Extend the number of capacitive inputs with SX8633 and ATmega328P
Touch, tap, and triumph
Published Feb 14, 2024
Click board™
Cap Extend Click
Dev. board
Arduino UNO Rev3
Compiler
NECTO Studio
MCU
ATmega328P
Shape the future of interaction and engineer solutions that captivate and empower users
A
A
Hardware Overview
How does it work?
Cap Extend Click is based on the SX8633, a low-power capacitive button touch controller with enhanced LED drivers and proximity sensing from Semtech. It is a fully integrated 12-channel solution that requires no external components. The SX8633 IC has a 10-bit ADC and up to 100pF offset capacitance compensation at full sensitivity. Thanks to the high resolution, it supports a wide variety of touchpad sizes and shapes to be used with this Click board™. An overlay material up to 5mm thick can also be used for extremely robust ESD immune system design, simplifying integration into touch panels, control units, and similar applications. The SX8633 features auto offset calibration to eliminate false triggers due to temperature and humidity and is initiated on power-up. The principle of touch buttons and proximity sensing operation is almost identical. The only difference is that proximity sensing is done several centimeters through the air above the overlay, while as a button, it has an ON state if
a finger or hand touches it and OFF if it is far from the sensor. The Analog Sensing Interface (ASI) converts the sensors' charge into digitally processed ticks in both applications. The ASI consists of an ADC, DAC, multiplexer, analog switches, a reference voltage, and an external integration capacitor. In LED applications, the Auto-light mode can initiate the LED fade effect individually for each GPIO, with 256 PWM steps of linear and logarithmic control. The SX8633 has three operating modes. The Active mode has fast scan periods with a typical reaction time of up to 30ms, in which interval all enabled sensors are scanned, and data is processed. The Doze mode can increase scan period time, thus and the reaction time up to 195ms. In Sleep mode, the SX8633 goes OFF except for the communication interface and GPI peripheral, at which time it does not do any sensor scanning. Users can manipulate those scan periods for Active and Doze modes in relation to power consumption. To enter the Active
mode from Doze, the user can simply touch any button. The Cap Extend Click uses an I2C 2-Wire interface in standard and fast mode with a maximum clock frequency of 400KHz to communicate with the host microcontroller. The interrupt INT pin is also available and is updated in Active or Doze once every scan period. The interrupt will be asserted when a button event or a GPI edge occurs when entering Active or Doze and will be cleared as soon as the host MCU performs a read. In addition, there is an RST pin for resetting the SX8633 with active LOW. 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, it comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.
Features overview
Development board
Arduino UNO is a versatile microcontroller board built around the ATmega328P chip. It offers extensive connectivity options for various projects, featuring 14 digital input/output pins, six of which are PWM-capable, along with six analog inputs. Its core components include a 16MHz ceramic resonator, a USB connection, a power jack, an
ICSP header, and a reset button, providing everything necessary to power and program the board. The Uno is ready to go, whether connected to a computer via USB or powered by an AC-to-DC adapter or battery. As the first USB Arduino board, it serves as the benchmark for the Arduino platform, with "Uno" symbolizing its status as the
first in a series. This name choice, meaning "one" in Italian, commemorates the launch of Arduino Software (IDE) 1.0. Initially introduced alongside version 1.0 of the Arduino Software (IDE), the Uno has since become the foundational model for subsequent Arduino releases, embodying the platform's evolution.
Microcontroller Overview
MCU Card / MCU
Architecture
AVR
MCU Memory (KB)
32
Silicon Vendor
Microchip
Pin count
28
RAM (Bytes)
2048
You complete me!
Accessories
Click Shield for Arduino UNO has two proprietary mikroBUS™ sockets, allowing all the Click board™ devices to be interfaced with the Arduino UNO board without effort. The Arduino Uno, a microcontroller board based on the ATmega328P, provides an affordable and flexible way for users to try out new concepts and build prototypes with the ATmega328P microcontroller from various combinations of performance, power consumption, and features. The Arduino Uno has 14 digital input/output pins (of which six can be used as PWM outputs), six analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an ICSP header, and reset button. Most of the ATmega328P microcontroller pins are brought to the IO pins on the left and right edge of the board, which are then connected to two existing mikroBUS™ sockets. 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 Arduino UNO board with our Click Shield for Arduino UNO, 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 Arduino UNO Rev3 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 Cap Extend Click driver.
Key functions:
capextend_reset- This function does a software reset of the click modulecapextend_read_msb_buttons- This function reads the MSB button map datacapextend_read_lsb_buttons- This function reads the LSB button map data
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
* \brief CapExtend Click example
*
* # Description
* This example showcases the initialization and configuration of the logger and Click modules
* and later on shows how to read and display the 16-bit button map ( LSB + MSB ).
*
* The demo application is composed of two sections :
*
* ## Application Init
* This function initializes and configures the Click and logger modules.
*
* ## Application Task
* This function collects map data and displays the 16-bit button map, where each bit that has
* the value 1 represents a button that has been pressed.
*
* \author MikroE Team
*
*/
// ------------------------------------------------------------------- INCLUDES
#include "board.h"
#include "log.h"
#include "capextend.h"
// ------------------------------------------------------------------ VARIABLES
static capextend_t capextend;
static log_t logger;
// ------------------------------------------------------ APPLICATION FUNCTIONS
void application_init ( )
{
log_cfg_t log_cfg;
capextend_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.
capextend_cfg_setup( &cfg );
CAPEXTEND_MAP_MIKROBUS( cfg, MIKROBUS_1 );
capextend_init( &capextend, &cfg );
capextend_reset( &capextend );
}
void application_task ( )
{
uint16_t buttons = 0;
buttons = capextend_read_buttons( &capextend );
log_printf( &logger, " * ---------BUTTTONS--------- * \r\n" );
for ( uint8_t counter = 0; counter < 12; counter++ )
{
if ( ( buttons >> ( 11 - counter ) ) & 1 )
{
log_printf( &logger, " * " );
}
else
{
log_printf( &logger, " o " );
}
}
log_printf( &logger, "\r\n * ------------------------------- * \r\n\r\n" );
Delay_ms ( 500 );
}
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
Additional Support
Resources
Category:Capacitive
