Platform is Arduino Uno.I have worked for the whole day long and still could not access anything from MPU. I tried for the Arduino playground code as well as github code. Arduino playground code gives -1 value for all ax,ay,az,gx,gy,gz,mx,my,mz whereas github code gives 0 value for all this. To check what is wrong I tried for i2c_scanner function which searches for slave I2C devices and returns slave address on serial moniter. It displayed a message that no device is connected.
I checked for the SCL and SDA pins on MPU using oscilloscope and found out that no signal is carried at all when i2c_scanner is running on arduino.
My hardware connections were:
Arduino ---MPU9150
3.3V VCC
GND GND
A5 SCL(4 cases: No pull up resistor connected, 1kohm, 10k ohm, 1M ohm resistor connected)
A4 SDA(Same 4 cases as above were tried)
This did not work. So in addition to above circuit, I connected AD0 to GND, CIN to GND, FSYNC to GND and INT, COUT, ESD, ESC left unconnected.(This is mentioned in MPU product specification sheet).
This too didn't work.
So I researched further. I realized that A4 and A5 pins voltage is controlled by a 5V source. Means arduino output pins can reach upto 5V. And my device MPU has VCC 3.3V. When I checked for voltage of those pins(SCL and SDA) of MPU with ARDUINO PLAYGROUND code running, I found that SCL had voltage(in DC mode of multimeter) of 4.7 V and SDA had voltage of 3.6V. This is high then desired voltage at these pins. So I checked out for whether MPU is damaged or not. When I looked at its datasheet, it mentioned that SCL and SDA maximum tolerable voltage is 6.5V but device may not operate in other ranges. Typically voltage on SDA and SCL lines should be around VLOGIC~1.8V(please correct me if I am wrong).
Then I connected 1M ohm as pullup resistor. Due to this SCL voltage reduced to around 2V and SDA reduced to 0.2V(Dc mode of multimeter). But this did not work.
At the end I found that 2 devices with different voltage levels cannot be connected directly. Voltage shifter should be used to connect to the 2 devices.Now I do not have a voltage shifter and I have heard that using transistors(which transistors BJT or MOSFET??) same thing can be achieved.
So could anyone please tell me where am I wrong? What should be the hardware connections and how do I account for level shift. At least arduino detects MPU on its driven bus.