Ensure every word is heard with precision using MCP6022 and PIC32MZ2048EFM100
Mic up and stand out
Published Oct 02, 2023
Click board™
MIC 2 Click
Dev.Board
Curiosity PIC32 MZ EF
Compiler
NECTO Studio
MCU
PIC32MZ2048EFM100
Build a top-quality microphone setup that meets your unique needs and specifications.
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Hardware Overview
How does it work?
MIC 2 Click is based on a small omnidirectional electret microphone, accompanied by a digitally controlled pre-amp section. The pre-amp consists of the MCP6022, a dual, rail-to-rail, low noise operational amplifier from Microchip. This op-amp has a wide bandwidth of 10MHz, very low noise, and extremely low total harmonic distortion (THD). These features make it perfectly suitable to be used to build a microphone pre-amplifier (pre-amp). By adding a digital potentiometer IC in the feedback loop, it is possible to set the gain ratio by the host MCU. The AD5171, a digital potentiometer IC with 64 positions from Analog Devices is used in the feedback loop to digitally control the gain ratio. This device contains an OTP memory (a fuse) which can be used to lock the wiper in a permanent position. The wiper data can be changed indefinitely until the internal protection fuse is blown. This can be done by a special command. However, the Click board™ must be operated at 5V in order to successfully blow up the fuse and lock down the wiper position
permanently. Please consult the AD5171 for more details about the OTP memory programming and permanent lock-down of the wiper position. The AD5171 uses the I2C interface to communicate with the host MCU. The slave I2C address of this device can be changed using the SMD jumper, labeled as ADDR SEL. This jumper sets the LSB of the address, allowing it to be selected between 0b0101100x, and 0b0101101x, where (x) represents the R/W bit. The datasheet of the AD5171 offers a comprehensive explanation of its operation. However, it is supported by a mikroSDK compatible set of libraries. These functions greatly simplify the use, ensuring that the accidental lock-down is avoided if not wanted. One half of the MCP6022 is configured as a non-inverting amplifier, with the digital potentiometer connected as a rheostat in its feedback loop. The digital rheostat affects the feedback loop gain, allowing the host MCU to control it over the I2C interface. The input of the op-amp is biased by a voltage divider, so it stays at half the power supply
voltage when there is no signal. This way when the signal appears at the input, it can swing both down to 0V and up to VCC. A minimum gain of the op-amp is 23. It can be increased as the AD5171 is moved away from the 0 position. After power ON, the wiper of the AD5171 is in the middle position (i.e. 25K, if it is not locked down to some other value). The second op-amp of the MCP6022 serves as a unity-gain buffer, allowing the host MCU to sample the output over the AN pin of the mikroBUS™. Depending on the applied gain ratio, the output voltage may peak up to VCC. Therefore, care should be taken when selecting the voltage for the Click board™. 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. Also, this 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
Curiosity PIC32 MZ EF development board is a fully integrated 32-bit development platform featuring the high-performance PIC32MZ EF Series (PIC32MZ2048EFM) that has a 2MB Flash, 512KB RAM, integrated FPU, Crypto accelerator, and excellent connectivity options. It includes an integrated programmer and debugger, requiring no additional hardware. Users can expand
functionality through MIKROE mikroBUS™ Click™ adapter boards, add Ethernet connectivity with the Microchip PHY daughter board, add WiFi connectivity capability using the Microchip expansions boards, and add audio input and output capability with Microchip audio daughter boards. These boards are fully integrated into PIC32’s powerful software framework, MPLAB Harmony,
which provides a flexible and modular interface to application development a rich set of inter-operable software stacks (TCP-IP, USB), and easy-to-use features. The Curiosity PIC32 MZ EF development board offers expansion capabilities making it an excellent choice for a rapid prototyping board in Connectivity, IOT, and general-purpose applications.
Microcontroller Overview
MCU Card / MCU
Architecture
PIC32
MCU Memory (KB)
2048
Silicon Vendor
Microchip
Pin count
100
RAM (Bytes)
524288
Used MCU Pins
mikroBUS™ mapper
Take a closer look
Schematic
Step by step
Project assembly
Start by selecting your development board and Click board™. Begin with the Curiosity PIC32 MZ EF as your development board.
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.
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™.
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.
Software Support
Library Description
This library contains API for MIC 2 Click driver.
Key functions:
mic2_set_potentiometer- This function set the value of digital potentiometermic2_read_an_pin_value- This function reads results of AD conversion of the AN pinmic2_read_an_pin_voltage- This function reads results of AD conversion of the AN pin and converts them to proportional voltage level.
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 Mic2 Click example
*
* # Description
* This range is suited for audio and/or speech applications.
*
* The demo application is composed of two sections :
*
* ## Application Init
* Initializes driver init, ADC init and sets digital pot.
*
* ## Application Task
* Reads ADC data calculates dB value and logs data to serial plotter.
*
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "mic2.h"
#include "math.h"
// ------------------------------------------------------------------ VARIABLES
uint16_t plot_time;
static mic2_t mic2;
static log_t logger;
static mic2_data_t adc_value;
void application_init ( void )
{
log_cfg_t log_cfg;
mic2_cfg_t 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.
mic2_cfg_setup( &cfg );
MIC2_MAP_MIKROBUS( cfg, MIKROBUS_1 );
mic2_init( &mic2, &cfg );
mic2_set_potentiometer( &mic2, 35 );
}
void application_task ( void )
{
adc_value = mic2_generic_read ( &mic2 );
float db_val = ( adc_value + 83.2073 ) / 11.003;
log_printf( &logger, "%.2f dB\r\n", db_val );
Delay_ms( 100 );
}
void main ( void )
{
application_init( );
for ( ; ; )
{
application_task( );
}
}
// ------------------------------------------------------------------------ END
