10 min

Add RFID reader/writer capabilities to your project with CR95HF and STM32F071VB

RFID (Radio Frequency Identification) multi-protocol contactless transceiver

RFid Click with UNI Clicker

Published Jun 19, 2023

Click board™

RFid Click

Development board

UNI Clicker


NECTO Studio



Achieve communication with RFID tags and supports various applications such as tracking, security systems, and identification



Hardware Overview

How does it work?

RFid Click is based on the CR95HF, a multi-protocol contactless transceiver from STMicroelectronics. This board supports ISO/IEC 14443 type A and B, ISO/IEC 15693, and ISO/IEC 18092 communication protocols (tags). In addition, it also supports the detection, reading, and writing of NFC forum type 1, 2, 3, and 4 tags with incorporated internal antenna. The CR95HF integrates an Analog Front End to provide the 13.56MHz Air Interface. It manages frame coding and decoding in Reader mode for standard applications such as near-field communication (NFC), proximity, and vicinity standards. The CR95HF has two operating modes: Wait for Event

(WFE) and Active Mode of operation. In Active mode, the CR95HF communicates actively with a tag or an external host. The WFE mode includes four low-consumption states: Power-up, Hibernate, Sleep, and Tag Detector, allowing the transceiver to switch from one mode to another. All states except Power-Up are software-accessible. While the CR95HF is in any of these, communication with the MCU is impossible. For normal communication, the transceiver must be woken up first. RFid Click can communicate with the host MCU using UART or SPI serial interfaces over the mikroBUS™ socket. This Click board™ comes with A and B jumpers with which the function of two multiplex pins is

selected. Depending on their position, the pins can be used as UART or interrupt (input and output) pins (interrupt by default). These jumpers must be set to the B position for use with the UART interface, thus losing the interrupt function pins. The SSSI0 and SSI1 pins serve for communication interface selection based on their logic states. This Click board™ can only be operated with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.

RFid Click hardware overview image

Features overview

Development board

UNI Clicker is a compact development board designed as a complete solution that brings the flexibility of add-on Click boards™ to your favorite microcontroller, making it a perfect starter kit for implementing your ideas. It supports a wide range of microcontrollers, such as different ARM, PIC32, dsPIC, PIC, and AVR from various vendors like Microchip, ST, NXP, and TI (regardless of their number of pins), four mikroBUS™ sockets for Click board™ connectivity, a USB connector, LED indicators, buttons, a debugger/programmer connector, and two 26-pin headers for interfacing with external electronics. Thanks to innovative manufacturing technology, it allows you to build

gadgets with unique functionalities and features quickly. Each part of the UNI Clicker development kit contains the components necessary for the most efficient operation of the same board. In addition to the possibility of choosing the UNI Clicker programming method, using a third-party programmer or CODEGRIP/mikroProg connected to onboard JTAG/SWD header, the UNI Clicker board also includes a clean and regulated power supply module for the development kit. It provides two ways of board-powering; through the USB Type-C (USB-C) connector, where onboard voltage regulators provide the appropriate voltage levels to each component on the board, or using a Li-Po/Li

Ion battery via an onboard battery connector. All communication methods that mikroBUS™ itself supports are on this board (plus USB HOST/DEVICE), including the well-established mikroBUS™ socket, a standardized socket for the MCU card (SiBRAIN standard), and several user-configurable buttons and LED indicators. UNI Clicker is an integral part of the Mikroe ecosystem, allowing you to create a new application in minutes. Natively supported by Mikroe software tools, it covers many aspects of prototyping thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

UNI clicker double image

Microcontroller Overview

MCU Card / MCU



8th Generation


ARM Cortex-M0

MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


You complete me!


RFID tag operating at 13.56MHz adheres to the ISO14443-A standard, ensuring high-frequency communication. This proximity card technology, often exemplified by MIFARE cards, facilitates secure and contactless interactions in applications like access control, public transport, and payment systems. The ISO14443-A standard defines the communication protocol, incorporating anti-collision mechanisms for simultaneous card handling. These RFID tags possess variable memory capacities, ranging from a few bytes to kilobytes, catering to diverse application needs. Ensuring data security, the standard integrates features such as encryption and authentication. These tags, exemplified by MIFARE technology, are widely used for their efficiency and are vital in enhancing convenience and security in diverse identification and access scenarios.

RFid Click accessories image

Used MCU Pins

mikroBUS™ mapper

Interface Selection
Interface Selection
SPI Chip Select
SPI Clock
Power Supply
Interrupt Output
Interrupt Output

Take a closer look


RFid Click Schematic schematic

Step by step

Project assembly

UNI Clicker front image hardware assembly

Start by selecting your development board and Click board™. Begin with the UNI Clicker as your development board.

UNI Clicker front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for STM32F745VG front image hardware assembly
Prog-cut hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
UNI Clicker Access MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

After loading the code example, pressing the "DEBUG" button builds and programs it on the selected setup.

Application Output Step 1

After programming is completed, a header with buttons for various actions available in the IDE appears. By clicking the green "PLAY "button, we start reading the results achieved with Click board™.

Application Output Step 3

Upon completion of programming, the Application Output tab is automatically opened, where the achieved result can be read. In case of an inability to perform the Debug function, check if a proper connection between the MCU used by the setup and the CODEGRIP programmer has been established. A detailed explanation of the CODEGRIP-board connection can be found in the CODEGRIP User Manual. Please find it in the RESOURCES section.

Application Output Step 4

Software Support

Library Description

This library contains API for RFID Click driver.

Key functions:

  • rfid_select_communication_interface - Select communication interface

  • rfid_get_tag_uid - Get RFID tag uid function

  • rfid_get_device_id - RFID get device id function

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

 * @file main.c
 * @brief RFID Click example
 * # Description
 * This example demonstrates the use of RFID Click board 
 * by reading MIFARE ISO/IEC 14443 type A tag UID.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver, selects the communication interface and performs
 * the click default configuration.
 * ## Application Task
 * If there's a tag detected, it reads its UID and displays it on USB UART.
 * @note
 * It is recommended to tie SSI_0, SSI_1 to VCC/GND at power-up, depending on 
 * the communication interface selection by A and B on-board jumpers. 
 * SSI_0 - UART: 0 SPI: 1
 * SSI_1 - UART: 0 SPI: 0
 * Only tags with 4-byte or 7-byte UIDs are compatible with this example.
 * We recommend MIKROE-1475 - an RFiD tag 13.56MHz compliant with ISO14443-A standard.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "rfid.h"

static rfid_t rfid;
static log_t logger;

void application_init ( void ) 
    log_cfg_t log_cfg;  /**< Logger config object. */
    rfid_cfg_t rfid_cfg;  /**< Click config object. */

     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, " Application Init " );
    Delay_ms( 100 );

    // Click initialization.

    rfid_cfg_setup( &rfid_cfg );
    RFID_MAP_MIKROBUS( rfid_cfg, MIKROBUS_1 );
    err_t error_flag = rfid_init( &rfid, &rfid_cfg );
    if ( error_flag != RFID_OK ) 
        log_error( &logger, " Please, run program again... " );
        for ( ; ; );
    log_printf( &logger, " Selecting communication interface... \r\n" );
    error_flag = rfid_select_communication_interface ( &rfid, RFID_SPI );
    if ( error_flag != RFID_OK ) 
        log_error( &logger, " Please, run program again... " );
        for ( ; ; );
    log_printf( &logger, " Configuring the device... \r\n" );
    error_flag = rfid_default_cfg ( &rfid );
    if ( error_flag != RFID_OK ) 
        log_error( &logger, " Please, run program again... " );
        for ( ; ; );
    log_printf( &logger, " The device has been configured! \r\n" );

void application_task ( void ) 
    uint8_t tag_uid[ 20 ] = { 0 };
    uint8_t tag_len = rfid_get_tag_uid( &rfid, RFID_ISO_14443A, tag_uid );
    if ( tag_len > 0 )
        log_printf( &logger, " TAG UID: " );
        for ( uint8_t cnt = 0; cnt < tag_len; cnt++ )
            log_printf( &logger, "0x%.2X ", ( uint16_t ) tag_uid[ cnt ] );
        log_printf( &logger, "\r\n----------------------------------\r\n" );
        Delay_ms( 1000 );

void main ( void ) 
    application_init( );

    for ( ; ; ) {
        application_task( );

// ------------------------------------------------------------------------ END

Additional Support