MPU6050 Drivers

[digitaldanny]

Describe the solution you'd like

• Finish the drivers to read the MPU6500 accelerometer / gyroscope raw sensor values.
• Do some extra research on using the DMP for easy 6DOF calculation.

Additional context

• 39 - Gyro / Accel connections.

• MSP432 to MPU6500 pinout included below. The PCB includes the option to use SPI or I2C communication methods.

MSP432 to MPU6500 breakout connections for I2C	MSP432 Pin	MSP432 Pin Mux	MPU6500 Breakout Pin
P6.4	SDA	SDA
P6.5	SCL	SCL

[digitaldanny]

This University of Illinois edit to the MPU9250 SPI interface is extremely helpful. Page 4 includes a timing diagram to compare with my waveforms output.

[digitaldanny]

Still having trouble getting any response from the MPU6500. I am trying to read from the WHO_AM_I register (address 0x75) through both the I2C and SPI interfaces, and I am documenting what I have tried below.

I2C

• Only receiving a NACK response when attempting to write the WHO_AM_I register address to the device.
• AD0 is pulled low with on-board pull down resistors.
• SCL and SDA are both pulled up with on-board 10k pull up resistors. Double checked that this was not the issue by adding external 10k resistors between these pins and Vcc.
• Tested both I2C addresses documented in the MPU6500 and MPU9250 datasheets (0x68 and 0x69). Although, the on-board pull down resistor for AD0 should force 0x68 to be the I2C address.
• Clock speeds 400k, 100k, 10k.
• Tried using a different MPU6500 breakout board and could not get response from that device either.

MSP432 to MPU6500 breakout connections for I2C	MSP432 Pin	MSP432 Pin Mux	MPU6500 Breakout Pin
P6.4	SDA	SDA
P6.5	SCL	SCL

SPI

• Loopback test to check that my MSP432 SPI drivers were working correctly for receiving data. When I write 0xF5.12.12.12.12 in a loop, I consistently read back 0x12. I am not sure why I never see 0xF5.
• Clock speeds 1MHz, 100KHz, 10KHz.
• High and low clock polarity (clock rests high or low).
• High and low phase (capture on rising or falling edge).
• Writing to all address ranges 0-127 and breakpointing when I receive a value >0. The MSP432 never hits this breakpoint because the value is consistently 0.
• Powered up the MPU6500 breakout board with 5V to handle the dropout voltage of the regulator that is on the breakout board. Also confirmed that there was 3.3V power on the breakout board.
• Tried adding a 2 us delay after CLR_CS and before SET_CS to give CS setup and hold times. During my first run, I saw 0xbe.cd.e0.11.ff.ff.ff.ff.ff.ff.ff.ff.ff.ff.ff...... return after I sent out 0xF5.12.12.12.12. I am not able to reproduce that output though, and I am now seeing all 0's returning again.

MSP432 to MPU6500 breakout connections for SPI	MSP432 Pin	MSP432 Pin Mux	MPU6500 Breakout Pin
P1.5	SCLK	SCL
P1.6	MOSI	SDA
P1.7	MISO	AD0
P3.5	GPIO CS	nCS

[digitaldanny]

Got an Arduino Nano in today. I'm going to use this with the Arduino's MPU6500 library to check if my breakout board's are defective. If I can read the WHO_AM_I register with the Arduino, there is something wrong with my MSP432 SPI/I2C drivers. If not, my breakout boards are defective and I will switch to using the MPU6050 instead.

[digitaldanny]

I was able to use the Arduino as an I2C scanner. The scanner returned "No device found" for both MPU6500 breakout boards, but I am seeing a device found at 0x68 for the MPU6050 breakout boards. This test confirms that both of my MPU6500 breakout boards are defective, so I will be switching to the MPU6050 and will have to do the sensor fusion algorithm on the MSP432 instead of offloading to the DMP.

[digitaldanny]

Using the Arduino files included here for the MPU6050, and I am seeing the following sensor outputs. I will port this library to work with the MSP432.

[digitaldanny]

Also, this link has some Arduino code for calculating the MPU6050 offsets.

https://42bots.com/tutorials/arduino-script-for-mpu-6050-auto-calibration/

[digitaldanny]

This library is based on the Jeff Rowberg drivers, but requires dynamic memory. Going to try avoiding this for now if possible.

[digitaldanny]

This library uses floating point math and requires this compile flag (--float_support=fpv4spd16).

[digitaldanny]

Having trouble with the MPU6050's DMP. I am going to simply read the raw accelerometer / gyroscope values and convert to euler angles using this repo. It looks like there are not any external dependencies for the algorithm, so it should be (as close as possible) to plug and play.

[digitaldanny]

Need to implement a "millis()" function to capture the amount of time elapsed since last capture. This is critical to the quaternion calculations.

[digitaldanny]

I am going to keep the mpu6050 DMP library in for now because I think the millis function may affect the data I am seeing. Right now, I am hardcoding the millis function to 0, so there is never a time delta.

[digitaldanny]

TODO

• Add a millis function to capture time deltas.
• Create a high-level API for the mpu6050 (mpu6050.init, mpu6050.updateSensors).
• Use the sensor fusion library to get euler angle data.

[digitaldanny]

I wanted to try using SPI for this because noise over the lines will not matter as much, and I will not hang for i2c NACK issues. Look like my breakout board does not provide a pin for the CS line. Since my SPI lines are also controlling the LCD, the CS line is important for this application. Will have to make the i2c drivers work for this.

Going to focus on getting the main program developed and the DSP Effects Rack project up and running. Will come back to this before my final demo as long as everything else is working right.

[digitaldanny]

Arduino Raw Value Burst Read

MSP432 Raw Value Burst Read Hang

[digitaldanny]

Looks like the I2C hang issue was solved by switching to my I2C drivers from the MicroMania project. Still seeing all 0 data being returned. Currently looking into this issue.

[digitaldanny]

Figured out why the device was returning only 0's. My configuration to wake up the device by writing to the PWR_MGMT register was pointing to the wrong address. Previous I wrote to address 0x68 when the correct address is 0x6B.

/* MPU6050_PWR_MGMT_1 */ {0x6B, 0x00}, // Wake up device