TouchKey Click

How does it work?

TouchKey Click is based on the TTP224, a four key touch pad detector from TonTouch. The TTP224 has a stable sensing method that can cover diverse conditions and acts as a human interface control panel through non-conductive dielectric materials. It features auto-calibration for life, with a re-calibration period of about 4 seconds when a key has not been touched. The TouchKey Click can detect all four pad activations at once. There are two operating modes, Low Power and Fast mode. Unlike the Low Power operating mode, which has a slower response for the first touch, the Fast mode, in addition to a much faster response, also has a slightly higher consumption. When working in Fast mode, if no touch is detected after 8 seconds, the board automatically switches to Low Power mode.

The TouchKey Click has four pads labeled A, B, C, and D. To communicate with the host MCU, the TTP224 uses four digital inputs of the mikroBUS™ socket, labeled just as the pads above, A, B, C, and D. Every touch on the corresponding pad will send the digital state to its assigned pin.

The TTP224 has various features that can be addressed on this Click board™ over four solder jumpers. The Low Power or Fast mode option can be set over an LPMB solder jumper (Low Power as a default), while the TOG jumper sets output mode, direct or toggle (direct as a default). Depending on the output state needs, this Click board™ can use active High or Low over the AHLB solder jumper, where the active High is set by default. Objects used to cover the sensor pads can cause a change in sensing detection. To prevent this change, the maximum key duration time can be set from 16 seconds to infinite via the MOT0 solder jumper (infinite is set as default). Open drain or CMOS output can also be set via the OD solder jumper, with CMOS as the default. The last is an SM solder jumper used to set single or multi-key options, with the multi-key set as the default.

This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWR 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.

Specifications

Pinout diagram

This table shows how the pinout on TouchKey Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
Touchpad B Detection	B	1	AN	PWM	16	C	Touchpad C Detection
Touchpad A Detection	A	2	RST	INT	15	D	Touchpad D Detection
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

TouchKey Click electrical specifications

Software Support

We provide a library for the TouchKey Click as well as a demo application (example), developed using Mikroe compilers. The demo can run on all the main Mikroe development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager (recommended), downloaded from our LibStock™ or found on Mikroe github account.

Library Description

This library contains API for TouchKey Click driver.

Key functions

• Function gets state of “a” (RST) pin on TouchKey Click board.

• Function gets state of “b” (AN) pin on TouchKey Click board.

• Function gets state of “c” (PWM) pin on TouchKey Click board.

• Function gets state of “d” (INT) pin on TouchKey Click board.

Example Description

This application has four capacitive pads powered by TTP224, a touchpad detector IC. Capacitive buttons like these can be toggled even when placed under a layer of glass or paper.

 void application_task ( void ) 
 { 

     key_state = touchkey_a( &touchkey ) | touchkey_b( &touchkey ) | touchkey_c( &touchkey ) | touchkey_d( &touchkey ); 

     if( key_state == 1 && key_state_old == 0  ) 
     { 
         log_info( &logger,"Pressed : " ); 

         if( touchkey_a( &touchkey ) ) 
         { 
             log_info( &logger, "A " ); 
         } 
         if( touchkey_b( &touchkey) ) 
         { 
             log_info( &logger, "B " ); 
         } 
         if( touchkey_c( &touchkey ) ) 
         { 
             log_info( &logger, "C " );; 
         } 
         if( touchkey_d( &touchkey ) ) 
         { 
             log_info( &logger, "D " ); 
         } 

         log_info( &logger, "" ); 
         key_state_old = 1; 
     } 
     if ( key_state == 0 && key_state_old == 1 ) 
     { 
         key_state_old = 0; 
     } 

 }

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager (recommended), downloaded from our LibStock™ or found on Mikroe github account.

Other Mikroe Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.TouchKey

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 Click or RS232 Click to connect to your PC, for development systems with no UART to USB interface available on the board. UART terminal is available in all Mikroe compilers.

mikroSDK

This Click board™ is supported with mikroSDK – Mikroe Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.