Displays the intensity of an audio signal using LM3914 and STM32F413ZH
Volume Unit Meter
Published Feb 14, 2024
Click board™
VU Meter Click
Dev. board
Nucleo 144 with STM32F413ZH MCU
Compiler
NECTO Studio
MCU
STM32F413ZH
Lighten the bar graph display according to the sound quality
A
A
Hardware Overview
How does it work?
VU Meter Click is based on the LM3914, a monolithic integrated circuit that senses analog voltage levels and drives a 10-segment bar graph display from Texas Instruments. This solution is a compact volume unit meter. This analog-controlled driver means it can control display by an analog input voltage and eliminates the need for additional programming. A volume unit meter represents a device that displays the intensity of an audio signal; more specifically, it is used to visualize analog signals. That's why VU Meter Click is suitable as a volume measurement gadget. The LM3914 is configured to work in bar mode, where all parts of the bar graph display below a certain point turn on. This board is manufactured with an onboard sound-detecting device (microphone), the MC33072 Op-Amp, and the LM3914, which gleams the bar graph display according to the sound's quality.
Initially, the microphone captures and transforms the sound into linear voltages to sound amplitude. The capacitor then stops the DC component of the transmission, allowing the AC input from the microphone to enter the MC33072 Op-Amp. One part of the MC33072 represents a variable gain inverting amplifier using the TPL0501, an SPI-configurable digital potentiometer from Texas Instruments, while the second part represents a signal buffer. After filtration and amplification, these filtered and amplified signals are finally provided to LM3914. Considering that this driver is analog controlled, this Click board™ also provides the ability to monitor the analog signal by the MCU via the AN pin of the mikroBUS™ socket. The LM3914 operates in a voltmeter format and lights the XGURUGX10D, a ten-segment bar graph array, according to the strength of the given signal.
The onboard bar graph display segments are bright and uniformly colored, providing pleasant and clean visual feedback. Each segment is composed of green and red-colored LEDs, making it possible to have various essential states marked in a different colors. It can use green, red, and a combination of these two, resulting in amber-colored segments. 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. However, the 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.
Features overview
Development board
Nucleo-144 with STM32F413ZH MCU board offers an accessible and adaptable avenue for users to explore new ideas and construct prototypes. It allows users to tailor their experience by selecting from a range of performance and power consumption features offered by the STM32 microcontroller. With compatible boards, the
internal or external SMPS dramatically decreases power usage in Run mode. Including the ST Zio connector, expanding ARDUINO Uno V3 connectivity, and ST morpho headers facilitate easy expansion of the Nucleo open development platform. The integrated ST-LINK debugger/programmer enhances convenience by
eliminating the need for a separate probe. Moreover, the board is accompanied by comprehensive free software libraries and examples within the STM32Cube MCU Package, further enhancing its utility and value.
Microcontroller Overview
MCU Card / MCU
Architecture
ARM Cortex-M4
MCU Memory (KB)
1536
Silicon Vendor
STMicroelectronics
Pin count
144
RAM (Bytes)
327680
You complete me!
Accessories
Click Shield for Nucleo-144 comes equipped with four mikroBUS™ sockets, with one in the form of a Shuttle connector, allowing all the Click board™ devices to be interfaced with the STM32 Nucleo-144 board with no effort. This way, MIKROE allows its users to add any functionality from our ever-growing range of Click boards™, such as WiFi, GSM, GPS, Bluetooth, ZigBee, environmental sensors, LEDs, speech recognition, motor control, movement sensors, and many more. Featuring an ARM Cortex-M microcontroller, 144 pins, and Arduino™ compatibility, the STM32 Nucleo-144 board offers limitless possibilities for prototyping and creating diverse applications. These boards are controlled and powered conveniently through a USB connection to program and efficiently debug the Nucleo-144 board out of the box, with an additional USB cable connected to the USB mini port on the board. Simplify your project development with the integrated ST-Link debugger and unleash creativity using the extensive I/O options and expansion capabilities. This Click Shield also has several switches that perform functions such as selecting the logic levels of analog signals on mikroBUS™ sockets and selecting logic voltage levels of the mikroBUS™ sockets themselves. Besides, the user is offered the possibility of using any Click board™ with the help of existing bidirectional level-shifting voltage translators, regardless of whether the Click board™ operates at a 3.3V or 5V logic voltage level. Once you connect the STM32 Nucleo-144 board with our Click Shield for Nucleo-144, you can access hundreds of Click boards™, working with 3.3V or 5V logic voltage levels.
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Click board™ Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Nucleo 144 with STM32F413ZH MCU as your development board.
Track your results in real time
Application Output
1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.
2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.
3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.
Software Support
Library Description
This library contains API for VU Meter Click driver.
Key functions:
vumeter_read_an_pin_voltageThis function reads the results of the AD conversion of the AN pin and converts them to a proportional voltage level.vumeter_set_gain_levelThis function sets the input signal gain level (the microphone sensitivity).vumeter_calculate_vu_levelThis function calculates the VU level from the analog voltage input.
Open Source
Code example
The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.
/*!
* @file main.c
* @brief VUMeter Click example
*
* # Description
* This example demonstrates the use of VU Meter Click board.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes the driver and sets the gain level (the microphone sensitivity) to maximum.
*
* ## Application Task
* Calculates VU level from the analog voltage read from AN pin, and displays the results
* on the USB UART approximately every 100ms.
*
* @author Stefan Filipovic
*
*/
#include "board.h"
#include "log.h"
#include "vumeter.h"
static vumeter_t vumeter;
static log_t logger;
void application_init ( void )
{
log_cfg_t log_cfg; /**< Logger config object. */
vumeter_cfg_t vumeter_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.
vumeter_cfg_setup( &vumeter_cfg );
VUMETER_MAP_MIKROBUS( vumeter_cfg, MIKROBUS_1 );
err_t init_flag = vumeter_init( &vumeter, &vumeter_cfg );
if ( SPI_MASTER_ERROR == init_flag )
{
log_error( &logger, " Application Init Error. " );
log_info( &logger, " Please, run program again... " );
for ( ; ; );
}
vumeter_set_gain_level ( &vumeter, VUMETER_GAIN_LEVEL_MAX );
log_info( &logger, " Application Task " );
}
void application_task ( void )
{
log_printf( &logger, " VU level: %.3f VU\r\n", vumeter_calculate_vu_level ( &vumeter, 100 ) );
}
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;
}
// ------------------------------------------------------------------------ END
