why when I run the GY521_pitch_roll_yaw example code, all the numbers slowly increase 0 -> 359 -> 0? about gy521

[mw66]

I also tried another library, at lease the output numbers are stable, does not auto-incremental over time when the chip is not moving at all.

But I have another data conversion issue:

jrowberg/i2cdevlib#763

[RobTillaart]

@mw66
Thanks for reporting this issue, not seen this drift in my tests so far.
I have not enough information to analyze this problem
As the other library seems to work well - can you provide a link? Might give a clue what they do differently.

In the data you provided I see a repeating pattern that every 3 or 4 measurements the data changes a bit.
This is not strange as e.g. getYaw() returns an internal variable that only is updated after a call to read().
As read() is throttled, not all reads are factual reads to keep the load on the device within certain limits.
This GY521_THROTTLE_TIME is default 10 milliseconds.

You might try to switch of the throttling by setThrottle(false) and see if that improves your readings.

---

But I have another data conversion issue:

Your other issue, could it be that you need to calibrate ? line 200-210
You state you have output 28 at 90 degrees.
What value do you get at zero degrees?

[mw66]

I got ~+/- 0.xx at zero degrees.

[RobTillaart]

Can you run - GY521_test_1.ino for a few minutes?
you may change these line to be all float's to get a bit more detail (I'll make an issue to patch the example)

  int ax = sensor.getAccelX();
  int ay = sensor.getAccelY();
  int az = sensor.getAccelZ();
  int gx = sensor.getGyroX();
  int gy = sensor.getGyroY();
  int gz = sensor.getGyroZ();
  int t = sensor.getTemperature();

[mw66]

Capture another try, number going down this time:

CNT	PITCH	ROLL	YAW
1040	0.268	2.047	0.001
1041	0.268	2.047	0.001
1042	0.636	2.528	0.001
1043	0.636	2.528	0.001
1044	0.636	2.528	0.001
1045	0.636	2.528	0.001
1046	0.636	2.528	0.001
1047	359.995	3.084	0.001
1048	359.995	3.084	0.001
1049	359.995	3.084	0.001

CNT	PITCH	ROLL	YAW
1050	359.995	3.084	0.001
1051	0.336	2.654	0.001
1052	0.336	2.654	0.001
1053	0.336	2.654	0.001
1054	0.336	2.654	0.001
1055	0.948	2.108	0.000
1056	0.948	2.108	0.000
1057	0.948	2.108	0.000
1058	0.948	2.108	0.000
1059	0.948	2.108	0.000

CNT	PITCH	ROLL	YAW
1060	0.706	2.335	359.999
1061	0.706	2.335	359.999
1062	0.706	2.335	359.999
1063	0.706	2.335	359.999
1064	0.611	2.540	359.998
1065	0.611	2.540	359.998
1066	0.611	2.540	359.998
1067	0.611	2.540	359.998
1068	0.620	2.600	359.998
1059.996
1074	0.306	2.285	359.996
1075	0.306	2.285	359.996
1076	0.722	1.748	359.995
1077	0.722	1.748	359.995
1078	0.722	1.748	359.995
1079	0.722	1.748	359.995

[mw66]

looks like:

setThrottle(false)

fix the drifting problem, now the numbers are stable.

[RobTillaart]

The raw measurements look indeed stable - maybe longer run needed to be sure.

looks like:

setThrottle(false)

fix the drifting problem, now the numbers are stable.

It might be that the default throttle time is too large (10 milliseconds), need to investigate how it would affect the math.

[mw66]

Actually I concluded to quickly, it still drift slowly, but not as steady in one direction as not setting setThrottle(false).

with setThrottle(false), longer output:

CNT	PITCH	ROLL	YAW
15300	358.378	359.556	0.346
15301	358.414	359.785	0.345
15302	358.751	359.422	0.346
15303	358.763	359.415	0.346
15304	358.566	359.638	0.346
15305	358.440	359.743	0.345
15306	358.672	359.528	0.346
15307	358.598	359.509	0.346
15308	358.286	359.817	0.346
15309	358.459	359.618	0.347

CNT	PITCH	ROLL	YAW
15310	358.452	359.706	0.347
15311	358.498	359.341	0.347
15312	358.498	359.636	0.347
15313	358.679	359.504	0.348
15314	358.401	359.779	0.348
15315	358.670	359.529	0.348
15316	358.573	359.623	0.348
15317	358.595	359.394	0.348
15318	358.783	359.413	0.348
15319	358.867	359.310	0.348
...

CNT	PITCH	ROLL	YAW
48170	348.432	357.415	1.723
48171	348.701	357.050	1.723
48172	348.600	357.196	1.723
48173	348.437	357.374	1.723
48174	347.974	357.733	1.722
48175	348.146	357.647	1.722
48176	348.115	357.695	1.722
48177	348.110	357.199	1.722
48178	348.486	357.243	1.722
48179	348.973	356.692	1.721

CNT	PITCH	ROLL	YAW
48180	348.947	356.909	1.721
48181	348.215	357.329	1.722
48182	348.255	357.405	1.722
48183	348.592	357.262	1.722
48184	348.044	357.813	1.723
48185	347.883	357.908	1.723

PITCH 358.378 => 347.883
ROLL 359.556 => 357.908
YAW 0.346 => 1.723

Is there any caching going on? why the math error accumulate?

[mw66]

Can you run - GY521_test_1.ino for a few minutes? you may change these line to be all float's to get a bit more detail (I'll make an issue to patch the example)

  int ax = sensor.getAccelX();
  int ay = sensor.getAccelY();
  int az = sensor.getAccelZ();
  int gx = sensor.getGyroX();
  int gy = sensor.getGyroY();
  int gz = sensor.getGyroZ();
  int t = sensor.getTemperature();

here is the output with floats:

GY521_LIB_VERSION: 0.5.1
start...

	ACCELEROMETER		GYROSCOPE		TEMPERATURE
	ax	ay	az	gx	gy	gz	T
0	0.06	-0.01	-1.07	-5.73	-1.62	-0.71	17.19
1	0.06	-0.01	-1.06	-5.48	-1.58	-0.50	17.09
2	0.06	-0.00	-1.06	-5.91	-1.53	-0.50	17.09
3	0.06	-0.01	-1.06	-5.76	-1.66	-0.55	17.19
4	0.06	-0.01	-1.06	-5.83	-1.73	-0.66	17.19
5	0.06	-0.01	-1.06	-5.89	-1.61	-0.57	17.24
6	0.06	-0.01	-1.06	-5.76	-1.37	-0.67	17.24
7	0.06	-0.01	-1.07	-5.91	-1.68	-0.45	17.19
8	0.06	-0.01	-1.07	-5.80	-1.34	-0.83	17.19
9	0.06	-0.01	-1.05	-5.59	-1.63	-0.65	17.14

	ACCELEROMETER		GYROSCOPE		TEMPERATURE
	ax	ay	az	gx	gy	gz	T
10	0.06	-0.01	-1.06	-5.77	-1.47	-0.56	17.19
11	0.06	-0.01	-1.07	-5.85	-1.66	-0.60	17.14
12	0.06	-0.01	-1.06	-5.73	-1.53	-0.53	17.14
13	0.06	-0.01	-1.05	-5.88	-1.48	-0.53	17.19
14	0.06	-0.00	-1.06	-5.80	-1.56	-0.73	17.19
15	0.06	-0.01	-1.07	-5.80	-1.68	-0.50	17.09
16	0.06	-0.01	-1.06	-5.82	-1.44	-0.67	17.19
17	0.06	-0.01	-1.06	-5.84	-1.53	-0.27	17.19
18	0.06	-0.02	-1.06	-5.98	-1.65	-0.62	17.19
19	0.07	-0.01	-1.07	-5.69	-1.60	-0.52	17.19

...

	ACCELEROMETER		GYROSCOPE		TEMPERATURE
	ax	ay	az	gx	gy	gz	T
360	0.06	-0.01	-1.06	-5.93	-1.60	-0.46	17.89
361	0.06	-0.01	-1.07	-5.93	-1.54	-0.76	17.94
362	0.06	-0.01	-1.07	-5.86	-1.54	-0.54	17.89
363	0.06	-0.01	-1.06	-6.00	-1.48	-0.72	17.99
364	0.06	-0.01	-1.06	-5.79	-1.44	-0.47	17.99
365	0.06	-0.01	-1.07	-5.80	-1.60	-0.56	17.94
366	0.07	-0.01	-1.07	-5.72	-1.56	-0.61	17.94
367	0.06	-0.01	-1.06	-5.83	-1.82	-0.56	17.94
368	0.06	-0.01	-1.06	-5.81	-1.41	-0.51	17.89
369	0.06	-0.01	-1.06	-5.71	-1.47	-0.46	18.04

	ACCELEROMETER		GYROSCOPE		TEMPERATURE
	ax	ay	az	gx	gy	gz	T
370	0.06	-0.01	-1.06	-5.70	-1.45	-0.57	17.94
371	0.06	-0.01	-1.06	-5.78	-1.73	-0.32	17.94
372	0.06	-0.00	-1.06	-5.84	-1.63	-0.63	17.99
373	0.06	-0.01	-1.08	-5.85	-1.62	-0.40	17.99
374	0.06	-0.01	-1.07	-5.79	-1.63	-0.60	17.99
375	0.06	-0.01	-1.06	-5.63	-1.36	-0.52	17.85
376	0.06	-0.01	-1.07	-5.78	-1.66	-0.82	17.89
377	0.07	-0.01	-1.07	-5.84	-1.84	-0.53	17.89
378	0.06	-0.00	-1.06	-5.54	-1.60	-0.61	17.94
379	0.06	-0.00	-1.06	-5.77	-1.64	-0.50	17.85

	ACCELEROMETER		GYROSCOPE		TEMPERATURE
	ax	ay	az	gx	gy	gz	T
380	0.07	-0.01	-1.06	-5.93	-1.59	-0.73	17.85
381	0.06	-0.01	-1.06	-5.80	-1.52	-0.53	17.94
382	0.05	-0.01	-1.06	-5.66	-1.75	-0.68	17.99

[RobTillaart]

Looks stable to me now, some random noise.

[mw66]

Looks stable to me now, some random noise.

PITCH 358.378 => 347.883

~10 degree, still random noise?

[RobTillaart]

Looks stable to me now, some random noise.

PITCH 358.378 => 347.883

~10 degree, still random noise?

Sorry, my comment was on the Accelerometer gyroscope temperature data from the - GY521_test_1.ino.
I should have been more explicit on that.

I need to investigate why the raw values are stable and the PITCH ROLL YAW are drifting.
Hope to find some time coming days or next week to recreate the issue.

[RobTillaart]

Note:
Combine GY521_test_1.ino with pitch roll yaw demo, ==> put the data in a spreadsheet format.
new demo sketch GY521_debug.ino or so.

[RobTillaart]

@mw66

Created a debug sketch that combines the raw accel + gyro + temp with the derived angle and pitch, roll yaw values.

Can you generate e.g. 10-20 lines ?

//
//    FILE: GY521_test_debug.ino
//  AUTHOR: Rob Tillaart
// PURPOSE: output raw and cooked data from sensor for analyzing.
//     URL: https://github.com/RobTillaart/GY521


#include "GY521.h"

GY521 sensor(0x68);

uint32_t counter = 0;


void setup()
{
  Serial.begin(115200);
  Serial.println();
  Serial.println(__FILE__);
  Serial.print("GY521_LIB_VERSION: ");
  Serial.println(GY521_LIB_VERSION);

  Wire.begin();

  delay(100);
  while (sensor.wakeup() == false)
  {
    Serial.print(millis());
    Serial.println("\tCould not connect to GY521: please check the GY521 address (0x68/0x69)");
    delay(1000);
  }
  sensor.setAccelSensitivity(0);  //  2g
  sensor.setGyroSensitivity(0);   //  250 degrees/s

  sensor.setThrottle();
  Serial.println("start...");

  //  set calibration values from calibration sketch.
  sensor.axe = 0;
  sensor.aye = 0;
  sensor.aze = 0;
  sensor.gxe = 0;
  sensor.gye = 0;
  sensor.gze = 0;

  Serial.println("\n\tACCELEROMETER\t\tGYROSCOPE\t\tTEMP\tPRY\t\t\tANGLE");
  Serial.println("\tax\tay\taz\tgx\tgy\tgz\tT\tPITCH\tROLL\tYAW\tX\tY\tZ");
}


void loop()
{
  sensor.read();
  float ax    = sensor.getAccelX();
  float ay    = sensor.getAccelY();
  float az    = sensor.getAccelZ();
  float gx    = sensor.getGyroX();
  float gy    = sensor.getGyroY();
  float gz    = sensor.getGyroZ();
  float t     = sensor.getTemperature();

  float pitch = sensor.getPitch();
  float roll  = sensor.getRoll();
  float yaw   = sensor.getYaw();

  float x     = sensor.getAngleX();
  float y     = sensor.getAngleY();
  float z     = sensor.getAngleZ();

  Serial.print(counter);
  Serial.print('\t');
  Serial.print(ax, 3);
  Serial.print('\t');
  Serial.print(ay, 3);
  Serial.print('\t');
  Serial.print(az, 3);
  Serial.print('\t');
  Serial.print(gx, 3);
  Serial.print('\t');
  Serial.print(gy, 3);
  Serial.print('\t');
  Serial.print(gz, 3);
  Serial.print('\t');
  Serial.print(t, 3);
  Serial.print('\t');
  Serial.print(pitch, 3);
  Serial.print('\t');
  Serial.print(roll, 3);
  Serial.print('\t');
  Serial.print(yaw, 3);
  Serial.print('\t');
  Serial.print(x, 1);
  Serial.print('\t');
  Serial.print(y, 1);
  Serial.print('\t');
  Serial.print(z, 1);
  Serial.println();

  counter++;
  // delay(1000);
}


//  -- END OF FILE --

[RobTillaart]

Added the above sketch to the version 0.5.2 PR.

[RobTillaart]

@mw66
Did some investigation of the status of the GY521 code and the Pitch Roll Yaw part is not correct and needs a lot of work.
I will make this explicit in the readme file of the 0.5.2 version.
Must find a long timeslot to dive into and redo the math needed.

Sorry for the inconvenience.

[mw66]

Can you generate e.g. 10-20 lines ?

Here you are:

12344	0.080	-0.027	-1.069	-5.824	-1.389	-0.420	16.954	216.632	166.603	298.401	-1.4	-4.3	-85.5
12345	0.083	-0.016	-1.063	-5.794	-1.473	-0.679	17.095	216.602	166.535	298.390	-0.9	-4.5	-85.5
12346	0.083	-0.016	-1.063	-5.794	-1.473	-0.679	17.095	216.602	166.535	298.390	-0.9	-4.5	-85.5
12347	0.090	-0.019	-1.072	-5.702	-1.427	-0.695	17.095	216.567	166.443	298.379	-1.0	-4.8	-85.1
12348	0.078	-0.020	-1.064	-5.847	-1.588	-0.802	17.001	216.577	166.387	298.372	-1.1	-4.2	-85.7
12349	0.078	-0.020	-1.064	-5.847	-1.588	-0.802	17.001	216.577	166.387	298.372	-1.1	-4.2	-85.7
12350	0.080	-0.021	-1.062	-5.756	-1.405	-0.511	17.048	216.551	166.299	298.364	-1.1	-4.3	-85.5
12351	0.080	-0.021	-1.062	-5.756	-1.405	-0.511	17.048	216.551	166.299	298.364	-1.1	-4.3	-85.5
12352	0.085	-0.030	-1.065	-5.779	-1.733	-0.626	17.001	216.515	166.194	298.354	-1.6	-4.5	-85.2
12353	0.087	-0.021	-1.056	-5.893	-1.282	-0.557	17.048	216.497	166.160	298.349	-1.1	-4.7	-85.1
12354	0.081	-0.023	-1.062	-5.901	-1.573	-0.603	16.954	216.498	166.103	298.343	-1.2	-4.3	-85.5
12355	0.081	-0.023	-1.062	-5.901	-1.573	-0.603	16.954	216.498	166.103	298.343	-1.2	-4.3	-85.5
12356	0.081	-0.017	-1.072	-5.649	-1.443	-0.511	17.001	216.477	166.032	298.335	-0.9	-4.3	-85.6
12357	0.081	-0.017	-1.072	-5.649	-1.443	-0.511	17.001	216.477	166.032	298.335	-0.9	-4.3	-85.6
12358	0.088	-0.021	-1.061	-5.840	-1.656	-0.702	16.954	216.436	165.936	298.324	-1.1	-4.7	-85.1
12359	0.088	-0.021	-1.061	-5.840	-1.656	-0.702	16.954	216.436	165.936	298.324	-1.1	-4.7	-85.1
12360	0.077	-0.021	-1.061	-5.939	-1.458	-0.603	16.954	216.438	165.846	298.315	-1.1	-4.1	-85.7
12361	0.077	-0.021	-1.061	-5.939	-1.458	-0.603	16.954	216.438	165.846	298.315	-1.1	-4.1	-85.7
12362	0.080	-0.023	-1.064	-5.802	-1.573	-0.664	16.906	216.408	165.754	298.304	-1.2	-4.3	-85.5
12363	0.080	-0.023	-1.064	-5.802	-1.573	-0.664	16.906	216.408	165.754	298.304	-1.2	-4.3	-85.5
12364	0.088	-0.022	-1.058	-5.863	-1.359	-0.618	17.001	216.370	165.667	298.295	-1.2	-4.7	-85.1
12365	0.088	-0.022	-1.058	-5.863	-1.359	-0.618	17.001	216.370	165.667	298.295	-1.2	-4.7	-85.1
12366	0.081	-0.024	-1.064	-5.924	-1.405	-0.863	16.954	216.362	165.571	298.281	-1.3	-4.4	-85.4
12367	0.081	-0.024	-1.064	-5.924	-1.405	-0.863	16.954	216.362	165.571	298.281	-1.3	-4.4	-85.4
12368	0.079	-0.023	-1.065	-5.962	-1.527	-0.656	17.048	216.344	165.480	298.270	-1.3	-4.2	-85.6
12369	0.081	-0.021	-1.068	-5.855	-1.305	-0.725	16.954	216.329	165.433	298.263	-1.1	-4.3	-85.5
12370	0.081	-0.021	-1.068	-5.855	-1.305	-0.725	16.954	216.329	165.433	298.263	-1.1	-4.3	-85.5
12371	0.085	-0.021	-1.069	-5.863	-1.473	-0.580	16.954	216.298	165.346	298.254	-1.1	-4.5	-85.3
12372	0.085	-0.021	-1.069	-5.863	-1.473	-0.580	16.954	216.298	165.346	298.254	-1.1	-4.5	-85.3
12373	0.078	-0.019	-1.061	-5.786	-1.443	-0.611	17.001	216.290	165.262	298.245	-1.0	-4.2	-85.7
12374	0.080	-0.024	-1.071	-5.832	-1.366	-0.504	17.095	216.276	165.200	298.240	-1.3	-4.3	-85.6
12375	0.080	-0.024	-1.071	-5.832	-1.366	-0.504	17.095	216.276	165.200	298.240	-1.3	-4.3	-85.6
12376	0.084	-0.020	-1.063	-5.832	-1.427	-0.603	16.954	216.243	165.122	298.231	-1.1	-4.5	-85.3
12377	0.081	-0.019	-1.067	-5.977	-1.573	-0.603	17.001	216.236	165.070	298.225	-1.0	-4.4	-85.5
12378	0.081	-0.019	-1.067	-5.977	-1.573	-0.603	17.001	216.236	165.070	298.225	-1.0	-4.4	-85.5
12379	0.073	-0.018	-1.061	-5.908	-1.466	-0.756	17.001	216.231	164.985	298.213	-0.9	-3.9	-86.0
12380	0.073	-0.018	-1.061	-5.908	-1.466	-0.756	17.001	216.231	164.985	298.213	-0.9	-3.9	-86.0
12381	0.085	-0.023	-1.055	-5.840	-1.458	-0.626	17.001	216.183	164.886	298.204	-1.2	-4.6	-85.2
12382	0.085	-0.023	-1.055	-5.840	-1.458	-0.626	17.001	216.183	164.886	298.204	-1.2	-4.6	-85.2
12383	0.084	-0.019	-1.074	-5.969	-1.435	-0.733	17.048	216.167	164.805	298.192	-1.0	-4.5	-85.4
12384	0.084	-0.019	-1.074	-5.969	-1.435	-0.733	17.048	216.167	164.805	298.192	-1.0	-4.5	-85.4
12385	0.080	-0.018	-1.067	-5.954	-1.374	-0.634	17.001	216.152	164.718	298.182	-0.9	-4.3	-85.6
12386	0.080	-0.018	-1.067	-5.954	-1.374	-0.634	17.001	216.152	164.718	298.182	-0.9	-4.3	-85.6

Thanks for looking into this issue.

[mw66]

@RobTillaart Just want to let you know, according to the discussion of the issue in other library, I may have a faulty chip, the data and conversation is here:

ElectronicCats/mpu6050#74

[RobTillaart]

@mw66
Thanks for the table, looking per column the standard deviation is small which indicates the values are stable.
Within the accuracy of the decimals printed I could reconstruct the three angle columns (last three).

For PRY I need more time to dive into the math, expect it will take a lot of time to understand.
(as there are many other issues and work etc to be done).
alas it is on my todo list for 2024.

[RobTillaart]

@RobTillaart Just want to let you know, according to the discussion of the issue in other library, I may have a faulty chip, the data and conversation is here:

ElectronicCats/mpu6050#74

The words of jrowberg is about the math I need to dive into.

To be continued

[mw66]

@RobTillaart Just want to let you know, according to the discussion of the issue in other library, I may have a faulty chip, the data and conversation is here:
ElectronicCats/mpu6050#74

The words of jrowberg is about the math I need to dive into.

To be continued

You may also check this library:

https://github.com/gabriel-milan/TinyMPU6050

where I can get stable ~80 degree reading for 90 degree chip position, so I think there maybe a bug in i2cdevlib (and mpu6050 since it uses the former).

[RobTillaart]

Checking other peoples code is good to do after studying the math, just copying it without understanding is risky.