ST25R3911B with VDD powered by 3.3V reports 0V for VDD, VSP_A, VSP_D & VSP_RF

[BNaya.1]

I have ported the STM32F4 firmware written for NFC05A1 board and got it to run well on a Nucleo STM32F0 board.

Since then, I have since designed and prototyped a custom board with with the NFC05A1 reference design copied and controlled with an STM32F0.

The only difference between this board and my Nucleo paired evaluation board set-up is that I have 3.3V going to both VDD and VDD_IO of the ST25R3911B, unlike the reference design which has a VDD of 5V.

My design does not seem to be working properly, even though the SPI interface is working correctly and I can read/write registers.

I have noticed this:

When I run my firmware on the NFC05A1, I can read the correct values for the Power Supplies using the Measure Voltage command, ie:

VDD = 5.1V

VRF = 5.1V

VSA = 3..4V

VSD = 3.4V

BUT, when I run the same firmware on my board (even if I set the sup3_V bit in the IO Config Register 2), I get ZERO for all these 4 supplies.

Am I doing something wrong?

Do I need to change something in the reference firmware for the NFC05A1 to accommodate the VDD value of 3.3V?

Please advise.

Thanks.

Bob N

[Travis Palmer]

Hello BNaya,

you can easily crosscheck your code using the X-NUCLEO-NFC05A1.

The ST25R3911B is powered by 3.3V when removing L101 and connecting the 5V filtering (C100) to the 3.3V supply (red line).

The 3.3V LDO (LD39050) of the Nucleo64 is capable of driving 500mA.

BR Travis

[BNaya.1]

Thanks, Travis. I followed your directions and modified my NFC05A1.

And yes, the firmware reported the correct value of 3.3V for VDD, VRF, VSA and VSD on the NFC05A1.

I don't know what could be wrong with my hardware design. I copied the NFC05A1 reference design completely.

I am attaching my schematic here.

Please let me know if you see anything wrong.

Thanks.

BN

[Travis Palmer]

Hello Bob,

When reading back the IC Identity register, what is its content? Can you for example turn the field on? (To check in which direction the communication is working)

I have not seen any issues with the supply (VDD, VDD_IO)

MCU + ST25R3911B has the same 3V3 supply, which should work.

I would recommend to check the SPI lines using a scope and compare the signals with the above mentioned NFC05A1.

BR Travis

[BNaya.1]

Thanks for the reply, Travis.

The IC identity register reads back as 0x0D on my newly assembled custom board and as 0x0B on my 3-year-old NFC05A1.

I guess this means that I have a revision r4.1 silicon chip, right?

The SPI communication seems to be fine.

When you say "turn the field on", are you asking me to issue command C8?

Thanks.

Bob N

[Ulysses HERNIOSUS]

Hi Bob,

I think Travis was referring to simply setting 'tx_en' bit in operation control register. Then with a field detector or a loop on you scope tip you can see if a 13.56 MHz is emitted.

Before going there you can also check if Oszillator is enabled ('en' bit) and I_osc got signaled (alternatively check Auxiliary Display Register with its 'osc_ok' bit).

Regards, Ulysses

[BNaya.1]

Thanks, Ulysses. Here is what I found out:

The 'EN' bit (bit 7 of Operation control register) and the 27.12 MHz bit (bit 3 of IO Conf Reg 1) are both set.

However, the 'OSC_OK' bit of the Auxiliary Display Register is CLEAR.

Please help me understand how I can debug this.

We copied the layout of the NFC05A1 and I populated a 27.12 MHz crystal.

Thanks for your guidance.

Bob N

[Ulysses HERNIOSUS]

Hi Bob,

some (stupid) questions:

• You talk about a crystal, so it seems not the one we are using:
  • Does it have a compatible pin-out?
  • Is it correctly mounted?
  • Are the used capacitances in the right order for this crystal?
• Use multimeter + oscilloscope to verify voltages and waveforms of supply pins and XTI/XTO

I guess @Travis Palmer_O​ will be able to give you more hints on how waveforms for a starting/working oscillator should look like.

Regards, Ulysses

[BNaya.1]

Ulysses,

These are not silly questions. I think I may be in the same situation as the guy who Travis helped in this link: https://community.st.com/s/question/0D53W00000Br63mSAB/st25r3911b-rfal-library-st25r3911oscon-giving-error1-on-custom-board

To answer your question, I am using the same 27.12 MHz crystal from the NFC05A1 BOM, ie Murata P/N XRCGB27M120F3M00R0, which seems to have capacitance of 6pF. I used 8.2 pF like the NFC05A1 did. That should be OK, right?

Trying to measure the waveforms now.

BN

[BNaya.1]

Ulysses / Travis: is there an error in the NFCA05A1 schematic diagram?

It shows that the two leads of Y200 (27.12 MHz crystal) that are not going to XTI/XTO are connected to Ground.

Yet, when I look at the datasheet for the crystal (Murata P/N XRCGB27M120F3M00R0), it shows that these pins should be floating.

Please advise.

Thanks.

Bob N