MEMS reading at higher frequency Topic is solved

[Azra]

Hello,

I have the STM32F407 Discovery board and I get that the embedded MEMS is the lsi3dsh. I saw that a driver was available in the SPI-LIS3DH project.

I am a total noob with ChibiOS and I have been messing around with the code for the accelerometer published by Rocco Marco Guglielmi.

I made some measurements and the time between to measurements is 15 millisec. For my application I need a sampling rate 10 millisec.

I tried to increase the ODR frequency to 1600Hz but the result is still the same : 15 millisec.

As a test, I also got rid of the transmission over the USB serial communication to avoid further delay and the time betwen measures is still 15 millisec.

Any suggestion as how to get to 10 millisec would be most welcome !

[RoccoMarco]

Hi,
can you explain me what version of ChibiOS are you using and if you are referring to a specific demo?

[Azra]

Hello Rocco,

I am working on this sample of code :

https://github.com/ChibiOS/ChibiOS/tree/master/testex/STM32/STM32F4xx/SPI-LIS3DSH

Thanks you for your help !

[RoccoMarco]

Ok, I am going to take a look.
Thanks for reporting.

[RoccoMarco]

Can you share your main?

[Azra]

I edited the link : it was not the right MEMS...

Here is my main : it is basically the same as in the demo. I just modified it by printing in a char buffer before sending over serial usb. And removed some of the for loops.

Code: Select all

/*
    ChibiOS - Copyright (C) 2006..2016 Giovanni Di Sirio

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

#include "ch.h"
#include "hal.h"

//#define LIS3DSH_USE_ADVANCED    0

#define CHAR_BUFF_SIZE 512
#define MAX_MEASURES 128

#include "usbcfg.h"
//#include "string.h"
#include "shell.h"
#include "chprintf.h"

#include "lis3dsh.h"

/*===========================================================================*/
/* Mailbox related                                                           */
/*===========================================================================*/
mailbox_t data_queue;

/*===========================================================================*/
/* LIS3DSH related.                                                          */
/*===========================================================================*/

/* LIS3DSH Driver: This object represent an LIS3DSH instance */
static LIS3DSHDriver LIS3DSHD1;

static int32_t rawdata[LIS3DSH_NUMBER_OF_AXES];
static float cookeddata[LIS3DSH_NUMBER_OF_AXES];

//static char axisID[LIS3DSH_NUMBER_OF_AXES] = {'X', 'Y', 'Z'};
//static uint32_t i;

static const SPIConfig spicfg = {
  NULL,
  GPIOE,                                     /* port of LIS3DSH CS.*/
  GPIOE_CS_SPI,                              /* pin of LIS3DSH CS.*/
  SPI_CR1_BR_0 | SPI_CR1_CPOL | SPI_CR1_CPHA,/* CR1 register.*/
  0                                          /* CR2 register.*/
};

static LIS3DSHConfig lis3dshcfg = {
  &SPID1,                                    /* Pointer to SPI Driver.*/
  &spicfg,                                   /* Pointer to SPI Configuration.*/
  NULL,                                      /* Use default sensitivity.*/
  NULL,                                      /* Use default bias.*/
  LIS3DSH_FS_2G,                             /* Full scale value.*/
//  LIS3DSH_ODR_100HZ,                         /* Output data rate.*/
  LIS3DSH_ODR_1600HZ,                        /* Output data rate.*/
#if LIS3DSH_USE_ADVANCED || defined(__DOXYGEN__)
  LIS3DSH_BW_400HZ,                          /* AA filter bandwidth.*/
  LIS3DSH_BDU_CONTINUOUS,                    /* Block data update continuous.*/
#endif
};

/*===========================================================================*/
/* Command line related.                                                     */
/*===========================================================================*/

/* Enable use of special ANSI escape sequences.*/
//#define CHPRINTF_USE_ANSI_CODE      TRUE
#define SHELL_WA_SIZE               THD_WORKING_AREA_SIZE(2048)

static void cmd_read(BaseSequentialStream *chp, int argc, char *argv[]) {

  systime_t time0, time;
  int16_t updated = 0;

  static char buffer[CHAR_BUFF_SIZE];

  (void)argv;
  if (argc != 1) {
    chprintf(chp, "Usage: read [raw|cooked]\r\n");
    return;
  }

  time0 = chVTGetSystemTime();

  while (chnGetTimeout((BaseChannel *)chp, 150) == Q_TIMEOUT) {
    updated = -1;
    if (!strcmp (argv[0], "raw")) {
#if CHPRINTF_USE_ANSI_CODE
      chprintf(chp, "\033[2J\033[1;1H");
#endif
      accelerometerReadRaw(&LIS3DSHD1, rawdata);
//      chprintf(chp, "LIS3DSH Accelerometer raw data...\r\n");
//      for(i = 0; i < LIS3DSH_NUMBER_OF_AXES; i++) {
//        chprintf(chp, "%c-axis: %d\r\n", axisID[i], rawdata[i]);
//      }
      time = chVTGetSystemTime();
      chsnprintf(buffer, CHAR_BUFF_SIZE, "%lu;%ld;%ld;%ld\r\n", ST2MS(time-time0), rawdata[0], rawdata[1], rawdata[2]);

      updated=0;
    }
    else if (!strcmp (argv[0], "cooked")) {
#if CHPRINTF_USE_ANSI_CODE
      chprintf(chp, "\033[2J\033[1;1H");
#endif
      accelerometerReadCooked(&LIS3DSHD1, cookeddata);
//      chprintf(chp, "LIS3DSH Accelerometer cooked data...\r\n");
//      for(i = 0; i < LIS3DSH_NUMBER_OF_AXES; i++) {
//        chprintf(chp, "%c-axis: %.4f mg\r\n", axisID[i], cookeddata[i]);
//      }
      time = chVTGetSystemTime();
      chsnprintf(buffer, CHAR_BUFF_SIZE , "%lu;%.4f;%.4f;%.4f\r\n", ST2MS(time-time0), cookeddata[0], cookeddata[1], cookeddata[2]);
      updated=0;
    }
    else {
      chprintf(chp, "Usage: read [raw|cooked]\r\n");
      return;
    }
    if(updated == 0)
    {
        chprintf(chp, "%s", buffer);
      updated = -1;
    }
  }
  chprintf(chp, "Stopped\r\n");

}

static void cmd_fullscale(BaseSequentialStream *chp, int argc, char *argv[]) {
  (void)argv;
  if (argc != 1) {
    chprintf(chp, "Usage: fullscale [2G|4G|6G|8G|16G]\r\n");
    return;
  }
#if CHPRINTF_USE_ANSI_CODE
    chprintf(chp, "\033[2J\033[1;1H");
#endif
  if(!strcmp (argv[0], "2G")) {
    accelerometerSetFullScale(&LIS3DSHD1, LIS3DSH_FS_2G);
    chprintf(chp, "LIS3DSH Accelerometer full scale set to 2G...\r\n");
  }
  else if(!strcmp (argv[0], "4G")) {
    accelerometerSetFullScale(&LIS3DSHD1, LIS3DSH_FS_4G);
    chprintf(chp, "LIS3DSH Accelerometer full scale set to 4G...\r\n");
  }
  else if(!strcmp (argv[0], "6G")) {
    accelerometerSetFullScale(&LIS3DSHD1, LIS3DSH_FS_6G);
    chprintf(chp, "LIS3DSH Accelerometer full scale set to 6G...\r\n");
  }
  else if(!strcmp (argv[0], "8G")) {
    accelerometerSetFullScale(&LIS3DSHD1, LIS3DSH_FS_8G);
    chprintf(chp, "LIS3DSH Accelerometer full scale set to 8G...\r\n");
  }
  else if(!strcmp (argv[0], "16G")) {
    accelerometerSetFullScale(&LIS3DSHD1, LIS3DSH_FS_16G);
    chprintf(chp, "LIS3DSH Accelerometer full scale set to 16G...\r\n");
  }
  else {
    chprintf(chp, "Usage: fullscale [2G|4G|6G|8G|16G]\r\n");
    return;
  }
}

static const ShellCommand commands[] = {
  {"read", cmd_read},
  {"fullscale", cmd_fullscale},
  {NULL, NULL}
};

static const ShellConfig shell_cfg1 = {
  (BaseSequentialStream *)&SDU1,
  commands
};


/*===========================================================================*/
/* Main code.                                                                */
/*===========================================================================*/

/*
 * LED blinker thread, times are in milliseconds.
 */
static THD_WORKING_AREA(waThread1, 128);
static THD_FUNCTION(Thread1, arg) {

  (void)arg;
  chRegSetThreadName("blinker");
  while (true) {
    systime_t time;

    time = serusbcfg.usbp->state == USB_ACTIVE ? 250 : 500;
    palClearLine(LINE_LED6);
    chThdSleepMilliseconds(time);
    palSetLine(LINE_LED6);
    chThdSleepMilliseconds(time);
  }
}

/*
 * Application entry point.
 */
int main(void) {

  /*
   * System initializations.
   * - HAL initialization, this also initializes the configured device drivers
   *   and performs the board-specific initializations.
   * - Kernel initialization, the main() function becomes a thread and the
   *   RTOS is active.
   */
  halInit();
  chSysInit();

  /* Initializes a serial-over-USB CDC driver.*/
  sduObjectInit(&SDU1);
  sduStart(&SDU1, &serusbcfg);

  /*
   * Activates the USB driver and then the USB bus pull-up on D+.
   * Note, a delay is inserted in order to not have to disconnect the cable
   * after a reset.
   */
  usbDisconnectBus(serusbcfg.usbp);
  chThdSleepMilliseconds(1500);
  usbStart(serusbcfg.usbp, &usbcfg);
  usbConnectBus(serusbcfg.usbp);

  /* Creates the blinker thread.*/
  chThdCreateStatic(waThread1, sizeof(waThread1), NORMALPRIO + 1, Thread1, NULL);

  /* LIS3DSH Object Initialization.*/
  lis3dshObjectInit(&LIS3DSHD1);

  /* Activates the LIS3DSH driver.*/
  lis3dshStart(&LIS3DSHD1, &lis3dshcfg);

  /* Shell manager initialization.*/
  shellInit();

  while(TRUE) {
    if (SDU1.config->usbp->state == USB_ACTIVE) {
      thread_t *shelltp = chThdCreateFromHeap(NULL, SHELL_WA_SIZE,
                                              "shell", NORMALPRIO + 1,
                                              shellThread, (void *)&shell_cfg1);

      chThdWait(shelltp);               /* Waiting termination.             */
    }
    chThdSleepMilliseconds(1000);
  }
  lis3dshStop(&LIS3DSHD1);
  return 0;
}

[RoccoMarco]

I think the problem could be that:

Code: Select all

while (chnGetTimeout((BaseChannel *)chp, 150) == Q_TIMEOUT) {

which waits 15ms for a character. If receives a char it breaks the loop...


I suggest you to use a simpler code like

Code: Select all

/* LIS3DSH Object Initialization.*/
lis3dshObjectInit(&LIS3DSHD1);

/* Activates the LIS3DSH driver.*/
lis3dshStart(&LIS3DSHD1, &lis3dshcfg);

while(TRUE) {
  accelerometerReadCooked(&LIS3DSHD1, cookeddata);
  chThdSleepMilliseconds(1);
}

[Azra]

Ahahah that is sooo obvious.... Silly me !

Thanks for the tip, I'll try your suggestion !

[RoccoMarco]

No problem,
keep me updated and thanks for reporting.

[Azra]

For my application it was simpler to change the timeout threshold as I had already written a desktop application using the shell commands.

Code: Select all

while (chnGetTimeout((BaseChannel *)chp, 100) == Q_TIMEOUT)