MPU6050 I2C communication is not possible

[agcaahmet]

Although I2C Scanner sketch is able to found the device, it is not possible to communicate with MPU6050 using jrowberg/i2cdevlib library. On the other hand, using esp8266 board works with the same sketch and library.

[nkolban]

By any chance do you have a logic analyzer that you can attach to the SDA and CLK to see what is being sent?

[me-no-dev]

I have looked many times at libs like this and never came up with a reason to why I2Cdev lib calls Wire.beginTransmission before reading data from I2C slave. That is a really wrong approach ;) begin and end transmission are used only for writing to slaves and not reading. I remember doing some hacking to the I2C lib for ESP8266 in order to get that resolved, but it's bad code non the less.
Will look into screwing with the lib again to make it compatible, but in general I find this to be the wrong thing to do ;)

[me-no-dev]

hmm... I looked at the code and there is nothing to prevent even this from working. It will send a probe after reading and that is all that will happen

[agcaahmet]

@nkolban Unfortunately, I dont have a logic analyzer :(
@me-no-dev I will try your trick in your first message (comment out begin and end transmission statements for reading) but I could not understand what you mean exactly in your second message

[agcaahmet]

By the way, the same problem exists with the following "Short example sketch" in Arduino website which is free of I2C library.

// MPU-6050 Short Example Sketch
// By Arduino User JohnChi
// August 17, 2014
// Public Domain
#include<Wire.h>
const int MPU_addr=0x68; // I2C address of the MPU-6050
int16_t AcX,AcY,AcZ,Tmp,GyX,GyY,GyZ;
void setup(){
Wire.begin();
Wire.beginTransmission(MPU_addr);
Wire.write(0x6B); // PWR_MGMT_1 register
Wire.write(0); // set to zero (wakes up the MPU-6050)
Wire.endTransmission(true);
Serial.begin(9600);
}
void loop(){
Wire.beginTransmission(MPU_addr);
Wire.write(0x3B); // starting with register 0x3B (ACCEL_XOUT_H)
Wire.endTransmission(false);
Wire.requestFrom(MPU_addr,14,true); // request a total of 14 registers
AcX=Wire.read()<<8|Wire.read(); // 0x3B (ACCEL_XOUT_H) & 0x3C (ACCEL_XOUT_L)
AcY=Wire.read()<<8|Wire.read(); // 0x3D (ACCEL_YOUT_H) & 0x3E (ACCEL_YOUT_L)
AcZ=Wire.read()<<8|Wire.read(); // 0x3F (ACCEL_ZOUT_H) & 0x40 (ACCEL_ZOUT_L)
Tmp=Wire.read()<<8|Wire.read(); // 0x41 (TEMP_OUT_H) & 0x42 (TEMP_OUT_L)
GyX=Wire.read()<<8|Wire.read(); // 0x43 (GYRO_XOUT_H) & 0x44 (GYRO_XOUT_L)
GyY=Wire.read()<<8|Wire.read(); // 0x45 (GYRO_YOUT_H) & 0x46 (GYRO_YOUT_L)
GyZ=Wire.read()<<8|Wire.read(); // 0x47 (GYRO_ZOUT_H) & 0x48 (GYRO_ZOUT_L)
Serial.print("AcX = "); Serial.print(AcX);
Serial.print(" | AcY = "); Serial.print(AcY);
Serial.print(" | AcZ = "); Serial.print(AcZ);
Serial.print(" | Tmp = "); Serial.print(Tmp/340.00+36.53); //equation for temperature in degrees C from datasheet
Serial.print(" | GyX = "); Serial.print(GyX);
Serial.print(" | GyY = "); Serial.print(GyY);
Serial.print(" | GyZ = "); Serial.println(GyZ);
delay(333);
}

The result of this sketch on serial line is:
AcX = 0 | AcY = 0 | AcZ = 0 | Tmp = 36.53 | GyX = 0 | GyY = 0 | GyZ = 0

[me-no-dev]

I'll give it a go

[me-no-dev]

hey can you pull the latest master and give this another go?

AcX = -1836 | AcY = 152 | AcZ = 15844 | Tmp = 30.32 | GyX = -375 | GyY = -111 | GyZ = -148
AcX = -1844 | AcY = 220 | AcZ = 15884 | Tmp = 30.32 | GyX = -376 | GyY = -98 | GyZ = -134
AcX = -1724 | AcY = 128 | AcZ = 15752 | Tmp = 30.27 | GyX = -393 | GyY = -127 | GyZ = -145
AcX = -1768 | AcY = 272 | AcZ = 15932 | Tmp = 30.27 | GyX = -388 | GyY = -95 | GyZ = -152
AcX = -1724 | AcY = 192 | AcZ = 15884 | Tmp = 30.22 | GyX = -427 | GyY = -113 | GyZ = -136

[agcaahmet]

Thank you for your great effort, now the "Short Example Sketch" works. However, I could not still make it work with the I2CDev library. I am trying possible modifications on I2CDev.cpp file but haven't found any solution :(

[me-no-dev]

If I2CDev tests the return endTarnsaction, it will receive error, because MPU does not send ACK. Maybe that is causing it to fail?

[agcaahmet]

Arduino-MPU6050-Example sketch (base code).txt

The attached base code (directly taken from website http://playground.arduino.cc/Main/MPU-6050) is also not working. The serial monitor result is:
MPU-6050
Read accel, temp and gyro, error = 2
accel x,y,z: 0, 0, 0
temperature: 36.506 degrees Celsius
gyro x,y,z : 0, 0, 0,

I tried to comment out endTransmission return statement but it didnt help. Below is the serial monitor result:
MPU-6050
Read accel, temp and gyro, error = -11
accel x,y,z: 0, 0, 0
temperature: 36.506 degrees Celsius
gyro x,y,z : 0, 0, 0,

I will try to monitor the SDA and SCL lines and post here the results if I can :)

[me-no-dev]

make sure that the module has pull-ups or add ones yourself. Pins are floating

[agcaahmet]

Unfortunately, pull-up resistors didn't make any difference. I think the module has already pull-ups.

[me-no-dev]

Ok, I have 6050 somewhere around. I'll try to find it and give it a go.