30 min

Expand I/O capabilities and streamline data management with PCAL6524 and STM32F427ZI

Versatile I/O expansion: Unlock I/O potential with ease!

Expand 10 Click with UNI-DS v8

Published Oct 07, 2023

Click board™

Expand 10 Click

Development board



NECTO Studio



Transform your electronics design with our I/O expansion solution, offering a reliable and efficient means for connecting and controlling a wide range of devices and peripherals



Hardware Overview

How does it work?

Expand 10 Click is based on the PCAL6524, a 24-bit ultra-low-voltage translating general-purpose I/O expander from NXP Semiconductors. This port expander is a simple solution for when additional I/Os are needed while keeping interconnections to a minimum. It is particularly great for system monitoring applications, industrial controllers, and portable equipment. The PCAL6524 has a built-in level shifting feature that makes it highly flexible in power supply systems where communication between incompatible I/O voltages is required. The PCAL6524 implements Agile I/O features designed to enhance the I/O. These additional features are programmable output drive strength, latchable inputs, programmable

pull-up/pull-down resistors, maskable interrupt, interrupt status register, and programmable open-drain or push-pull outputs. Expand 10 Click communicates with MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting a Fast Mode Plus operation up to 1MHz. At the Power-On sequence, the I/Os are configured as inputs. However, the host MCU can enable the I/Os as inputs or outputs by writing to the I/O configuration bits. In addition to I2C communication, two GPIO pins connected to the mikroBUS™ socket pins are also used. The reset pin routed to the RST pin of the mikroBUS™ socket, is used to place the PCAL6524 registers in their default state, while the interrupt, routed

to the INT pin of the mikroBUS™ socket, may be configured as an interrupt to notify the host MCU of incoming data on any port. Besides, it also allows the choice of the least significant bit of its I2C slave address by positioning the SMD jumper labeled ADDR SEL to an appropriate position marked as 1 and 0. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VCC SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

Expand 10 Click top side image
Expand 10 Click bottom side image

Features overview

Development board

UNI-DS v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different STM32, Kinetis, TIVA, CEC, MSP, PIC, dsPIC, PIC32, and AVR MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, UNI-DS v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the UNI-DS v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART, USB

HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. UNI-DS v8 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

UNI-DS v8 horizontal image

Microcontroller Overview

MCU Card / MCU



8th Generation


ARM Cortex-M4

MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Power Supply
I2C Clock
I2C Data
Power Supply

Take a closer look


Expand 10 Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the UNI-DS v8 as your development board.

Fusion for PIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
v8 SiBRAIN 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 Compiler Selection Step Image hardware assembly
NECTO Output Selection Step Image hardware assembly
Necto image step 6 hardware assembly
Necto image step 7 hardware assembly
Necto image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Necto PreFlash Image hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

UART Application Output Step 1

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

UART Application Output Step 2

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

UART Application Output Step 3

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

UART Application Output Step 4

Software Support

Library Description

This library contains API for Expand 10 Click driver.

Key functions:

  • expand10_set_pin_direction - This function sets the direction of the selected pins

  • expand10_set_pin_value - This function sets the value of the selected pins

  • expand10_read_port_value - This function reads the value of the selected port input pins

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 Expand10 Click example
 * # Description
 * This example demonstrates the use of Expand 10 click board.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver and performs the click default configuration which sets the first two ports
 * as output and the third port as input with pull-down enabled.
 * ## Application Task
 * Sets the pins of the first two ports and then reads and displays the status of 
 * all ports on the USB UART approximately once per second.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "expand10.h"

static expand10_t expand10;
static log_t logger;

void application_init ( void ) 
    log_cfg_t log_cfg;            /**< Logger config object. */
    expand10_cfg_t expand10_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 " );

    // Click initialization.
    expand10_cfg_setup( &expand10_cfg );
    EXPAND10_MAP_MIKROBUS( expand10_cfg, MIKROBUS_1 );
    err_t init_flag = expand10_init( &expand10, &expand10_cfg );
    if ( I2C_MASTER_ERROR == init_flag ) 
        log_error( &logger, " Application Init Error. " );
        log_info( &logger, " Please, run program again... " );
        for ( ; ; );
    init_flag = expand10_default_cfg ( &expand10 );
    if ( EXPAND10_ERROR == init_flag ) 
        log_error( &logger, " Default Config Error. " );
        log_info( &logger, " Please, run program again... " );
        for ( ; ; );
    log_info( &logger, " Application Task " );

void application_task ( void ) 
    uint8_t port_value = 0;
    for ( uint16_t pin_num = EXPAND10_PIN_0_MASK; pin_num <= EXPAND10_PIN_7_MASK; pin_num <<= 1 )
        expand10_set_all_pins_value( &expand10, pin_num );
        expand10_read_port_value( &expand10, EXPAND10_PORT_0, &port_value );
        log_printf( &logger, " Status P0 (output): 0x%.2X\r\n", ( uint16_t ) port_value );
        expand10_read_port_value( &expand10, EXPAND10_PORT_1, &port_value );
        log_printf( &logger, " Status P1 (output): 0x%.2X\r\n", ( uint16_t ) port_value );
        expand10_read_port_value( &expand10, EXPAND10_PORT_2, &port_value );
        log_printf( &logger, " Status P2 (input) : 0x%.2X\r\n\r\n", ( uint16_t ) port_value );
        Delay_ms( 1000 );

void main ( void ) 
    application_init( );

    for ( ; ; ) 
        application_task( );

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

Additional Support