Data Structures
struct	filter_t

Macros
#define	FILTER_BUFFER_SIZE 10

Functions
void	Filter_Init (filter_t *f_ptr, int16_t offset, float scale)
	Initializes all struct variables and calculates the shift based on scale input for linear transfer function. new_value = raw_value * scale + offset. More...

void	Filter_Update (int16_t raw_value, filter_t *f_ptr)
	computes the new value after going through the transfer function and inputs it into filter buffer array More...

int16_t	Filter_Get (filter_t *f_ptr)
	Filter_Get will retrieve the current value from the filter instance. More...

void	Filter_SetMin (filter_t f_ptr, int16_t threshold, void(callback)(int16_t))
	Filter_SetMin will set the MIN value in the filter to the threshold specified. Calls the callback function with the current value when the value drops below the threshold. More...

void	Filter_SetMax (filter_t f_ptr, int16_t threshold, void(callback)(int16_t))
	Filter_SetMin will set the MAX value in the filter to the threshold specified. Calls the callback function with the current value when the value goes above the threshold. More...

int16_t	MovingAvgFilter (int16_t *values, uint16_t index, uint16_t size, int16_t Last_Value)
	Moving Average filter - Default filter that adds the previous X values and divides by number of values to compute a rolling mean. More...

void	Filter_SetFilter (filter_t f_ptr, int16_t(new_filter)(int16_t *values, uint16_t index, uint16_t size, int16_t last_value))
	Method that allows user to pass a function to a pointer a different type of filter (i.e IIR, FIR) More...

Detailed Description

This module implements a Filter using a linear transfer function that takes in scale/offset in order to calculate new values new_value = raw_value * scale + offset

This module defaults to a MovingAvg Filter function. The user is resposible for implementing a filter based on application. It can be changed using the Set_Filter function

Example, MSP9700 temperature sensor, output voltage directly proportional to measured temperature MCP9700 can accurately measure temperature from -40C to +150C. The output of the MCP9700 is calibrated to a slope of 10mV/°C and has a DC offset of 500mV. The offset allows reading negative temperatures without the need for a negative supply.

V = T_c * 10mV + 500 mV

T_c = 0.322*V - 50

scale = 0.322 offset = -50

Example for implementation with ADC module

//example threshold values
int16_t MinThreshold = 100;
int16_t MaxThreshold = 150;
int16_t offset = -50;
float scale = 0.322;
// void
ADC_Init();
//(filter_t * f_ptr, int16_t  offset, float scale);
Filter_Init(f_ptr, offset,scale);
//(int16_t raw_value, filter_t * f_ptr)
Filter_Update(raw_value, f_ptr);
//(filter_t * f_ptr, int16_t threshold, void(*callback)(int16_t))
Filter_SetMax(f_ptr, MinThreshold, 0);
Filter_SetMin( f_ptr, MaxThreshold,0 );

Author: Neil Surti; Alexander Revolous; Michael Muhlbaier

Macro Definition Documentation

#define FILTER_BUFFER_SIZE 10

Function Documentation

int16_t Filter_Get ( filter_t * f_ptr )

Filter_Get will retrieve the current value from the filter instance.

Returns: int16_t value stored in filter_t->value

void Filter_Init	(	filter_t *	f_ptr,
		int16_t	offset,
		float	scale
	)

Initializes all struct variables and calculates the shift based on scale input for linear transfer function. new_value = raw_value * scale + offset.

Parameters

scale	- Value that multiples with the input
offset	- A constant value added to the linear transfer function to compute the desired result if needed

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void Filter_SetFilter	(	filter_t *	f_ptr,
		int16_t()(int16_t values, uint16_t index, uint16_t size, int16_t last_value)	new_filter
	)

Method that allows user to pass a function to a pointer a different type of filter (i.e IIR, FIR)

Parameters

new_filter * - function pointer to the new filter

void Filter_SetMax	(	filter_t *	f_ptr,
		int16_t	threshold,
		void(*)(int16_t)	callback
	)

Filter_SetMin will set the MAX value in the filter to the threshold specified. Calls the callback function with the current value when the value goes above the threshold.

Parameters

threshold - max value

void Filter_SetMin	(	filter_t *	f_ptr,
		int16_t	threshold,
		void(*)(int16_t)	callback
	)

Filter_SetMin will set the MIN value in the filter to the threshold specified. Calls the callback function with the current value when the value drops below the threshold.

Parameters

threshold - min value

void Filter_Update	(	int16_t	raw_value,
		filter_t *	f_ptr
	)

computes the new value after going through the transfer function and inputs it into filter buffer array

Parameters

raw_value - Values from ADC module that will go through the linear transfer function

int16_t MovingAvgFilter	(	int16_t *	values,
		uint16_t	index,
		uint16_t	size,
		int16_t	Last_Value
	)

Moving Average filter - Default filter that adds the previous X values and divides by number of values to compute a rolling mean.

Parameters

*values	- pointer to the values
index	- location in array
size	- size of data
Last_Value	- last value in the array

Returns: - returns the average value as int16_t

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Data Structures

Macros

Functions

Detailed Description

Macro Definition Documentation

Function Documentation