frdm-kl25z-marg-fusion's Introduction

FRDM-KL25Z MARG fusion

Evaluation of a regular Kalman filter based Direction Cosine Matrix estimation through MARG (IMU) sensor fusion, implemented on bare metal Freescale FRDM-KL25Z.

A demonstration video is available here.

Implemented so far

Inertial Sensing

(on-board) MMA8451Q accelerometer driver, sensor data dumping in 14-bit non-fifo mode
MPU6050 accelerometer, gyroscope and temperature sensor driver
HMC5883L magnetometer sensor driver
Full configuration fetch and store over I2C
Automatic endian conversion based on system settings
Interrupt-based update notification and polling
MATLAB interfacing at up 800 Hz over serial port
- serial protocol decoder
- visual representation of the measured accelerations at 60 FPS with virtual horizon. For an older version, see https://www.youtube.com/watch?v=RunpaR2PdHQ.

Sensor Fusion

Standard Kalman filter in 32bit Q16 fixed point using libfixkalman
Direct estimation of DCM axes based on A DCM Based Orientation Estimation Algorithm with an Inertial Measurement Unit and a Magnetic Compass (Nguyen Ho Quoc Phuong et al., J.UCS 15.4), but using TRIAD approach instead of magnetometer tilt-compensation.
Quaternion conversion for transfer
C# demonstration program using OpenTK available in branch orientation-opengl

System

Clock in PLL engaged mode (PEE) with 48 MHz core, 24 MHz bus
SysTick timer running at 0.25ms
delay_ms() function with low power wait support (WFI)

Communication

UART0 on pins PTA1/PTA2 with 115.2 kbaud
interrupt-decoupled UART0 using custom ring buffers
simple IO layer for data output over UART
- binary single and bulk transfer
- integer-to-string, basically itoa() without arrays
- Q2.12 fixed point to string (nice for the MMA8451Q 14bit mode)
simple escaping protocol encoder with preamble and length header
I2C driver for I2C0 (currently hardcoded, but easy to change)
- arbiter that sets pin configurations on demand per requested device (e.g. when I2C0 is used from different ports)