A lot of people have asked how I got the readings from the Gyro, Accelerometer, and Compass inertial measurement unit(IMU) which is used to keep PiBBOT upright.
UPDATED And updated guide has been published here, with cleaner and simpler code.
In this guide I will explain how to get readings from the IMU and convert these raw readings into usable angles. I will also show how to read some of the information in the datasheets for these devices. The theory and principals below can be applied to any digital IMU, just some minor modifications need to be made. Eg register values, sensitivity level...
The code can be found here;
https://github.com/mwilliams03/Raspberry-Gyro-Acc
A note about Gyros and Accelerometers
When using the IMU to calculate angles, readings from both the gyro and accelerometer are needed, which are then combined. This is because using either on their own will result in inaccurate readings.
Here is why;
Gyros - A gyro measures the rate of rotation, which has to be tracked over time to calculate the current angle. This tracking causes the gyro to drift. However, gyros are good at measuring quick sharp movements.
Accelerometers - Accelerometers are used to sense both static (e.g. gravity) and dynamic (e.g. sudden starts/stops) acceleration. They don’t need to be tracked like a gyro and can measure the current angle at any given time. Accelerometers however are very noisy and are only useful for tracking angles over a long period of time.
Here is an excellent tutorial about accelerometers and gyros;
http://www.instructables.com/id/Accelerometer-Gyro-Tutorial/?ALLSTEPS
Setting up the IMU and I2C
The IMU I use is a MinIMU-9 v2 Gyro, Accelerometer, and Compass which uses a L3GD20 3-axis gyroscope and a LSM303DLHC 3-axis accelerometer and 3-axis magnetometer.
The datasheets are needed if you want to use these devices;
L3GD20 datasheet
LSM303DLHC datasheet
This IMU communicates via the I2C interface.
From the images below, you can see how to connect it to the Raspberry Pi. You can also see the orientation of the X, Y and Z axis.
 |  |  |
Once connected, you need to install the I2C-tools
You will then need to comment out the driver from the blacklist. currently the I2C driver isn't being loaded.
Place a hash '#' in front of blacklist i2c-bcm2708
You now need to edit the modules conf file.
Add these two lines;
i2c-dev
i2c-bcm2708
Now reboot.
Once your Raspberry Pi reboots, you should see the addresses of the components on the IMU when using i2cdetect;
Or port 0 on the older Raspberry Pi
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- 19 -- -- -- -- 1e --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- 6b -- -- -- --
70: -- -- -- -- -- -- -- --
pi@raspberrypi ~ $
The gyro (L3GD2) is using the address of 0x6b, this can also be verified with page 23 on the datasheet.
Quoted from the datasheet with the address highlighted;
"The Slave ADdress (SAD) associated with the L3GD20 is 110101xb. The SDO pin can be used to modify the less significant bit of the device address. If the SDO pin is connected to voltage supply, LSb is ‘1’ (address 1101011b). Otherwise, if the SDO pin is connected to ground, the LSb value is ‘0’ (address 1101010b). This solution allows to connect and address two different gyroscopes to the same I2C bus"
The accelerometer (LSM303DLHC) is using address 0x19, this can be seen on page 20 of the datasheet;
"For linear acceleration the default (factory) 7-bit slave address is 0011001b."
The third address shown above, 0x1e, is used for the magnetometer on the LSM303DLHC, from the datasheet;
"For magnetic sensors the default (factory) 7-bit slave address is 0011110xb."
I will not be covering the magnetometer in this post.
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Reading and Writing to the Accelerometer and Gyro
We read and write values from different register in the above addresses to do different things. Eg Turn the Gyro on, set the sensitivity level, read accelerometer values. etc..
The git repository includes i2c-dev.h, which contains the functions to write and read to the I2C bus.
The git repository also includes the files for the L3GD20 and LSM303DLHC which lists all the registers used by these sensors.
We use ioctl calls to read and write information to the I2C bus.
Open I2C Bus
First, you need to open the I2C bus device file, as follows;
char filename[20];
sprintf(filename, "/dev/i2c-%d", 1);
file = open(filename, O_RDWR);
if (file<0) {
printf("Unable to open I2C bus!");
exit(1);
}
Enable the Accelerometer
// Enable accelerometer. writeAccReg(LSM303_CTRL_REG1_A, 0b01010111); // z,y,x axis enabled , 100Hz data rate writeAccReg(LSM303_CTRL_REG4_A, 0b00101000); // +/- 8G full scale: FS = 10 on DLHC, high resolution output mode
To enable to accelerometer, we need to write a byte to the CTRL_REG1_A(0x20) register on the LSM303. This can be see on page 24 of the datasheet, where you will also find other values that can be used.
After this, we then need to write a byte to the CTRL_REG4_A(0x23) register to set our sensitivity. This information is on page 26 of the datasheet.
Enable the Gyro
Enabling the gyro is very similar to the accelerometer.
// Enable Gyro writeGyrReg(L3G_CTRL_REG1, 0b00001111); // Normal power mode, all axes enabled writeGyrReg(L3G_CTRL_REG4, 0b00110000); // Continuous update, 2000 dps full scale
Reading the Values from the Accelerometer and Gyro
Once you enable the accelerometer and gyro, you can start reading the raw values from these sensors.
Reading the accelerometer
void readACC(int *a)
{
uint8_t block[6];
selectDevice(file,LSM9DS0_ACC_ADDRESS);
readBlock(0x80 | LSM9DS0_OUT_X_L_A, sizeof(block), block);
// Combine readings for each axis.
*a = (int16_t)(block[0] | block[1] << 8);
*(a+1) = (int16_t)(block[2] | block[3] << 8);
*(a+2) = (int16_t)(block[4] | block[5] << 8);
}The above function will read the raw values from the accelerometer, here is a description of what is happening;
- An array of 6 bytes is first created to store the values.
- The I2C slave address is selected for the accelerometer, by passing the accelerometer address of ACC_ADDRESS or 0x19 (0x32 >> 1) to the selectDevice() function.
- Using the readBlock() function from i2c-dev.h, we read 6 bytes starting at LSM303_OUT_X_L_A (0x28). This is shown on page 28 of the datasheet.
- The values are expressed in 2’s complement (MSB for the sign and then 15 bits for the value) so we need to combine;
block[0] & block[1] for X axis
block[2] & block[3] for Y axis
block[4] & block[5] for Z axis
Reading the gyro
void readGYR(int *g)
{
uint8_t block[6];
selectDevice(file,LSM9DS0_GYR_ADDRESS);
readBlock(0x80 | LSM9DS0_OUT_X_L_G, sizeof(block), block);
// Combine readings for each axis.
*g = (int16_t)(block[0] | block[1] << 8);
*(g+1) = (int16_t)(block[2] | block[3] << 8);
*(g+2) = (int16_t)(block[4] | block[5] << 8);
}
The above function reads the values from the gyro. It is very similar to the readACC() function.
Once we have the raw values, we can start converting them into meaningful angle values.
Convert the Raw Values to Usable Angles
Gyro
//Convert Gyro raw to degrees per second rate_gyr_x = (float) *gyr_raw * G_GAIN; rate_gyr_y = (float) *(gyr_raw+1) * G_GAIN; rate_gyr_z = (float) *(gyr_raw+2) * G_GAIN;
For the gyro, we need to work out how fast it is rotating in degrees per second(dps). This is easily done by multiplying the raw value by the sensitivity level that was used when enabling the gyro. G_GAIN = 0.07, which is based off a sensitivity level of 2000 dps. Looking at the table on page 9 of the datasheet, we can see that we need to multiple it by 0.07 to get degrees per second. The table shows it as 70 mdps (milli degrees per second). Another example: Looking at the table, if we chose a sensitivity level of 250dps when enabling the gyro, then we would have to multiply the raw values by 0.00875.
We now need to track this gyro overtime.
//Calculate the angles from the gyro
gyroXangle+=rate_gyr_x*DT;
gyroYangle+=rate_gyr_y*DT;
gyroZangle+=rate_gyr_z*DT; DT = loop period. I use a loop period of 20ms. so DT = 0.02.
gyroXangle = is the current X angle calculated from the gyro X data.
I have DT set to 20ms. This is how long it takes to complete one cycle of the main loop. This loop period has to be constant and accurate, otherwise your gyro will drift more then it should.
Accelerometer
//Convert Accelerometer values to degrees
AccXangle = (float) (atan2(*(acc_raw+1),*(acc_raw+2))+M_PI)*RAD_TO_DEG;
AccYangle = (float) (atan2(*(acc_raw+2),*acc_raw)+M_PI)*RAD_TO_DEG;
The angles can be calculated by using trigonometry and the raw values from the other accelerometer axis. This is done using the Atan2 function to return the principal value of the tangent of the other angles, expressed in radians. We add π to the radians so that we get a result between 0 and 2. We then convert the radians to degrees by multiplying the radians by 57.29578 (180/π).
M_PI = 3.14159265358979323846
RAD_TO_DEG = 57.29578 , 1 radian = 57.29578 degrees
Change rotation value of Accelerometer
//Change the rotation value of the accelerometer to -/+ 180
if (AccXangle > 180)
{
AccXangle -= (float)360.0;
}
if (AccYangle > 180)
AccYangle -= (float)360.0;
The above code will convert the values for the X and Y axis on the accelerometer so that the values is 0 when the IMU is upright. This isn't needed, however I like all axis to be 0 when the device is upright.
Combining Angles from the Accelerometer and Gyro
Once you have the both the angles from both sensors, you will have to combined them to overcome the gyro drift and the accelerometer noise.
We can do this by using a filter which will trust the gyro for short periods of time and the accelerometer for longer periods of time.
There are two filers you could use, the Kalman Filter or the Complementary Filter. I used the Complementary filter as it is simple to understand and less CPU intensive. The Kalman filter is way to far complex and would be very processor intensive.
Complementary filter;
Current angle = 98% x (current angle + gyro rotation rate) + (2% * Accelerometer angle)
or
CFangleX=AA*(CFangleX+rate_gyr_x*DT) +(1 - AA) * AccXangle; CFangleY=AA*(CFangleY+rate_gyr_y*DT) +(1 - AA) * AccYangle;
CFangleX & CFangleY are the final angles to use.
Timing
The gyro tracking will not be accurate if you can not run a well timed loop.
The code includes the mymillis() function for the timing.
At the start of each loop, we get the current time;
startInt = mymillis();
then at the end of the loop, we make sure that at least 20ms has passed before continuing;
//Each loop should be at least 20ms.
while(mymillis() - startInt < 20)
{
usleep(100);
}
If your loop takes longer than 20ms to run, 45ms for example. Jut update the above value to make sure that every loop cycle runs at the same speed and set this value in DT for the gyro tracking.
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Is it possible to write the values to a txt file?
I don’t see why it isn’t possible.
Right at the end of the main loop you would use the values in these variables;
gyroXangle = Gyro X angle
AccXangle = Acce X angle
CFangleX = Filtered X angle, which is the angel to use for your application
gyroYangle = Gyro Y angle
AccYangle = Acce Y angle
CFangleY = Fitlered Y angle, which is the angel to use for your application
he doesn’t say it is not possible, he asks how to do it
This is awesome. Thank you for posting.
Did you try something like this using cheap electronics from dx? (e.g. http://dx.com/p/gy-52-mpu-6050-3-axis-gyroscope-triaxial-accelerometer-6-axis-stance-tilt-module-for-arduino-148654)
Really wonderful. Thanks for documenting the whole work.
Thanks for this tutorial. I would like to add a correction in your guide. You will also need to install libi2c-dev to be able to properly detect all i2c devices normally.
replace the line :
sudo apt-get install i2c-tools
with :
sudo apt-get install i2c-tools libi2c-dev
If libi2c-dev is missing then i2cdetect will return an empty result without any error This can be confusing and you might wonder if you have connected your multiimu correctly.
PS: I am using a altimu board, which is the same device as minimu except with a added altimeter/barometer chip which also gives you altitude readings. That’s useful for my own hobby project.
Cheers!
-Shantanu Bhadoria
thanks Shantanu, I have updated the blog.
This is wonderful posting. Thank you.
I have a question. How do you get DT?
i’m using a STM32 MCU with Keil but I don’t konw how to get DT data.
can you help me, please?
This is something you define. You can see it being defined at the start of the code;
#define DT 0.02 // [s/loop] loop period. 20msHi Mark, Thanks very much for your blog – it’s very valuable and interesting. I’m just about to start working on connecting a Mini-IMU-9 to RPi. Likely use will involve movement at speed and rapid acceleration / deceleration. I assume it’s very important that the IMU is securely mounted to get accurate readings. Any tips on (or pix of) physical mounting and connectivity of the IMU? Thanks!
To try and reduce vibrations from the device mine is attached to, I placed a small piece of foam about 2cm square under the IMU. I than used an elastic band to keep it secure. I’m thinking of removing the elastic band and using a screw. Still keeping the foam in-between the device and the IMU.
Great, thanks – I will play around with that (once the jumper cables arrive)
Colud I rotate raspberry desktop with gyro like tablet ?
My whole project is written in python. I came across the website of Marcin as well (http://mpolaczyk.pl/?p=257). The only thing is that his python code doesn’t include the accelerometer and magentometer. Can anyone help me with code snippets in order to add them to Marcin’s python script as well?
I’m a pretty bad coder and any help is greatly appreciated…
this page may help, it has some python code for the LSM303DLHC ;
http://forums.adafruit.com/viewtopic.php?f=50&t=36212&start=0&hilit=lsm303
Than only thing you would need to worry about is converting the raw data to usable angles:
AccXangle = (float) (atan2(*(acc_raw+1),*(acc_raw+2))+M_PI)*RAD_TO_DEG;
AccYangle = (float) (atan2(*(acc_raw+2),*acc_raw)+M_PI)*RAD_TO_DEG;
So what I did is using Marcin’s Python script in order to get the Gyro data with his script and the following code:
# Fetch angle data from MinIMU-9 V2 L3GD20 sensor
# Calculate angle
angleX = 0
angleY = 0
angleZ = 0
dxyz = s.Get_CalOut_Value()
angleX += dxyz[0]*sleepTime;
angleY += dxyz[1]*sleepTime;
angleZ += dxyz[2]*sleepTime;
Then I added the LSM303DLHC python code that you’ve suggested and the following code in order to get usable angles:
# Fetch Acceleration, Magnetic Gauss, Temperature and Heading from MinIMU-9 V2 LSM303DLHC sensor
acceleration = lsm.readAccelerationsG()
magnetic = lsm.readMagneticsGauss()
temp3 = lsm.readTemperatureCelsius()
heading = lsm.readMagneticHeading()
angleDegX = math.degrees(math.atan2(acceleration.y, acceleration.z))
angleDegY = math.degrees(math.atan2(acceleration.z, acceleration.x))
angleDegZ = math.degrees(math.atan2(acceleration.x, acceleration.y))
# Change the rotation value of the Accelerometer to +/- 180
if (angleDegX > 180):
angleDegX -= 360
if (angleDegY > 180):
angleDegY -= 360
if (angleDegZ > 180):
angleDegZ -= 360
# Complementary filter used to combine the Accelerometer and Gyro values
cfAngleX=0.98*(cfAngleX+angleX)+(1-0.98)*angleDegX
cfAngleY=0.98*(cfAngleY+angleY)+(1-0.98)*angleDegY
cfAngleZ=0.98*(cfAngleZ+angleZ)+(1-0.98)*angleDegZ
*Note: I’ve removed the DT as in my case I’ve multiplied it before already (angleX += dxyz[0]*sleepTime;)
The values look like this:
Gyro-X-Angle: 0.00
Gyro-Y-Angle: 0.00
Gyro-Z-Angle: 0.00
Accel X: 0.000 G
Accel Y: 92.095 G
Accel Z: -90.000 G
Magn X: 0.166 Gauss
Magn Y: -0.901 Gauss
Magn Z: -0.877 Gauss
CF-Angle X: 0.000
CF-Angle Y: 1.842
CF-Angle Z: -1.800
Heading: -79.551
Does that code and the values make sense to you?
Some of your results don’t look right. even if the IMU isn’t moving, you should have values that are not 0.
Its best to start seeing if the raw angles you have are correct. Because if this isn’t correct, then you will never have the final angles correct.
The data below is when my IMU is upright an not moving.
Loop Time 35 gyrXraw -18 gyrXrate -1.260 gyroXangle -0.078
Loop Time 35 gyrXraw -16 gyrXrate -1.120 gyroXangle -0.118
Loop Time 35 gyrXraw -11 gyrXrate -0.770 gyroXangle -0.145
Loop Time 35 gyrXraw -19 gyrXrate -1.330 gyroXangle -0.191
Loop Time 35 gyrXraw -15 gyrXrate -1.050 gyroXangle -0.228
Loop Time 35 gyrXraw -12 gyrXrate -0.840 gyroXangle -0.257
Loop Time 35 gyrXraw -13 gyrXrate -0.910 gyroXangle -0.289
Loop Time 35 gyrXraw -20 gyrXrate -1.400 gyroXangle -0.338
Loop Time 35 gyrXraw -16 gyrXrate -1.120 gyroXangle -0.377
Loop Time 35 gyrXraw -16 gyrXrate -1.120 gyroXangle -0.417
Loop Time 35 gyrXraw -15 gyrXrate -1.050 gyroXangle -0.453
Loop Time 35 gyrXraw -18 gyrXrate -1.260 gyroXangle -0.497
Loop Time 35 gyrXraw -14 gyrXrate -0.980 gyroXangle -0.532
Loop Time 35 gyrXraw -12 gyrXrate -0.840 gyroXangle -0.561
Loop Time 35 gyrXraw -17 gyrXrate -1.190 gyroXangle -0.603
Loop Time 35 gyrXraw -15 gyrXrate -1.050 gyroXangle -0.639
Loop Time 35 gyrXraw -11 gyrXrate -0.770 gyroXangle -0.666
Loop Time 35 gyrXraw -20 gyrXrate -1.400 gyroXangle -0.715
Loop Time 35 gyrXraw -17 gyrXrate -1.190 gyroXangle -0.757
hey mwilliams03,
the reason for the 0-values of the gyro is that at that point in time it already has been calibrated with no movement.
So, I’ll take out the gyro and keep the Accelerometer, Magnetometer and heading.
The raw values look like this (except for the CF and heading values which are not raw of course):
Accel X: 1.160 G
Accel Y: 86.756 G
Accel Z: 70.346 G
Magn X: -0.363 Gauss
Magn Y: -0.644 Gauss
Magn Z: -0.619 Gauss
CF-Angle X: 0.023
CF-Angle Y: 1.735
CF-Angle Z: 1.407
Heading: -119.363
How do I know or how can I check if those values make any sense.
Are there proper values I can check against with, any further measurements, or websites with calculation tools!?
Even without movement, the gyro will drift. My raw log i pasted in is when the IMU is not moving, however the values for gyro and accelerometer are still changing. This is normal.
Can you log the results for about 30 loops and include the gyro raw
Thanks so much for this great post. Just one question:
For the gyro, how do you know that the “register address order is X,Z,Y with high bytes first”?
I wasn’t able to deduce this by looking at the datasheet. In fact, the orders of sensor readings for the gyro seem exactly like the accelerometer (according to both their datasheets).
you are absolutely right. The gyro is the same as the accelerometer.
We worked this out some time ago, I removed the statement from the GIT repository.. but I forgot to update the blog.
BTW: it is the MAG that is xzy.
Hi, your work is very great: Thank you for that!
If i would like to have the acceleration in the three directions of space, did i just want to take *acc_raw, *(acc_raw+1) and *(acc_raw+2) and put them in a file, or not? With these values, it should be easy to have the speed and the position of my device, isn’t it?
Thank you
Yes and no. 🙂
You can measure the acceleration in Gs. Which you then can use to calculate distance and direction over time. However, you will notice drift and the drift gets worse,to the point that it is not useful anymore. This is due to the noise of the accelerometer.
If you are still interested, google “accelerometer double integration”
Here is my gyro raw data (somehow I was not able to reply to your last comment):
Calibrating axis X, please do not move sensor…
Done: (min=-334;mean=-319.85;max=-304)
Calibrating axis Y, please do not move sensor…
Done: (min=74;mean=94.25;max=112)
Calibrating axis Z, please do not move sensor…
Done: (min=-511;mean=-320.35;max=21)
(-15.149999999999977, 0, 0)
(-16.149999999999977, 30.75, 0)
(16.850000000000023, 0, 0)
(30.850000000000023, 0, 0)
(16.850000000000023, 0, 0)
(23.850000000000023, 0, 0)
(-16.149999999999977, 24.75, 0)
(-23.149999999999977, 0, 0)
(24.850000000000023, 0, 0)
(16.850000000000023, -25.25, 0)
(20.850000000000023, 0, 0)
(24.850000000000023, 0, 0)
(0, 0, 345.35000000000002)
where it is (x, y, z)
Mmmm.. the values don’t look right…are they the raw values?. The results should be a whole number, not a decimal.
The raw values from the gyro are read as 2’s complement
Yea, I thought the same thing… I modified the code a bit (using https://github.com/mpolaczyk/Gyro-L3GD20-Python/blob/master/Example_ReadRawData.py) so that it displays not only the z but x and y axis as well.
Here is the modified part:
s.CalibrateX()
s.CalibrateY()
s.CalibrateZ()
plotEnabled = False
if plotEnabled:
plt.subplot(111)
# Read values loop
starttime = time.time() # this is our start time
t = 0
prev_x = 0
prev_y = 0
prev_z = 0
tmax = 10
T = []
X = []
Y = []
Z = []
while t < tmax:
while s.Get_AxisDataAvailable_Value()[2] == 0:
time.sleep(0.001)
t = time.time() – starttime
x = s.Get_CalOutX_Value()
y = s.Get_CalOutY_Value()
z = s.Get_CalOutZ_Value()
T.append(t)
X.append(x)
Y.append(y)
Z.append(z)
print(x, y, z);
if plotEnabled:
plt.plot(T, X, 'ro')
plt.plot(T, Y, 'ro')
plt.plot(T, Z, 'ro')
plt.show()
I had a look through that code.
The actual values are not raw, as the values being printed to the screen are after the GAIN has been applied.
And I think the wrong gain is being applied.
I dont use python often, however I have updated the code in two files;
Example_ReadRawData.py http://pastebin.com/6fzZv3AS
and
L3GD20.py, I only made a change to Get_RawOutX_Value(), I hard coded the correct GAIN value. http://pastebin.com/1tf16bqW
Wow, thank you SO much for your help!
Using your code, the result looks like this:
Calibrating axis X, please do not move sensor…
Done: (min=-5.53;mean=-5.159875;max=-4.83)
Initiating…
Gain set to:0.00875
Gyro X Raw 0 Gyro X Turn Rate = 0.000000 Gyro X Angle 9.900000
loopTime 0.020137 Gyro X Raw 0 Gyro X Turn Rate = 0.000000 Gyro X Angle 9.943295
loopTime 0.020088 Gyro X Raw 0 Gyro X Turn Rate = 0.000000 Gyro X Angle 9.943295
loopTime 0.020129 Gyro X Raw 0 Gyro X Turn Rate = 0.000000 Gyro X Angle 9.943295
loopTime 0.020107 Gyro X Raw 0 Gyro X Turn Rate = 0.000000 Gyro X Angle 9.943295
loopTime 0.020104 Gyro X Raw 0 Gyro X Turn Rate = 0.000000 Gyro X Angle 9.943295
loopTime 0.020037 Gyro X Raw 0 Gyro X Turn Rate = -0.008452 Gyro X Angle 9.942490
Gyro X Raw is always “0”, Gyro X Turn Rate ist mostly “0” but gets the value “0.007647” and “-0.008452” during the whole run.
That still doesn’t look right.. Raw can sometimes be 0.. but not all the time, the noise should cause it to show other values.
I made some more changes to a number of files and uploaded to my site. You can get the new files like this;
wget http://www.ozzmaker.com/downloads/Gyro-L3GD20-Python-update.tar
Untar them and run Example_ReadRaw.
This is what my output looks like when the IMU is not moving;
loopTime 0.020520 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.017640
loopTime 0.020132 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.017640
loopTime 0.020053 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.017640
loopTime 0.020068 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.017640
loopTime 0.020074 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.017640
loopTime 0.020028 raw 00006 @@@GAIN@@@ 0.00875 xrate 0.483000 Xangle = 0.002940
loopTime 0.020059 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.002940
loopTime 0.020017 raw 00006 @@@GAIN@@@ 0.00875 xrate 0.483000 Xangle = 0.012600
loopTime 0.020027 raw 00007 @@@GAIN@@@ 0.00875 xrate 0.553000 Xangle = 0.023660
loopTime 0.020123 raw -0009 @@@GAIN@@@ 0.00875 xrate -0.637000 Xangle = 0.010920
loopTime 0.020036 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.010920
loopTime 0.020024 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.010920
And this is when I rotate it 180 degrees;
loopTime 0.020084 raw -0225 @@@GAIN@@@ 0.00875 xrate -15.816500 Xangle = 3.250660
loopTime 0.020027 raw -0590 @@@GAIN@@@ 0.00875 xrate -41.366500 Xangle = 2.423330
loopTime 0.020075 raw -4575 @@@GAIN@@@ 0.00875 xrate -320.316500 Xangle = -145.672520
loopTime 0.020071 raw -4105 @@@GAIN@@@ 0.00875 xrate -287.416500 Xangle = -151.420850
loopTime 0.020083 raw -1904 @@@GAIN@@@ 0.00875 xrate -133.346500 Xangle = -154.087780
loopTime 0.020039 raw -1489 @@@GAIN@@@ 0.00875 xrate -104.296500 Xangle = -156.173710
loopTime 0.020108 raw -1297 @@@GAIN@@@ 0.00875 xrate -90.856500 Xangle = -157.990840
loopTime 0.020017 raw -1771 @@@GAIN@@@ 0.00875 xrate -124.036500 Xangle = -172.494420
loopTime 0.020124 raw -1690 @@@GAIN@@@ 0.00875 xrate -118.366500 Xangle = -174.861750
loopTime 0.020024 raw -1245 @@@GAIN@@@ 0.00875 xrate -87.216500 Xangle = -176.606080
loopTime 0.020041 raw -0365 @@@GAIN@@@ 0.00875 xrate -25.616500 Xangle = -177.118410
Brilliant!
This is my output when IMU is not moving at all:
loopTime 0.020092 raw 00003 @@@GAIN@@@ 0.00875 xrate 0.262500 Xangle = 0.136150
loopTime 0.020135 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.136150
loopTime 0.020144 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.157150
loopTime 0.020038 raw 00003 @@@GAIN@@@ 0.00875 xrate 0.262500 Xangle = 0.162400
loopTime 0.020033 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
loopTime 0.020098 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
loopTime 0.020121 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
loopTime 0.020113 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
loopTime 0.020108 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
loopTime 0.020087 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
loopTime 0.020035 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.162400
raw is mostly “0” but changes to “0003” inbetween.
xrate is mostly 0.00000 but changes to “0.262500” inbetween.
looks much better now i guess.
This is what I get when I move the IMU 180 degrees:
loopTime 0.020037 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.000000
loopTime 0.020067 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = 0.000000
loopTime 0.020051 raw -0016 @@@GAIN@@@ 0.00875 xrate -1.141000 Xangle = -0.467040
loopTime 0.020034 raw -0013 @@@GAIN@@@ 0.00875 xrate -0.931000 Xangle = -0.485660
loopTime 0.020053 raw -0013 @@@GAIN@@@ 0.00875 xrate -0.931000 Xangle = -0.504280
loopTime 0.020019 raw -0016 @@@GAIN@@@ 0.00875 xrate -1.141000 Xangle = -0.527100
loopTime 0.020027 raw -0020 @@@GAIN@@@ 0.00875 xrate -1.421000 Xangle = -0.555520
loopTime 0.020054 raw -0032 @@@GAIN@@@ 0.00875 xrate -2.261000 Xangle = -1.220800
loopTime 0.020076 raw 00006 @@@GAIN@@@ 0.00875 xrate 0.469000 Xangle = -2.313080
loopTime 0.020106 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = -2.313080
loopTime 0.020063 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = -2.313080
loopTime 0.020094 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = -2.313080
loopTime 0.020109 raw 00006 @@@GAIN@@@ 0.00875 xrate 0.469000 Xangle = -2.303700
loopTime 0.020116 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = -2.303700
Hi Mark,
any news on my last results?
It might be easier to do a Skype session (or something similar) in order to finally get the IMU working.
Would that be possible? I can’t find any properly working solution on Python basis including the gyro, accelerometer and magenetometer on the whole www.
those last results look good. What does it look like when you turn the IMU 90 degrees along the X-asis?
Please have a look of the second part of those values, beginning with: “This is what I get when I move the IMU 180 degrees:”
sorry… I missed that.
It doesn’t look correct.
Can you tar up all the source, send it to me and I’ll see if it works with my IMU.
mark<@>ozzmaker.com
did you receive my files?
yes I did. I replied the same day, but it must not have gone through.
I downloaded your code… uncompressed it and ran it without changing anything. And it works.
Maybe there is something wrong with your IMU?
Are you rotating it at all along the X?
what IMU do you have?
This is me rotating it 180 degrees;
loopTime 0.020065 raw -0139 @@@GAIN@@@ 0.00875 xrate -9.789500 Xangle = -0.393540
loopTime 0.020126 raw -0223 @@@GAIN@@@ 0.00875 xrate -15.669500 Xangle = -0.706930
loopTime 0.020081 raw -0665 @@@GAIN@@@ 0.00875 xrate -46.609500 Xangle = -1.639120
loopTime 0.020132 raw -1152 @@@GAIN@@@ 0.00875 xrate -80.699500 Xangle = -3.253110
loopTime 0.020096 raw -2035 @@@GAIN@@@ 0.00875 xrate -142.509500 Xangle = -6.103300
loopTime 0.020115 raw -3571 @@@GAIN@@@ 0.00875 xrate -250.029500 Xangle = -11.103890
loopTime 0.020051 raw -6191 @@@GAIN@@@ 0.00875 xrate -433.429500 Xangle = -19.772480
loopTime 0.020075 raw -8905 @@@GAIN@@@ 0.00875 xrate -623.409500 Xangle = -32.240670
loopTime 0.020046 raw -12687 @@@GAIN@@@ 0.00875 xrate -888.149500 Xangle = -50.003660
loopTime 0.020111 raw -6898 @@@GAIN@@@ 0.00875 xrate -482.919500 Xangle = -59.662050
loopTime 0.020061 raw -3447 @@@GAIN@@@ 0.00875 xrate -241.349500 Xangle = -64.489040
loopTime 0.020035 raw -2668 @@@GAIN@@@ 0.00875 xrate -186.819500 Xangle = -68.225430
loopTime 0.020068 raw -2813 @@@GAIN@@@ 0.00875 xrate -196.969500 Xangle = -72.164820
loopTime 0.020032 raw -2738 @@@GAIN@@@ 0.00875 xrate -191.719500 Xangle = -75.999210
loopTime 0.020037 raw -3229 @@@GAIN@@@ 0.00875 xrate -226.089500 Xangle = -80.521000
loopTime 0.020121 raw -3053 @@@GAIN@@@ 0.00875 xrate -213.769500 Xangle = -84.796390
loopTime 0.020195 raw -1975 @@@GAIN@@@ 0.00875 xrate -138.309500 Xangle = -87.562580
loopTime 0.020119 raw -1373 @@@GAIN@@@ 0.00875 xrate -96.169500 Xangle = -89.485970
loopTime 0.020135 raw -1109 @@@GAIN@@@ 0.00875 xrate -77.689500 Xangle = -91.039760
loopTime 0.020187 raw 01157 @@@GAIN@@@ 0.00875 xrate 81.000500 Xangle = -89.419750
loopTime 0.020131 raw -6097 @@@GAIN@@@ 0.00875 xrate -426.849500 Xangle = -97.956740
loopTime 0.020018 raw -10283 @@@GAIN@@@ 0.00875 xrate -719.869500 Xangle = -112.354130
loopTime 0.020059 raw -12267 @@@GAIN@@@ 0.00875 xrate -858.749500 Xangle = -129.529120
loopTime 0.020116 raw -11152 @@@GAIN@@@ 0.00875 xrate -780.699500 Xangle = -145.143110
loopTime 0.020110 raw -9977 @@@GAIN@@@ 0.00875 xrate -698.449500 Xangle = -159.112100
loopTime 0.020123 raw -3595 @@@GAIN@@@ 0.00875 xrate -251.709500 Xangle = -164.146290
loopTime 0.020082 raw -1933 @@@GAIN@@@ 0.00875 xrate -135.369500 Xangle = -166.853680
loopTime 0.020390 raw -0856 @@@GAIN@@@ 0.00875 xrate -59.979500 Xangle = -168.053270
loopTime 0.020095 raw -0296 @@@GAIN@@@ 0.00875 xrate -20.779500 Xangle = -168.468860
loopTime 0.020087 raw -0058 @@@GAIN@@@ 0.00875 xrate -4.119500 Xangle = -168.551250
loopTime 0.020115 raw -0102 @@@GAIN@@@ 0.00875 xrate -7.199500 Xangle = -168.695240
loopTime 0.020111 raw -0269 @@@GAIN@@@ 0.00875 xrate -18.889500 Xangle = -169.073030
loopTime 0.020026 raw -0170 @@@GAIN@@@ 0.00875 xrate -11.959500 Xangle = -169.312220
loopTime 0.020102 raw -0065 @@@GAIN@@@ 0.00875 xrate -4.609500 Xangle = -169.404410
loopTime 0.020305 raw -0017 @@@GAIN@@@ 0.00875 xrate -1.249500 Xangle = -169.429400
loopTime 0.020159 raw -0024 @@@GAIN@@@ 0.00875 xrate -1.739500 Xangle = -169.464190
loopTime 0.020058 raw -0057 @@@GAIN@@@ 0.00875 xrate -4.049500 Xangle = -169.545180
loopTime 0.020094 raw -0043 @@@GAIN@@@ 0.00875 xrate -3.069500 Xangle = -169.606570
loopTime 0.020126 raw -0022 @@@GAIN@@@ 0.00875 xrate -1.599500 Xangle = -169.638560
loopTime 0.020101 raw -0010 @@@GAIN@@@ 0.00875 xrate -0.759500 Xangle = -169.653750
loopTime 0.020097 raw -0009 @@@GAIN@@@ 0.00875 xrate -0.689500 Xangle = -169.667540
loopTime 0.020080 raw -0011 @@@GAIN@@@ 0.00875 xrate -0.829500 Xangle = -169.684130
loopTime 0.020088 raw -0015 @@@GAIN@@@ 0.00875 xrate -1.109500 Xangle = -169.706320
loopTime 0.020104 raw -0029 @@@GAIN@@@ 0.00875 xrate -2.089500 Xangle = -169.748110
loopTime 0.020037 raw -0020 @@@GAIN@@@ 0.00875 xrate -1.459500 Xangle = -169.777300
loopTime 0.020086 raw -0011 @@@GAIN@@@ 0.00875 xrate -0.829500 Xangle = -169.793890
loopTime 0.020066 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = -169.793890
loopTime 0.020085 raw -0010 @@@GAIN@@@ 0.00875 xrate -0.759500 Xangle = -169.809080
loopTime 0.020030 raw -0009 @@@GAIN@@@ 0.00875 xrate -0.689500 Xangle = -169.822870
loopTime 0.020120 raw -0010 @@@GAIN@@@ 0.00875 xrate -0.759500 Xangle = -169.838060
loopTime 0.020063 raw 00000 @@@GAIN@@@ 0.00875 xrate 0.000000 Xangle = -169.838060
loopTime 0.020014 raw -0010 @@@GAIN@@@ 0.00875 xrate -0.759500 Xangle = -169.853250
loopTime 0.020076 raw -0009 @@@GAIN@@@ 0.00875 xrate -0.689500 Xangle = -169.867040
loopTime 0.020025 raw -0011 @@@GAIN@@@ 0.00875 ^Cxrate -0.829500 Xangle = -169.883630
I’m using the MinIMU-9 V2 (http://www.pololu.com/product/1268 using the L3GD20 and LSM303DLHC) on a breadboard which is connected via a flatcable to my RasPi and the RasPi is connected with the ethernet and power cables. Using the cables, it’s a bit hard to do a proper 180° turn. So that might be the issue.
Ok the code outputs the values for the Gyro now, adding the accelerometer and magnetometer would be an amazing benefit and my project would finally reach the finishing line, thanks to you mark!
Would it be possible to add those values as well?
Thank you for this post !
The code works as well with “FLORA Accelerometer/Compass Sensor – LSM303″
3 lines to put in comments since there is no gyro :
main.c line 114 : // readGYR(Pgyr_raw);
sensor.c line 130 : // writeGyrReg(L3G_CTRL_REG1, 0b00001111);
sensor.c line 131 : // writeGyrReg(L3G_CTRL_REG4, 0b00110000);
And replace :
main.c line 149 by : printf (” AccXangle \e[m %7.3f \t AccYangle %7.3f \n”,AccXangle,AccYangle);
Now I can play!
i need to interface the raspberry pi with accelerometer…. i need coding to interface that. can you help me… my mail id is hsjabbal19@yahoo.com
what type of accelerometer?
I am working at Self balancing robot.Can u give me the code of this robot..?
my email id is kpalizai08@gmail.com
Also please tell me the setting of accelerometer sensitivity in c laguange code?
pleasee…………………..
Have a look here,
https://ozzmaker.com/2013/08/12/pibbot-v2-balancing-robot-using-a-raspberry-pi/
There is a link to the code on the above page
Hello I am new to the raspberry pi and I am looking forward to building my Pibbot. I purchased all the parts needed to construct it along with the LCD 20×2 + extras. I am having a hard time understanding the pins configuration for all the components to the raspberry pi. I see in the Pibbot V2 master there is a read me for the pins, but I am having a hard time understanding it. Could you please put it in dummy form so that In may get my Pibbot balancing. Thank you.
I would try and get the IMU going first.
The instructions for this are on the web page.
Hello just a little confused about a couple of things. (Actually 5)
1. Is LCD_E connected to GPIO 0(SDA) along with the IMU?
2. Encoder pin 2 says it is going to GPIO 1 which is 3V3. Is that right? And if thats true are you using one or two encoders?
3. Are Wheel gain , and LCD_7 both grouped together on GPIO pin 5.
4. Is LCD_ Green going to GPIO pin 2 witch is 5 volts ?
5. And am I grounding backlights Red, Green, and Blue?
Thank you for you help. If you could please explain in detail. I would appreciate it.
I see your issue. You are GPIO pin numbers.. when you should be using WiringPi pin numbers.
http://wiringpi.com/pins/
1. These are WiringPi pin numbers. WiringPi = 0, BCM = 17, GPIO = 0
2. Using WiringPi numbers, pin 1 is GPIO1 (BCM18).
3. That WHEELGAIN is commented out.. so it isnt being used. You can delete it. WiringPi pin number 5 (BCM24).
4. Again, WiringPi pin numbers
5. Only ground the colour you want to use for the back light.
Thank you so very much for the quick reeply.
Hey there, love the code. It’s worked best out of all the options I’ve come across in my search!
I’m trying to now adapt the imu data for use in an AUV…but for some reason whatever changes I make to the main.c file don’t come into effect when I run
sudo ./main
Could someone please point me in the direction of a python tute which could explain what i’m doing wrong – i don’t doubt it’s elementary…but that’s where I’m stuck!
Regards and thanks,
Jim
Hi Jim
I’m not aware of any python tutorials, but I do know there is some Python code out there on the Net for the Adafruit IMU. I just had a look but I couldn’t find it, sorry.
Are you recompiling after you make the changes?
BTW: This may interest you, I will soon post eanentry on how to use the magnetometer and accelerometer as a tilt compensated compass.
Hi Mark, thanks alot for the tutorial, but something’s not working here…
I’ve already debugged the code and it seems that things are going wrong, as soon as I call “writeGyrReg(L3G_CTRL_REG1, 0b00001111)”, here
i2c_smbus_access, in the return statement “ioctl(file,I2C_SMBUS,&args);”
is it because of the I2C_SMBUS?
I have a similar IMU, the ALTIMU, the devices aren’t the same, except the gyro, that’s the only thing that I’m trying to teste.
Thanks,
Tiago
Does the i2c address in the code match up with the i2c addresses used by your sensors?
It looks like you’ve invented the protester’s 3rd arm. If anything, that thing could march around and fly a sign.
Thanks a bunch for the code. By the way this is useful on any Linux board with i2c bus, not just RasPi. For example, works on Minnowboard MAX and would also for beaglebone….
Do you have something similar for Arduino???
I haven’t sorry.
The math and IMU registers would be the same, the code would just have to be ported over to Arduino
First, let me thank you very much for the hardware product, and also the python files. Everything worked for me!
The inclinometer functions perfectly when rotated about the x and y axis. So giving the x and y angles you use in the example showing the inclination of the car.
I had hoped to use the device to also allow me to determine the rotation of the device. ie keeping the device flat and level, and rotating it to measure the direction. For such a orientation CF angle X and Y remain constant.
I assume I need to compute a different set of angles, but cannot see which combination to use. I set up the equivalent of CF Angle Z, but that too stays constant. (which at least i did expect!).
Would you have any suggestions?
To measure rotation around the Z axis , you will need to use the gyro Z axis and the Compass (Magnetometer) heading axis. First try with just the compass heading, this may be good enough.
Here, the heading is calculated using python;
https://github.com/mwilliams03/BerryIMU/tree/master/python-LSM9DS0-gryo-accel-compass
Here it is calculated using C;
https://github.com/mwilliams03/BerryIMU/tree/master/compass_tutorial01_basics
And with tilt compensation;
https://github.com/mwilliams03/BerryIMU/tree/master/compass_tutorial02_tilt_compensation
BTW: you can not use the accelerometer to measure rotation around the Z axis as the accelerometer measures gravity, gravity doesn’t change when it is being rotated on this axis.
Thank you for your prompt reply. I suspected that it was not possible.
I did make use of your python program and used the heading. And of course I found that the motors in the machine were distorting the magnetic field, so although the heading did change as the unit rotated, it was not in correct relation!
I will now investigate how to mount the IMU where it is less impacted by the motors fields. Or even try to screen the motors a bit.
Regards
For the compass, you could try calibration for hard iron distortion.. But to be honest, I not sure what the magnet field of a spinning motor would look like.
If you want to have a look at some information on compass calibration;
https://ozzmaker.com/2015/01/23/compass3/nice tutorial,but im so confused to run that main.c?
how to run your program,im first time use program c in raspberry
like python to run like “python ./(name file).py
how to program c?
thanks alot dude
Very good tutorial, man! Congratulations!
I’m using the Pololu MinIMU-9 v3, every time I try to run the program I always get the message “Failed to write byte to I2C Acc.” I’ve tried many things but without success. How can I fix it and make the program run?
Thanks!!!!
make sure you can see the IMU… what is the output of
sudo /usr/sbin/i2cdetect -y 1I have a Pololu MinIMU-9 v2
i also get this message
Failed to write byte to I2C Acc.
i2cdetect -y 1 works for me and i see this..
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: — — — — — — — — — — — — —
10: — — — — — — — — — 19 — UU — — 1e —
20: — — — — — — — — — — — — — — — —
30: — — — — — — — — — — — UU — — — —
40: — — — — — — — — — — — — — — — —
50: — — — — — — — — — — — — — — — —
60: — — — — — — — — — — — 6b — — — —
Any ideas what is wrong?
Thanks
Did you run the program with ‘sudo’?
yes i ran the program with sudo
Still says
Failed to write byte to I2C Acc
I’ve also tried alot of things to try get it to work but no success:(
is it possible the new use of device trees in the linux kernel breaks this code?
i2c_smbus_write_byte_data
is the function it is failing on, it always returns -1, no idea why, as i cant seem to find what the -1 means.
debugged it a little bit further,
the low level call ioctl(file,I2C_SMBUS,&args);
with last strerror(errno)) shows 0x03: Input/output error.
This confuses me even though sudo i2cdetect -y 1 works.
Shoot me now and put me out of my misery lol
any ideas on this?
Me and Wesley both get the same error message
Failed to write byte to I2C Acc.
Have you tried on a fresh install?
We have a Pololu MinIMU-9 v2 and I was able to test successfully.
pi@raspberrypi ~/Raspberry-Gyro-Acc $ i2cdetect -y 10 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- 19 -- -- -- -- 1e --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- 6b -- -- -- --
70: -- -- -- -- -- -- -- --
This is what I did, using a B+;
1.Burn 2015-05-05-raspbian-wheezy.img to SD card
2.
sudo raspi-config(expended file system only)3.Follow these instructions to enable i2c https://ozzmaker.com/i2c/
4.
git clone https://github.com/mwilliams03/Raspberry-Gyro-Acc5.
cd Raspberry-Gyro-Acc6.
gcc -o main -l rt main.c -lm7.
sudo ./mainLoop Time 20 GyroX -2.244 AccXangle -66.218 CFangleX -37.661 GyroY 1.058 AccYangle 166.218 CFangleY 91.262
Loop Time 20 GyroX -2.306 AccXangle -66.038 CFangleX -38.289 GyroY 1.121 AccYangle 166.281 CFangleY 92.824
Loop Time 20 GyroX -2.348 AccXangle -65.813 CFangleX -38.881 GyroY 1.182 AccYangle 165.900 CFangleY 94.344
Loop Time 20 GyroX -2.411 AccXangle -66.125 CFangleX -39.487 GyroY 1.218 AccYangle 165.710 CFangleY 95.807
Loop Time 20 GyroX -2.471 AccXangle -65.376 CFangleX -40.064 GyroY 1.242 AccYangle 165.456 CFangleY 97.223
Loop Time 20 GyroX -2.513 AccXangle -65.908 CFangleX -40.622 GyroY 1.256 AccYangle 165.256 CFangleY 98.598
Hi thanks for the reply.
I just tried with a fresh install, followed the instructions you gave to the letter but it fails like before.
I have a raspberry pi model B.
I get the same results.
i2cdetect -y 1, i can see the 3 addresses.
But
when run sudo ./main, i get the following
Failed to write byte to I2C Acc
Mark
I am running RPi 2 with minimu9 v3
I get the same “Failed to write byte to I2C ACC” error as Wesley and rhubarb.
On this same RPi I am running David Graysons code who has a link to your site.
It’s running kernel 3.19.2
I have a kernel 4.0.5 that won’t load his code, so I thought I would give your code a try and
that’s where the above error started showing up.
I know I saw some people having i2c failings on 3.18.
Curious to what kernel you,Wesley and rhubard run?
uname -r should tell.
I am going to run an older RPi to see if I can attain some success with your code.
It looks easier to implement. If I have success I will reply.
I just did another test on a clean image and it worked for both 3.18 kernel and 4.0.6 kernel
1.Burn 2015-05-05-raspbian-wheezy.img to SD card
2.sudo raspi-config (expended file system only)
3.Follow these instructions to enable i2c https://ozzmaker.com/i2c/
4.git clone https://github.com/mwilliams03/Raspberry-Gyro-Acc
5. cd Raspberry-Gyro-Acc
6. gcc -o main -l rt main.c -lm
7. sudo ./main WORKS
8. uname -a = 3.18.11+
9.rpi-update, reboot
10.uname -a = 4.0.6+
11.gcc -o main -l rt main.c -lm
12. sudo ./main WORKS
I will look into raspi-config as I did go into advanced settings to turn i2c on.
Under expanded file system stated there was no /dev/root.
Are you running default settings on boot up?
I am sure it is my set up that is at fault.
I am running a special kernel that has modified DVB drivers, which I want GPIO to work
on.
Thank you for your extra effort.
I did turn on i2c in raspi-config…but it still seam to not work. So I then did everything on this page; https://ozzmaker.com/i2c/
Other then that, nothing was changed from a vanilla install.
I tested with minimu9 v2… you may need to update the i2c addresses in the code to support the minimu9 v3.
Thanks Mark,
I will look into that.
Thats 3 people with the error “Failed to write byte to I2C ACC”.
Me, Wesley and andyinyakima.
uname -r
gives me 3.18.11+
I am using a raspberry pi model B and followed the instructions as stated by mark
1.Burn 2015-05-05-raspbian-wheezy.img to SD card
2.sudo raspi-config (expended file system only)
3.Follow these instructions to enable i2c https://ozzmaker.com/i2c/
4.git clone https://github.com/mwilliams03/Raspberry-Gyro-Acc
5. cd Raspberry-Gyro-Acc
6. gcc -o main -l rt main.c -lm
7. sudo ./main
It maybe works for mark (the author) because he is using a model B+ and not B. There are lots more IO pins on the B+.
Did you have any success andyinyakima??
I have not pursued it, but will try this weekend on an old ‘RPi b’. Most of my time is being spent on the newer RPi2b and custom built kernels; these kernels are not concerned with i2c except that the i2c bus is used to communicate with drivers. I want to use the minimu9 in an az-el mover and I think the older RPis will do the job for me.
so what works for u andyinyakima?
hey If i have angle X and angle Y in gyroscope but if i want to find the third angel in it so how it is possible or which calculation should i do ? please help me.. and try to reply me as soon as possible.. thanks you very much..
The code above already shows the output of Z from the gyro;
rate_gyr_z = (float) *(gyr_raw+2) * G_GAIN;Thanks a lott Mark Williams. Thank you very much for your great support.
you said in paragraph of ‘Timing’ loops must be run in function of mymillis().
please tel me what did u mean by ‘loops’ ??? you are talking about which ‘loops’??
The main while loop.
The looptime needs to be constant and it needs to match the value in DT
Giving error “permission denied” while editing “raspi-blacklist.conf” pl reply fast…
Did you use “sudo”?
Mark Williams – wow, what a thread! Congrats on your program! We’re looking for something similar for our GY-85 9DOF IMU, connected to a Raspi B. We’re able to get
root@Primerpi:/dev/input# i2cdetect -y 0
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: — — — — — — — — — — — — —
10: — — — — — — — — — — — — — — 1e —
20: — — — — — — — — — — — — — — — —
30: — — — — — — — — — — — — — — — —
40: — — — — — — — — — — — — — — — —
50: — — — 53 — — — — — — — — — — — —
60: — — — — — — — — 68 — — — — — — —
70: — — — — — — — —
and by using this program, we can get bearing…
#!/usr/bin/python
import smbus
import time
import math
bus = smbus.SMBus(0)
address = 0x1e
def read_byte(adr):
return bus.read_byte_data(address, adr)
def read_word(adr):
high = bus.read_byte_data(address, adr)
low = bus.read_byte_data(address, adr+1)
val = (high <= 0x8000):
return -((65535 – val) + 1)
else:
return val
def write_byte(adr, value):
bus.write_byte_data(address, adr, value)
write_byte(0, 0b01110000) # Set to 8 samples @ 15Hz
write_byte(1, 0b00100000) # 1.3 gain LSb / Gauss 1090 (default)
write_byte(2, 0b00000000) # Continuous sampling
scale = 0.92
x_out = read_word_2c(3) * scale
y_out = read_word_2c(7) * scale
z_out = read_word_2c(5) * scale
bearing = math.atan2(y_out, x_out)
if (bearing Can any of your program be adapted to work with this particular IMU? i’m not even a programmer and will be trying to fit these subroutines into Jay Dosher’s python program he wrote for solar tracking. We’re trying to get one-axis tracking (instead of using the LEDs board) for our solar hot water heater proyect.
i hope i’ve got the question correct – lol.
Have a great day and again – congrats! 🙂
I am not familiar with that IMU or your code.
The code has errors and the maths isnt correct.
I did try and improve it, I also commented out the scale. The problem with this code is that it does not include tilt compensation.
You can see our full python code here;https://github.com/mwilliams03/BerryIMU/blob/master/python-LSM9DS0-gryo-accel-compass/berryIMU.py
#!/usr/bin/python
import smbus
import time
import math
bus = smbus.SMBus(0)
address = 0x1e
def read_byte(adr):
return bus.read_byte_data(address, adr)
def read_word_2c(adr):
high = bus.read_byte_data(address, adr)
low = bus.read_byte_data(address, adr+1)
mag_combined = (low | high <<8) return mag_combined if mag_combined < 32768 else mag_combined - 65536 def write_byte(adr, value): bus.write_byte_data(address, adr, value) write_byte(0, 0b01110000) # Set to 8 samples @ 15Hz write_byte(1, 0b00100000) # 1.3 gain LSb / Gauss 1090 (default) write_byte(2, 0b00000000) # Continuous sampling #scale = 0.92 x_out = read_word_2c(3)# * scale y_out = read_word_2c(7)# * scale z_out = read_word_2c(5)# * scale #Calculate heading heading = 180 * math.atan2(y_out,x_out)/M_PI print ("HEADING %5.2f " % heading)
Martk – thanks for replying. Am sorry that you are not familiar with our IMU. Perhaps someone else can give us a hand. i’ll also try and run your corrected code and see how it compares to what we found online – as i mentioned before, i don’t code, but if i locate it’s source, i’ll upload it with your comments so that the original coder might take them into consideration.
Thanks again for all your work and have a great evening! 🙂
Hi Mark and others,
I stumbled onto your very interesting blog, in an attempt to gain more
knowledge and insight in the world of IMU’s. I am embarking on a hobby-project where I would like to detect the tapping of a finger or hand palm on a eg circular plate (dia ~ 60m) I would like to determine the intensity of the tap (iow how ‘hard’ the tap) as well as in which area of the plate, eg on the edge or towards the middle of the plate. My idea is then, by detecting the tap intensity and location, to
play different sounds.
In your sage experience, would this be possible to achieve using an IMU with Accel & Gyro, maybe mounted in the middle of the plate? I assume I will have to use a sensitive accel ~2g?
Thank you for your feedback or any pointers which can me realize my hobby project.
Regards,
In theory it would be possible. If we assume the IMU is up the correct way, you could use the Z Axis of the accelerometer to measure the force of the tap and you could use the angle to determined if it was tapped in the middle and at any edge.
I would first start at setting a threshold, E.g. if value is over 1.2g, play soundB else if value is over 1.8g, play soundC.
The edge detection may be a bit harder as you would have to use the angle of the IMU to determine if the tap is at the edge, and I assume that the IMU would only tilt a very small amounts when the plate is tapped at the edge. Something like, if X angle = 0.1 Deg, play soundA if X angle = -0.1 play soundB.
would you tell me what program you use ?? 🙂
Thanks for doing this.
GOD BLESS YOU
Hi Mark,
Thanks for this amazing post.
I’m trying to understand your code (sorry I’m new to programming) and have a question about selectDevice function:
why are you comparing address to 1 {if(addr==1)} and where the “device” is being used?
That is to select the different i2c address for the sensor.
Have a look at the updated guide in the link below, which has cleaner and simpler code.
https://ozzmaker.com/berryimu/
Hi, i am using raspberry pi 3 which have android os and i want to use this gyroscope with same. how can i use it?
hile(mymillis() – startInt < 20)
Encoding problems. Nice article BTW.
thanks.. i fixed the errors
i would like to thanks you for your forum.
i am working on my project. i am using gyro, accelerometer and compass to find out location. i am not good in programming.
i need a source code for sensors in python. any help will be appreciated.
thanks
Hi sir Iam trying to interface mpu6050 gyroscope sensor and I used basic code but iam facing compiling error in mpu6050 sensor and I also included mpu library and i2c library also included Arduino library manager but the code was not compiling please tell me how to resolve it thank you sir
Hi
I am using the HiLetGo GY-521 MPU-6050
I am not getting Accelerometer data and getting the following error
root@raspberrypi:/opt/CANBUS/GYRO/Raspberry-Gyro-Acc-master# ./main
Failed to write byte to I2C Acc.root@raspberrypi:/opt/CANBUS/GYRO/Raspberry-Gyro-Acc-master#
Can you please let me know what is wrong
root@raspberrypi:/opt/CANBUS/GYRO/Raspberry-Gyro-Acc-master# sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: — — — — — — — — — — — — —
10: — — — — — — — — — — — — — — — —
20: — — — — — — — — — — — — — — — —
30: — — — — — — — — — — — — — — — —
40: — — — — — — — — — — — — — — — —
50: — — — — — — — — — — — — — — — —
60: — — — — — — — — 68 — — — — — — —
70: — — — — — — — —