switches.c

eaayarm101自制小车源代码 周立功公司原创

//*****************************************************************************
//
// switches.c - Code for the push button.
//
// Copyright (c) 2005-2007 Luminary Micro, Inc.  All rights reserved.
//
// Software License Agreement
//
// Luminary Micro, Inc. (LMI) is supplying this software for use solely and
// exclusively on LMI's microcontroller products.
//
// The software is owned by LMI and/or its suppliers, and is protected under
// applicable copyright laws.  All rights are reserved.  Any use in violation
// of the foregoing restrictions may subject the user to criminal sanctions
// under applicable laws, as well as to civil liability for the breach of the
// terms and conditions of this license.
//
// THIS SOFTWARE IS PROVIDED "AS IS".  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.
// LMI SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR
// CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
//
// This is part of revision 199 of an01245.
//
//*****************************************************************************

#include "../../hw_gpio.h"
#include "../../hw_memmap.h"
#include "../../hw_nvic.h"
#include "../../hw_types.h"
#include "car.h"
#include "compiler.h"
#include "switches.h"
#include "system.h"

//*****************************************************************************
//
//! \page switches_intro Introduction
//!
//! There is a single momentary push button switch on the car that is used to
//! provide basic control of the car's operation.  The switch does not have any
//! hardware debouncing (such as an RC low pass filter), so it is the
//! responsibility of software to provide debouncing of the switch input.
//!
//! Debouncing is accomplished by sampling the switch at a relatively fast rate
//! (relative to a human's ability to press and release the button).  The
//! sampled state of the switch must match for four consecutive samples before
//! it is assumed to be in the given state.  So, as the switch bounces due to a
//! press or release, it it not sampled in the same state and therefore the
//! bouncing is ignored.
//!
//! The code for handling the switches is contained in <tt>switches.c</tt>,
//! with <tt>switches.h</tt> containing the API definitions for use by the
//! remainder of the application.
//
//*****************************************************************************

//*****************************************************************************
//
//! \defgroup switches_api Definitions
//! @{
//
//*****************************************************************************

//*****************************************************************************
//
//! The GPIO port that contains the pin to which the push button is connected.
//
//*****************************************************************************
#define PUSH_BUTTON_PORT        GPIO_PORTC_BASE

//*****************************************************************************
//
//! The GPIO pin to which the push button is connected.
//
//*****************************************************************************
#define PUSH_BUTTON             (1 << 4)

//*****************************************************************************
//
//! The debounced state of the switch(es).  There is only one switch on the
//! car, so only bit zero it utilized.
//
//*****************************************************************************
ZERO_INIT unsigned long g_ulSwitches;

//*****************************************************************************
//
//! This structure describes the state of the switch debouncer.  The debouncre
//! uses four consecutive samples with the switch in the non-debounced state
//! to detect a change in the state of the switch.  This structure and
//! algorithm allows up to eight switches to be debounced in parallel, though
//! only one is utilized by the car.
//
//*****************************************************************************
typedef struct
{
    //
    //! This is the low order bit of the clock used to count the number of
    //! samples with the switch in the non-debounced state.
    //
    unsigned char ucClockA;

    //
    //! This is the high order bit of the clock used to count the number of
    //! samples with the switch in the non-debounced state.
    //
    unsigned char ucClockB;

    //
    //! This is the count of the number of samples during which the switch has
    //! been pressed; it is used to distinguish a button press from a button
    //! hold.
    //
    unsigned short usCount;
}
tSwitchState;

//*****************************************************************************
//
//! The current state of the switch debouncer.
//
//*****************************************************************************
static ZERO_INIT tSwitchState g_sSwitchState;

//*****************************************************************************
//
//! Handles the SysTick interrupt.
//!
//! This fucntion is called when SysTick generates an interrupt.  The state of
//! the push button will be sampled, debounced, and the appropriate action
//! taken when required.
//!
//! Pressing the button will call the CarStop() function on the button press
//! and the CarRun() function in the button release.  Holding the button for an
//! extended period of time (controlled by #DIAG_HOLD_TIME) will call the
//! CarDiagnostic() function when the timeout period expires (and therefore
//! CarRun() is not called).
//!
//! On every SysTick interrupt, the CarTick() function is called to allow the
//! car to make decisions about how to proceed.
//!
//! \return None.
//
//*****************************************************************************
void
SysTickHandler(void)
{
    unsigned char ucValue, ucDelta;

    //
    // Read the current switch input value.
    //
    ucValue = HWREG(PUSH_BUTTON_PORT + GPIO_O_DATA + (PUSH_BUTTON << 2));

    //
    // Determine the switches that are at a different state than the debounced
    // state.
    //
    ucDelta = ucValue ^ (g_ulSwitches & 0xff);

    //
    // Increment the clocks by one.
    //
    g_sSwitchState.ucClockA ^= g_sSwitchState.ucClockB;
    g_sSwitchState.ucClockB = ~g_sSwitchState.ucClockB;

    //
    // Reset the clocks corresponding to switches that have not changed state.
    //
    g_sSwitchState.ucClockA &= ucDelta;
    g_sSwitchState.ucClockB &= ucDelta;

    //
    // Get the new debounced switch state.
    //
    g_ulSwitches &= (g_sSwitchState.ucClockA | g_sSwitchState.ucClockB);
    g_ulSwitches |= ((~(g_sSwitchState.ucClockA | g_sSwitchState.ucClockB)) &
                     ucValue);

    //
    // Determine the switches that just changed debounced state.
    //
    ucDelta ^= (g_sSwitchState.ucClockA | g_sSwitchState.ucClockB);

    //
    // See if the push button just changed state.
    //
    if(ucDelta & PUSH_BUTTON)
    {
        //
        // See if the push button was just pressed or released.
        //
        if(!(g_ulSwitches & PUSH_BUTTON))
        {
            //
            // The button was just pressed, so reset the hold time counter.
            //
            g_sSwitchState.usCount = 0;

            //
            // If currently in run mode, switch to stop mode immediately.
            //
            CarStop();
        }
        else
        {
            //
            // The button was just released, so see if it was held less than
            // the diag mode hold time.
            //
            if(g_sSwitchState.usCount < (DIAG_HOLD_TIME * SYSTICK_CLOCK))
            {
                //
                // If currently in stop mode, switch to run mode.
                //
                CarRun();
            }
        }
    }

    //
    // See if the push button is currently pressed.
    //
    if(!(g_ulSwitches & PUSH_BUTTON))
    {
        //
        // Increment the hold counter if it is not maxed out.
        //
        if(g_sSwitchState.usCount < 65535)
        {
            g_sSwitchState.usCount++;
        }

        //
        // See if the button has pressed for 5 seconds.
        //
        if(g_sSwitchState.usCount == (DIAG_HOLD_TIME * SYSTICK_CLOCK))
        {
            //
            // Switch to diag mode.
            //
            CarDiagnostic();
        }
    }

    //
    // Call the car's tick handler.
    //
    CarTick();
}

//*****************************************************************************
//
//! Configures the switch input.
//!
//! This function prepares the push button switch for normal operation.  The
//! corresponding pin is configured as an input and the SysTick counter is
//! configured to generate periodic interrupts.
//!
//! The default debounced state of the switch is taken to be the state of the
//! switch during initialization.  If the switch is being pressed or released
//! during initialization, the default debounced state may end up incorrect.
//! In this case, the debouncing of the switch will quickly rectify the
//! situation, though a spurious press or release event may result.
//!
//! \return None.
//
//*****************************************************************************
void
SwitchesInit(void)
{
    //
    // Make the push button pin be an input.
    //
    HWREG(PUSH_BUTTON_PORT + GPIO_O_DIR) &= ~(PUSH_BUTTON);

    //
    // Read the current switch input values.  This becomes the default
    // debounced switch state.
    //
    g_ulSwitches = HWREG(PUSH_BUTTON_PORT + GPIO_O_DATA + (PUSH_BUTTON << 2));

    //
    // Setup SysTick to interrupt at the appropriate rate.
    //
    HWREG(NVIC_ST_RELOAD) = (SYSTEM_CLOCK / SYSTICK_CLOCK) - 1;
    HWREG(NVIC_ST_CTRL) = (NVIC_ST_CTRL_CLK_SRC | NVIC_ST_CTRL_INTEN |
                           NVIC_ST_CTRL_ENABLE);
}

//*****************************************************************************
//
// Close the Doxygen group.
//! @}
//
//*****************************************************************************