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LM4F120H5QR的ADC转换问题



我想做一个多通道的AD 转换,这是我的程序:

//*****************************************************************************
//
// project0.c - Example to demonstrate minimal StellarisWare setup
//
// 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 "driverlib/pin_map.h"
#include "inc/hw_ints.h"
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "driverlib/sysctl.h"
#include "driverlib/gpio.h"
#include "driverlib/uart.h"
#include "inc/hw_nvic.h"
#include "inc/hw_gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/adc.h"
//*****************************************************************************
unsigned long ulADC0_Value[2];
//! \addtogroup example_list
//! <h1>Project Zero (project0)</h1>
//!
//! This example demonstrates the use of StellarisWare to setup the clocks
//! and toggle GPIO pins to make the LED's blink. This is a good place to
//! start understanding your launchpad and the tools that can be used to
//! program it. See http://www.ti.com/stellaris-launchpad/project0 for more
//! information and tutorial videos.
//!
//
//*****************************************************************************


//*****************************************************************************
//
// Main 'C' Language entry point.  Toggle an LED using StellarisWare.
// See www.ti.com/stellaris-launchpad/project0 for more information and
// tutorial videos.
//
//*****************************************************************************
int
main(void)
{
    //
    // Setup the system clock to run at 50 Mhz from PLL with crystal reference
   
    SysCtlClockSet(SYSCTL_SYSDIV_4|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|
                    SYSCTL_OSC_MAIN);
  SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);           //Enable ADC0
 SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);      //E port Enable
 GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3|GPIO_PIN_2);       //PE3 as ADC input  AIN0  PE2 for AIN1
 /******************************/
//  GPIOPinTypeGPIOInput(GPIO_PORTA_BASE,GPIO_PIN_7);
//  GPIOIntTypeSet(GPIO_PORTA_BASE, GPIO_PIN_7, GPIO_RISING_EDGE);
//  GPIOPinIntEnable(GPIO_PORTA_BASE, GPIO_PIN_7);
//  GPIOADCTriggerEnable(GPIO_PORTA_BASE,GPIO_PIN_7);       //PA7 as ADC trggier
 /******************************/
 ADCSequenceConfigure(ADC0_BASE,0,ADC_TRIGGER_PROCESSOR,0);  //Sequence0
 ADCSequenceStepConfigure(ADC0_BASE, 0, 1,ADC_CTL_IE | ADC_CTL_END | ADC_CTL_CH0|ADC_CTL_CH1);
 ADCSequenceEnable(ADC0_BASE, 0);
 ADCIntClear(ADC0_BASE,0);
    while(1)
    {
   ADCProcessorTrigger(ADC0_BASE,0);
   while(!ADCIntStatus(ADC0_BASE, 0, false))
   {}
   IntPendClear(INT_ADC0SS0);
   ADCIntClear(ADC0_BASE,0);
   ADCSequenceDataGet(ADC0_BASE, 0, ulADC0_Value);
    }
}

可是ADC转换后的结果却只显示一个通道的值;我看了看手册,上边说,这个ADCSequenceDataGet(ADC0_BASE, 0, ulADC0_Value);只返回最新的值,但是,也是FIFO寄存器的数值啊;还有,为什么手册上说ADC0音序器0的FIFO有8级深度,可看他的寄存器,却只能找到一个FIFO?

  • 我明白了, ADCSequenceStepConfigure(ADC0_BASE, 0,0,ADC_CTL_CH9);
     ADCSequenceStepConfigure(ADC0_BASE, 0,1,ADC_CTL_CH1);
     ADCSequenceStepConfigure(ADC0_BASE, 0,2,ADC_CTL_IE | ADC_CTL_END |ADC_CTL_CH2);

    就OK了。是这个voidADCSequenceStepConfigure(unsigned long ulBase, unsigned long ulSequenceNum,unsigned long ulStep, unsigned long ulConfig)

    中的ulStep一直不理解;这个的具体意思,大家可以看看我的这三句程序,debug一下,看看寄存器配置明白了

  • 在EK-LM4F120XL Launchpad中,

    我分别用

    AIN0(PE3口)采样1.3V电压

    AIN1(PE2口)采样0.65V电压,

    AIN8(PE5口)采样1.95V电压,

    AIN9(PE4口)采样2.6V电压,

    假如以3.0V作为参考电压,那么在数据寄存器中采样结果应该是:

    1775,对应1.3V电压

    888,对应采样0.65V电压,

    2659,对应采样1.95V电压,

    3563,对应采样2.6V电压,

    但是实际结果是:

    AIN0:1645,根据1.3*4096/1645=3.23,参考电压为3.23V,

    AIN1:1005,根据0.65*4096/1005=2.65,参考电压为2.65V,

    AIN8:2175,根据1.95*4096/2175=3.76,参考电压为3.67V,

    AIN9:2765,根据2.61*4096/2765=3.87,参考电压为3.87V,

    如上,每次的结果都不一样。这是为什么呢?(如果参考电压假定为3.3V,结果也是类似的)

    我的源程序如下(采样时只要修改相应的端口就可以了):


    #include"inc/hw_ints.h"
    #include"inc/hw_types.h"
    #include"inc/hw_memmap.h"

    #include"driverlib/sysctl.h"
    #include"driverlib/interrupt.h"
    #include"driverlib/adc.h"
    #include"driverlib/gpio.h"


    unsigned char adc_endflag=0;


    void enable_adc_pin()
    {

    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE,GPIO_PIN_2);

    }

    void config_adc()
    {
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlADCSpeedSet(SYSCTL_ADCSPEED_125KSPS);

    ADCSequenceConfigure(ADC0_BASE, 0, ADC_TRIGGER_PROCESSOR, 0);
    ADCSequenceStepConfigure(ADC0_BASE,0,0,ADC_CTL_CH1|ADC_CTL_END|ADC_CTL_IE);
    ADCSequenceEnable(ADC0_BASE, 0);

    ADCIntEnable(ADC0_BASE,0);
    IntEnable(INT_ADC0);
    IntMasterEnable();

    }

    unsigned long start_adc_sample()
    {
    unsigned long ulvalue;

    ADCProcessorTrigger(ADC0_BASE,0);
    while(adc_endflag==0);
    adc_endflag=0;


    ADCSequenceDataGet(ADC0_BASE,0,&ulvalue);

    return(ulvalue);

    }
    void main()
    {

    //SysCtlClockSet(SYSCTL_SYSDIV_4|SYSCTL_USE_PLL|
    // SYSCTL_OSC_MAIN|SYSCTL_XTAL_16MHZ);


    SysCtlClockSet(SYSCTL_SYSDIV_10 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN |
    SYSCTL_XTAL_16MHZ);

    unsigned int ulva[40]={0};
    unsigned char i=0;
    enable_adc_pin();
    config_adc();


    while(1)
    {
    ulva[i]=start_adc_sample();
    if(ulva[i]>4000)
    ulva[i]=0;
    i+=1;
    if(i==40)
    i=0;
    SysCtlDelay(20000);

    }


    }


    void adc_int_isr()
    {
    ADCIntClear(ADC0_BASE,0);
    adc_endflag=1;

    }