LPC824 lite入门教程七 ADC

原来的你 · 发表于 2016-11-10 22:58:19

本节我们讲解LPC824的ADC功能，LPC824的ADC特性如下：
QQ截图20161110223724.png

int main(void)
{
uint32_t rawSample;
int j;

SystemCoreClockUpdate();
Board_Init();
DEBUGSTR("ADC sequencer demo\r\n");
DEBUGOUT("System Clock: %uMHz\r\n", SystemCoreClock / 1000000);
DEBUGOUT("Device ID: 0x%x\r\n", Chip_SYSCTL_GetDeviceID());

/* Setup ADC for 12-bit mode and normal power */
Chip_ADC_Init(LPC_ADC, 0);//初始化ADC为12位，正常供电模式

/* Need to do a calibration after initialization and trim */
Chip_ADC_StartCalibration(LPC_ADC);//校准ADC
while (!(Chip_ADC_IsCalibrationDone(LPC_ADC))) {}//等待ADC校准完成
/* Setup sequencer A for ADC channel 3, EOS interrupt */
/* Setup a sequencer to do the following:
   Perform ADC conversion of ADC channels 3 only */
Chip_ADC_SetupSequencer(LPC_ADC, ADC_SEQA_IDX,
(ADC_SEQ_CTRL_CHANSEL(BOARD_ADC_CH) | ADC_SEQ_CTRL_MODE_EOS));

/* Enable the clock to the Switch Matrix */
Chip_Clock_EnablePeriphClock(SYSCTL_CLOCK_SWM);//使能开关矩阵时钟

/* Configure the SWM for P0-23 as the input for the ADC1 */
Chip_SWM_EnableFixedPin(SWM_FIXED_ADC3);//配置P0-23为ADC1输入脚

/* Disable the clock to the Switch Matrix to save power */
Chip_Clock_DisablePeriphClock(SYSCTL_CLOCK_SWM);//关闭开关矩阵时钟节能

/* Setup threshold 0 low and high values to about 25% and 75% of max */
Chip_ADC_SetThrLowValue(LPC_ADC, 0, ((1 * 0xFFF) / 4));//设置ADC最低转换门限有25%
Chip_ADC_SetThrHighValue(LPC_ADC, 0, ((3 * 0xFFF) / 4));//设置ADC最高转换门限有75%

/* Clear all pending interrupts */
Chip_ADC_ClearFlags(LPC_ADC, Chip_ADC_GetFlags(LPC_ADC));//清除ADC中断标志

/* Enable ADC overrun and sequence A completion interrupts */
Chip_ADC_EnableInt(LPC_ADC, (ADC_INTEN_SEQA_ENABLE | ADC_INTEN_OVRRUN_ENABLE));//使能ADC超限和转换完成中断

/* Use threshold 0 for ADC channel and enable threshold interrupt mode for
   channel as crossing */
Chip_ADC_SelectTH0Channels(LPC_ADC, ADC_THRSEL_CHAN_SEL_THR1(BOARD_ADC_CH));//选择门限通道
Chip_ADC_SetThresholdInt(LPC_ADC, BOARD_ADC_CH, ADC_INTEN_THCMP_CROSSING);//使能门限中断

/* Enable ADC NVIC interrupt */
NVIC_EnableIRQ(ADC_SEQA_IRQn);//使能ADC NVIC

/* Enable sequencer */
Chip_ADC_EnableSequencer(LPC_ADC, ADC_SEQA_IDX);//使能ADC转换

/* This example uses the periodic sysTick to manually trigger the ADC,
   but a periodic timer can be used in a match configuration to start
   an ADC sequence without software intervention. */
SysTick_Config(SystemCoreClock / TICKRATE_HZ);

/* Endless loop */
while (1) {
/* Sleep until something happens */
__WFI();

if (thresholdCrossed) {
thresholdCrossed = false;
DEBUGSTR("********ADC threshold event********\r\n");
}

/* Is a conversion sequence complete? */
if (sequenceComplete) {
sequenceComplete = false;

/* Get raw sample data for channels 0-11 */
for (j = 0; j < 12; j++) {
rawSample = Chip_ADC_GetDataReg(LPC_ADC, j);

/* Show some ADC data */
if (rawSample & (ADC_DR_OVERRUN | ADC_SEQ_GDAT_DATAVALID)) {
DEBUGOUT("Chan: %d Val: %d\r\n", j, ADC_DR_RESULT(rawSample));
DEBUGOUT("Threshold range: 0x%x ", ADC_DR_THCMPRANGE(rawSample));
DEBUGOUT("Threshold cross: 0x%x\r\n", ADC_DR_THCMPCROSS(rawSample));
DEBUGOUT("Overrun: %s \r\n", (rawSample & ADC_DR_OVERRUN) ? "true" : "false");
DEBUGOUT("Data Valid: %s\r\n\r\n", (rawSample & ADC_SEQ_GDAT_DATAVALID) ? "true" : "false");
}
}
}
}
}

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