stm32f3discovery read gyro acc mag data take long time

[jipeng]

Posted on March 18, 2015 at 05:47

I have a stm32f3discovery board，I want read the sensor's data, I use the driver in demo, but it take about 700 mseconds to get it, is this normal? but i want to handle these data under 20Hz.

      seconds0 = millis();

          seconds = seconds0 - seconds1;

          if (seconds >= 5) {

           sprintf(output, ''seconds is %d'', seconds);

           uartPrint(output);

            GyroReadAngRate(gyro);

            CompassReadMag(mag);

            CompassReadAcc(acc);

          seconds1 = seconds0;

          }

[AvaTar]

Posted on March 18, 2015 at 11:48

  seconds0 = millis();

 

This is a semantic contradiction.  Don't know this millis() function.

  seconds = seconds0 - seconds1;

Are you sure 'seconds1' is initialised at this point ?

  uartPrint(output);

 

Is this call blocking ?

I want read the sensor's data, I use the driver in demo, but it take about 700 mseconds to get it, is this normal ?

 

No.

Your loop my run with this cycle time, but the sensor read-out is definitely faster.

Either add GPIO toggles and use a scope, or configure a timer unit to measure the runtime of those calls (only sensor read funtions, NOT including opaque stuff like uartPrint(). Or use the runtime measurement facilities of your IDE/Debugger, if present.

[jipeng]

Posted on March 25, 2015 at 02:58

thx, I checked my code,

            GyroReadAngRate(gyro1);

            CompassReadMag(mag1);

            CompassReadAcc(acc1);

this three line run in 5 milliseconds.

and

              sprintf(output, ''e0:%f e1:%f e2:%f\r\n'', euler[0], euler[1], euler[2]);

              uartPrint(output);

run in about 40 milliseconds.

how to improve usart's performance.below is my usart code:

/*

 * usart.c

 *

 *  Created on: 2014å¹´8月12æ—¥

 *      Author: sunjipeng

 */

#include ''stdio.h''

#include ''usart.h''

#include ''stm32f30x_usart.h''

void USART1_Configuration(void)

{

    /* Enable GPIO clock */

      RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);

      /* Enable USART clock */

      RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);

  USART_InitTypeDef USART_InitStructure;

  GPIO_InitTypeDef GPIO_InitStructure;

  /************************************************************************************/

  /*for usart1*/

  /* Configure USART Tx as alternate function push-pull */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

//  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

  GPIO_Init(GPIOA, &GPIO_InitStructure);

//  GPIO_Init(GPIOB, &GPIO_InitStructure);

  /* Configure USART Rx as alternate function push-pull */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

//  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;

  GPIO_Init(GPIOA, &GPIO_InitStructure);

//  GPIO_Init(GPIOB, &GPIO_InitStructure);

  /* Connect PA9 to USART1_Tx */

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_7);

//  GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_7);

  /* Connect PA10 to USART1_Rx */

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_7);

//  GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_7);

  /* USART resources configuration (Clock, GPIO pins and USART registers) ----*/

  /* USART configured as follow:

        - BaudRate = 115200 baud

        - Word Length = 8 Bits

        - One Stop Bit

        - No parity

        - Hardware flow control disabled (RTS and CTS signals)

        - Receive and transmit enabled

  */

  USART_InitStructure.USART_BaudRate = 9600;

  USART_InitStructure.USART_WordLength = USART_WordLength_8b;

  USART_InitStructure.USART_StopBits = USART_StopBits_1;

  USART_InitStructure.USART_Parity = USART_Parity_No;

  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

  /* USART configuration */

  USART_Init(USART1, &USART_InitStructure);

  /* Enable USART */

  USART_Cmd(USART1, ENABLE);

}

int USART1_PutChar(char ch)

{

    USART_SendData(USART1, ch); // Send 'I'

    while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET); // Wait for Empty

    return ch;

}

//�定义fputc函数

int fputc(int ch, FILE *f)

{

    USART1_PutChar(ch);

  return ch;

}

void uartPrint(char *str)

{

    while (*str){

        USART1_PutChar(*(str++));

//        do {

//            USART_SendData(USART1, *(str++));

//        }while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET); // Wait for Empty

//        // Send 'I'

    }

}

[AvaTar]

Posted on March 25, 2015 at 08:52

    sprintf(output, ''e0:%f e1:%f e2:%f\r\n'', euler[0], euler[1], euler[2]);

 

    uartPrint(output);

 

run in about 40 milliseconds.

 

how to improve usart's performance.below is my usart code:

 

By not busy-waiting on individual characters, as done here:

    USART_SendData(USART1, ch); // Send 'I'

 

    while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET); // Wait for Empty

 

You could use the TXE interrupt instead, or feed the UART per DMA.

However, this does not eliminate your problem. You still produce your send data in a much faster rate than you can send it, at least with your current baudrate setting (9600).