Beginner
10 min

Combine MPR121 with PIC32MZ1024EFF144 and create any capacitive application you can think of

Seven clamps, endless possibilities!

TouchClamp Click with Fusion for PIC v8

Published Aug 06, 2023

Click board™

TouchClamp Click

Dev Board

Fusion for PIC v8

Compiler

NECTO Studio

MCU

PIC32MZ1024EFF144

Designed to enhance user experience, our solution facilitates the seamless integration of conductive materials, allowing them to serve as intuitive input buttons

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Hardware Overview

How does it work?

TouchClamp Click is based on the MPR121, a proximity capacitive touch sensor controller from NXP Semiconductors. The MPR121 uses seven electrodes/capacitance sensing inputs, four of which are multifunctional for LED driving (H, C, B, A) and GPIO. One electrode is an extra capacitive button in the middle of the board labeled H. It also features the 8th simulated electrode, which represents the simultaneous charging of all electrodes connected together. The MPR121 has integrated independent autocalibration and autoconfiguration for each electrode input and separate touch and release trip thresholds for each, providing hysteresis and electrode independence. The easiest way to experiment with TouchClamp click is to use wires with alligator clips. Let your imagination roam free when choosing conductive objects such as cans, fruit, jar lids, and more. The MPR121 chip has several features in addition that simplify development and integration. First, it applies three levels of digital filtering to the raw ADC data to remove high and low-frequency noise, ensuring that

the interrupts are properly registered in a broad range of applications. The auto-calibration function, according to the vendor's datasheet, "continually learns the background baseline capacitance of each individual electrode, so the system only has to program the amount of small change from these baselines that represents a touch or release." The auto-configuration uses the given target charge level so the chip can automatically run to get an optimized charge current and charge time setting for each electrode without knowing the specific capacitance value on the electrode input. The capacitance sensing uses a constant DC current capacitance sensing scheme and can measure capacitances ranging from 10pF to over 2000pF, with resolutions up to 0.01pF. The voltage measured on the input sensing node is inversely proportional to the capacitance and is sampled by an internal 10-bit ADC. The touch sensing compares the baseline value with the current immediate electrode data to determine if a touch or a release has occurred, with the ability to set a touch/release threshold.

The proximity sensing acts as the near proximity sensing system, where all electrodes can be summoned together to create a single large electrode, thus covering a much larger area. Touch sensing and proximity sensing can be used at the same time. Among 12 electrodes, eight of them can be used as a GPIO and can be used to drive LEDs or for GPIO. The TouchClamp Click uses an I2C 2-Wire interface to communicate with the host MCU. It also has an ADDR SEL jumper to choose between the two available I2C addresses and can be connected to VDD or VSS (VSS position set by default). In addition, the TouchClamp Click comes with an interrupt INT pin, which is triggered anytime a touch or release is detected. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. 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.

TouchClamp Click hardware overview image

Features overview

Development board

Fusion for PIC v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different PIC, dsPIC, PIC24, and PIC32 MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, Fusion for PIC v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the Fusion for PIC v8 development board contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART, USB

HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet are also included, including the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options (graphical and character-based LCD). Fusion for PIC v8 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.

Fusion for PIC v8 horizontal image

Microcontroller Overview

MCU Card / MCU

default

Type

8th Generation

Architecture

PIC32

MCU Memory (KB)

1024

Silicon Vendor

Microchip

Pin count

144

RAM (Bytes)

262144

Used MCU Pins

mikroBUS™ mapper

NC
NC
AN
NC
NC
RST
NC
NC
CS
NC
NC
SCK
NC
NC
MISO
NC
NC
MOSI
Power Supply
3.3V
3.3V
Ground
GND
GND
NC
NC
PWM
Interrupt
PD0
INT
NC
NC
TX
NC
NC
RX
I2C Clock
PA2
SCL
I2C Data
PA3
SDA
NC
NC
5V
Ground
GND
GND
1

Take a closer look

Schematic

TouchClamp Click Schematic schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Fusion for PIC v8 as your development board.

Fusion for PIC v8 front image hardware assembly
GNSS2 Click front image hardware assembly
SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
v8 SiBRAIN 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 image step 7 hardware assembly
Necto image step 8 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 TouchClamp Click driver.

Key functions:

  • etouchclamp_get_touch_data - Get touch data 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 TouchClamp Click example
 * 
 * # Description
 * This demo-app shows the touch position using TouchClamp click.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Configuring clicks and log objects.
 * Setting the click in the default configuration.
 * 
 * ## Application Task  
 * Detect and dispay touch position when the click is triggered.
 * 
 * \author Nenad Filipovic
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "touchclamp.h"

// ------------------------------------------------------------------ VARIABLES

static touchclamp_t touchclamp;
static log_t logger;
uint16_t touch_data;
uint16_t touch_data_old;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
{
    log_cfg_t log_cfg;
    touchclamp_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.

    touchclamp_cfg_setup( &cfg );
    TOUCHCLAMP_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    touchclamp_init( &touchclamp, &cfg );
    Delay_ms( 100 );
    
    touchclamp_soft_reset( &touchclamp );
    Delay_ms( 100 );
    
    touchclamp_default_cfg( &touchclamp );
    Delay_ms( 100 );
    
    touch_data_old = TOUCHCLAMP_NO_TOUCH;
    
    log_printf( &logger, "-------------------\r\n" );
    log_printf( &logger, " Touch Clamp Click \r\n" );
    log_printf( &logger, "-------------------\r\n" );
}

void application_task ( void )
{
    touch_data = touchclamp_get_touch_data( &touchclamp );
    
    if ( touch_data_old != touch_data )
    {
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_H )
            log_printf( &logger, "  - - - - - - - H\r\n" );
            
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_G )
            log_printf( &logger, "  - - - - - - G -\r\n" );
            
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_F )
            log_printf( &logger, "  - - - - - F - -\r\n" );
                                                       
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_E )                       
            log_printf( &logger, "  - - - - E - - -\r\n" );
                                                       
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_D )                       
            log_printf( &logger, "  - - - D - - - -\r\n" );
                                                       
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_C )                       
            log_printf( &logger, "  - - C - - - - -\r\n" );
                                                       
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_B )                       
            log_printf( &logger, "  - B - - - - - -\r\n" );
                                                       
        if ( touch_data == TOUCHCLAMP_TOUCH_POSITION_A )                       
            log_printf( &logger, "  A - - - - - - -\r\n" );
      
        touch_data_old = touch_data;
    }
}

void main ( void )
{
    application_init( );

    for ( ; ; )
    {
        application_task( );
    }
}


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

Additional Support

Resources