ST25 NFC/RFID tags and readers

So our System works fine most of the time but sometimes the Reader does not detect the tag and we observe that rfalNfcState are just keep fluctuating between RFAL_NFC_STATE_POLL_TECHDETECT and  RFAL_NFC_STATE_LISTEN_TECHDETECT  same as when no tag present in the field of Reader and it is not able to satisfy this if condition.“if( rfalNfcIsDevActivated( rfalNfcGetState() ) ) // this if condition”We observed that even if we do controller reset it doesn’t fix the issue only when we power cycle the reader{st25r3911b} it start working again normally.I’m attaching the code with this i want your team to review it to let us know what exactly we are doing wrong which leading to this state where our rfal state machine not switching properly, With Restart_flag we are doing reinitialization i want you to review that whatever sequence we are following is correct or not  Main.c  {Rfid Reinitialization sequence}Please help us fix this issue and could you provide or help us that through software funct

Hi, I have designed a board with a total antenna width of 10 mm and 7 turns, and a rectangular antenna.But it doesn’t read by smartphone (NFC-enabled) or Readers. Can you please help me with the problems? 

 Hello ST Team,I am currently working on a project using the ST25R3916B NFC reader, and I would like to study and reference the PCB design shown in Figure 6, “Device used for single ended antenna with cable,” of application note AN5592.Could you please provide the editable PCB project files for this reference design, such as the Altium schematic and PCB layout files?I have checked the application note and the ST website, but I could not find the corresponding PCB source files.Application note reference:https://www.st.com/resource/en/application_note/an5592-st25r-single-ended-antenna-matching-stmicroelectronics.pdfThank you very much for your support!

This is not a real question, this is just knowledge sharing… For the context, I would read first. At this point I had x86 NFC Tag Programming application, I have been waiting for the STM to release x64-bit version of the DLLs so I could update my application to x64.I have been lurking around the community and finally found but this did not help as with the release of v3.0.0, it did came with x64 bit of DLLs but I had real hard time integrating them into my project!! Quite disappointing, eh?!! I gave up the idea of updating my application to x64 until very recently I stumble upon another question based on the question title, I clicked on it with a lot of hope and what I found was quite disappointing. Basically I felt I was in a ditch where I could not update my application to x64 even though I have x64 bit DLLs!

Setup Board: X-NUCLEO-NFC09A1 (ST25R100), brand new, unmodified, no jumpers/solder bridges changed Host: STM32, custom C++17 driver (register-level, not RFAL) SPI: confirmed working — bring-up sequence completes, all register reads/writes verified against DS14139 Rev 4 SymptomThe autonomous wake-up measurement cycle (triggered internally by the WUT every wut period) never emits any RF onto RFO1/RFO2, confirmed directly on an oscilloscope. However, the CALIBRATE_WU_MEASUREMENT direct command (0x74), issued manually once during bring-up, reliably emits a real RF burst every time (5 sub-pulses of ~26 µs each, ~130 µs total).This has been reproduced consistently across many test runs, with the following independently confirmed facts: wu_en is set and read back correctly (OPERATION = 0x01). The WU timer itself is confirmed running: with wuti (WU_CONTROL_1 bit 3) set, I_wut fires reliably in IRQ_STATUS_3 on schedule, tested at both wut = 77.3 ms and wut = 9.7 ms. IRQ_MASK_3 correctly

Hello,I am designing an NFC reader based on the ST25R300, using the STEVAL-D25R300A schematic as a reference for the antenna matching network. My board uses the same component values on each side of the differential output:L1/L2 = 120 nH (EMC filter series)C11/C8 = 390 pF (EMC filter shunt)C1/C12 = 82 pF each, in parallel (series matching)C14 = 120 pF (shunt)C67 = 39 pF (shunt)C59 = 10 pF, C16 = 150 pF (RFI divider)R3/R4 = 2.2 ohmI could not find the antenna coil parameters in the user manual or the design files. Could you please provide the following for the antenna used on STEVAL-D25R300A?1. Coil inductance at 13.56 MHz2. Coil AC resistance (or Q) at 13.56 MHz3. Whether the antenna is a PCB trace coil or a discrete component, and if it is a PCB trace, the outer dimensions and number of turns4. The target differential impedance the matching network above was designed for Thank you.

Dear ST Support Team,We are currently developing a board based on the ST25DV04K and would appreciate your guidance regarding the antenna interface.In our schematic, we have placed a π coupling filter (series inductors and shunt capacitors) between the AC0/AC1 pins and the antenna matching circuit, upstream of the latter, for coupling at 13.56 MHz, as shown in the attached schematic.Could you please clarify whether the use of this π coupling filter, positioned before the matching circuit, is recommended by ST, or whether it is not necessary in this configuration?Thank you in advance for your support — we look forward to your recommendations.Best regards, 

Hi team,I am working on a firmware upgrade implementation using the ST25DV04KC NFC tag in FTM (Fast Transfer Mode).I have successfully ported the ST25FTM library to my target microcontroller. Basic commands and demos—such as checking the board version and sending passwords—work consistently.However, I am experiencing a severe reliability issue with the actual Firmware Upgrade process. The upgrade fails roughly 90% of the time. It only succeeds occasionally (~10% success rate). The target 8 Bit PIC18 microcontroller.I have attached the console log of a failed session below for reference. Could you please help me identify what might be causing these frequent failures, or let me know if you need any additional logs or hardware details from my side? Thanks.Console Logs:Jul 09, 2026 8:49:50 AM com.st.st25sdk.STLog i INFO: mState = PREPARE_PACKET Jul 09, 2026 8:49:50 AM com.st.st25sdk.STLog i INFO: sendNextPacket Jul 09, 2026 8:49:50 AM com.st.st25sdk.STLog i INFO: preparePacket Jul 09, 2026

Hi,We are using the ST25R3920B NFC reader IC along with the NXP S32K312 MCU running an AUTOSAR OS for NFC card detection.We have observed that, after the NFC wake-up event, the NFC initialization and polling sequence takes approximately 300 ms before a card is detected. This startup time is longer than expected and is impacting our application requirements.Could you please suggest any configuration changes, RFAL optimizations, or best practices to reduce the NFC initialization and polling time? If there are any recommended settings for use with an AUTOSAR-based system or the ST25R3920B that can help improve startup performance, we would greatly appreciate your guidance.Thanks,Anitha

Hello Team,I am facing RF read and write issues with the M24LR16E‑R EEPROM.The exact problem is as follows:When I take a new EEPROM and write data to it using an RF NFC reader for the first time, the operation is successful. However, during subsequent attempts to read and write: In some EEPROMs, RF read works but write fails but I2C read/Write working. In some devices, both read and write operations fail but I2C read/Write working. A few EEPROMs work correctly without any issues. In our application, we are using Sector 2 and Sector 3 for user data storage.When I read data from the problematic EEPROMs through St25 mobile application, I observe the following:Sector 0 and Sector 1 Security Status is 0x00. And the data read and write is working in these 2 sectors. Sector 2 to Sector 15 Security status: Current Security Status: 0x09 New Security Status: 0x09 Additionally, I receive the warning:“Sector locked. Security Status can only be changed through I2C.”I am not sure why the security

Hello, I currently using the STM32F401RCT and the ST25R100-CMET.Its a battery powered device and want to put the ST25 chip in sleep. in rfal_nfc.c I found rfalNfcDeactivate for disabling, but I don’t get it enabled.//Power saving functionsvoid NFC_Enable(void){ printf("Enabling NFC chip\r\n"); rfalNfcInitialize(); rfalNfcDiscover(&discParamNfc);}void NFC_Disable(void){ printf("Disabling NFC chip\r\n"); rfalNfcDeactivate(RFAL_NFC_DEACTIVATE_IDLE);}Right now when I enable the chip it doesn’t detect tags. It does work and detect tags without the power saving functions.I have been reading through this file: RF/NFC abstraction layer (RFAL) - User manual But haven’t found a solution.Have I missed anything?Kind regards, William  

I’m designing a tag coil for the ST25DV-04k. I am planning to use the ST25 to harvest NFC energy from a phone tap for a bioimpedance sensor (MAX30002). The ST25DV will then relay the sensor measurement to the phone via NFC again. I used an online calculator to design the tag coil, and these were the parameters I chose. Parameters for tag coilHowever, I am unsure if my quality factor is too high. “59.77” is before coupling, and I assume it will be lower after that. I understand that a high Q is great for energy harvesting, but it can limit the bandwidth and garble communication between the tag and the reader.Is my Q too high right now? If so, what is the optimal Q factor range? Anything else that stands out from my coil design?

Hello,I am using the ST25R200 evaluation board with the STSW-ST25R020 firmware package.I am planning to develop a custom Python GUI that displays a specific text string whenever an NFC tag is detected by the board. To achieve this, I want to modify the C firmware so it actively streams out a text string via UART/VCP as soon as a tag enters the field.Could you please guide me on the following?Which specific source file and function in the STSW-ST25R020 package handle the successful tag detection/inventory loop where the tag's UID is retrieved? Where is the best place to insert a custom printf or logging function to stream this text data out via UART immediately upon detection? Thank you very much for your help!

Hi, Could you please confirm whether an external NFC antenna can be connected to the X-NUCLEO-NFC08A1 board? I see P200 and P202 in the schematic, but it is not clear to me whether these are intended for external antenna connection or only for optional/test points. If an external antenna can be used, could you explain how the on-board etched PCB antenna should be disconnected from the ST25R3916B antenna path, where the external antenna should be connected instead, and what antenna inductance or electrical parameters should be targeted before tuning the matching network?Thanks!Best regards, Jose 

Hello, I have a STM32F401RCT connected to a ST25R100.In the ioc file I enabled the X-CUBE-NFC9 library with all the necesary dependencies.All the IOs also have pins assigned to them.Plus Pull ups enabled on the IRQ (open drain) and NFC_Reset.Currently I have found out that it crashes somewhere after MX_X_CUBE_NFC9_Init();ret code: 0NFC BSP COM = 100Welcome to X-NUCLEO-NFC09A1 entered error handlerThis is what I get in my console. I added some printfs in the code already.When I run it in debug mode to check were it calls the error handler it for some reason does not hit the error handler but it gets stuck in stm32F4xx_il_usb.c; when I click pauze, this seems rather odd.HAL_StatusTypeDef USB_FlushTxFifo(USB_OTG_GlobalTypeDef *USBx, uint32_t num){ __IO uint32_t count = 0U; /* Wait for AHB master IDLE state. */ do { count++; if (count > HAL_USB_TIMEOUT) { return HAL_TIMEOUT; } } while ((USBx->GRSTCTL & USB_OTG_GRSTCTL_AHBIDL) == 0U); /* Flush TX Fifo

Hi,I am evaluating the ST25R200 using the ST25R200 Eval GUI. In Reader Mode, there is a Field Measurement tab that displays a numerical value together with a circular indicator. However, the displayed value does not appear to have any unit.Could you please clarify:What exactly is being measured in this tab? Does the value correspond to a physical quantity (e.g., magnetic field strength, ADC count, RSSI, amplitude, etc.)? Is there a conversion from the displayed value to a standard unit (A/m, µT, V, etc.)? Which ST25R200 registers or measurement circuitry are used to obtain this value? Is this functionality available through the ST25R200 firmware/API so that it can be implemented in a custom application?Any explanation of the measurement principle and interpretation of the displayed value would be greatly appreciated.Thank you.

I am using the STEVAL-25R300KA board with ST25PC-NFC version 3.0.2 on a PC running Windows 11.The software opens for a few seconds and then closes automatically by itself. I have already tried the following steps:Reinstalled the softwareRestarted my PCInstalled both x64 and x86 versions of the Microsoft Visual C++ Redistributable packagesChecked the Windows Event Viewer / Journal logs for any related errorsUnfortunately, none of these steps resolved the issue, and no specific error was detected in the logs.Could you please let me know what I can do to fix this problem and use the software properly?Thank you for your support.

Hello everyone,Has anyone successfully used the "ST25R95 EMI FILTER CALCULATION.xlsm" spreadsheet?I'm currently trying to use it for tuning the matching network of an ST25R95 design, but it doesn't seem to work correctly on my side. As soon as I modify any parameter or use the reset function, all the graphs disappear and I can no longer obtain any meaningful results.At the moment, this tool would be very useful for optimizing the matching network, and without it I'm having some difficulties proceeding with the tuning process.Has anyone experienced the same issue? Is there a specific Excel version, macro setting, or workaround required to make the spreadsheet work properly?Any suggestions, advice, or alternative methods for tuning the matching network would be greatly appreciated.Thank you in advance for your help.Marco

Hi again,Since the new version of ST Community I can't find my previous post, so I'm creating a new topic to follow up on the old one. The replies from @AScha.3 and @Brian TIDAL on that thread helped me a lot before it disappeared.As I mentioned, I'm a beginner in this field. The full context is in my earlier post:I have just one more question. You mentioned that building an external antenna is easy, but is it really doable for a beginner? I'd like to know whether I can realistically do it myself if I buy the right equipment to measure inductance, or whether I need an expert to guide me.Also, in addition to AN6065, I found AN2866, which is more readable in my opinion and provides a step-by-step procedure. I don't understand everything yet, but I'll work through it.Thanks!

Hello,I start testing with the STEVAL-M25R16B Board and use this Time the self compiled Demo from ST to test it. All works find.Then i made an own PCB with Reader IC  and Antenna on it and connect it to your MCU /Display Board.The Board is connected to 3.3V, GND and the SPI / IRQ Lines. The Antenna on my PCB is very small, only 21x26mm. Inductance measured with Siglent VNA 770nH.( 0.5mm Track Width, 0.3mm Distance, 3 Turns) The from your Tools calculated Values and my final Values after tuning differ..My Result: L=270nH, Cemv 680pF, Cs 220pF, CTune 430pF, Rs 0.68R I tuned the Circuit using my VNA and get a Reading Distance of about 25mm for 14443 Keyfobs and Cardsand about 6cm for ISO15693 Card.This all works fine.  Smith Chart looks perfect.The Rx Voltage is about 1.5Vpp. The Voltage Divider Capacitors are 33p/120p.ST25RProblem: Tags are working but in Emulate Mode i got no Reaction. With the Original Antenna (66x66mm) all is fine.Need a little help

Hi STM teams , i have developed a custom NFC board using the STM32L476RCT6 and the ST25R3916B NFC reader, based on the reference design of STEVAL-D25R16B (https://www.st.com/resource/en/schematic_pack/steval-25r3916b-schematic.pdf). I am using an external sticker antenna (Manufacturer Part Number: V2089-013-A-01). Currently, the board detects only the STEVAL-SMARTAG2 NFC tag card (https://www.st.com/resource/en/schematic_pack/steval-smartag2-schematic.pdf), while other NFC cards are not being detected. However, when I connect the custom NFC board to the DK antenna, it successfully detects the STEVAL-SMARTAG2 card as well as all other NFC cards. so i think issue may be sticker antenna Could anyone suggest a suitable sticker antenna or recommend an alternative external antenna solution? I have attached pictures of the sticker antenna, the STEVAL-SMARTAG2 card, and the other NFC tags for reference.

Hi everyone! I'm working with the NFC07A1 board associated with the Nucleo L053R8, with the intention of being able to perform ADC readings. I configured everything(ADC, pin, NFC07A1, etc.) on CubeMx, and then, opened the generated file on CubeIde. After writing the code for reading the ADC in the main file, i tried to run it, but even though there were no errors in the code, the  "startup_stm32l053r8tx.s" tab opens by pointing to line 51 (as well as Reset_Handler: ldr r0, =_estack). Consequently, the values acquired via the ADC are not printed on the screen, but the only thing printed on the sreen is "welcome to x-cube-nfc7 example". Could you help me solve the problem?

Hello There,I am currently trying to use the ST25R200 with the X-CUBE-NFC10 Software package.First thing am not sure about: In the "Software Packs Component Selector" I have to configure the "Board Extension NFC/NFC10A1" even when i don't plan to use this board. Otherwise i get a warning that "NFC10Boardlface" requires "NFC/NFC10A1". If I don't select the board part, I get a simmilar warning from the RFAL component.If i either don't add NFC/NFC10A1 in the component selector or don't select "Board Part NFC10Boardlface" in the Mode selection for the X-CUBE-NFC10 package, CubeMX seems to have problems generating the header "nfc_conf.h", which i have attached to this post.This is how the configuration looks, which generated nfc_conf.h:Am I using this library not correctly? Or rather which components of this library am i supposed to configure if i want to use the library with a custom board based on the ST25R200?Best Regards, Cecil

Hi,I have derived this code from the ST25NFCLib, and the software works correctly when interfacing with the NUCLEO-L476RG board.However, when I connect the same setup to my proto board, I observe a difference during the following I2C transaction.During the initialization process, the master sends command 0xDF (Measure Power Supply) and then waits for the IRQ signal.In the working setup, the IRQ status registers (1Ah–1Dh) return the values:00, 80, 00, 00Whereas in the non-working setup, the IRQ status registers return:00, 00, 00, 00I am not sure why the IRQ response is different in the proto board setup.Please note the following:Both the working and non-working setups use the same ST25R3918 daughter board.Both setups use the same interface signals: 3.3V, GND, IRQ, SCL, and SDA.The I2C communication speed is identical on both setups.I am attaching the I2C transaction screenshots for reference:The upper transaction belongs to the non-working setup.The lower transaction belongs to the work

Hello ST TeamI am using the ST25R3911B-DISCO board with an ST25DV16KC tag.I am trying to communicate with the tag directly from Python using the ST25R3911DISCOComm.dll from STSW-ST25R001.My setup is:ST25R3911B-DISCOST25DV16KCWindows PCPython 3.13ctypesThe DLL loads successfully.Reader connection works correctly.RF initialization works correctly.These APIs return success:rfalInitializeiso14443aInitrfalFieldOnAndStarGTcheckConnectionThe ST GUI software works correctly and can:detect the tagselect the tagread UIDread tag dataFrom Python I cannot:detect the tagselect the tagread UIDread memoryThe DLL exports these APIs:iso14443aSelectiso14443aRATSiso14443aPPStxrxBytesnfcTxNBytesnfcRxNBytesrfalStartTransceiverfalTransceiveBlockingTxrfalTransceiveBlockingRxrfalTransceiveBlockingTxRxrfalISO14443ATransceiveShortFramerfalISO14443ATransceiveAnticollisionFramerfalIsoDepInitializerfalIsoDepStartApduTransceivepollInterruptObserved issues:iso14443aSelect causes access violation.t2tRead4Pages returns