Slow DMP reading with an Arduino Due

[Spymon]

Hello everybody,

First of all, thanks a lot for the Library, this saved me a lot of precious time!

 

I'm here to ask for a little help :

I'm using an Arduino Due (using arduino 1.5.5-r2 software) to read the data from my MPU6050, using the DMP. I read the angles using the same code as in the example code for the DMP and I tried a lot of different configurations, without any change.

I noticed that reading the values takes my approximately 6ms. This is a little bit long for me, but the interesting thing is that the sketch spends 5ms of the 6 in the call of this function:

// read a packet from FIFO
mpu.getFIFOBytes(fifoBuffer, packetSize);

I don't understand how this can be so long. This is just reading registers and the packetSize is only 42...

 

So here are my questions. Is this normal with an MPU6050 or is there effectively something strange ? Does anybody have any idea why this is happening? When this function is called, the data should be ready, so why do I loose so much time ?

 

 

I hope somebody will be able to help me with this, because otherwise I'll have to read the raw data and process them by myself. So thanks in advance for your answers!

[luisrodenas]

What I2c speed are you using? MPU supports up to 500KHz and Arduino's default is only 100KHz

[Spymon]

Hello, tanks for your answer. That was the problem. I tried several ways to change the speed, but in fact none of them was really working (as I'm using a Due it is different)... So I had to modify a define in the Wire library in the folder sam of hardware. So the problem is now solved,thanks!

But is there a solution I could put in the code, instead of modifying the library? And this would be useful to update the examples in the library to work properly with an arduino Due.

[luisrodenas]

Glad it worked. I don't know if it is possible to change it in the program, I always change it in the library.

[Spymon]

Ok, thanks a lot for your reply !

[adik1323]

Hello I've had the same problem today. Thanks for the idea to change the I2C speed. I've solved it through the code (without lib modify).

Just one code line:

Wire.setclock(500000L);

This line sets the data transfer speed to 500kHz (example speed).