rt-thread/bsp/lm3s/driverlib/adc.c

//*****************************************************************************
//
// adc.c - Driver for the ADC.
//
// Copyright (c) 2005-2009 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.  You may not combine
// this software with "viral" open-source software in order to form a larger
// program.  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 4694 of the Stellaris Peripheral Driver Library.
//
//*****************************************************************************

//*****************************************************************************
//
//! \addtogroup adc_api
//! @{
//
//*****************************************************************************

#include "inc/hw_adc.h"
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/adc.h"
#include "driverlib/debug.h"
#include "driverlib/interrupt.h"

//*****************************************************************************
//
// These defines are used by the ADC driver to simplify access to the ADC
// sequencer's registers.
//
//*****************************************************************************
#define ADC_SEQ                 (ADC_O_SSMUX0)
#define ADC_SEQ_STEP            (ADC_O_SSMUX1 - ADC_O_SSMUX0)
#define ADC_SSMUX               (ADC_O_SSMUX0 - ADC_O_SSMUX0)
#define ADC_SSCTL               (ADC_O_SSCTL0 - ADC_O_SSMUX0)
#define ADC_SSFIFO              (ADC_O_SSFIFO0 - ADC_O_SSMUX0)
#define ADC_SSFSTAT             (ADC_O_SSFSTAT0 - ADC_O_SSMUX0)

//*****************************************************************************
//
// The currently configured software oversampling factor for each of the ADC
// sequencers.
//
//*****************************************************************************
static unsigned char g_pucOversampleFactor[3];

//*****************************************************************************
//
//! Registers an interrupt handler for an ADC interrupt.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param pfnHandler is a pointer to the function to be called when the
//! ADC sample sequence interrupt occurs.
//!
//! This function sets the handler to be called when a sample sequence
//! interrupt occurs.  This will enable the global interrupt in the interrupt
//! controller; the sequence interrupt must be enabled with ADCIntEnable().  It
//! is the interrupt handler's responsibility to clear the interrupt source via
//! ADCIntClear().
//!
//! \sa IntRegister() for important information about registering interrupt
//! handlers.
//!
//! \return None.
//
//*****************************************************************************
void
ADCIntRegister(unsigned long ulBase, unsigned long ulSequenceNum,
               void (*pfnHandler)(void))
{
    unsigned long ulInt;

    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Determine the interrupt to register based on the sequence number.
    //
    ulInt = INT_ADC0 + ulSequenceNum;

    //
    // Register the interrupt handler.
    //
    IntRegister(ulInt, pfnHandler);

    //
    // Enable the timer interrupt.
    //
    IntEnable(ulInt);
}

//*****************************************************************************
//
//! Unregisters the interrupt handler for an ADC interrupt.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This function unregisters the interrupt handler.  This will disable the
//! global interrupt in the interrupt controller; the sequence interrupt must
//! be disabled via ADCIntDisable().
//!
//! \sa IntRegister() for important information about registering interrupt
//! handlers.
//!
//! \return None.
//
//*****************************************************************************
void
ADCIntUnregister(unsigned long ulBase, unsigned long ulSequenceNum)
{
    unsigned long ulInt;

    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Determine the interrupt to unregister based on the sequence number.
    //
    ulInt = INT_ADC0 + ulSequenceNum;

    //
    // Disable the interrupt.
    //
    IntDisable(ulInt);

    //
    // Unregister the interrupt handler.
    //
    IntUnregister(ulInt);
}

//*****************************************************************************
//
//! Disables a sample sequence interrupt.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This function disables the requested sample sequence interrupt.
//!
//! \return None.
//
//*****************************************************************************
void
ADCIntDisable(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Disable this sample sequence interrupt.
    //
    HWREG(ulBase + ADC_O_IM) &= ~(1 << ulSequenceNum);
}

//*****************************************************************************
//
//! Enables a sample sequence interrupt.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This function enables the requested sample sequence interrupt.  Any
//! outstanding interrupts are cleared before enabling the sample sequence
//! interrupt.
//!
//! \return None.
//
//*****************************************************************************
void
ADCIntEnable(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Clear any outstanding interrupts on this sample sequence.
    //
    HWREG(ulBase + ADC_O_ISC) = 1 << ulSequenceNum;

    //
    // Enable this sample sequence interrupt.
    //
    HWREG(ulBase + ADC_O_IM) |= 1 << ulSequenceNum;
}

//*****************************************************************************
//
//! Gets the current interrupt status.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param bMasked is false if the raw interrupt status is required and true if
//! the masked interrupt status is required.
//!
//! This returns the interrupt status for the specified sample sequence.
//! Either the raw interrupt status or the status of interrupts that are
//! allowed to reflect to the processor can be returned.
//!
//! \return The current raw or masked interrupt status.
//
//*****************************************************************************
unsigned long
ADCIntStatus(unsigned long ulBase, unsigned long ulSequenceNum,
             tBoolean bMasked)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Return either the interrupt status or the raw interrupt status as
    // requested.
    //
    if(bMasked)
    {
        return(HWREG(ulBase + ADC_O_ISC) & (1 << ulSequenceNum));
    }
    else
    {
        return(HWREG(ulBase + ADC_O_RIS) & (1 << ulSequenceNum));
    }
}

//*****************************************************************************
//
//! Clears sample sequence interrupt source.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! The specified sample sequence interrupt is cleared, so that it no longer
//! asserts.  This must be done in the interrupt handler to keep it from being
//! called again immediately upon exit.
//!
//! \note Since there is a write buffer in the Cortex-M3 processor, it may take
//! several clock cycles before the interrupt source is actually cleared.
//! Therefore, it is recommended that the interrupt source be cleared early in
//! the interrupt handler (as opposed to the very last action) to avoid
//! returning from the interrupt handler before the interrupt source is
//! actually cleared.  Failure to do so may result in the interrupt handler
//! being immediately reentered (since NVIC still sees the interrupt source
//! asserted).
//!
//! \return None.
//
//*****************************************************************************
void
ADCIntClear(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arugments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Clear the interrupt.
    //
    HWREG(ulBase + ADC_O_ISC) = 1 << ulSequenceNum;
}

//*****************************************************************************
//
//! Enables a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! Allows the specified sample sequence to be captured when its trigger is
//! detected.  A sample sequence must be configured before it is enabled.
//!
//! \return None.
//
//*****************************************************************************
void
ADCSequenceEnable(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arugments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Enable the specified sequence.
    //
    HWREG(ulBase + ADC_O_ACTSS) |= 1 << ulSequenceNum;
}

//*****************************************************************************
//
//! Disables a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! Prevents the specified sample sequence from being captured when its trigger
//! is detected.  A sample sequence should be disabled before it is configured.
//!
//! \return None.
//
//*****************************************************************************
void
ADCSequenceDisable(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arugments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Disable the specified sequences.
    //
    HWREG(ulBase + ADC_O_ACTSS) &= ~(1 << ulSequenceNum);
}

//*****************************************************************************
//
//! Configures the trigger source and priority of a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param ulTrigger is the trigger source that initiates the sample sequence;
//! must be one of the \b ADC_TRIGGER_* values.
//! \param ulPriority is the relative priority of the sample sequence with
//! respect to the other sample sequences.
//!
//! This function configures the initiation criteria for a sample sequence.
//! Valid sample sequences range from zero to three; sequence zero will capture
//! up to eight samples, sequences one and two will capture up to four samples,
//! and sequence three will capture a single sample.  The trigger condition and
//! priority (with respect to other sample sequence execution) is set.
//!
//! The \e ulTrigger parameter can take on the following values:
//!
//! - \b ADC_TRIGGER_PROCESSOR - A trigger generated by the processor, via the
//!                              ADCProcessorTrigger() function.
//! - \b ADC_TRIGGER_COMP0 - A trigger generated by the first analog
//!                          comparator; configured with ComparatorConfigure().
//! - \b ADC_TRIGGER_COMP1 - A trigger generated by the second analog
//!                          comparator; configured with ComparatorConfigure().
//! - \b ADC_TRIGGER_COMP2 - A trigger generated by the third analog
//!                          comparator; configured with ComparatorConfigure().
//! - \b ADC_TRIGGER_EXTERNAL - A trigger generated by an input from the Port
//!                             B4 pin.
//! - \b ADC_TRIGGER_TIMER - A trigger generated by a timer; configured with
//!                          TimerControlTrigger().
//! - \b ADC_TRIGGER_PWM0 - A trigger generated by the first PWM generator;
//!                         configured with PWMGenIntTrigEnable().
//! - \b ADC_TRIGGER_PWM1 - A trigger generated by the second PWM generator;
//!                         configured with PWMGenIntTrigEnable().
//! - \b ADC_TRIGGER_PWM2 - A trigger generated by the third PWM generator;
//!                         configured with PWMGenIntTrigEnable().
//! - \b ADC_TRIGGER_ALWAYS - A trigger that is always asserted, causing the
//!                           sample sequence to capture repeatedly (so long as
//!                           there is not a higher priority source active).
//!
//! Note that not all trigger sources are available on all Stellaris family
//! members; consult the data sheet for the device in question to determine the
//! availability of triggers.
//!
//! The \e ulPriority parameter is a value between 0 and 3, where 0 represents
//! the highest priority and 3 the lowest.  Note that when programming the
//! priority among a set of sample sequences, each must have unique priority;
//! it is up to the caller to guarantee the uniqueness of the priorities.
//!
//! \return None.
//
//*****************************************************************************
void
ADCSequenceConfigure(unsigned long ulBase, unsigned long ulSequenceNum,
                     unsigned long ulTrigger, unsigned long ulPriority)
{
    //
    // Check the arugments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);
    ASSERT((ulTrigger == ADC_TRIGGER_PROCESSOR) ||
           (ulTrigger == ADC_TRIGGER_COMP0) ||
           (ulTrigger == ADC_TRIGGER_COMP1) ||
           (ulTrigger == ADC_TRIGGER_COMP2) ||
           (ulTrigger == ADC_TRIGGER_EXTERNAL) ||
           (ulTrigger == ADC_TRIGGER_TIMER) ||
           (ulTrigger == ADC_TRIGGER_PWM0) ||
           (ulTrigger == ADC_TRIGGER_PWM1) ||
           (ulTrigger == ADC_TRIGGER_PWM2) ||
           (ulTrigger == ADC_TRIGGER_ALWAYS));
    ASSERT(ulPriority < 4);

    //
    // Compute the shift for the bits that control this sample sequence.
    //
    ulSequenceNum *= 4;

    //
    // Set the trigger event for this sample sequence.
    //
    HWREG(ulBase + ADC_O_EMUX) = ((HWREG(ulBase + ADC_O_EMUX) &
                                   ~(0xf << ulSequenceNum)) |
                                  ((ulTrigger & 0xf) << ulSequenceNum));

    //
    // Set the priority for this sample sequence.
    //
    HWREG(ulBase + ADC_O_SSPRI) = ((HWREG(ulBase + ADC_O_SSPRI) &
                                    ~(0xf << ulSequenceNum)) |
                                   ((ulPriority & 0x3) << ulSequenceNum));
}

//*****************************************************************************
//
//! Configure a step of the sample sequencer.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param ulStep is the step to be configured.
//! \param ulConfig is the configuration of this step; must be a logical OR of
//! \b ADC_CTL_TS, \b ADC_CTL_IE, \b ADC_CTL_END, \b ADC_CTL_D, and one of the
//! input channel selects (\b ADC_CTL_CH0 through \b ADC_CTL_CH7).
//!
//! This function will set the configuration of the ADC for one step of a
//! sample sequence.  The ADC can be configured for single-ended or
//! differential operation (the \b ADC_CTL_D bit selects differential
//! operation when set), the channel to be sampled can be chosen (the
//! \b ADC_CTL_CH0 through \b ADC_CTL_CH7 values), and the internal temperature
//! sensor can be selected (the \b ADC_CTL_TS bit).  Additionally, this step
//! can be defined as the last in the sequence (the \b ADC_CTL_END bit) and it
//! can be configured to cause an interrupt when the step is complete (the
//! \b ADC_CTL_IE bit).  The configuration is used by the ADC at the
//! appropriate time when the trigger for this sequence occurs.
//!
//! The \e ulStep parameter determines the order in which the samples are
//! captured by the ADC when the trigger occurs.  It can range from zero to
//! seven for the first sample sequence, from zero to three for the second and
//! third sample sequence, and can only be zero for the fourth sample sequence.
//!
//! Differential mode only works with adjacent channel pairs (for example, 0
//! and 1).  The channel select must be the number of the channel pair to
//! sample (for example, \b ADC_CTL_CH0 for 0 and 1, or \b ADC_CTL_CH1 for 2
//! and 3) or undefined results will be returned by the ADC.  Additionally, if
//! differential mode is selected when the temperature sensor is being sampled,
//! undefined results will be returned by the ADC.
//!
//! It is the responsibility of the caller to ensure that a valid configuration
//! is specified; this function does not check the validity of the specified
//! configuration.
//!
//! \return None.
//
//*****************************************************************************
void
ADCSequenceStepConfigure(unsigned long ulBase, unsigned long ulSequenceNum,
                         unsigned long ulStep, unsigned long ulConfig)
{
    //
    // Check the arugments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);
    ASSERT(((ulSequenceNum == 0) && (ulStep < 8)) ||
           ((ulSequenceNum == 1) && (ulStep < 4)) ||
           ((ulSequenceNum == 2) && (ulStep < 4)) ||
           ((ulSequenceNum == 3) && (ulStep < 1)));

    //
    // Get the offset of the sequence to be configured.
    //
    ulBase += ADC_SEQ + (ADC_SEQ_STEP * ulSequenceNum);

    //
    // Compute the shift for the bits that control this step.
    //
    ulStep *= 4;

    //
    // Set the analog mux value for this step.
    //
    HWREG(ulBase + ADC_SSMUX) = ((HWREG(ulBase + ADC_SSMUX) &
                                  ~(0x0000000f << ulStep)) |
                                 ((ulConfig & 0x0f) << ulStep));

    //
    // Set the control value for this step.
    //
    HWREG(ulBase + ADC_SSCTL) = ((HWREG(ulBase + ADC_SSCTL) &
                                  ~(0x0000000f << ulStep)) |
                                 (((ulConfig & 0xf0) >> 4) << ulStep));
}

//*****************************************************************************
//
//! Determines if a sample sequence overflow occurred.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This determines if a sample sequence overflow has occurred.  This will
//! happen if the captured samples are not read from the FIFO before the next
//! trigger occurs.
//!
//! \return Returns zero if there was not an overflow, and non-zero if there
//! was.
//
//*****************************************************************************
long
ADCSequenceOverflow(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Determine if there was an overflow on this sequence.
    //
    return(HWREG(ulBase + ADC_O_OSTAT) & (1 << ulSequenceNum));
}

//*****************************************************************************
//
//! Clears the overflow condition on a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This will clear an overflow condition on one of the sample sequences.  The
//! overflow condition must be cleared in order to detect a subsequent overflow
//! condition (it otherwise causes no harm).
//!
//! \return None.
//
//*****************************************************************************
void
ADCSequenceOverflowClear(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Clear the overflow condition for this sequence.
    //
    HWREG(ulBase + ADC_O_OSTAT) = 1 << ulSequenceNum;
}

//*****************************************************************************
//
//! Determines if a sample sequence underflow occurred.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This determines if a sample sequence underflow has occurred.  This will
//! happen if too many samples are read from the FIFO.
//!
//! \return Returns zero if there was not an underflow, and non-zero if there
//! was.
//
//*****************************************************************************
long
ADCSequenceUnderflow(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Determine if there was an underflow on this sequence.
    //
    return(HWREG(ulBase + ADC_O_USTAT) & (1 << ulSequenceNum));
}

//*****************************************************************************
//
//! Clears the underflow condition on a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This will clear an underflow condition on one of the sample sequences.  The
//! underflow condition must be cleared in order to detect a subsequent
//! underflow condition (it otherwise causes no harm).
//!
//! \return None.
//
//*****************************************************************************
void
ADCSequenceUnderflowClear(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Clear the underflow condition for this sequence.
    //
    HWREG(ulBase + ADC_O_USTAT) = 1 << ulSequenceNum;
}

//*****************************************************************************
//
//! Gets the captured data for a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param pulBuffer is the address where the data is stored.
//!
//! This function copies data from the specified sample sequence output FIFO to
//! a memory resident buffer.  The number of samples available in the hardware
//! FIFO are copied into the buffer, which is assumed to be large enough to
//! hold that many samples.  This will only return the samples that are
//! presently available, which may not be the entire sample sequence if it is
//! in the process of being executed.
//!
//! \return Returns the number of samples copied to the buffer.
//
//*****************************************************************************
long
ADCSequenceDataGet(unsigned long ulBase, unsigned long ulSequenceNum,
                   unsigned long *pulBuffer)
{
    unsigned long ulCount;

    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Get the offset of the sequence to be read.
    //
    ulBase += ADC_SEQ + (ADC_SEQ_STEP * ulSequenceNum);

    //
    // Read samples from the FIFO until it is empty.
    //
    ulCount = 0;
    while(!(HWREG(ulBase + ADC_SSFSTAT) & ADC_SSFSTAT0_EMPTY) && (ulCount < 8))
    {
        //
        // Read the FIFO and copy it to the destination.
        //
        *pulBuffer++ = HWREG(ulBase + ADC_SSFIFO);

        //
        // Increment the count of samples read.
        //
        ulCount++;
    }

    //
    // Return the number of samples read.
    //
    return(ulCount);
}

//*****************************************************************************
//
//! Causes a processor trigger for a sample sequence.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//!
//! This function triggers a processor-initiated sample sequence if the sample
//! sequence trigger is configured to \b ADC_TRIGGER_PROCESSOR.
//!
//! \return None.
//
//*****************************************************************************
void
ADCProcessorTrigger(unsigned long ulBase, unsigned long ulSequenceNum)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 4);

    //
    // Generate a processor trigger for this sample sequence.
    //
    HWREG(ulBase + ADC_O_PSSI) = 1 << ulSequenceNum;
}

//*****************************************************************************
//
//! Configures the software oversampling factor of the ADC.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param ulFactor is the number of samples to be averaged.
//!
//! This function configures the software oversampling for the ADC, which can
//! be used to provide better resolution on the sampled data.  Oversampling is
//! accomplished by averaging multiple samples from the same analog input.
//! Three different oversampling rates are supported; 2x, 4x, and 8x.
//!
//! Oversampling is only supported on the sample sequencers that are more than
//! one sample in depth (that is, the fourth sample sequencer is not
//! supported).  Oversampling by 2x (for example) divides the depth of the
//! sample sequencer by two; so 2x oversampling on the first sample sequencer
//! can only provide four samples per trigger.  This also means that 8x
//! oversampling is only available on the first sample sequencer.
//!
//! \return None.
//
//*****************************************************************************
void
ADCSoftwareOversampleConfigure(unsigned long ulBase,
                               unsigned long ulSequenceNum,
                               unsigned long ulFactor)
{
    unsigned long ulValue;

    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 3);
    ASSERT(((ulFactor == 2) || (ulFactor == 4) || (ulFactor == 8)) &&
           ((ulSequenceNum == 0) || (ulFactor != 8)));

    //
    // Convert the oversampling factor to a shift factor.
    //
    for(ulValue = 0, ulFactor >>= 1; ulFactor; ulValue++, ulFactor >>= 1)
    {
    }

    //
    // Save the sfiht factor.
    //
    g_pucOversampleFactor[ulSequenceNum] = ulValue;
}

//*****************************************************************************
//
//! Configures a step of the software oversampled sequencer.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param ulStep is the step to be configured.
//! \param ulConfig is the configuration of this step.
//!
//! This function configures a step of the sample sequencer when using the
//! software oversampling feature.  The number of steps available depends on
//! the oversampling factor set by ADCSoftwareOversampleConfigure().  The value
//! of \e ulConfig is the same as defined for ADCSequenceStepConfigure().
//!
//! \return None.
//
//*****************************************************************************
void
ADCSoftwareOversampleStepConfigure(unsigned long ulBase,
                                   unsigned long ulSequenceNum,
                                   unsigned long ulStep,
                                   unsigned long ulConfig)
{
    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 3);
    ASSERT(((ulSequenceNum == 0) &&
            (ulStep < (8 >> g_pucOversampleFactor[ulSequenceNum]))) ||
           (ulStep < (4 >> g_pucOversampleFactor[ulSequenceNum])));

    //
    // Get the offset of the sequence to be configured.
    //
    ulBase += ADC_SEQ + (ADC_SEQ_STEP * ulSequenceNum);

    //
    // Compute the shift for the bits that control this step.
    //
    ulStep *= 4 << g_pucOversampleFactor[ulSequenceNum];

    //
    // Loop through the hardware steps that make up this step of the software
    // oversampled sequence.
    //
    for(ulSequenceNum = 1 << g_pucOversampleFactor[ulSequenceNum];
        ulSequenceNum; ulSequenceNum--)
    {
        //
        // Set the analog mux value for this step.
        //
        HWREG(ulBase + ADC_SSMUX) = ((HWREG(ulBase + ADC_SSMUX) &
                                      ~(0x0000000f << ulStep)) |
                                     ((ulConfig & 0x0f) << ulStep));

        //
        // Set the control value for this step.
        //
        HWREG(ulBase + ADC_SSCTL) = ((HWREG(ulBase + ADC_SSCTL) &
                                      ~(0x0000000f << ulStep)) |
                                     (((ulConfig & 0xf0) >> 4) << ulStep));
        if(ulSequenceNum != 1)
        {
            HWREG(ulBase + ADC_SSCTL) &= ~((ADC_SSCTL0_IE0 |
                                            ADC_SSCTL0_END0) << ulStep);
        }

        //
        // Go to the next hardware step.
        //
        ulStep += 4;
    }
}

//*****************************************************************************
//
//! Gets the captured data for a sample sequence using software oversampling.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulSequenceNum is the sample sequence number.
//! \param pulBuffer is the address where the data is stored.
//! \param ulCount is the number of samples to be read.
//!
//! This function copies data from the specified sample sequence output FIFO to
//! a memory resident buffer with software oversampling applied.  The requested
//! number of samples are copied into the data buffer; if there are not enough
//! samples in the hardware FIFO to satisfy this many oversampled data items
//! then incorrect results will be returned.  It is the caller's responsibility
//! to read only the samples that are available and wait until enough data is
//! available, for example as a result of receiving an interrupt.
//!
//! \return None.
//
//*****************************************************************************
void
ADCSoftwareOversampleDataGet(unsigned long ulBase, unsigned long ulSequenceNum,
                             unsigned long *pulBuffer, unsigned long ulCount)
{
    unsigned long ulIdx, ulAccum;

    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(ulSequenceNum < 3);
    ASSERT(((ulSequenceNum == 0) &&
            (ulCount < (8 >> g_pucOversampleFactor[ulSequenceNum]))) ||
           (ulCount < (4 >> g_pucOversampleFactor[ulSequenceNum])));

    //
    // Get the offset of the sequence to be read.
    //
    ulBase += ADC_SEQ + (ADC_SEQ_STEP * ulSequenceNum);

    //
    // Read the samples from the FIFO until it is empty.
    //
    while(ulCount--)
    {
        //
        // Compute the sum of the samples.
        //
        ulAccum = 0;
        for(ulIdx = 1 << g_pucOversampleFactor[ulSequenceNum]; ulIdx; ulIdx--)
        {
            //
            // Read the FIFO and add it to the accumulator.
            //
            ulAccum += HWREG(ulBase + ADC_SSFIFO);
        }

        //
        // Write the averaged sample to the output buffer.
        //
        *pulBuffer++ = ulAccum >> g_pucOversampleFactor[ulSequenceNum];
    }
}

//*****************************************************************************
//
//! Configures the hardware oversampling factor of the ADC.
//!
//! \param ulBase is the base address of the ADC module.
//! \param ulFactor is the number of samples to be averaged.
//!
//! This function configures the hardware oversampling for the ADC, which can
//! be used to provide better resolution on the sampled data.  Oversampling is
//! accomplished by averaging multiple samples from the same analog input.  Six
//! different oversampling rates are supported; 2x, 4x, 8x, 16x, 32x, and 64x.
//! Specifying an oversampling factor of zero will disable hardware
//! oversampling.
//!
//! Hardware oversampling applies uniformly to all sample sequencers.  It does
//! not reduce the depth of the sample sequencers like the software
//! oversampling APIs; each sample written into the sample sequence FIFO is a
//! fully oversampled analog input reading.
//!
//! Enabling hardware averaging increases the precision of the ADC at the cost
//! of throughput.  For example, enabling 4x oversampling reduces the
//! throughput of a 250 Ksps ADC to 62.5 Ksps.
//!
//! \note Hardware oversampling is available beginning with Rev C0 of the
//! Stellaris microcontroller.
//!
//! \return None.
//
//*****************************************************************************
void
ADCHardwareOversampleConfigure(unsigned long ulBase, unsigned long ulFactor)
{
    unsigned long ulValue;

    //
    // Check the arguments.
    //
    ASSERT((ulBase == ADC0_BASE) || (ulBase == ADC1_BASE));
    ASSERT(((ulFactor == 0) || (ulFactor == 2) || (ulFactor == 4) ||
           (ulFactor == 8) || (ulFactor == 16) || (ulFactor == 32) ||
           (ulFactor == 64)));

    //
    // Convert the oversampling factor to a shift factor.
    //
    for(ulValue = 0, ulFactor >>= 1; ulFactor; ulValue++, ulFactor >>= 1)
    {
    }

    //
    // Write the shift factor to the ADC to configure the hardware oversampler.
    //
    HWREG(ulBase + ADC_O_SAC) = ulValue;
}

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