MPU 9250 C Library. Shivansh Singla

Transcription

1 MPU 9250 C Library Shivansh Singla

2 PREFACE These application notes are used for communicating with MPU 9250 via I2C protocol based on the application notes [1] released by Daniel Fiske, Michael Lam and Daniel Tiam in winter The I2C drivers written by them were used without any modification to talk to MPU9250 which is an Inertial Measurement Unit (IMU) provided by SparkFun. These notes can also be used for any other IMUs by changing the read/write registers appropriately. The MPU 9250 library written by us, has been originally provided by SparkFun [2] and written for Arduino, but it has been translated to C and appropriate modifications have been made to fulfill the requirements of our project. 1

3 Table of Contents INTRODUCTION..3 PROJECT SETUP..4 SOFTWARE LIBRARY....5 SAMPLE CODE. 7 REFERENCES...8 2

4 INTRODUCTION The MPU 9250 is the latest 9-axis MEMS sensor from InvenSense. It is a combination of two chips: the MPU-6500, which contains a 3-axis gyroscope as well as a 3-axis accelerometer, and the AK8963, which features a 3-axis magnetometer. The magnetometer is not included in the library provided. The embedded Digital Motion Processor (DMP) is located within the MPU-9250 and offloads computation of motion processing algorithms from the host processor. The DMP acquires data from accelerometers, gyroscopes, magnetometers and additional 3rd party sensors,and processes the data. The resulting data can be read from the DMP s registers. Communication with all registers of the device is performed using either I2C at 400kHz or SPI at 1MHz. Our library uses I2C protocol for communication. More information about MPU9250, including the datasheet and the register map, can be obtained from SparkFun [3]. Fig: 1 MPU

5 Project Setup Qsys 1. Add a PIO from the component library under Peripherals > Microcontroller Peripherals > PIO: I. Set Width to 1 bit. Set Direction to output. Click finish. II. Rename the component to 'I2C_SCL'. 2. Add a second PIO for data: I. Set Width to 1 bit. Set Direction to bidir. Click finish. II. Rename the component to 'I2C_SDA'. 3. Hookup the components and export the conduit. 4. Click System > Assign Base Addresses to assign proper addresses. 5. Generate the SOPC file. Fig: 2 Qsys configuration Quartus In your top level.vhd file: 1. Add GPIO_0 : inout std_logic_vector(35 downto 0) := (others =>'X') in the entity ports declaration. 2. Add 'i2c_scl_external_connection_export : out std_logic;' and 'i2c_sda_external_connection_export : inout std_logic := 'X';' to the NiosII component declaration ports. 3. Add 'i2c_scl_external_connection_export => GPIO_0(X1)' and 'i2c_sda_external_connection_export=> GPIO_(X2)' to the NiosII component instantiation port map where X1 and X2 are integers corresponding to available GPIO pins. We used pins 24 and Compile the design. 4

6 NiosII Software Build Tools for Eclipse Download I2C.c and I2C.h and add them to your project. Include I2C.h where necessary. Next, download mpu9250.c and mpu9250.h and add them to your project. Include mpu9250.h wherever necessary. Mpu9250.h contains all the register definitions and the function definitions. Please check that the register addresses are correct if you plan to use a newer version of mpu9250 that may be launched in the future. Software Library void getares(float* ares); * Sets the resolution of the accelerometer param - ares * a pointer to a float variable where * the calculated value will be stored. void getgres(float* gres); * Sets the resolution of the gyroscope param - gres * a pointer to a float variable where * the calculated value will be stored. void readacceldata(alt_16 * destination); * Reads the accelerometer data param - destination * a pointer to a 16-bit array to store the 16-bit * signed accelerometer sensor output. 5

7 void readgyrodata(alt_16 * destination); * Reads the gyroscope data param - destination * a pointer to a 16-bit array to store the 16-bit * signed gyroscope sensor output. void initmpu9250(); * Initialize the IMU to Active/Read mode void calibratempu9250(float * gyrobias, float * accelbias); Function which accumulates gyro and accelerometer data after device * initialization. It calculates the average of the at-rest readings and then * loads the resulting offsets into accelerometer and gyro bias registers. param - gyrobias, accelbias * a pointer to a float array to store the calculated * gyroscope and accelerometer bias values used for error correction. void MPU9250SelfTest(float * destination); Accelerometer and gyroscope self test; Check calibration wrt factory settings * Should return percent deviation from factory trim values, +/- 14 or less * deviation is a pass. param - destination * a pointer to a float array to store the calculated % difference * (from factory value) in gyroscope and accelerometer values 6

8 Sample Code: 7

9 Sample Output from the above code: REFERENCES [1] G5%20-%20I2C%20Driver%20Appnote.pdf [2] [3] Shivansh Singla 8