cannot detect any tag on ST25R3916

[Gaston]

Hi,

I have made a custom design for reading/writing NTAG213 tags based on the X-NUCLEO-NFC06A1 board. I have adapted the firmware that works on this demo board (along with all the drivers related to the ST25R3916 and RFAL) into a STM32G030K8T6 microcontroller.

I have neither capacitive sensing nor AAT implemented in Hardware and I have also disabled these mechanisms in the Firmware according to this post.

The antenna design is very similar to the ST25R3916 Discovery Board (2 turns, 65mm x 85 mm). For the the antenna analysis I have measured its real parameters following the indications of the AN5276 Application Note:

This is LANT = 1.03 uH RSDC = 440m Ohms fres = 60.19 MHz Rp @ fres = 7.29 Kohms

 

Buy using the ST25R Antenna Matching Tool I get the following values for the custom board:

 

On the Firmware side the Initialization is successful (ERR_NONE)... but does not detect any tag during execution of the detection cycle routines.

I have checked the presence of any signal near the antenna by means of a small loop made with the oscilloscope probe. I see that the antenna is actually emitting at 13.56MHz every second.

 

Everything seems to be correct but why can't I detect any tag?

gaston

[Ulysses HERNIOSUS]

Hi Gaston,

can you already rule out that there is an issue in your ported software? Does it for example work with a cross-connected NFC6?

Regards, Ulysses

[Travis Palmer]

Hello Gaston,

can you measure the voltage on the RFI pins using the direct command "Measure Amplitude" ?

Please execute the command with and without card in the field and post its result.

BR Travis

[Gaston]

Hi Ulysses,

The porting was done from the STM32L476RG-Nucleo project. I will perform another porting starting from the STM32L053R8-Nucleo, which is a M0 + cortex like the one in my custom design.

gaston

[Gaston]

Hi Travis,

I've measured the voltage after demoIni() initialization function.

err = st25r3916ReadRegister(0xD3U, &result);

In both cases (with and without a card) the result is zero.

I've reproduced the same reading in the NUCLEO-NFC06A1 project with the same result.

Am I performing the right procedure to measure the voltage on the RFI pins?

gaston

[Ulysses HERNIOSUS]

Hi Gaston,

Please execute:

st25r3916MeasureAmplitude() or rfalChipMeasureAmplitude(). It will execute the D3 command , wait for the interrupt and retrieve the result from AD converter register.

Regards, Ulysses

[Ulysses HERNIOSUS]

Hi Gaston,

My idea was mainly for not opening two construction sites at the same time: Port to new MCU and new reader HW. IMO no need to repeat porting, just do a cross-connection of your port to and NFC06 board to see your port is working properly (disconnect/disable the 3916 on your board).

Regards, Ulysses

[Gaston]

Thank you.

ADC 8-bit result in the NUCLEO-NFC06A1 board (4 turns, 30x45 mm antenna):

153 (without tag)

134 (with tag)

ADC 8-bit result in the custom board (2 turns, 65x85 mm antenna):

109 (without tag)

108 (with tag)

gaston

[Travis Palmer]

Hello Gaston,

153 * 0.01306 = 1.998V

109 * 0.01306 = 1.424V

Both voltages should be sufficient to read tags. It might be that there is no analog problem. Could you do SPI traces and share them with us?

BR Travis

[Gaston]

Hi Travis,

Here's the SPI traces:

During Initialization

 

Work Cycle

Decoded SPI files (during init & cycle loop) are attached in zip format.

regards,

gaston