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？

Zhang Lei：

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

maoxin xu：

回复 Zhang Lei:

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;

}