30 min

Optimize pin utilization and reduce board complexity with CY8C9540A and STM32F303VE

Upgrade your I/O game!

EXPAND 7 Click with UNI Clicker

Published Sep 23, 2023

Click board™

EXPAND 7 Click

Development board

UNI Clicker


NECTO Studio



Experience the versatility of our I/O pin expansion solution, tailored to provide you with the flexibility and control needed to optimize your projects, reduce complexity, and enhance connectivity



Hardware Overview

How does it work?

EXPAND 7 Click is based on the CY8C9540A, 40-bit I/O expander with EEPROM, and eight independently configurable 8-bit PWM outputs from Infineon. The main blocks of the CY8C9540A include the control unit, PWMs, EEPROM, and I/O ports. The I/O expander's data pins can be independently assigned as inputs, outputs, or PWM outputs and can be configured as open-drain or collector, strong drive (10 mA source, 25 mA sink), resistively pulled up or down, or high impedance which can be selected in the Port Drive Mode register. It operates as two I2C peripheral devices, where the first device is a multi-port I/O expander (single I2C address to access all ports through registers), and the second is a serial EEPROM with 11 Kbyte address space. Configuration and output register settings are storable as the user defaults in a dedicated section

of the EEPROM. If user defaults were stored in EEPROM, they are restored to the ports at the Power-Up sequence. The EEPROM is byte-readable and supports byte-by-byte writing. A pin 3 of Port 2 on this Click board™ can be configured as an EEPROM Write Disable (WD) input that blocks write operations when set high. The configuration registers can also turn off EEPROM operations. EXPAND 7 Click communicates with MCU using the standard I2C 2-Wire interface with a maximum frequency of 100kHz. The CY8C9540A has, by default, two possible I2C slave address formats: the first is used to access the multi-port device, and the second is to access the EEPROM. This selection of I2C slave addresses is performed by setting the logic level on the A0 pin of the CY8C9540A, which can be done using the SMD jumper labeled ADDR SEL. It also generates a

programmable interrupt signal routed on the INT pin of the mikroBUS™, which can inform the system master that there is incoming data on its ports or that the PWM output state has changed. The reset signal routed on the RST pin of the mikroBUS™ socket is similar to the POR (Power-ON Reset) function. When the CY8C9540A is held in Reset, all In and Out pins are held at their default High-Z State. 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 7 Click top side image
EXPAND 7 Click bottom side 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-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 7 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 EXPAND 7 Click driver.

Key functions:

  • expand7_reset - Reset function

  • expand7_write_all - Set all OUTPUT pins' logic levels function

  • expand7_write_pin - Set a single OUTPUT pin's logic level 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 
 * \brief Expand7 Click example
 * # Description
 * This example demonstrates the use of the EXPAND 7 click.
 * The demo application is composed of two sections :
 * ## Application Init 
 * Initalizes I2C driver and makes an initial log.
 * ## Application Task  
 * This example shows the capabilities of the EXPAND 7 click by toggling 
 * each of the 40 available pins.
 * \author MikroE Team
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "expand7.h"

// ------------------------------------------------------------------ VARIABLES

static expand7_t expand7;
static log_t logger;

uint8_t pin_num;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
    log_cfg_t log_cfg;
    expand7_cfg_t cfg;

     * 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.

    expand7_cfg_setup( &cfg );
    expand7_init( &expand7, &cfg );
    Delay_ms( 100 );
    expand7_reset( &expand7 );
    Delay_ms( 1000 );
    log_printf( &logger, "------------------- \r\n" );
    log_printf( &logger, "   EXPAND 7 click   \r\n" );
    log_printf( &logger, "------------------- \r\n" );

void application_task ( void )
    expand7_write_all ( &expand7, 0xFF );
    log_printf( &logger, "All pins set to HIGH logic level!\r\n" );
    log_printf( &logger, "---------------------------------\r\n" );
    Delay_ms( 2000 );
    for ( pin_num = 0; pin_num < 40; pin_num++ )
        expand7_write_pin( &expand7, pin_num, EXPAND7_LOW );
        log_printf( &logger, "Pin %u is set to LOW logic level!\r\n", ( uint16_t) pin_num );
        Delay_ms( 300 );
    log_printf( &logger, "---------------------------------\r\n" );
    Delay_ms( 1000 );

void main ( void )
    application_init( );

    for ( ; ; )
        application_task( );

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

Additional Support