Python & CircuitPython

It's easy to use the CAP1188 sensor with Python or CircuitPython and the Adafruit CircuitPython CAP1188 module.  This module allows you to easily write Python code that reads capacitive touch from the sensor.

You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.

CircuitPython Microcontroller Wiring

First wire up a CAP1188 to your board exactly as shown on the previous pages for Arduino.  You can use either I2C or SPI wiring, although it's recommended to use I2C for simplicity.

Here's an example of wiring a Feather M0 to the sensor with I2C:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board SCK to sensor SCK
  • Board SDA to sensor SDA

And an example of a Feather M0 wired with hardware SPI:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board GND to sensor AD
  • Board SCK to sensor SCK
  • Board MOSI to sensor MOSI
  • Board MISO to sensor MISO
  • Board D5 to sensor CS (or use any other free digital I/O pin)

Python Computer Wiring

Since there's dozens of Linux computers/boards you can use we will show wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported

Here's the Raspberry Pi wired with I2C:

  • Pi 3V3 to sensor VIN
  • Pi GND to sensor GND
  • Pi SCL to sensor SCK
  • Pi SDA to sensor SDA

And an example on the Raspberry Pi wired with SPI:

  • Pi 3V3 to sensor VIN
  • Pi GND to sensor GND
  • Pi GND to sensor AD
  • Pi MOSI to sensor MOSI
  • Pi MISO to sensor MISO
  • Pi SCLK to sensor SCK
  • Pi GPIO5 to sensor CS (or use any other free GPIO pin)

CircuitPython Installation of CAP1188 Library

You'll need to install the Adafruit CircuitPython CAP1188 library on your CircuitPython board.

First make sure you are running the latest version of Adafruit CircuitPython for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle.  Our CircuitPython starter guide has a great page on how to install the library bundle.

For non-express boards like the Trinket M0 or Gemma M0, you'll need to manually install the necessary libraries from the bundle:

  • adafruit_cap1188
  • adafruit_bus_device

Before continuing make sure your board's lib folder or root filesystem has the adafruit_cap1188, and adafruit_bus_device files and folders copied over.

Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.

Python Installation of CAP1188 Library

You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!

Once that's done, from your command line run the following command:

  • sudo pip3 install adafruit-circuitpython-cap1188

If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!

CircuitPython & Python Usage

To demonstrate the usage of the sensor we'll initialize it and read capacitive touch from the board's Python REPL.

If you're using an I2C connection run the following code to import the necessary modules and initialize the I2C connection with the sensor:

Download: file
import board
import busio
from adafruit_cap1188.i2c import CAP1188_I2C
i2c = busio.I2C(board.SCL, board.SDA)
cap = CAP1188_I2C(i2c)

Or if you're using a SPI connection run this code instead to setup the SPI connection and sensor:

Download: file
import board
import busio
import digitalio
from adafruit_cap1188.spi import CAP1188_SPI
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
cs = digitalio.DigitalInOut(board.D5)
cap = CAP1188_SPI(spi, cs)

Now you're ready to read capacitive touch from the sensor using any of these properties:

  • value - Whether the pin is being touched or not.
  • raw_value - The raw touch measurement.

For example, to print when pin 1 is touched:

Download: file
while True:
    if cap[1].value:
        print("Pin 1 touched!")

Or, to print when any pin is touched:

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while True:
    for i in range(1, 9):
        if cap[i].value:
            print("Pin {} touched!".format(i))

That's all there is to using CAP1188 with CircuitPython!

Full Example Code

import board
import busio

# I2C setup
from adafruit_cap1188.i2c import CAP1188_I2C
i2c = busio.I2C(board.SCL, board.SDA)
cap = CAP1188_I2C(i2c)

# SPI setup
# from digitalio import DigitalInOut, Direction
# from adafruit_cap1188.spi import CAP1188_SPI
# spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
# cs = DigitalInOut(board.D5)
# cap = CAP1188_SPI(spi, cs)

while True:
    for i in range(1, 9):
        if cap[i].value:
            print("Pin {} touched!".format(i))
This guide was first published on Jan 10, 2014. It was last updated on Jan 10, 2014. This page (Python & CircuitPython) was last updated on Nov 16, 2019.