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//*****************************************************************************
//
// CTS_HAL.c - Capacative Sense Library Hardware Abstraction Layer.
//
// Copyright (c) 2012 Texas Instruments Incorporated. All rights reserved.
// Software License Agreement
//
// Texas Instruments (TI) is supplying this software for use solely and
// exclusively on TI's microcontroller products. The software is owned by
// TI and/or its suppliers, and is protected under applicable copyright
// laws. You may not combine this software with "viral" open-source
// software in order to form a larger program.
//
// THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
// NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
// NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
// CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
// DAMAGES, FOR ANY REASON WHATSOEVER.
//
// This is part of revision 9453 of the EK-LM4F120XL Firmware Package.
//
//*****************************************************************************
#include "inc/hw_types.h"
#include "inc/hw_gpio.h"
#include "inc/hw_memmap.h"
#include "inc/hw_nvic.h"
#include "drivers/CTS_structure.h"
#include "drivers/CTS_HAL.h"
//*****************************************************************************
//
// Function to get a capacitance reading from a single-pin RC-based capacitive
// sensor. This function assumes that the capacitive sensor is charged by a
// GPIO, and then discharged through a resistor to GND. The same GPIO used to
// perform the charging will be used as an input during discharge to sense when
// the capacitor's voltage has decreased to at least VIL. The function will
// execute several cycles of this, and report how long the process took in
// units of SysTick counts. This count should be proportional to the current
// capacitance of the sensor, and the resistance of the discharge resistor.
//
//*****************************************************************************
void
CapSenseSystickRC(const tSensor *group, unsigned long *counts)
{
unsigned char ucIndex;
//
// Run an RC based capacitance measurement routine on each element in the
// sensor array.
//
for(ucIndex = 0; ucIndex < (group->ucNumElements); ucIndex++)
{
//
// Reset Systick to zero (probably not necessary for most cases, but we
// want to make sure that Systick doesn't roll over.)
//
HWREG(NVIC_ST_CURRENT) = 0x0;
//
// Grab a count number from the capacitive sensor element.
//
counts[ucIndex] =
CapSenseElementSystickRC(group->Element[ucIndex]->ulGPIOPort,
group->Element[ucIndex]->ulGPIOPin,
group->ulNumSamples);
}
}
//*****************************************************************************
//
//
//
//
//*****************************************************************************
unsigned long
CapSenseElementSystickRC(unsigned long ulGPIOPort, unsigned long ulGPIOPin,
unsigned long ulNumSamples)
{
volatile unsigned long ulStartTime;
volatile unsigned long ulEndTime;
unsigned long ulIndex;
unsigned long ulGPIODataReg;
unsigned long ulGPIODirReg;
//
// Save off our GPIO information.
//
ulGPIODataReg = (ulGPIOPort + (GPIO_O_DATA + (ulGPIOPin << 2)));
ulGPIODirReg = ulGPIOPort + GPIO_O_DIR;
//
// Grab the time
//
ulStartTime = HWREG(NVIC_ST_CURRENT);
//
// Loop until we have the requisite number of samples.
//
for(ulIndex = 0; ulIndex < ulNumSamples; ulIndex++)
{
//
// Drive up.
//
//GPIOPinWrite(ulGPIOPort, ulGPIOPin, ulGPIOPin);
HWREG(ulGPIODataReg) = 0xFF;
//
// Configure as input
//
//GPIOPinTypeGPIOInput(ulGPIOPort, ulGPIOPin);
HWREG(ulGPIODirReg) = (HWREG(ulGPIODirReg) & ~(ulGPIOPin));
//
// Wait until the capacitor drains away to ground
//
//while(GPIOPinRead(ulGPIOPort, ulGPIOPin))
while(HWREG(ulGPIODataReg))
{
}
//
// Configure as an output.
//
//GPIOPinTypeGPIOOutput(ulGPIOPort, ulGPIOPin);
HWREG(ulGPIODirReg) = (HWREG(ulGPIODirReg) | ulGPIOPin);
}
//
// Grab the time, and calculate the difference
//
ulEndTime = HWREG(NVIC_ST_CURRENT);
//
// Return the time difference
//
return(ulStartTime - ulEndTime);
}
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