【NUCLEO-L4R5ZI评测】STM32的ADC原来可以超频？
先使用TIM1输出160KHz 50%占空比的方波然后将PWM输出连接到ADC的输入用STM32L4R5的ADC测量PWM信号下边是用示波器测量的PWM输出 配置ADCAdcHandle.Init.ClockPrescaler=ADC_CLOCK_SYNC_PCLK_DIV1; AdcHandle.Init.Resolution= ADC_RESOLUTION_12B;sConfig.SamplingTime =ADC_SAMPLETIME_2CYCLES_5; /* ### - 1 - Initialize ADC peripheral #################################### */AdcHandle.Instance = ADCx;
if (HAL_ADC_DeInit(&AdcHandle) != HAL_OK)
{
/* ADC de-initialization Error */
Error_Handler();
}
AdcHandle.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV1; /* Synchronous clock mode, input ADC clock divided by 2*/
AdcHandle.Init.Resolution = ADC_RESOLUTION_12B; /* 12-bit resolution for converted data */
AdcHandle.Init.DataAlign = ADC_DATAALIGN_RIGHT; /* Right-alignment for converted data */
AdcHandle.Init.ScanConvMode = DISABLE; /* Sequencer disabled (ADC conversion on only 1 channel: channel set on rank 1) */
AdcHandle.Init.EOCSelection = ADC_EOC_SINGLE_CONV; /* EOC flag picked-up to indicate conversion end */
AdcHandle.Init.LowPowerAutoWait = DISABLE; /* Auto-delayed conversion feature disabled */
AdcHandle.Init.ContinuousConvMode = ENABLE; /* Continuous mode enabled (automatic conversion restart after each conversion) */
AdcHandle.Init.NbrOfConversion = 1; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.DiscontinuousConvMode = DISABLE; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.NbrOfDiscConversion = 1; /* Parameter discarded because sequencer is disabled */
AdcHandle.Init.ExternalTrigConv = ADC_SOFTWARE_START; /* Software start to trig the 1st conversion manually, without external event */
AdcHandle.Init.ExternalTrigConvEdge= ADC_EXTERNALTRIGCONVEDGE_NONE; /* Parameter discarded because software trigger chosen */
AdcHandle.Init.DMAContinuousRequests = ENABLE; /* ADC DMA continuous request to match with DMA circular mode */
AdcHandle.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN; /* DR register is overwritten with the last conversion result in case of overrun */
AdcHandle.Init.OversamplingMode = DISABLE; /* No oversampling */
/* Initialize ADC peripheral according to the passed parameters */
if (HAL_ADC_Init(&AdcHandle) != HAL_OK)
{
Error_Handler();
}
/* ### - 2 - Start calibration ############################################ */
if (HAL_ADCEx_Calibration_Start(&AdcHandle, ADC_SINGLE_ENDED) !=HAL_OK)
{
Error_Handler();
}
/* ### - 3 - Channel configuration ######################################## */
sConfig.Channel = ADCx_CHANNEL; /* Sampled channel number */
sConfig.Rank = ADC_REGULAR_RANK_1; /* Rank of sampled channel number ADCx_CHANNEL */
sConfig.SamplingTime = ADC_SAMPLETIME_2CYCLES_5; /* Sampling time (number of clock cycles unit) */
sConfig.SingleDiff = ADC_SINGLE_ENDED; /* Single-ended input channel */
sConfig.OffsetNumber = ADC_OFFSET_NONE; /* No offset subtraction */
sConfig.Offset = 0; /* Parameter discarded because offset correction is disabled */
if (HAL_ADC_ConfigChannel(&AdcHandle, &sConfig) != HAL_OK)
{
Error_Handler();
}
/* ### - 4 - Start conversion in DMA mode ################################# */
if (HAL_ADC_Start_DMA(&AdcHandle,
(uint32_t *)aADCxConvertedData,
ADC_CONVERTED_DATA_BUFFER_SIZE
) != HAL_OK)
{
Error_Handler();
} 添加DMA中断，断点打在__NOP();上，在__NOP();之前一定要先关掉ADC，否则读取的数据会中篡位的void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *AdcHandle)
{
HAL_ADC_Stop_DMA(AdcHandle);
__NOP();
/* ### - 4 - Start conversion in DMA mode ################################# */
if (HAL_ADC_Start_DMA(AdcHandle,
(uint32_t *)aADCxConvertedData,
ADC_CONVERTED_DATA_BUFFER_SIZE
) != HAL_OK)
{
Error_Handler();
}
} 将ADC输入和PWM输出短接 编译、运行然后查看aADCxConvertedData变量的数据 数一下低电平的数量（小于20的数）平均23个左右高电平的数量（大于4080的数）平均24个左右160KHz*(23+24) = 7.52MSPS将AdcHandle.Init.Resolution改为 ADC_RESOLUTION_6B;使用6位模式编译运行，计数高低电平数量平均40个左右160KHz*（40+40）= 12.8MSPS 数据手册中12位的采样率是5.33，6位采样率是8.88，实际采样率怎么会比数据手册还高？ 看到数据手册中ADC clock frequency是80MHz，可能是我的例程里使用了120MHz的时钟？如果按照80MHz时钟计算，结果和数据手册接近160KHz*(23+24) = 7.52MSPS/120MHz * 80MHz =5.01MSPS160KHz*（40+40）= 12.8MSPS /120MHz* 80MHz=8.53MSPS难道ADC也能超频？或者是我计算错了？ 为了验证我的计算，我在STM32L496ZG的板子上跑了一下相同的例程，12位模式下高低电平的数量分别为17左右，6位模式下高低电平分别为27左右160KHz*(17+17)=5.44MSPS160KHZ*(27+27)=8.64MSPS因为STM32L496主频最高为80MHz，这个结果和数据手册接近
从目前的测试来看，STM32L4R5的ADC主频貌似可以在120MHz时运行不过使用120MHz的ADC时钟时会对测量出来的结果造成多大影响以及是否会对ADC造成不可逆转的损坏还不得而知
下边把两个板子的测试工程放出来，欢迎网友一起来测试
沙发，只要能配置，哪个clock都能oc.
人有多大胆，地有多大产{:1_137:} 误差变大了！
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