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June 28, 2013
about 2 years ago
I am trying to set the sampling rate for the accelerometer and the gyroscope.
From the register map (http://www.invensense.com/mems/gyro/documents/RM-MPU-9150A-00.pdf), (page 11 of 60):
Register 25 – Sample Rate Divider
The Sample Rate is generated by dividing the gyroscope output rate by SMPLRT_DIV: Sample Rate = Gyroscope Output Rate / (1 + SMPLRT_DIV) where Gyroscope Output Rate = 8kHz when the DLPF is disabled (DLPF_CFG = 0 or 7), and 1kHz when the DLPF is enabled (see Register 26).
The accelerometer output rate is 1kHz. This means that for a Sample Rate greater than 1kHz, the same accelerometer sample may be output to the FIFO, DMP, and sensor registers more than once.
In my understanding, if the DLPF (Digital Low Pass Filter) is enabled then both the gyroscope and the accelerometer sample at 1kHz and setting a value of say 4 in register 25 will make the sample rate: 1kHz / (1+4) = 200Hz for BOTH the accelerometer and the gyroscope. Is that correct? Does enabling the DLPF not affect the sampling rate of the accelerometer as it does for the gyroscope
I want to eventually design a digital filter by converting a continuous time filter (using conventional Bode plot techniques) and need to know the sampling rate for the conversion.
about 2 years ago
I am having problems communicating the MPU9150 to the Arduino Micro. I am using a logic level converter as the Arduino runs at 5V while the sensor runs at 3.3V. I read in some places that I might not need it but I thought it’s just better to have one in place.
Logic Level Converter - https://www.sparkfun.com/products/8745
MPU9150 IMU Sensor - https://www.sparkfun.com/products/11486
Arduino Micro - http://arduino.cc/en/Main/arduinoBoardMicro
Here are my connections:
ARDUINO Logic Level Converter MPU9150
5V HV N/A
3.3V LV N/A
GND GND (Both) N/A
A4 Chan1 Tx SDA
A5 Chan2 Tx SCL
GND N/A GND
3.3V N/A VCC
I also have two 4.7k pull up resistors on the A4 and A5 on the Arduino connected to 5V and two 10k pull up resistors on the SCL and SDA on the IMU connected to 3.3V.
I have NOT connected anything on the IMU INT or AD0 pins.
I am running a standard I2C scanner code found here: http://playground.arduino.cc/Main/I2cScanner
My Arduino is unable to talk to the IMU I also tried this config with a friends IMU (which was confirmed to work) and it did not work with that either.
Is there something I am missing here? Please advise.
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