Intermediate
30 min

Make interactions more intuitive with CAP1293 and STM32F405RG

Start with just a touch

TouchKey 4 click with SparkFun MicroMod mikroBUS Carrier Board

Published Aug 07, 2023

Click board™

TouchKey 4 click

Development board

SparkFun MicroMod mikroBUS Carrier Board

Compiler

NECTO Studio

MCU

STM32F405RG

Join the movement and create interfaces that come alive with touch functions

A

A

Hardware Overview

How does it work?

TouchKey 4 Click is based on the CAP1293, 3-channel capacitive touch sensor with proximity detection from Microchip. This IC has three independently configurable capacitive touch channels with the auto-calibration function. It uses the I2C protocol for the communication, with the I2C bus pins routed to the respective mikroBUS™ pins: SMCLK is the I2C clock pin, routed to the SCK pin of the mikroBUS™ and the SMDATA is the I2C data pin, routed to the SDA pin of the mikroBUS™. Additionally, an #ALERT pin is routed to the mikroBUS™ INT pin, which triggers interrupts on the host MCU. The board has three PCB pads used to sense touch or proximity events. These pads are the only elements on the top side of the board, allowing the installation of the protective acrylic glass layer. The capacitive sensor channels feature a programmable sensitivity threshold and an automatic recalibration to compensate for environmental changes. The device can work in several power modes, with separate input settings for the Active and Standby modes. The recalibration procedure can be triggered either automatically or on-demand, and it is used to set the base register value for the “not touched” state of the input channel. The CAP1293 IC also integrates sections that provide efficient interference protection. The EMI and RFI detection

sections protect by discarding the corrupted bytes if the detected noise threshold is exceeded. Also, false input readings, such as the negative values and “stuck button” events, are handled by the internal algorithms, which will set the respective bits to indicate the problem, and can be set to trigger a recalibration procedure. In general, the device always reverts to a power-saving mode when idling. If the programmed cycling time through all the enabled channels is long enough, sampling all the enabled channels will be finished before the cycle ends. When this happens, the device will revert to a power-saving mode, waiting for another cycle to begin. If there is insufficient time to sample all the channels, the device will not revert to a power-saving mode. This will affect the overall power consumption. Multiple touch pattern detection (MTPD) sets the pattern to generate a touch event. This pattern may consist of multiple specific sensors touched at once, a minimal number of touched sensors, or when their noise flag bit is set in the status register. This function can be used to detect a closed lid or similar event. The interrupt engine differentiates between the simple touch and touch and holds events. The interrupt can be generated once when a pad touch is detected/released or repeatedly generated while the pad is touched.

A special case of touch detection is the Power Button mode. This mode requires the button to be pressed for a programmed interval before an interrupt is generated. This allows a simple Power Button functionality to be implemented in any application. The interrupt can be generated for various other events, such as the failure to calibrate and similar auxiliary events. The press and hold mode is useful for developing volume control applications. The programmable interval timer is started after the first touch event on a specific channel. The interrupt is generated in the programmed intervals if no release event is detected after the timer expires. This can be used to implement volume up/down buttons, light-dimming buttons, and similar applications. Any interrupt event will drive the #ALERT pin to a LOW logic state. This pin is routed to the mikroBUS™ INT pin and is used to trigger an interrupt event on the host MCU. More information about the registers and their functions can be found in the CAP1293 IC datasheet. However, the provided click library offers a function for easy and simple control of the Touch Key 4 Click. The provided application example demonstrates their functionality and can be used as a reference for custom projects.

TouchKey 4 Click top side image
TouchKey 4 Click bottom side image

Features overview

Development board

SparkFun MicroMod mikroBUS Carrier board takes advantage of the MicroMod, Qwiic, and mikroBUS™ ecosystems making it easy to prototype with each combined rapidly. The MicroMod M.2 socket and mikroBUS™ 8-pin header allow users to experiment with any processor board in the MicroMod ecosystem and any Click board™ in the mikroBUS™ ecosystem,

respectively. This board also features two Qwiic connectors to seamlessly integrate hundreds of Qwiic sensors and accessories into your project. The mikroBUS™ socket comprises a pair of 8-pin female headers with a standardized pin configuration. The pins consist of three groups of communications pins (SPI, UART, and I2C), six additional pins (PWM, Interrupt, Analog input,

Reset, and Chip select), and two power groups (3.3V and 5V). While a modern USB-C connector makes programming easy, the Carrier Board is also equipped with an MCP73831 single-cell Lithium-Ion/Lithium-Polymer charge IC so you can charge an attached single-cell Li-Po battery. The charge IC receives power from the USB connection and can source up to 450mA to charge an attached battery.

SparkFun MicroMod mikroBUS Carrier double side image

Microcontroller Overview

MCU Card / MCU

default

Architecture

ARM Cortex-M4

MCU Memory (KB)

1024

Silicon Vendor

STMicroelectronics

Pin count

64

RAM (Bytes)

196608

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
PC0
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

Touch Key 4 click Schematic schematic

Step by step

Project assembly

SparkFun MicroMod mikroBUS Carrier front image hardware assembly

Start by selecting your development board and Click board™. Begin with the SparkFun MicroMod mikroBUS Carrier Board as your development board.

SparkFun MicroMod mikroBUS Carrier front image hardware assembly
Thermo 28 Click front image hardware assembly
Prog-cut hardware assembly
SparkFun MicroMod mikroBUS Carrier Board - 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
SparkFun MicroMod 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 TouchKey 4 Click driver.

Key functions:

  • touchkey4_detect_touch - This function detects touch on sensor inputs and checks is touch detected or released

  • touchkey4_set_active_mode - This function puts device in Active mode and enables desired inputs in Active mode

  • touchkey4_set_standby_mode - This function puts device in Standby mode and enables desired inputs in Standby 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 
 * \brief TouchKey4 Click example
 * 
 * # Description
 * This demo performs touch & release detection click functionality.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Device and driver initialization.
 * 
 * ## Application Task  
 * Calls function to check touch detection (is interrupt occured) and shows message on
 * USB UART if touch is detected or if touch is released on enabled inputs.
 *
 * *note:*
 * <pre>
 * TouchKey 4 is configured to work in Combo mode (Active and Standby mode). Input 1 is
 * enabled in Active mode, input 3 is enabled in Standby mode, and input 2 is enabled to
 * work in both modes. In this example the interrupt will be generated when touch is
 * detected and when touch is released. 
 * Standby mode should be used when fewer sensor inputs are enabled, and when
 * they are programmed to have more sensitivity.
 * Sometimes it is neccessary to cycle the board power supply if click doesn't work. 
 * </pre>
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "touchkey4.h"

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

static touchkey4_t touchkey4;
static log_t logger;

static uint8_t sensor_results[ 3 ];
static uint8_t cnt;

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

void application_init ( void )
{
    log_cfg_t log_cfg;
    touchkey4_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.

    touchkey4_cfg_setup( &cfg );
    TOUCHKEY4_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    touchkey4_init( &touchkey4, &cfg );

    Delay_ms( 1000 );
    
    touchkey4_default_cfg( &touchkey4 );
    log_info( &logger, "---- Configured and ready ----" );
}

void application_task ( void )
{
    touchkey4_detect_touch( &touchkey4, sensor_results );
    for ( cnt = 0; cnt < 3; cnt++ )
    {
        if ( sensor_results[ cnt ] == 1 )
        {
            if ( cnt == 0 )
            {
                log_info( &logger, "Input 1 is touched\r\n" );
            }
            else if ( cnt == 1 )
            {
                log_info( &logger, "Input 2 is touched\r\n" );
            }
            else
            {
                log_info( &logger, "Input 3 is touched\r\n" );
            }
        }
        else if ( sensor_results[ cnt ] == 2 )
        {
            if ( cnt == 0 )
            {
                log_info( &logger, "Input 1 is released\r\n" );
            }
            else if ( cnt == 1 )
            {
                log_info( &logger, "Input 2 is released\r\n" );
            }
            else
            {
                log_info( &logger, "Input 3 is released\r\n" );
            }
        }
    }
    Delay_ms( 300 );
}


void main ( void )
{
    application_init( );

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


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

Additional Support

Resources