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CAP1188 SPI Arduino Communication

The CAP1188 is a turnkey capacitive touch controller providing a wide variety of button and proximity functionality. The CAP1188 also contains 8 LED drivers that offer full-on / off, variable rate blinking, dimness controls, and breathing. Each of the LED drivers may be linked to one of the sensor inputs to be actuated when a touch is detected. As well, each LED driver may be individually controlled via a host controller. Low-cost and robust touch interfaces. It works on I2C and SPI protocol. In this blog we’ll be using SPI interfacing.

Key Features: -
8 Capacitive Touch Sensor Inputs
8 LED Driver Outputs
Programmable sensitivity
Automatic recalibration
Individual thresholds for each button
Proximity Detection
Multiple Button Pattern Detection
Analog Filtering for System Noise Sources
Press and Hold feature for Volume-like Applications
Low Power Operation

Hardware connection: -
CAP1188                        Arduino       
GND                                    GND
5V                                         Vin
MISO                                     11
MOSI                                     12
SCK                                        13
CS                                          10
RESET                                     9
IRQ                                         3
A0                                        GND 

Source code: -


Download the library:-

First up, we'll download the Arduino library from the Arduino library manager.
Open the Arduino library manager:

Search for the Adafruit CAP1188 library and install it

After you've restarted, you should be able to load up the File -> Examples -> Adafruit_CAP1188-> cap1188test sketch           

Wireup the connection as shown in above hardware connection

Upload the sketch and open the serial console at 9600 baud. You should see that the CAP1188 is found (good!) and then you can touch the C1 thru C8 pads with your fingers to see the touch sensor go off. When you touch a pin, you'll also see the matching LED light up

OUTPUT : 


Explanation:
1) Include all the files such as adafruit_cap1188.
  • #include <Wire.h>
  • #include <SPI.h>
  • #include <Adafruit_CAP1188.h>
2)Make all the SPI connection with cap1188. Define all the pins according in the code. Reset Pin is used for I2C or SPI. CS pin is used for software or hardware SPI. MOSI, MISO and CLK are pins used for SPI communication.
  • #define CAP1188_RESET  9

    #define CAP1188_CS  10

    #define CAP1188_MOSI  11
    #define CAP1188_MISO  12
    #define CAP1188_CLK  13
3) Initialize cap1188 SPI function.
  • Adafruit_CAP1188 cap = Adafruit_CAP1188(CAP1188_CLK, CAP1188_MISO, CAP1188_MOSI, CAP1188_CS, CAP1188_RESET);
4)  Initialize cap1188 sensor with address if you are using I2C method otherwise follow below code.
  • // if (!cap.begin(0x28)) {
      cap.begin();                     //custom changes

      Serial.println("CAP1188 found!");
      pinMode(3, INPUT);
5) Turn off multitouch functionality so only one button will press at a time. The function cap.writeRegister has may configurations regarding multi touch, led and interrupt.
  •   cap.writeRegister(0x2A, 0x80);  // 0x2A default 0x80 use 0x41  — Set multiple touches back to off
      cap.writeRegister(0x41, 0x39);  // 0x41 default 0x39 use 0x41  — Set "speed up" setting back to off
      cap.writeRegister(0x72, 0x00);  // 0x72 default 0x00  — Sets LED links back to off (default)
      cap.writeRegister(0x44, 0x41);  // 0x44 default 0x40 use 0x41  — Set interrupt on press but not release
      cap.writeRegister(0x28, 0x00);  // 0x28 default 0xFF use 0x00  — Turn off interrupt repeat on button hold
      EIFR = 1; // clear flag for interrupt 1
      attachInterrupt(1, routine_Interrupt_CAP1188, FALLING);
    }
6) In the loop function check if any touch is detected according to pin the output will be display.
Check for interrupt. In the loop whenever touch is detected due to cap.writeRegister(0x44, 0x41). The interrupt function routine_Interrupt_CAP1188() is invoked. This increments the value of interrupt and the loop is continued.
  • void loop() {

      uint8_t touched = cap.touched();

      if (touched == 0) {
        // No touch detected
        // return;
      }

      for (uint8_t i=0; i<8 i="" nbsp="" p="">    if (touched & (1 << i)) {
          Serial.print("C"); Serial.print(i+1); Serial.print("\t");
        }
      }
      Serial.println();
      delay(50);
      Serial.print("Interrupt: ");  Serial.println(interrupt);
    }

    void routine_Interrupt_CAP1188()  {
      ++interrupt;
    }
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CAP1188 SPI Arduino Communication Reviewed by Avotrix.Author on Tuesday, July 21, 2020 Rating: 5

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