Beginner
10 min

Convert analog voltage into PWM signals with LTC6992CS6-1 and STM32F407VGT6

Generate PWM signals at frequencies up to 1 MHz, providing flexibility for high-speed applications

AN to PWM 2 Click with Clicker 4 for STM32F4

Published Mar 15, 2024

Click board™

AN to PWM 2 Click

Dev Board

Clicker 4 for STM32F4

Compiler

NECTO Studio

MCU

STM32F407VGT6

Achieve precise analog-to-PWM signal conversion, enabling smooth control over devices like LEDs, heaters, and servo motors with minimal effort

A

A

Hardware Overview

How does it work?

AN to PWM 2 Click is based on the LTC6992CS6, a voltage-controlled PWM generator from Analog Devices. This device is chosen because it keeps its output clocking at all times and offers glitch-free, a first cycle-accurate startup within 500μs of Power-On. The output of this Click board™ can source or sink up to 16 mA, and it has a linear response, so applying a voltage in a range of -2.5 to 2.5V on its input will result in generating the PWM pulse train with a duty cycle linearly proportional to the input voltage. The output PWM signal is brought to the INT pin of the mikroBUS™ socket to enable fast and precise duty cycle measurement using the interrupt routines. The LTC6992CS6 has a MOD pin, which represents pulse-width modulation input where it is necessary to bring an analog signal. To bring the corresponding signal to that pin, this Click

board™ uses an analog circuitry made of OpAmp AD8616ARZ from Analog Devices. In the first part of the circuit, amplifier OPA1 adjusts the input signal through a reference voltage of 2.5V by the MCP1525 from Microchip and applies input voltage in a range of -2.5 to 2.5V. The next part of the circuit is the voltage divider and amplifier OPA2, which has the function of a buffer, after which the signal required by the MOD pin of the LTC6992CS6 is obtained. The output frequency can range up from 3.81Hz to 1MHz and is controlled via the AD5171, a 64-position (OTP) digital potentiometer from Analog Devices, which programs the LTC6992CS6’s internal master oscillator frequency. The output frequency is determined by this master oscillator and an internal frequency divider programmable to eight settings from 1 to 16384. It

communicates with MCU using the standard I2C serial interface that operates at clock rates up to 400 kHz and represents the most accurate way to set the frequency. It also left the possibility of adjusting the frequency via resistors RH and RL by placing appropriate resistors. This Click board™ is designed to be operated only with a 5V logic level. A proper logic voltage level conversion should be performed before the AN to PWM 2 Click is used with MCUs with different logic levels. More information about the LTC6992CS6’s functionality, electrical specifications, and typical performance can be found in the attached datasheet. However, the Click board™ comes equipped with a library that contains easy-to-use functions and a usage example that can be used as a reference for the development.

AN to PWM 2 Click hardware overview image

Features overview

Development board

Clicker 4 for STM32F4 is a compact development board designed as a complete solution that you can use to quickly build your own gadgets with unique functionalities. Featuring an STM32F407VGT6 MCU, four mikroBUS™ sockets for Click boards™ connectivity, power management, and more, it represents a perfect solution for the rapid development of many different types of applications. At its core is an STM32F407VGT6 MCU, a powerful microcontroller by STMicroelectronics based on the high-performance

Arm® Cortex®-M4 32-bit processor core operating at up to 168 MHz frequency. It provides sufficient processing power for the most demanding tasks, allowing Clicker 4 to adapt to any specific application requirements. Besides two 1x20 pin headers, four improved mikroBUS™ sockets represent the most distinctive connectivity feature, allowing access to a huge base of Click boards™, growing on a daily basis. Each section of Clicker 4 is clearly marked, offering an intuitive and clean interface. This makes working with the

development board much simpler and, thus, faster. The usability of Clicker 4 doesn’t end with its ability to accelerate the prototyping and application development stages: it is designed as a complete solution that can be implemented directly into any project, with no additional hardware modifications required. Four mounting holes [4.2mm/0.165”] at all four corners allow simple installation by using mounting screws.

Clicker 4 for STM32F4 double image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M4

MCU Memory (KB)

10

Silicon Vendor

STMicroelectronics

Pin count

100

RAM (Bytes)

100

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
NC
NC
3.3V
Ground
GND
GND
NC
NC
PWM
PWM Output
PD0
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PB10
SCL
I2C Data
PB11
SDA
Power Supply
5V
5V
Ground
GND
GND
1

Take a closer look

Schematic

AN to PWM 2 Click Schematic schematic

Step by step

Project assembly

Clicker 4 for STM32F4 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Clicker 4 for STM32F4 as your development board.

Clicker 4 for STM32F4 front image hardware assembly
LTE IoT 5 Click front image hardware assembly
LTE IoT 5 Click complete accessories setup image hardware assembly
Clicker 4 STM32F4 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
Clicker 4 for STM32F4 HA MCU Step 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 AN to PWM 2 Click driver.

Key functions:

  • antopwm2_set_frequency - This function sets a frequency output in a range from 500kHz to 1MHz by setting the digipot resistance

  • antopwm2_set_frequency_otp - This function sets a frequency output in a range from 500kHz to 1MHz by setting the digipot resistance in OTP mode

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 AN to PWM 2 Click example
 *
 * # Description
 * This example demonstrates the use of AN to PWM 2 click board by changing the PWM output
 * frequency from 500kHz to 1MHz in steps of 50kHz.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and logger.
 *
 * ## Application Task
 * Changes the PWM output frequency every 5 seconds in steps of 50kHz going through the full range
 * from 500kHz to 1MHz. The currently set frequency will be displayed on the USB UART.
 * 
 * @note
 * Applying a voltage of -2.5 to 2.5V on the input will generate the PWM pulse train
 * with a duty cycle linearly proportional to the input voltage.
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "antopwm2.h"

static antopwm2_t antopwm2;
static log_t logger;

void application_init ( void ) 
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    antopwm2_cfg_t antopwm2_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.
    antopwm2_cfg_setup( &antopwm2_cfg );
    ANTOPWM2_MAP_MIKROBUS( antopwm2_cfg, MIKROBUS_1 );
    if ( I2C_MASTER_ERROR == antopwm2_init( &antopwm2, &antopwm2_cfg ) ) 
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    static uint32_t freq = ANTOPWM2_FREQ_MIN;
    if ( ANTOPWM2_OK == antopwm2_set_frequency ( &antopwm2, freq ) )
    {
        log_printf ( &logger, " Frequency: %lu Hz\r\n\n", freq );
    }
    freq += 50000;
    if ( freq > ANTOPWM2_FREQ_MAX )
    {
        freq = ANTOPWM2_FREQ_MIN;
    }
    Delay_ms ( 5000 );
}

int main ( void ) 
{
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

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

Additional Support

Resources