CapacitiveSensor.cpp

/*
 CapacitiveSense.h - Capacitive Sensing Library for 'duino / Wiring
 https://github.com/PaulStoffregen/CapacitiveSensor
 http://www.pjrc.com/teensy/td_libs_CapacitiveSensor.html
 http://playground.arduino.cc/Main/CapacitiveSensor
 Copyright (c) 2009 Paul Bagder
 Updates for other hardare by Paul Stoffregen, 2010-2016
 vim: set ts=4:

 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
 to deal in the Software without restriction, including without limitation
 the rights to use, copy, modify, merge, publish, distribute, sublicense,
 and/or sell copies of the Software, and to permit persons to whom the
 Software is furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
*/

#if ARDUINO >= 100
#include "Arduino.h"
#else
#include "WProgram.h"
#include "pins_arduino.h"
#include "WConstants.h"
#endif

#include "CapacitiveSensor.h"

// Constructor /////////////////////////////////////////////////////////////////
// Function that handles the creation and setup of instances

CapacitiveSensor::CapacitiveSensor(uint8_t sendPin, uint8_t receivePin)
{
	// initialize this instance's variables
	// Serial.begin(9600);		// for debugging
	error = 1;
	loopTimingFactor = 310;		// determined empirically -  a hack

	CS_Timeout_Millis = (2000 * (float)loopTimingFactor * (float)F_CPU) / 16000000;
	CS_AutocaL_Millis = 20000;

	// Serial.print("timwOut =  ");
	// Serial.println(CS_Timeout_Millis);

	// get pin mapping and port for send Pin - from PinMode function in core

#ifdef NUM_DIGITAL_PINS
	if (sendPin >= NUM_DIGITAL_PINS) error = -1;
	if (receivePin >= NUM_DIGITAL_PINS) error = -1;
#endif

	pinMode(sendPin, OUTPUT);						// sendpin to OUTPUT
	pinMode(receivePin, INPUT);						// receivePin to INPUT
	digitalWrite(sendPin, LOW);

	sBit = PIN_TO_BITMASK(sendPin);					// get send pin's ports and bitmask
	sReg = PIN_TO_BASEREG(sendPin);					// get pointer to output register

	rBit = PIN_TO_BITMASK(receivePin);				// get receive pin's ports and bitmask
	rReg = PIN_TO_BASEREG(receivePin);

	// get pin mapping and port for receive Pin - from digital pin functions in Wiring.c
	leastTotal = 0x0FFFFFFFL;   // input large value for autocalibrate begin
	lastCal = millis();         // set millis for start
}

// Public Methods //////////////////////////////////////////////////////////////
// Functions available in Wiring sketches, this library, and other libraries

long CapacitiveSensor::capacitiveSensor(uint8_t samples)
{
	total = 0;
	if (samples == 0) return 0;
	if (error < 0) return -1;            // bad pin


	for (uint8_t i = 0; i < samples; i++) {    // loop for samples parameter - simple lowpass filter
		if (SenseOneCycle() < 0)  return -2;   // variable over timeout
}

		// only calibrate if time is greater than CS_AutocaL_Millis and total is less than 10% of baseline
		// this is an attempt to keep from calibrating when the sensor is seeing a "touched" signal
		unsigned long diff = (total > leastTotal) ? total - leastTotal : leastTotal - total;
		if ( (millis() - lastCal > CS_AutocaL_Millis) && diff < (int)(.10 * (float)leastTotal) ) {

			// Serial.println();               // debugging
			// Serial.println("auto-calibrate");
			// Serial.println();
			// delay(2000); */

			leastTotal = 0x0FFFFFFFL;          // reset for "autocalibrate"
			lastCal = millis();
		}
		/*else{                                // debugging
			Serial.print("  total =  ");
			Serial.print(total);

			Serial.print("   leastTotal  =  ");
			Serial.println(leastTotal);

			Serial.print("total - leastTotal =  ");
			x = total - leastTotal ;
			Serial.print(x);
			Serial.print("     .1 * leastTotal = ");
			x = (int)(.1 * (float)leastTotal);
			Serial.println(x);
		} */

	// routine to subtract baseline (non-sensed capacitance) from sensor return
	if (total < leastTotal) leastTotal = total;                 // set floor value to subtract from sensed value
	return(total - leastTotal);

}

long CapacitiveSensor::capacitiveSensorRaw(uint8_t samples)
{
	total = 0;
	if (samples == 0) return 0;
	if (error < 0) return -1;                  // bad pin - this appears not to work

	for (uint8_t i = 0; i < samples; i++) {    // loop for samples parameter - simple lowpass filter
		if (SenseOneCycle() < 0)  return -2;   // variable over timeout
	}

	return total;
}


void CapacitiveSensor::reset_CS_AutoCal(void){
	leastTotal = 0x0FFFFFFFL;
}

void CapacitiveSensor::set_CS_AutocaL_Millis(unsigned long autoCal_millis){
	CS_AutocaL_Millis = autoCal_millis;
}

void CapacitiveSensor::set_CS_Timeout_Millis(unsigned long timeout_millis){
	CS_Timeout_Millis = (timeout_millis * (float)loopTimingFactor * (float)F_CPU) / 16000000;  // floats to deal with large numbers
}

// Private Methods /////////////////////////////////////////////////////////////
// Functions only available to other functions in this library

int CapacitiveSensor::SenseOneCycle(void)
{
    noInterrupts();
	DIRECT_WRITE_LOW(sReg, sBit);	// sendPin Register low
	DIRECT_MODE_INPUT(rReg, rBit);	// receivePin to input (pullups are off)
	DIRECT_MODE_OUTPUT(rReg, rBit); // receivePin to OUTPUT
	DIRECT_WRITE_LOW(rReg, rBit);	// pin is now LOW AND OUTPUT
	delayMicroseconds(10);
	DIRECT_MODE_INPUT(rReg, rBit);	// receivePin to input (pullups are off)
	DIRECT_WRITE_HIGH(sReg, sBit);	// sendPin High
    interrupts();

	while ( !DIRECT_READ(rReg, rBit) && (total < CS_Timeout_Millis) ) {  // while receive pin is LOW AND total is positive value
		total++;
	}
	//Serial.print("SenseOneCycle(1): ");
	//Serial.println(total);

	if (total > CS_Timeout_Millis) {
		return -2;         //  total variable over timeout
	}

	// set receive pin HIGH briefly to charge up fully - because the while loop above will exit when pin is ~ 2.5V
    noInterrupts();
	DIRECT_WRITE_HIGH(rReg, rBit);
	DIRECT_MODE_OUTPUT(rReg, rBit);  // receivePin to OUTPUT - pin is now HIGH AND OUTPUT
	DIRECT_WRITE_HIGH(rReg, rBit);
	DIRECT_MODE_INPUT(rReg, rBit);	// receivePin to INPUT (pullup is off)
	DIRECT_WRITE_LOW(sReg, sBit);	// sendPin LOW
    interrupts();

#ifdef FIVE_VOLT_TOLERANCE_WORKAROUND
	DIRECT_MODE_OUTPUT(rReg, rBit);
	DIRECT_WRITE_LOW(rReg, rBit);
	delayMicroseconds(10);
	DIRECT_MODE_INPUT(rReg, rBit);	// receivePin to INPUT (pullup is off)
#else
	while ( DIRECT_READ(rReg, rBit) && (total < CS_Timeout_Millis) ) {  // while receive pin is HIGH  AND total is less than timeout
		total++;
	}
#endif
	//Serial.print("SenseOneCycle(2): ");
	//Serial.println(total);

	if (total >= CS_Timeout_Millis) {
		return -2;     // total variable over timeout
	} else {
		return 1;
	}
}