measuring the pulse with Pingi

[esovo1]

Posted on June 11, 2014 at 15:04

Hi,

I am measuring the distance with ultrasonicsensor that has both one pin for the echo and trigger signal. For this task I'am using 2 timers: TIM2 AND TIM3

TIM2 is responsible for the periodic trigger signal, every 60 ms a 5us pulse is present on PA6, and TIM3 measures the input pulse.

I am just switching the alterntive function of a pin. Is this the best way to do it or there are any other alternative? I have 750us time to switch the pin charecteristics. Although it has been working good when was sending the 5us pulse in the IRQHandler and toggling the led in the main. I haven't try the code yet, cause I have to implement the UART communication through USB.

main code:

/* Includes ------------------------------------------------------------------*/
#include ''main.h''
/* Strucutres ---------------------------------------------------------*/
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
TIM_ICInitTypeDef TIM_ICInitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
/* My functions and variables-----------------------------------------------*/
unsigned 
char
TIM2_flag=0;
void
Init_TIM2(
void
);
void
Init_TIM3(
void
);
void
Delay(__IO uint32_t nTime);
int
main(
void
)
{
//STM_EVAL_LEDInit(LED4);
//STM_EVAL_LEDInit(LED5);
/*initialize timers*/
Init_TIM2();
Init_TIM3();
while
(1)
{
if
(TIM2_flag == 1) 
// pulse_flag
{
//STM_EVAL_LEDToggle(LED4);
//Delay(80000);
//TIM2_flag = 0;
// Configure PA6 in input mode
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOC, &GPIO_InitStructure);
GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_1);
TIM_Cmd(TIM3, ENABLE);
}
}
}

TIM2 function and interrupt handler:

void
Init_TIM2(
void
) 
{
// Enable APB1 peripheral clock for TIM2
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
// TIM iniciatization
TIM_TimeBaseInitStruct.TIM_Prescaler = 71; 
// 1M Hz 
TIM_TimeBaseInitStruct.TIM_Period = 59999; 
// 60ms
TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up; 
TIM_TimeBaseInitStruct.TIM_ClockDivision = 0;
TIM_TimeBaseInit(TIM2,&TIM_TimeBaseInitStruct);
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE); 
// Enable the TIM2 interrupt
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; 
// Configure the TIM2 interrupts
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; 
// Set the priority group of the TIM2 interrupts
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; 
// Set the subpriority inside the group
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; 
// Globally enable the TIM2 interrupts
NVIC_Init(&NVIC_InitStructure); 
// Init NVIC structure
//Enable TIM counter
TIM_Cmd(TIM2, ENABLE);
}
void
TIM2_IRQHandler(
void
)
{
uint16_t i; 
if
(TIM_GetITStatus(TIM2,TIM_IT_Update) == SET) 
// Check interrupt status
{
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE); 
//enable the AHB bus to use GPIOA
/* Configure PA6 in output pushpull mode */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT; 
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; 
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; 
GPIO_Init(GPIOA, &GPIO_InitStructure); 
/* a 5us pulse on PA6 */
GPIO_SetBits(GPIOA, GPIO_Pin_6); 
for
(i=0;i<=35;i++)
{}; 
//kill time
GPIO_ResetBits(GPIOA, GPIO_Pin_6); 
//PA6 = 0 
TIM2_flag=1; 
// pulse has been sent
} 
if
(TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
{
TIM_ClearITPendingBit(TIM2, TIM_IT_Update); 
// Counter overflow, reset interrupt
}
} 

TIM3 function and interrupt handler:

void
Init_TIM3(
void
)
{
NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/*input chanel configuration*/
TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;
TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV8;
TIM_ICInitStructure.TIM_ICFilter = 0x2;
TIM_PWMIConfig(TIM3, &TIM_ICInitStructure);
TIM_ITConfig(TIM3, TIM_IT_CC1, ENABLE);
TIM_SelectInputTrigger(TIM3,TIM_TS_TI1FP1);
/* Select the slave Mode: Reset Mode */
TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);
//TIM_SelectMasterSlaveMode(TIM3,TIM_MasterSlaveMode_Enable);
}
void
TIM3_IRQHandler(
void
)
{
/*just an example*/
// aurt_buuffer= TIM_GetCapture1(TIM3); 
// sprintf(buf, ''\n%2X'', aurt_buuffer); //print a newline and integer value (in HEX) to the buf string
// VCP_PutStr(buf); //write a string variable to the VCP
// Delay(125); 
}

Tnx fot the help

#timers #stm32f3 #interrupts