10 min

Ensure a seamless and harmonious control over your external loads via J1031C3VDC.15S and PIC18F2458

Switch on success: MCU-driven relay revolution!

Relay 5 Click with EasyPIC v8

Published Nov 01, 2023

Click board™

Relay 5 Click

Development board

EasyPIC v8


NECTO Studio



Our solution ensures that external load management is not just controlled but orchestrated with precision and ease.



Hardware Overview

How does it work?

Relay 5 Click is based on three J1031C3VDC.15S, a high-current single-pole double-throw (SPDT) signal relays from CIT Relay and Switch, controlled in a very simple way through a port expander from NXP Semiconductors, the PCA9538A. The J1031C3VDC.15S relay is well known for its reliability and durability, high sensitivity, and low coil power consumption housed in a small package with PC pin mounting. Despite its size (12.5x7.5x10 millimeters (LxWxH)), the J1031C3VDC relay can withstand up to 2A and 125VAC/60VDC maximum. These relays are designed to easily activate their coils by relatively low currents and voltages, making them a perfect choice that any MCU can control. Besides, their durability is impressive, with over 5M of mechanical life cycles. The contact configuration of the J1031C3VDC.15S is a

single-pole double-throw (SPDT), meaning it has one pole and two throws. Based on the default position of the pole, one throw is considered normally open (NO) while the other is normally closed (NC), which is, in this case, its default position. When the coil is energized, it will attract the internal switching elements similar to a switch. For this purpose, the Relay 5 Click has three terminals for each relay that are adequately labeled. In addition, every relay has its status LED (REL1-3) for visual status presentation. As mentioned, the relays are not directly driven by the host MCU but by the PCA9538A, a low-voltage 8-bit I/O port with interrupt and reset from NXP Semiconductors. This I/O expander provides a simple solution when additional I/Os are needed while keeping interconnections to a minimum.

The Relay 5 Click uses the PCA9538A and 2-Wire I2C interface to communicate with the host MCU. The PCA9538A supports a fast mode of up to 400KHz of clock frequency. The I2C Address can be selected via the ADDR SEL jumpers, with 0 selected by default. The expander can be reset over the RST pin with active LOW, thus setting the registers to their default values without the need to power it off. 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.

Relay 5 Click hardware overview image

Features overview

Development board

EasyPIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports many high pin count 8-bit PIC microcontrollers from Microchip, regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer. 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, EasyPIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the EasyPIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board 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 DEVICE, and CAN are also included, including the well-established mikroBUS™ standard, two display options (graphical and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from the smallest PIC MCU devices with only eight up to forty pins. EasyPIC 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.

EasyPIC v8 horizontal image

Microcontroller Overview

MCU Card / MCU




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


Relay 5 Click Schematic schematic

Step by step

Project assembly

EasyPIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v8 as your development board.

EasyPIC v8 front image hardware assembly
LTE IoT 5 Click front image hardware assembly
MCU DIP 28 hardware assembly
LTE IoT 5 Click complete accessories setup image hardware assembly
EasyPIC v8 28pin-DIP Access - 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 DIP 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 Relay 5 Click driver.

Key functions:

  • relay5_set_relay1_open - This function sets the relay 1 to normally open state by setting the RL1 pin to low logic level.

  • relay5_set_relay1_close - This function sets the relay 1 to normally close state by setting the RL1 pin to high logic level.

  • relay5_switch_relay1 - This function switches the relay 1 state by toggling the RL1 pin logic level.

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 Relay 5 Click example
 * # Description
 * This example demonstrates the use of Relay 5 click board by toggling the relays state.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver and logger.
 * ## Application Task
 * Switches all relays state every 5 seconds and displays the state on the USB UART.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "relay5.h"

static relay5_t relay5;
static log_t logger;

void application_init ( void ) 
    log_cfg_t log_cfg;  /**< Logger config object. */
    relay5_cfg_t relay5_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.
    relay5_cfg_setup( &relay5_cfg );
    RELAY5_MAP_MIKROBUS( relay5_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == relay5_init( &relay5, &relay5_cfg ) ) 
        log_error( &logger, " Communication init." );
        for ( ; ; );
    if ( RELAY5_ERROR == relay5_default_cfg ( &relay5 ) )
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    log_info( &logger, " Application Task " );

void application_task ( void ) 
    relay5_set_relay1_open ( &relay5 );
    log_printf( &logger, " Relay 1 set to normally open state\r\n" );
    relay5_set_relay2_close ( &relay5 );
    log_printf( &logger, " Relay 2 set to normally close state\r\n" );
    relay5_set_relay3_open ( &relay5 );
    log_printf( &logger, " Relay 3 set to normally open state\r\n\n" );
    Delay_ms ( 5000 );

    relay5_set_relay1_close ( &relay5 );
    log_printf( &logger, " Relay 1 set to normally close state\r\n" );
    relay5_set_relay2_open ( &relay5 );
    log_printf( &logger, " Relay 2 set to normally open state\r\n" );
    relay5_set_relay3_close ( &relay5 );
    log_printf( &logger, " Relay 3 set to normally close state\r\n\n" );
    Delay_ms ( 5000 );

void main ( void ) 
    application_init( );

    for ( ; ; ) 
        application_task( );

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

Additional Support