Intermediate
30 min

Unleash the waveform symphony using AD9833 and STM32F031K6

Sine/triangle/square waveform generator

Waveform Click with Nucleo 32 with STM32F031K6 MCU

Published Oct 01, 2024

Click board™

Waveform Click

Dev Board

Nucleo 32 with STM32F031K6 MCU

Compiler

NECTO Studio

MCU

STM32F031K6

Explore this comprehensive waveform generator and add seamless signal generation to your solution

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Hardware Overview

How does it work?

Waveform Click is based on the AD9833, a low-power, programmable waveform generator from Analog Devices. This company is well-established in the high-quality Digital Signal Processing (DSP) solutions market. The AD9833 IC is based on Direct Digital Synthesis (DDS), producing a waveform with a programmable frequency and selectable wave shape at its output. The AD9833 and the AD5227, a digital potentiometer IC from the same company, are controlled over the SPI interface, allowing both the frequency and amplitude to be changed very quickly without additional latency. DDS produces an analog waveform by exploiting the fact that the signal's phase is changed linearly. For simple periodic functions such as the sine function, the phase changes linearly between 0 and 2π. This allows building the Numerically Controlled Oscillator (NCO) block, which outputs a numerical value that linearly changes over time, between 0 and 228 – 1 (since the AD9833 IC has a 28-bit phase accumulator). The continuously changing output of the NCO block is used as the index for the Lookup Table (LUT), which contains amplitudes of the output waveform. The faster the NCO output changes, the higher the output signal frequency,

which is a basis for DDS. The main advantage over other types of synthesis (PLL, for example) is its simplistic approach. The frequency can be changed in small steps (depending on the clock generator), while the maximum frequency can easily reach GHz. Besides the NCO and the LUT, the AD9833 contains other blocks necessary to produce the waveform at the output. It also features a 10-bit DAC, which translates the digital value into an analog voltage at the output. Since the ADC is only 10 bits wide, the LUT does not need to have too many elements. The resolution of the ADC is the bottleneck, so a slightly higher resolution is required for the LUT data. This further reduces the complexity and costs. The AD9833 can completely avoid using the LUT, producing a square wave (by using only the MSB of the DAC), with a frequency that can be further multiplied by 2, and a triangle wave (by redirecting the NCO directly to DAC instead using it for sweeping through the LUT). The operating modes of the AD9833 can be set up by using the config-register over the SPI interface. For more detailed information about the AD9833 IC, please refer to the datasheet of the AD9833. However, the mikroSDK compatible library contains functions

that simplify work with the AD9833 IC. The output of the AD9833 is routed to the AD5227 digital potentiometer, which is used to set the amplitude of the output signal. This potentiometer is used to scale down the amplitude between 0V and 3.3V. It is controlled over the SPI interface. The potentiometer is used since the AD9833 IC does not provide means to regulate the amplitude of the signal at the output. Waveform click uses the clock generator 25MHz, which allows changing the frequency in steps of 0.1Hz. The high speed of the clock allows very high frequencies to be produced so that this Click board™ can generate a very clean sine wave with a frequency of up to 5MHz and a square wave with a frequency of up to 12MHz. The integrated clock generator offers a STAND-BY pin, which turns the clock on or off. If this pin has a HIGH logic state, the clock generator will produce a 25MHz clock signal. This pin is pulled to VCC by a pull-up resistor, so the 25MHz clock generator is enabled by default. The output signal of the Click board™ is buffered by an ADA4891-1 low-noise op-amp, providing a constant impedance and limited protection to the whole circuit. It is available over the SMA connector, allowing the shielded coaxial cable to be used.

Waveform Click top side image
Waveform Click bottom side image

Features overview

Development board

Nucleo 32 with STM32F031K6 MCU board provides an affordable and flexible platform for experimenting with STM32 microcontrollers in 32-pin packages. Featuring Arduino™ Nano connectivity, it allows easy expansion with specialized shields, while being mbed-enabled for seamless integration with online resources. The

board includes an on-board ST-LINK/V2-1 debugger/programmer, supporting USB reenumeration with three interfaces: Virtual Com port, mass storage, and debug port. It offers a flexible power supply through either USB VBUS or an external source. Additionally, it includes three LEDs (LD1 for USB communication, LD2 for power,

and LD3 as a user LED) and a reset push button. The STM32 Nucleo-32 board is supported by various Integrated Development Environments (IDEs) such as IAR™, Keil®, and GCC-based IDEs like AC6 SW4STM32, making it a versatile tool for developers.

Nucleo 32 with STM32F031K6 MCU double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M0

MCU Memory (KB)

32

Silicon Vendor

STMicroelectronics

Pin count

32

RAM (Bytes)

4096

You complete me!

Accessories

Click Shield for Nucleo-32 is the perfect way to expand your development board's functionalities with STM32 Nucleo-32 pinout. The Click Shield for Nucleo-32 provides two mikroBUS™ sockets to add any functionality from our ever-growing range of Click boards™. We are fully stocked with everything, from sensors and WiFi transceivers to motor control and audio amplifiers. The Click Shield for Nucleo-32 is compatible with the STM32 Nucleo-32 board, providing an affordable and flexible way for users to try out new ideas and quickly create prototypes with any STM32 microcontrollers, choosing from the various combinations of performance, power consumption, and features. The STM32 Nucleo-32 boards do not require any separate probe as they integrate the ST-LINK/V2-1 debugger/programmer and come with the STM32 comprehensive software HAL library and various packaged software examples. This development platform provides users with an effortless and common way to combine the STM32 Nucleo-32 footprint compatible board with their favorite Click boards™ in their upcoming projects.

Click Shield for Nucleo-32 accessories 1 image

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
Chip Select for AD9833
PA11
RST
Chip Select for AD5227
PA4
CS
SPI Clock
PB3
SCK
NC
NC
MISO
SPI Data IN
PB5
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
Clock Generator Enable
PA8
PWM
NC
NC
INT
NC
NC
TX
NC
NC
RX
NC
NC
SCL
NC
NC
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Schematic

Waveform Click Schematic schematic

Step by step

Project assembly

Click Shield for Nucleo-144 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Nucleo 32 with STM32F031K6 MCU as your development board.

Click Shield for Nucleo-144 front image hardware assembly
Nucleo 144 with STM32L4A6ZG MCU front image hardware assembly
Stepper 22 Click front image hardware assembly
Prog-cut hardware assembly
Stepper 22 Click complete accessories setup image hardware assembly
Nucleo-32 with STM32 MCU 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
STM32 M4 Clicker HA MCU/Select 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 via Debug Mode

1. Once the code example is loaded, pressing the "DEBUG" button initiates the build process, programs it on the created setup, and enters Debug mode.

2. After the programming is completed, a header with buttons for various actions within the IDE becomes visible. Clicking the green "PLAY" button starts reading the results achieved with the Click board™. The achieved results are displayed in the Application Output tab.

DEBUG_Application_Output

Software Support

Library Description

This library contains API for Waveform Click driver.

Key functions:

  • waveform_sine_output - Sinusoide output function

  • waveform_triangle_output - Triangle output function

  • waveform_square_output - Square output function

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 
 * \brief Waveform Click example
 * 
 * # Description
 * This example demonstrates the use of Waveform click board.
 *
 * The application is composed of two sections :
 * 
 * ## Application Init 
 * Initializes the communication interface and configures the click board.
 * 
 * ## Application Task  
 * Predefined commands are inputed from the serial port.
 * Changes the signal frequency, waveform or amplitude depending on the receiver command.
 * 
 * \author MikroE Team 
 *
 */

#include "board.h"
#include "log.h"
#include "waveform.h"

static waveform_t waveform;
static log_t logger;

static uint32_t frequency = 200000;
static uint32_t frequency_step = 10000;

/**
 * @brief Waveform display commands function.
 * @details This function displays the list of supported commands on the USB UART.
 * @return None.
 * @note None.
 */
void waveform_display_commands ( void );

/**
 * @brief Waveform parse command function.
 * @details This function checks if the input command is supported and executes it.
 * @param[in] command : Command input, for more details refer to @b waveform_display_commands function.
 * @return None.
 * @note None.
 */
void waveform_parse_command ( uint8_t command );

void application_init ( void )
{
    log_cfg_t log_cfg;
    waveform_cfg_t waveform_cfg;

    /** 
     * 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.
    waveform_cfg_setup( &waveform_cfg );
    WAVEFORM_MAP_MIKROBUS( waveform_cfg, MIKROBUS_1 );
    if ( SPI_MASTER_ERROR == waveform_init( &waveform, &waveform_cfg ) )
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }

    waveform_sine_output( &waveform, frequency );
    log_printf( &logger, "Sine wave output set with approx. frequency: %lu Hz\r\n", frequency );
    waveform_display_commands ( );
    log_info( &logger, " Application Task " );
}

void application_task ( void )
{
    uint8_t command = 0;
    if ( 1 == log_read ( &logger, &command, 1 ) ) 
    {
        waveform_parse_command ( command );
    }
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

void waveform_display_commands ( void )
{
    log_printf( &logger, "-------------------------------------------\r\n" );
    log_info( &logger, "- UART commands list -\r\n" );
    log_printf( &logger, "'+' - Increase amplitude.\r\n" );
    log_printf( &logger, "'-' - Decrease amplitude.\r\n" );
    log_printf( &logger, "'S' - Select sine wave output and increase frequency.\r\n" );
    log_printf( &logger, "'s' - Select sine wave output and decrease frequency.\r\n" );
    log_printf( &logger, "'T' - Select triangle wave output and increase frequency.\r\n" );
    log_printf( &logger, "'t' - Select triangle wave output and decrease frequency.\r\n" );
    log_printf( &logger, "'Q' - Select square wave output and increase frequency.\r\n" );
    log_printf( &logger, "'q' - Select square wave output and decrease frequency.\r\n" );
    log_printf( &logger, "'L' or 'l' - Display commands list.\r\n" );
    log_printf( &logger, "-------------------------------------------\r\n" );
}

void waveform_parse_command ( uint8_t command )
{
    switch ( command )
    {
        case '+': 
        {
            log_printf( &logger, "Increasing amplitude of the current wave.\r\n" );
            waveform_digipot_inc ( &waveform );
            break;
        }
        case '-': 
        {
            log_printf( &logger, "Decreasing amplitude of the current wave.\r\n" );
            waveform_digipot_dec ( &waveform );
            break;
        }
        case 'S': 
        {
            log_printf( &logger, "Increasing frequency of the sine wave.\r\n" );
            frequency += frequency_step;
            waveform_sine_output( &waveform, frequency );
            log_printf( &logger, "Approx. frequency: %lu Hz\r\n", frequency );
            break;
        }
        case 's': 
        {
            log_printf( &logger, "Decreasing frequency of the sine wave.\r\n" );
            if ( frequency < frequency_step )
            {
                frequency = 0;
            }
            else
            {
                frequency -= frequency_step;
            }
            waveform_sine_output( &waveform, frequency );
            log_printf( &logger, "Approx. frequency: %lu Hz\r\n", frequency );
            break;
        }
        case 'T': 
        {
            log_printf( &logger, "Increasing frequency of the triangle wave.\r\n" );
            frequency += frequency_step;
            waveform_triangle_output( &waveform, frequency );
            log_printf( &logger, "Approx. frequency: %lu Hz\r\n", frequency );
            break;
        }
        case 't': 
        {
            log_printf( &logger, "Decreasing frequency of the triangle wave.\r\n" );
            if ( frequency < frequency_step )
            {
                frequency = 0;
            }
            else
            {
                frequency -= frequency_step;
            }
            waveform_triangle_output( &waveform, frequency );
            log_printf( &logger, "Approx. frequency: %lu Hz\r\n", frequency );
            break;
        }
        case 'Q': 
        {
            log_printf( &logger, "Increasing frequency of the square wave.\r\n" );
            frequency += frequency_step;
            waveform_square_output( &waveform, frequency );
            log_printf( &logger, "Approx. frequency: %lu Hz\r\n", frequency );
            break;
        }
        case 'q': 
        {
            log_printf( &logger, "Decreasing frequency of the square wave.\r\n" );
            if ( frequency < frequency_step )
            {
                frequency = 0;
            }
            else
            {
                frequency -= frequency_step;
            }
            waveform_square_output( &waveform, frequency );
            log_printf( &logger, "Approx. frequency: %lu Hz\r\n", frequency );
            break;
        }
        case 'L': case 'l': 
        {
            waveform_display_commands ( );
            break;
        }
        default :
        {
            log_error( &logger, "Wrong command." );
            break;
        }
    }
}

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

Additional Support

Resources

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