection. 

Is the IRQ_OUT properly connected in your application? As explained in the Datasheet, "In low power consumption mode the device does not support SPI poll mechanism. Application has to rely on IRQ_OUT before reading the answer to the Idle command." If your application does not use the IRQ_OUT but the SPI poll, the Idle command will not work properly (except if the HF oscillator is kept on but that drastically reduces the interest of the low power mode...)

Regarding the calibration issue, I believe this is caused by the matching circuit. Make sure to follow the AN5248  application note (ST25R95 transceiver antenna tuning circuit with EMI filter).

Rgds

BT

[Ashish_]

Hello,

Yes, IRQ_OUT is properly connected. 

Case 1: With value of WU control = 79 01, gRFAL.wum.cfg.indAmp.delta = 8U;

Result:

If I provide Low Pulse on IRQ_IN pin, wake up occurred successfully. <<<0x000108 Wake-up by low pulse

But Tag detection wake up Not work.

Case 2: with value of WU control = 79 01, gRFAL.wum.cfg.indAmp.delta = 4U;

Result: 

After sent a Idle command I monitor status of IRQ_OUT pin, Without Tag and Low pulse on IRQ_IN pin, it wake up, and response is <<<0x000102 Wake-up by tag detect

[Brian TIDAL]

Hi,

with WU control = 38 01, the device properly exit from wakeup mode when receiving an IRQ_IN pulse but does not send a response (no notification on IRQ_OUT). This case is managed by the RFAL code that polls the device for readiness before sending the next command after killing the Idle command. With WU control = 39 01, the device sends a response (notification on IRQ_OUT) when exiting after an IRQ_IN pulse. 

This is what you observe on your side (bit 6 of the WU Control is RFU and ignored so using 39 01 or 79 01 is similar).

Now back on your tag detection issue, this is likely caused by the matching circuit/antenna. Feel free to provide your schematics for review + gerber/layout. Make sure to have no shielding in the antenna area and to follow  AN5248  application note.

Rgds

BT

[Ashish_]

Hello, 

Here I'm attaching schematics. Can you please guide us is it seems ok or need any modifications?

component which mentioned NM, has not mounted on board. i.e. Cb, Cc, Rq.

Thanks.

[Brian TIDAL]

Hi,

what is the antenna impedance (Ra and La values)? have the Ra/La value been checked on real board or only estimated values? Is the antenna deported from the main board with a cable or is it printed on the reader PCB? what is the layout (feel free to provide the gerber)? Was  AN5248  followed?

Rgds

BT

[Ashish_]

An antenna impedance values are R = 5.2 ohm and La = 3.0 uH. 

Yes, an antenna deported from main board with a cable.

Thanks.

[Henry Crane]

Hello,

the ST25R95 antenna matching circuit shall be calculated based on the antenna impedance measured on the input of antenna cable. A good impedance matching in free air is necessary to maximize the tg detection mechanism. 5R/3uH impedance is measured at cable input or antenna without cable? 

best regards,

Henry Crane