30 min

Optimize pin utilization and reduce board complexity with CY8C9540A and PIC18F87K22

Upgrade your I/O game!

EXPAND 7 Click with UNI-DS v8

Published Sep 23, 2023

Click board™

EXPAND 7 Click

Development board



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-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



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

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 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

Additional Support