30 min

Experience the magic of protocol transformation with SC18IM704 and PIC18F47K42

UART to I2C wizardry: Your communication transformer!

UART to I2C Click with EasyPIC v8

Published Sep 04, 2023

Click board™

UART to I2C Click

Development board

EasyPIC v8


NECTO Studio



Unlock the potential of your UART devices by effortlessly integrating them into I2C networks using our transformation solution, simplifying data exchange and enhancing control



Hardware Overview

How does it work?

UART to I2C Click is based on the SC18IM704, a bridge between the standard UART port and a serial I2C bus from NXP Semiconductors. The SC18IM704 consists of a full-functional advanced UART interface that communicates with the host MCU through the commonly used RX and TX pins of the mikroBUS™ socket. It is also characterized by a high baud rate of up to 460.8 kbit/s and 256-byte FIFO for the transfer/receive data process. The serial data format is fixed to a one start bit, 8 data bits, and one stop bit. After the reset feature, the baud rate defaults to 9600 bit/s and can be changed through the Baud Rate Generator (BRG) registers. After a Power-Up sequence or already-mentioned hardware reset, achievable through the RST pin of the mikroBUS™ socket, the

SC18IM704 will send two continuous bytes to the host MCU to indicate a Start-Up condition. These two continuous bytes are 0x4F and 0x4B, representing an ‘OK’ state in the ASCII messages protocol. After the correct initial sequence, direct communication is enabled with other I2C-bus devices connected to the populated I2C-bus terminal. The I2C bus uses two wires (SCL and SDA) to transfer information between connected devices, providing a byte-oriented interface that supports data transfers up to 400kHz. The SC18IM704 can also be placed in a software-configurable low-power mode (Power-Down mode). Upon entering the Power-Down state, the UART RX pin is used to exit Deep Power-down mode. The bridge remains in the Deep

Power-down mode as long as the RX pin remains in a high logic state. Any character sent brings the bridge out of Deep Power-down mode but ignores the character. In addition to all these features, the SC18IM704 has several general-purpose I/O pins on the populated header with labeled GP pins. These pins have the option of software setting their function as push-pull, open-drain, or input-only. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

UART to I2C Click top side image
UART to I2C Click bottom side 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

Take a closer look


UART to I2C 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
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EasyPIC v8 Access DIPMB 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 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 UART to I2C Click driver.

Key functions:

  • uarttoi2c_gpio_write - This function writes a desired data to the gpio port

  • uarttoi2c_gpio_read - This function reads data from the gpio port

  • uarttoi2c_i2c_write_then_read - This function performs a write then read with a repeated start to the I2C target device.

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 UART to I2C Click Example.
 * # Description
 * This example demonstrates the use of USB to I2C click board by reading the device ID
 * of a 3D Hall 11 click board connected to the I2C port and controlling the GPIO pins.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver and performs the click default config which resets
 * the device and sets the GPIO pins 0-3 as push-pull output and others as input.
 * After that, reads and displays the chip firmware version.
 * ## Application Task
 * Reads the device ID of a 3D Hall 11 click board connected to the I2C port, 
 * toggles the output pins and displays the GPIO port state. The results will
 * be displayed on the USB UART approximately once per second.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "uarttoi2c.h"

// I2C target device configuration
#define DEVICE_NAME                 "3D Hall 11 click"
#define DEVICE_SLAVE_ADDRESS        0x35
#define DEVICE_REG_ID               0x0D
#define DEVICE_ID                   0x01

static uarttoi2c_t uarttoi2c;
static log_t logger;

void application_init ( void ) 
    log_cfg_t log_cfg;  /**< Logger config object. */
    uarttoi2c_cfg_t uarttoi2c_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.
    uarttoi2c_cfg_setup( &uarttoi2c_cfg );
    UARTTOI2C_MAP_MIKROBUS( uarttoi2c_cfg, MIKROBUS_1 );
    if ( UART_ERROR == uarttoi2c_init( &uarttoi2c, &uarttoi2c_cfg ) ) 
        log_error( &logger, " Communication init." );
        for ( ; ; );
    if ( UARTTOI2C_ERROR == uarttoi2c_default_cfg ( &uarttoi2c ) )
        log_error( &logger, " Default configuration." );
        for ( ; ; );
    uint8_t version[ 16 ] = { 0 };
    if ( UARTTOI2C_OK == uarttoi2c_read_version ( &uarttoi2c, version ) )
        log_printf( &logger, " Firmware version: %s\r\n", version );
    log_info( &logger, " Application Task " );

void application_task ( void ) 
    static uint8_t gpio_state = UARTTOI2C_NO_PIN_MASK;
    uint8_t slave_address = DEVICE_SLAVE_ADDRESS;
    uint8_t reg_addr = DEVICE_REG_ID;
    uint8_t device_id;
    if ( UARTTOI2C_OK == uarttoi2c_i2c_write_then_read ( &uarttoi2c, slave_address, 
                                                         &reg_addr, 1, &device_id, 1 ) )
        log_printf( &logger, " %s - Device ID read: %s\r\n", ( char * ) DEVICE_NAME,
                    ( char * ) ( ( DEVICE_ID == device_id ) ? "Success" : "Fail" ) );
    uarttoi2c_gpio_write ( &uarttoi2c, gpio_state );
    if ( UARTTOI2C_OK == uarttoi2c_gpio_read ( &uarttoi2c, &gpio_state ) )
        log_printf( &logger, " GPIO state: 0x%.2X\r\n\n", ( uint16_t ) gpio_state );
        gpio_state = ~gpio_state;
    Delay_ms ( 1000 );

void main ( void ) 
    application_init( );

    for ( ; ; ) 
        application_task( );

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

Additional Support