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I guess I have to add my main goal: I want to make the sending as fast for the arduino as possible. No extra calculations should be necessary (if possible). And: the reason for these shifts seems to be the some time delay (slowness). I suspect it to be a slow matlab reading, since I saw fluent processing scripts in HIL reading.

Full arduino code:

// Program to send the gyro/accel data via serialport
// corresponding matlab programs: sensing.m and sensing_binary.m
// 2 security loops to guarantee a constant sampling time

// #define DEBUG
#include "GY86.h"
#include "Wire.h"

GY86 gy86;
int16_t ax, ay, az;
int16_t gx, gy, gz;

uint32_t currenttime = 0;
uint32_t starttime = 0;
uint32_t starttime2 = 0;

// #define OUTPUT_ACCEL_COUNTS
#define OUTPUT_GYRO_COUNTS

// #define OUTPUT_ACCEL_BINARY
// #define OUTPUT_GYRO_BINARY


void setup () {
  Serial.begin(115200);
  gy86.setup();
}


void loop () {
  currenttime = millis();
  if (currenttime-starttime > 9)
  {
    while (micros()-starttime2 < 9000) { }
    starttime2 = micros();

    // read raw accel/gyro measurements from device
    gy86.getSensorValues(&ax, &ay, &az, &gx, &gy, &gz);
    // testing constants
    // gx = -29;
    // gy = 245;
    // gz = 17;

#ifdef OUTPUT_GYRO_COUNTS
    Serial.print((int)gx); Serial.print(F("\t"));
    Serial.print((int)gy); Serial.print(F("\t"));
    Serial.print((int)gz); Serial.print(F("\t"));
#endif
#ifdef OUTPUT_ACCEL_COUNTS
    Serial.print(ax);   Serial.print(F("\t"));
    Serial.print(ay);   Serial.print(F("\t"));
    Serial.println(az); Serial.print(F("\t"));
#endif
#if defined(OUTPUT_ACCEL_COUNTS) || defined(OUTPUT_GYRO_COUNTS)
    Serial.print(F("\n"));
#endif

#ifdef OUTPUT_ACCEL_BINARY
    Serial.write((uint8_t)(ax >> 8)); Serial.write((uint8_t)(ax & 0xFF));
    Serial.write((uint8_t)(ay >> 8)); Serial.write((uint8_t)(ay & 0xFF));
    Serial.write((uint8_t)(az >> 8)); Serial.write((uint8_t)(az & 0xFF));
#endif
#ifdef OUTPUT_GYRO_BINARY
    Serial.write((uint8_t)(gx >> 8)); Serial.write((uint8_t)(gx & 0xFF));
    Serial.write((uint8_t)(gy >> 8)); Serial.write((uint8_t)(gy & 0xFF));
    Serial.write((uint8_t)(gz >> 8)); Serial.write((uint8_t)(gz & 0xFF));
#endif

    starttime = currenttime;
  }
}

I guess I have to add my main goal: I want to make the sending as fast for the arduino as possible. No extra calculations should be necessary (if possible). And: the reason for these shifts seems to be the some time delay (slowness). I suspect it to be a slow matlab reading, since I saw fluent processing scripts in HIL reading. The errors have stopped however, since I turned the baude rate down. Only wrong numbers are the problem still.

May there be a possibility to loop around the fread and read just store the values after an added 'header'? So let's say a wrong ordering occures. Then I discard everything until the next 'a' char/byte and use the following 6 bytes to produce my 3 values. Then I wait for an 'a' again. For that I would have to loop fread(s,[1,1],'int8'); and search for the header.

Full arduino code:

// Program to send the gyro/accel data via serialport
// corresponding matlab programs: sensing.m and sensing_binary.m
// 2 security loops to guarantee a constant sampling time

// #define DEBUG
#include "GY86.h"
#include "Wire.h"

GY86 gy86;
int16_t ax, ay, az;
int16_t gx, gy, gz;

uint32_t currenttime = 0;
uint32_t starttime = 0;
uint32_t starttime2 = 0;

// #define OUTPUT_ACCEL_COUNTS
#define OUTPUT_GYRO_COUNTS

// #define OUTPUT_ACCEL_BINARY
// #define OUTPUT_GYRO_BINARY


void setup () {
  Serial.begin(9600);
  gy86.setup();
}


void loop () {
  currenttime = millis();
  if (currenttime-starttime > 9)
  {
    while (micros()-starttime2 < 9000) { }
    starttime2 = micros();

    // read raw accel/gyro measurements from device
    gy86.getSensorValues(&ax, &ay, &az, &gx, &gy, &gz);
    // testing constants
    // gx = -29;
    // gy = 245;
    // gz = 17;

#ifdef OUTPUT_GYRO_COUNTS
    Serial.print((int)gx); Serial.print(F("\t"));
    Serial.print((int)gy); Serial.print(F("\t"));
    Serial.print((int)gz); Serial.print(F("\t"));
#endif
#ifdef OUTPUT_ACCEL_COUNTS
    Serial.print(ax);   Serial.print(F("\t"));
    Serial.print(ay);   Serial.print(F("\t"));
    Serial.println(az); Serial.print(F("\t"));
#endif
#if defined(OUTPUT_ACCEL_COUNTS) || defined(OUTPUT_GYRO_COUNTS)
    Serial.print(F("\n"));
#endif

#ifdef OUTPUT_ACCEL_BINARY
    Serial.write((uint8_t)(ax >> 8)); Serial.write((uint8_t)(ax & 0xFF));
    Serial.write((uint8_t)(ay >> 8)); Serial.write((uint8_t)(ay & 0xFF));
    Serial.write((uint8_t)(az >> 8)); Serial.write((uint8_t)(az & 0xFF));
#endif
#ifdef OUTPUT_GYRO_BINARY
    Serial.write((uint8_t)(gx >> 8)); Serial.write((uint8_t)(gx & 0xFF));
    Serial.write((uint8_t)(gy >> 8)); Serial.write((uint8_t)(gy & 0xFF));
    Serial.write((uint8_t)(gz >> 8)); Serial.write((uint8_t)(gz & 0xFF));
#endif

    starttime = currenttime;
  }
}

Full arduino code:

// Program to send the gyro/accel data via serialport
// corresponding matlab programs: sensing.m and sensing_binary.m
// 2 security loops to guarantee a constant sampling time

// #define DEBUG
#include "GY86.h"
#include "Wire.h"

GY86 gy86;
int16_t ax, ay, az;
int16_t gx, gy, gz;

uint32_t currenttime = 0;
uint32_t starttime = 0;
uint32_t starttime2 = 0;

// #define OUTPUT_ACCEL_COUNTS
#define OUTPUT_GYRO_COUNTS

// #define OUTPUT_ACCEL_BINARY
// #define OUTPUT_GYRO_BINARY


void setup () {
  Serial.begin(115200);
  gy86.setup();
}


void loop () {
  currenttime = millis();
  if (currenttime-starttime > 9)
  {
    while (micros()-starttime2 < 9000) { }
    starttime2 = micros();

    // read raw accel/gyro measurements from device
    gy86.getSensorValues(&ax, &ay, &az, &gx, &gy, &gz);
    // testing constants
    // gx = -29;
    // gy = 245;
    // gz = 17;

#ifdef OUTPUT_GYRO_COUNTS
    Serial.print((int)gx); Serial.print(F("\t"));
    Serial.print((int)gy); Serial.print(F("\t"));
    Serial.print((int)gz); Serial.print(F("\t"));
#endif
#ifdef OUTPUT_ACCEL_COUNTS
    Serial.print(ax);   Serial.print(F("\t"));
    Serial.print(ay);   Serial.print(F("\t"));
    Serial.println(az); Serial.print(F("\t"));
#endif
#if defined(OUTPUT_ACCEL_COUNTS) || defined(OUTPUT_GYRO_COUNTS)
    Serial.print(F("\n"));
#endif

#ifdef OUTPUT_ACCEL_BINARY
    Serial.write((uint8_t)(ax >> 8)); Serial.write((uint8_t)(ax & 0xFF));
    Serial.write((uint8_t)(ay >> 8)); Serial.write((uint8_t)(ay & 0xFF));
    Serial.write((uint8_t)(az >> 8)); Serial.write((uint8_t)(az & 0xFF));
#endif
#ifdef OUTPUT_GYRO_BINARY
    Serial.write((uint8_t)(gx >> 8)); Serial.write((uint8_t)(gx & 0xFF));
    Serial.write((uint8_t)(gy >> 8)); Serial.write((uint8_t)(gy & 0xFF));
    Serial.write((uint8_t)(gz >> 8)); Serial.write((uint8_t)(gz & 0xFF));
#endif

    starttime = currenttime;
  }
}

I'm implementing a filter for my IMU Sensor and thus I want close to real time data visualized on the computer. I use binary serial communication to facilitate the sending part for the arduino (as far as I know the serial.print is pretty slow). So I split my int16_t in two bytes and send it, like:

Serial.write((uint8_t)(gx >> 8)); Serial.write((uint8_t)(gx & 0xFF));

After that i directly send the next number (3 in total by now, maybe up to 7 2byte numbers in the future). I read the thing in matlab with:

dt(k) = toc;
tic;
bindata([1:6],k) = fread(s,[6,1],'int8');
time = cumsum(dt(1:k));

Which reads 6 bytes (3 numbers) and then I recalculate the binary representation, concatenate them and get the original number (if someone can suggest an easier way.. I found matlab pretty unhandy here).

The problem is, that the numbers get mixed by the time. Somewhen one byte isn't read or anything, so the bytes get messed up and a nonsense number is produced.One full number (2byte) is skipped for one sample exactly. Instead of this number one number is there twice. The next sample the order is messed up (shifted, such that the first number is second). This process appears after maybe 30 sec, sometimes a few minutes. After the first time it keeps shifting and jumping around.

Can someone tell me, what to do here? Can I include some 'breakpoint'/line terminator, where the reader (matlab) knows, that we are at the start of the first number? Or how is this done actually?

Thanks for any help!

I'm implementing a filter for my IMU Sensor and thus I want close to real time data visualized on the computer. I use binary serial communication to facilitate the sending part for the arduino (as far as I know the serial.print is pretty slow). So I split my int16_t in two bytes and send it, like:

Serial.write((uint8_t)(gx >> 8)); Serial.write((uint8_t)(gx & 0xFF));

After that i directly send the next number (3 in total by now, maybe up to 7 2byte numbers in the future). I read the thing in matlab with:

dt(k) = toc;
tic;
bindata([1:6],k) = fread(s,[6,1],'int8');
time = cumsum(dt(1:k));

Which reads 6 bytes (3 numbers) and then I recalculate the binary representation, concatenate them and get the original number (if someone can suggest an easier way.. I found matlab pretty unhandy here).

The problem is, that the numbers get mixed by the time. Somewhen one byte isn't read or anything, so the bytes get messed up and a nonsense number is produced.One full number (2byte) is skipped for one sample exactly. Instead of this number one number is there twice. The next sample the order is messed up (shifted, such that the first number is second). This process appears after maybe 30 sec, sometimes a few minutes. After the first time it keeps shifting and jumping around.

Can someone tell me, what to do here? Can I include some 'breakpoint'/line terminator, where the reader (matlab) knows, that we are at the start of the first number? Or how is this done actually?

I guess I have to add my main goal: I want to make the sending as fast for the arduino as possible. No extra calculations should be necessary (if possible). And: the reason for these shifts seems to be the some time delay (slowness). I suspect it to be a slow matlab reading, since I saw fluent processing scripts in HIL reading.