ADCDMA技術解析

一、ADCDMA概述

ADCDMA是指將模擬信號轉換成數字信號，然後通過DMA技術將數字信號直接傳輸到內存中的一種技術。

ADCDMA技術在分佈式控制系統、自動化控制、通信系統等領域得到廣泛應用。

二、ADCDMA顯示波形

通過ADCDMA技術可以獲取模擬信號的數字信號，然後將其顯示成波形。

/* ADCDMA顯示波形代碼示例 */
#include 
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "inc/hw_adc.h"
#include "inc/hw_ints.h"
#include "driverlib/adc.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"
#include "driverlib/interrupt.h"

/* ADC初始化，設置採樣率為250KSPS */
void ADC_Init(void)
{
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3);
    ADCSequenceConfigure(ADC0_BASE, 1, ADC_TRIGGER_PROCESSOR, 0);
    ADCSequenceStepConfigure(ADC0_BASE, 1, 0, ADC_CTL_CH0);
    ADCSequenceStepConfigure(ADC0_BASE, 1, 1, ADC_CTL_CH0);
    ADCSequenceStepConfigure(ADC0_BASE, 1, 2, ADC_CTL_CH0);
    ADCSequenceStepConfigure(ADC0_BASE, 1, 3, ADC_CTL_CH0|ADC_CTL_IE|ADC_CTL_END);
    ADCSequenceEnable(ADC0_BASE, 1);
}

/* DMA初始化 */
void DMA_Init(void)
{
    SysCtlPeripheralEnable(SYSCTL_PERIPH_DMA);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_UDMA);
    uDMAEnable();
    uDMAControlBaseSet(g_psDMAControlTable);
    uDMAChannelAssign(UDMA_CH13_ADC0_1);
    uDMAChannelAttributeDisable(UDMA_CHANNEL_ADC0, UDMA_ATTR_ALL);
    uDMAChannelControlSet(UDMA_CHANNEL_ADC0 | UDMA_PRI_SELECT,
                          UDMA_SIZE_16 | UDMA_SRC_INC_NONE | UDMA_DST_INC_16 |
                          UDMA_ARB_64);
    uDMAChannelTransferSet(UDMA_CHANNEL_ADC0 | UDMA_PRI_SELECT,
                           UDMA_MODE_PINGPONG, (void*)(ADC0_BASE + ADC_O_SSFIFO1),
                           g_adcBuffer, ADC_BUFFER_SIZE/2);
    uDMAChannelEnable(UDMA_CHANNEL_ADC0);
}

/* 開始採樣 */
void ADC_Sample(void)
{
    /* ADCDMA採樣開始 */
    ADCProcessorTrigger(ADC0_BASE, 1);
    /* 等待DMA傳輸完成 */
    while(!uDMAChannelModeGet(UDMA_CHANNEL_ADC0 | UDMA_PRI_SELECT));
}

三、ADCDMA中斷多通道採集

ADCDMA中斷採集時，可以同步採集多個通道的信號。

/* ADCDMA中斷多通道採集代碼示例 */
#include 
#include "inc/hw_types.h"
#include "inc/hw_memmap.h"
#include "inc/hw_adc.h"
#include "inc/hw_ints.h"
#include "driverlib/adc.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"
#include "driverlib/interrupt.h"

#define ADC_CHANNEL_NUM 2
uint32_t g_adcValues[ADC_CHANNEL_NUM];

void ADCInit(void)
{
    /* ADC0採樣率配置 */
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3);
    ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
    ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0);
    ADCSequenceStepConfigure(ADC0_BASE, 3, 1, ADC_CTL_CH1|ADC_CTL_IE|ADC_CTL_END);
    ADCSequenceEnable(ADC0_BASE, 3);

    /* 中斷配置 */
    ADCIntEnable(ADC0_BASE, 3);
    ADCIntRegister(ADC0_BASE, 3, ADCIntHandler);
    IntPrioritySet(INT_ADC0SS3, 0x00);
    IntEnable(INT_ADC0SS3);
}

void ADCIntHandler(void)
{
    /* 清除中斷標誌位 */
    ADCIntClear(ADC0_BASE, 3);
    /* 獲取ADC數值 */
    ADCSequenceDataGet(ADC0_BASE, 3, g_adcValues);
}

void ADCCollect(void)
{
    /* ADC中斷採樣開始 */
    ADCProcessorTrigger(ADC0_BASE, 3);
    /* 等待中斷完成 */
    while(ADCIntStatus(ADC0_BASE, 3, false) == 0) {}
}

四、ADCDMA數據錯位

當ADCDMA採集數據出現錯位時，需要對數據進行調整或再次採樣。

五、ADCDMA只轉換了一次

如果只進行一次採集和轉換，可以採用CPU讀取方式，不需要使用DMA。

六、ADCDMA應用實例

以ADCDMA採集電流電壓信號並實時顯示為例，代碼如下：

/* ADCDMA電流電壓採集和顯示代碼示例 */
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "inc/hw_adc.h"
#include "driverlib/adc.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/timer.h"
#include "utils/uartstdio.h"

/* 定義ADC通道以及數組 */
#define ADC_SEQUENCE_NUM             0
#define ADC_SEQUENCE_PRIORITY        ADC_CTL_CH0
#define ADC_SEQUENCE_SAMPLE_RATE     8000
#define ADC_STATUS_BUF_DEPTH         8
#define ADC_RESULT_BUF_DEPTH         8
int32_t pui32ADC0Status[ADC_STATUS_BUF_DEPTH];
int32_t pui32ADC0Value[ADC_RESULT_BUF_DEPTH];
int32_t i32ADCSum;
uint32_t ADCCurrentValue;
uint32_t ADCVoltageValue;
uint32_t ui32ADCSampleCount = 0;

void ADCIntHandler(void)
{
    ADCSequenceDataGet(ADC0_BASE, ADC_SEQUENCE_NUM, pui32ADC0Value);
    ADCSequenceDataGet(ADC0_BASE, ADC_SEQUENCE_NUM | ADC_CTL_CMP0, pui32ADC0Status);
    ui32ADCSampleCount++;
    /* 計算平均值 */
    for(uint8_t i = 0; i < ADC_STATUS_BUF_DEPTH; i++)
    {
        i32ADCSum += pui32ADC0Status[i];
    }
    ADCCurrentValue = i32ADCSum/ADC_STATUS_BUF_DEPTH;
    i32ADCSum = 0;
    for(uint8_t i = 0; i < ADC_RESULT_BUF_DEPTH; i++)
    {
        i32ADCSum += pui32ADC0Value[i];
    }
    ADCVoltageValue = i32ADCSum/ADC_RESULT_BUF_DEPTH;
    i32ADCSum = 0;
}
void TimerIntHandler(void)
{
    /* 顯示電流電壓 */
    UARTprintf("Current is %d mA, voltage is %d mV\n", ADCCurrentValue, ADCVoltageValue);
    /* 清除中斷標誌位 */
    TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
}
int main(void)
{
    /* 系統時鐘設置至80MHz */
    SysCtlClockSet(SYSCTL_SYSDIV_2_5|SYSCTL_USE_PLL|SYSCTL_OSC_MAIN|SYSCTL_XTAL_16MHZ);

    /* IO口設置為ADC輸入 */
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3);
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_2);

    /* ADC採樣初始化 */
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL, 8);
    ADCSequenceConfigure(ADC0_BASE, ADC_SEQUENCE_NUM, ADC_TRIGGER_PROCESSOR | ADC_SEQUENCE_PRIORITY, 0);
    ADCSequenceStepConfigure(ADC0_BASE, ADC_SEQUENCE_NUM, 0, ADC_CTL_CH0 | ADC_CTL_IE | ADC_CTL_END);
    ADCSequenceStepConfigure(ADC0_BASE, ADC_SEQUENCE_NUM | ADC_CTL_CMP0, 0, ADC_CTL_CH1 | ADC_CTL_IE | ADC_CTL_END);
    ADCSequenceOverflowConfigure(ADC0_BASE, ADC_SEQUENCE_NUM, ADC_OVS_FIELD_NONE | ADC_OVS_RATE_HALF);
    ADCSequenceOverflowConfigure(ADC0_BASE, ADC_SEQUENCE_NUM | ADC_CTL_CMP0, ADC_OVS_FIELD_NONE | ADC_OVS_RATE_HALF);
    ADCSequenceDMAEnable(ADC0_BASE, ADC_SEQUENCE_NUM);
    ADCSequenceDMAEnable(ADC0_BASE, ADC_SEQUENCE_NUM | ADC_CTL_CMP0);
    ADCIntRegister(ADC0_BASE, ADC_SEQUENCE_NUM, ADCIntHandler);
    ADCIntEnable(ADC0_BASE, ADC_SEQUENCE_NUM | ADC_CTL_CMP0);
    ADCSequenceEnable(ADC0_BASE, ADC_SEQUENCE_NUM | ADC_CTL_CMP0);
    ADCProcessorTrigger(ADC0_BASE, ADC_SEQUENCE_NUM);
    int32_t i32Err;
    i32Err = TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC);
    TimerLoadSet(TIMER0_BASE, TIMER_A, SysCtlClockGet()/100); // 1秒鐘100次
    TimerIntRegister(TIMER0_BASE, TIMER_A, TimerIntHandler);
    TimerIntEnable(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
    TimerEnable(TIMER0_BASE, TIMER_A);

    /* 初始化UART輸出 */
    SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
    GPIOPinConfigure(GPIO_PA0_U0RX);
    GPIOPinConfigure(GPIO_PA1_U0TX);
    GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);
    UARTStdioConfig(0, 115200, SysCtlClockGet());

    while(1)
    {
    }
}

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