30 min

Achieve flexible power regulation with STPD01 and PIC18LF4682

DC-DC step-down switching regulator

Buck 19 Click with EasyPIC v7

Published Nov 01, 2023

Click board™

Buck 19 Click

Development board

EasyPIC v7


NECTO Studio



Programmable synchronous buck converter suitable to provide power supply in applications following USB power delivery specifications



Hardware Overview

How does it work?

Buck 19 Click is based on the STPD01, a programmable synchronous buck converter from STMicroelectronics, suitable to provide power supply in applications following USB power delivery specifications. This STPD01 features internal power MOS synch rectification, internal compensation, cable drop compensation, and two programmable switching frequencies with an optional clock dithering. It provides the desired voltage levels over the input voltage range from the VIN terminal from 6 up to 26V required by USB power delivery systems (USB PD 3.0) via I2C serial interface up to 60W output power, more precisely voltages in the range of 3V to 20V with a step of 20mV minimum, and currents from 0.1A to 3A with a minimum in steps of 50mA. The STPD01 includes extensive protection against overvoltage, overcurrent,

and overtemperature alongside additional built-in features, including embedded discharge circuitry, soft-start, undervoltage lockout, and a programmable watchdog timer that helps ensure a robust and safe system. This Click board™ communicates with MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting a Fast Mode operation up to 400kHz. Besides, it also allows the choice of the three least significant bits of its I2C slave address by positioning the SMD jumper labeled ADDR SEL to an appropriate position providing the user with a selection of four slave addresses. In addition to communication signals, the STPD01 uses a few other signals necessary for its operation. It can be enabled or disabled through the EN pin routed to the CS pin of the mikroBUS™ socket, hence, offering a switch operation

to turn ON/OFF power delivery to the STPD01. The PON pin, routed on the AN pin of the mikroBUS™ socket, provides information on the Start-up of the device; more precisely, it serves the user as an interface that indicates when VOUT reaches the regulation value after the Start-Up condition. And the last signal it uses is a standard interrupt signal, routed to the INT pin of the mikroBUS™ socket, to indicate different fault condition occurrences. This Click board™ can only be operated with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.

Buck 19 Click hardware overview image

Features overview

Development board

EasyPIC v7 is the seventh generation of PIC development boards specially designed to develop embedded applications rapidly. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has a broad set of unique functions, such as a powerful onboard mikroProg programmer and In-Circuit debugger over USB-B. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7 allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of

the EasyPIC v7 development board contains the components necessary for the most efficient operation of the same board. An integrated mikroProg, a fast USB 2.0 programmer with mikroICD hardware In-Circuit Debugger, offers many valuable programming/debugging options and seamless integration with the Mikroe software environment. Besides it also includes a clean and regulated power supply block for the development board. It can use various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-B (USB-B) connector. Communication options such as

USB-UART and RS-232 are also included, alongside the well-established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC v7 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 v7 horizontal image

Microcontroller Overview

MCU Card / MCU




MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Power-On Indicator
Power Supply
I2C Clock
I2C Data

Take a closer look


Buck 19 Click Schematic schematic

Step by step

Project assembly

EasyPIC v7 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v7 as your development board.

EasyPIC v7 front image hardware assembly
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
EasyPIC v7 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 DIP image step 7 hardware assembly
EasyPIC PRO v7a Display Selection Necto Step 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 Buck 19 Click driver.

Key functions:

  • buck19_write_register This function writes desired data to the selected register by using I2C serial interface.

  • buck19_set_vout This function sets the voltage output.

  • buck19_set_ilimit This function sets the current limit.

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 Buck 19 Click example
 * # Description
 * This example demonstrates the use of Buck 19 click board by
 * iterating through the entire output voltage range.
 * The demo application is composed of two sections :
 * ## Application Init
 * Initializes the driver and performs the click default configuration.
 * ## Application Task
 * Changes the output voltage every 3 seconds and displays on the USB UART
 * the currently set voltage output value.
 * @author Stefan Filipovic

#include "board.h"
#include "log.h"
#include "buck19.h"

static buck19_t buck19;
static log_t logger;

void application_init ( void ) 
    log_cfg_t log_cfg;  /**< Logger config object. */
    buck19_cfg_t buck19_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.
    buck19_cfg_setup( &buck19_cfg );
    BUCK19_MAP_MIKROBUS( buck19_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == buck19_init( &buck19, &buck19_cfg ) ) 
        log_error( &logger, " Communication init." );
        for ( ; ; );
    if ( BUCK19_ERROR == buck19_default_cfg ( &buck19 ) )
        log_error( &logger, " Default configuration." );
        for ( ; ; );

    log_info( &logger, " Application Task " );

void application_task ( void ) 
    static float vout = BUCK19_VOUT_MIN;
    if ( BUCK19_OK == buck19_set_vout ( &buck19, vout ) )
        log_printf ( &logger, " VOUT: %.2f V\r\n\n", vout );
    Delay_ms ( 3000 );
    vout += 0.5f;
        vout = BUCK19_VOUT_MIN;

void main ( void ) 
    application_init( );

    for ( ; ; ) 
        application_task( );

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

Additional Support