我使用超声波信号测量距离。STM32F1产生超声波信号，STM32F4用麦克风写入该信号。两个STM32都是使用另一个设备产生的信号同步的，他们连接了一根线。
问题：为什么信号会有不同的时间？虽然我没有移动接收器或发射器，但为什么信号的时间不同？它的误差为50mm。
接收器的代码在这里。
while (1)
{
if(HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_5) != 0x00)
{
Get_UZ_Signal(uz_signal);
Send_Signal(uz_signal);
}
}
void Get_UZ_Signal(uint16_t* uz_signal)
{
int i,j;
uint16_t uz_buf[10];
HAL_ADC_Start_DMA(&hadc1, (uint32_t*)&uz_buf, 300000);
for(i = 0; i<lenght_signal; i++)
{
j=10;
while(j>0)
{
j--;
}
uz_signal[i] = uz_buf[0];
}
HAL_ADC_Stop_DMA(&hadc1);
}
hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.ScanConvMode = DISABLE;
hadc1.Init.ContinuousConvMode = ENABLE;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.NbrOfConversion = 1;
hadc1.Init.DMAContinuousRequests = DISABLE;
hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
更多信息请点击这里
解决的问题
时间错误是由发射机造成的，我对它做了一些修改。现在同步信号在EXTI的帮助下，一直产生PWM，我用驱动器上的Enable或Disable引脚控制信号。现在我有5mm的色散，这对我来说已经足够了。
最终程序在这里
可能是时间处理的问题。声波的速度是343米秒。那么，50毫米大约是0.15毫秒。
你有没有想过从main()调用HAL_ADC_Start_DMA()。
uint16_t uz_buf[10];
HAL_ADC_Start_DMA(&hadc1, (uint32_t*)&uz_buf, 10 );//300000);
// Sizeof Buffer ---------------------^
你叫
void Get_UZ_Signal(uint16_t* uz_signal) {
int i;
// For debugging - Get the time to process
// Get the Time from the System Tick. This counter wrap around
// from 0 to SysTick->LOAD every 1 msec
int32_t startTime = SysTick->VAL;
__HAL_ADC_ENABLE(&hadc1); // Start the DMA
// return remaining data units in the current DMA Channel transfer
while(__HAL_DMA_GET_COUNTER(&hadc1) != 0)
;
for(i = 0; i<lenght_signal; i++) {
// uz_signal[i] = uz_buf[0];
// 0 or i ------------^
uz_signal[i] = uz_buf[i];
__HAL_ADC_DISABLE(&hadc1); // Stop the DMA
int32_t endTime = SysTick->VAL;
// check if negative, case of wrap around
int32_t difTime = endTime - startTime;
if ( difTime < 0 )
difTime += SysTick->LOAD
__HAL_DMA_SET_COUNTER(&hadc1, 10); // Reset the counter
// If the DMA buffer is 10, the COUNTER will start at 10
// and decrement
// Ref. Manual: 9.4.4 DMA channel x number of data register (DMA_CNDTRx)
在您的代码中
MX_USART1_UART_Init();
HAL_ADC_Start_DMA(&hadc1, (uint32_t*)&uz_signal, 30000);
// Must be stopped because is running now
// How long is the buffer: uint16_t uz_signal[ 30000 ] ?
__HAL_ADC_DISABLE(&hadc1); // must be disable
// reset the counter
__HAL_DMA_SET_COUNTER(&hdma_adc1, 30000);
while (1)
{
if(HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_5) != 0x00)
{
__HAL_ADC_ENABLE(&hadc1);
while(__HAL_DMA_GET_COUNTER(&hdma_adc1) != 0)
;
__HAL_ADC_DISABLE(&hadc1);
__HAL_DMA_SET_COUNTER(&hdma_adc1, 30000);
// 30,000 is the sizeof your buffer?
...
}
}
我用uC STM32F407 @ 168mHz做了一些测试。在测试过程中，我计算了处理ADC转换的时间，每次转换大约需要0.35uSec（60次）。每次转换大约需要0.35uSec（60次）。
Result
Size Corresponding
Array Time Distance
100 0.041ms 14mm
1600 0.571ms 196mm
10000 3.57ms 1225mm
在代码中，你会看到开始时间。小心，SysTick是一个递减计数器，从@uC速度开始（168MHz=从168000到0）。用HAL_GetTick()得到msec时间，用SysTick得到usec时间，是个好主意。
int main(void)
{
...
MX_DMA_Init();
MX_ADC1_Init();
// Configure the channel in the way you want
ADC_ChannelConfTypeDef sConfig;
sConfig.Channel = ADC_CHANNEL_0; //ADC1_CHANNEL;
sConfig.Rank = 1;
sConfig.SamplingTime = ADC_SAMPLETIME_3CYCLES;
sConfig.Offset = 0;
HAL_ADC_ConfigChannel(&hadc1, &sConfig);
// Start the DMA channel and Stop it
HAL_ADC_Start_DMA(&hadc1, (uint32_t*)&uz_signal, sizeof( uz_signal ) / sizeof( uint16_t ));
HAL_ADC_Stop_DMA( &hadc1 );
// The SysTick is a decrement counter
// Can be use to count usec
// https://www.sciencedirect.com/topics/engineering/systick-timer
tickLoad = SysTick->LOAD;
while (1)
{
// Set the buffer to zero
for( uint32_t i=0; i < (sizeof( uz_signal ) / sizeof( uint16_t )); i++)
uz_signal[i] = 0;
// Reset the counter ready to restart
DMA2_Stream0->NDTR = (uint16_t)(sizeof( uz_signal ) / sizeof( uint16_t ));
/* Enable the Peripheral */
ADC1->CR2 |= ADC_CR2_ADON;
/* Start conversion if ADC is effectively enabled */
/* Clear regular group conversion flag and overrun flag */
ADC1->SR = ~(ADC_FLAG_EOC | ADC_FLAG_OVR);
/* Enable ADC overrun interrupt */
ADC1->CR1 |= (ADC_IT_OVR);
/* Enable ADC DMA mode */
ADC1->CR2 |= ADC_CR2_DMA;
/* Start the DMA channel */
/* Enable Common interrupts*/
DMA2_Stream0->CR |= DMA_IT_TC | DMA_IT_TE | DMA_IT_DME | DMA_IT_HT;
DMA2_Stream0->FCR |= DMA_IT_FE;
DMA2_Stream0->CR |= DMA_SxCR_EN;
//===================================================
// The DMA is ready to start
// Your if(HAL_GPIO_ReadPin( ... ) will be here
HAL_Delay( 10 );
//===================================================
// Get the time
tickStart = SysTick->VAL;
// Start the DMA
ADC1->CR2 |= (uint32_t)ADC_CR2_SWSTART;
// Wait until the conversion is completed
while( DMA2_Stream0->NDTR != 0)
;
// Get end time
tickEnd = SysTick->VAL;
/* Stop potential conversion on going, on regular and injected groups */
ADC1->CR2 &= ~ADC_CR2_ADON;
/* Disable the selected ADC DMA mode */
ADC1->CR2 &= ~ADC_CR2_DMA;
/* Disable ADC overrun interrupt */
ADC1->CR1 &= ~(ADC_IT_OVR);
// Get processing time
tickDiff = tickStart - tickEnd;
//===================================================
// Your processing will go here
HAL_Delay( 10 );
//===================================================
}
}
这样，你就有了开始和结束时间。我想你必须在开始时间上做公式。
祝您好运
如果你想知道执行时间，你可以使用那个小函数。它返回微秒
static uint32_t timeMicroSecDivider = 0;
extern uint32_t uwTick;
// The SysTick->LOAD matchs the uC Speed / 1000.
// If the uC clock is 80MHz, the the LOAD is 80000
// The SysTick->VAL is a decrement counter from (LOAD-1) to 0
//====================================================
uint64_t getTimeMicroSec()
{
if ( timeMicroSecDivider == 0)
{
// Number of clock by micro second
timeMicroSecDivider = SysTick->LOAD / 1000;
}
return( (uwTick * 1000) + ((SysTick->LOAD - SysTick->VAL) / timeMicroSecDivider));
}