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; } //é‡�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).