utils.h File Reference

General utilities functions. More...

#include "FreeRTOS.h"

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Macros
#define	STR(x)   _STR(x)
	Stringify a macro.
#define	_STR(x)   #x
#define	STR_SIZE(x)   (sizeof(x) -1)
	Gets length of a macro string.

Functions
TickType_t	getTickDifference (TickType_t current_time, TickType_t start_time)
	Calculate the difference between 2 tick values.
uint8_t	calculate_chksum (uint8_t *buffer, uint8_t range)
	Calculate a n-byte message 2's complement checksum.
uint8_t	cmpBuffs (uint8_t *bufa, size_t len_a, uint8_t *bufb, size_t len_b)
	Compare 2 buffers.
uint8_t	isPowerOfTwo (uint8_t x)
	Check is a number is a power of 2.

Detailed Description

General utilities functions.

Author

Henrique Silva

Macro Definition Documentation

_STR

#define _STR

(

x

)

#x

STR

#define STR

(

x

)

_STR(x)

Stringify a macro.

Parameters

x	Value to be stringifyed

STR_SIZE

#define STR_SIZE

(

x

)

(sizeof(x) -1)

Gets length of a macro string.

Note

This macro behaviour is equivalent to strlen()

Parameters

x	Macro string

Function Documentation

calculate_chksum()

uint8_t calculate_chksum	(	uint8_t *	buffer,
		uint8_t	range )

Calculate a n-byte message 2's complement checksum.

The checksum byte is calculated by perfoming a simple 8bit 2's complement of the sum of all previous bytes. Since we're using a unsigned int to hold the checksum value, we only need to subtract all bytes from it.

Parameters

buffer	Pointer to the message bytes.
range	How many bytes will be used in the calculation.

Returns

Checksum of the specified bytes of the buffer.

cmpBuffs()

uint8_t cmpBuffs	(	uint8_t *	bufa,
		size_t	len_a,
		uint8_t *	bufb,
		size_t	len_b )

Compare 2 buffers.

Parameters

bufa	First buffer to compare
len_a	Length of bufa
bufb	Second buffer to compare
len_b	Length of bufb

Return values

0x00	Buffers are equal
0xFF	Buffers are different

getTickDifference()

TickType_t getTickDifference	(	TickType_t	current_time,
		TickType_t	start_time )

Calculate the difference between 2 tick values.

Since the tick counter can overflow, we need to check if the current value is higher than the start time before performing any calculations. The Tick counter is expected to overflow at the portMAX_DELAY value

Parameters

current_time	Current tick count
start_time	Start tick count

Returns

Tick difference between arguments

isPowerOfTwo()

uint8_t isPowerOfTwo

(

uint8_t

x

)

Check is a number is a power of 2.

Parameters

x	Number to be tested

Return values

1	Number is a power of two
0	Number is not a power of two