This library implements and expands upon DZL's version of Swept Frequency Capacitive Sensing as described in the Disney Research project known as Touché. It expands upon it by implementing multiple timers simultaneously which presumably allows for more sensors to be used as well. This library must also credit Mads Hobye and his instructable on implementing DZL's technique.
Note: Only for Arduino Mega and Uno (atmega328 boards) (other boards coming soon).
Git Clone or Download and place SweepingCapSense folder inside your Arduino/libraries folder. If you don't have a libraries folder create one (make sure it is lowercase) and place this library inside inside.
- Resistors: 10k, 1M, and 3.3k
- Capcitors: 100pf, 10nf (.01uf)
- Diode: 1N4148
- Inductor/Coil: 10mH
- Object: Foil,Plant, Water Bottle, pretty much any conductive object
The send pin you use depends which Arduino and which timer you use.
This library was developed with an Arduino Mega and so allows for the use of all four 16 bit timers. It should also be noted that when making changers to the hardware timers it effects all pins connected to that timer.
This library is made up of two classes SweepingCap and Touch. To use you must import SweepingCap.h and Touch.h into your Arduino sketch.
The SweepingCap class handles the Swept Frequency aspect of Swept Frequency Capacitive Sensing. It does so by using the hardware timers on the Arduino to generate a waveform at frequencies from 1.5Khz to 3.5Mhz. The class itself is fairly simple, the bulk of the code being several bit-shifting functions that handle the waveform generation on the timers.
When instantiating you call SweepingCap(unsigned char ), which sets up all 4 timers of the Arduino Mega and sets the number of frequencies to sweep (200 max), or SweepingCap(int , unsigned char ) to set up only one timer and the number of frequencies. When doing the latter please note that the 16 bit timers on the Mega are 1, 3, 4, and 5. I purposefully made it work with the specific timer number as a reinforcement of the knowledge that those timers are the 16 bit timers available. Other Arduino Boards will be added in the future.
In the setup you simply call .setup() on your SweepingCap object. Inside the main loop you will need a for loop which acts as the frequency sweep. You can use method .getNumFrequencies to setup the for loop and pass in the iterator to the .sweep(int freq) function, where all the bit shifting takes place.
Timer 1 uses Digi Pin 11 but also controls Pin 12. Timer 3 uses Digi Pin 5 but also controls Pin 2 and 3. Timer 4 uses Digi Pin 6 but also controls Pin 7 and 8. Timer 5 uses Digi Pin 46 but also controls Pin 45 and 44.
- SweepingCap(unsigned char howManyFrequencies)
Constructor - turns on all 4 16bit timers and sets the number of frequencies to be swept.
- SweepingCap(int whichTimer, unsigned char howManyFrequencies)
Constructor (overloaded) - turns on one timer and sets frequencies to be swept.
- setup()
Setup method, does all the actual setup for the timer pins to be used as waveform generators.
- sweep(int freq)
Main method, uses bit shifting methods to change the frequency on the waveform.
- getNumFrequencies()
Returns number of frequencies, to be used when setting up the iterator for sweeping. Max frequencies is 200.
Class acts as a container for touch data. Instantiate Touch class by setting the Analog Pin you want to use. Touch touch(0); // sets read pin to Analog Pin 0.
- readPin()
Performs an analogRead() on pin set by constructor. Stores value into private variable and returns the value as a 16 bit integer when called.
- getValue()
Returns value stored when readPin() is called. uni16_t
- setResults(uint16_t i, uint16_t v)
Set result value in results array, position and value
- getResults(uint16_t i)
Get result at i position
- setTopPoint( unsigned char tp )
Set Resonant Peak frequency
- setTopValue(unit16_t tv)
Set Top Value of resonant peak
- getTopPoint()
Returns stored top point
- getTopValue()
Returns stored top value
- interpolate()
Returns an interpolated top value
- reset()
Reset topPoint and topValue
- getPin()
Return pin number