Freescale Sensor Fusion Library for Kinetis MCUs, Rev. 0.7, 9/2015

Freescale Semiconductor, Inc.

2. Percentage of time spent in the core fusion routines = 100*sysTickfusion / total_sysTicks

2

3. Idd Current into the MCU is measured via power jumper on the board using a simple DVM

3

4. Fusion Idd = MCU Idd X percentage

5. All currents shown are in mA

6. Sample size = 1 board

For devices with floating point units, this may yield a somewhat optimistic number, as the computation

makes the assumption that all MCU instructions consume the same amount of power. In fact, we can

expect floating point instructions to consume a bit more.

5.2 Flash and RAM Required

5.2.1

Intent

These parameters are total RAM and flash memory required to implement and execute the Fusion

Library plus MQX-Lite RTOS. The projects for the binaries were created using both CodeWarrior and

Kinetis Design Studio. Values for Text, Data and BSS were read directly from the console window after

builds completed.

This includes space for code storage, static and dynamic (stack) variables. This metric must be

associated with a specific hardware configuration similar to those defined in earlier in this document.

5.2.2

Procedure

The text, data and bss sizes for each build were extracted using the technique outlined at MCU on

Eclipse; text, data and bss: Code and Data Size Explained.

1.

text; includes the user code, the vector table plus constants.

2.

data; is for initialized variables, and it counts for RAM and FLASH. The linker allocates the data in

FLASH which then is copied from ROM to RAM in the startup code.

3.

bss; is for the uninitialized data in RAM which is initialized with zero in the startup code.

Refer to Computation Metrics for statistics gathered using the 5.00 build.

5.3 Fusion Loop Execution Time

This is simply CPU cycle time X sysTickfusion as measured in Section 5.1.

5.4 Compass Heading Linearity and Accuracy

5.4.1

Intent

Linearity is defined as the deviation of measured data from a least squares straight line approximation

of that data.

Absolute accuracy is defined as the maximum difference between measured and ideal values.

2

Which is simply the clock rate of the MCU divided by the sensor fusion rate (nominally 25)

3

Consult the user guide / schematic for your Freedom board to determine the specific jumper number

applicable to that board.