NMEA Message support functions

Collaboration diagram for NMEA Message support functions:

Functions
void	nmea_calc_checksum (const nmea_msg_t *msg, uint8_t *cs)
	Calculate checksum for NMEA message. More...
void	nmea_set_checksum (nmea_msg_t *msg)
	Set checksum bytes for NMEA message. More...
bool	nmea_check_checksum (const nmea_msg_t *msg)
	Verify checksum bytes of NMEA message. More...
size_t	nmea_message_length (const nmea_msg_t *msg)
	Calculate number of bytes required to represent message. More...
size_t	nmea_flat_array (const nmea_msg_t *msg, char **out)
	Convert NMEA message to array of bytes for transmission. More...
char *	nmea_string_hex (const nmea_msg_t *msg)
	Return NMEA message as string. More...
void	nmea_print_hex (const nmea_msg_t *msg)
	Print NMEA message. More...
strarray *	nmea_parse_fields (const nmea_msg_t *nmsg)
	Parse raw data into fields. More...
struct tm *	nmea_parse_zda (const nmea_msg_t *msg)
	Get date/time from NMEA ZDA message. More...

Detailed Description

Convert and verify NMEA protocol messages

Function Documentation

nmea_calc_checksum()

void nmea_calc_checksum	(	const nmea_msg_t *	msg,
		uint8_t *	cs
	)

Calculate checksum for NMEA message.

Calculates the checksum for an NMEA0183 style message

Parameters

[in]	msg	Input message
[out]	cs	Checksum byte

Definition at line 37 of file NMEAMessages.c.

nmea_check_checksum()

bool nmea_check_checksum

(

const nmea_msg_t *

msg

)

Verify checksum bytes of NMEA message.

Calculates checksum with nmea_calc_checksum() and compares to checksumstored in the provided message.

Parameters

[in]

msg

Input message

Returns

Checksum validity (true/false)

Definition at line 85 of file NMEAMessages.c.

nmea_flat_array()

size_t nmea_flat_array	(	const nmea_msg_t *	msg,
		char **	out
	)

Convert NMEA message to array of bytes for transmission.

Allocates a new array of bytes and copies message into array in transmission order (e.g. out[0] to be sent first). Note that this will include a trailing CRLF pair!

Output array must be freed by caller.

Parameters

[in]	msg	Input message
[out]	out	Base address of output array

Returns

Size of output array

Definition at line 127 of file NMEAMessages.c.

nmea_message_length()

size_t nmea_message_length

(

const nmea_msg_t *

msg

)

Calculate number of bytes required to represent message.

Calculate the number of bytes/characters required to represent or transmit an NMEA message

Parameters

[in]

msg

Pointer to NMEA message structure

Returns

Bytes required

Definition at line 99 of file NMEAMessages.c.

nmea_parse_fields()

strarray* nmea_parse_fields

(

const nmea_msg_t *

nmsg

)

Parse raw data into fields.

Parses fields from raw into a string array

Parameters

[in]

nmsg

Pointer to NMEA message

Returns

Pointer to string array (NULL on failure)

Definition at line 203 of file NMEAMessages.c.

nmea_parse_zda()

struct tm* nmea_parse_zda

(

const nmea_msg_t *

msg

)

Get date/time from NMEA ZDA message.

Converts time encoded in message to a libc struct tm representation

Caller to free returned structure

Parameters

[in]

msg

Input message

Returns

Pointer to struct tm, or NULL on failure

Definition at line 240 of file NMEAMessages.c.

nmea_print_hex()

void nmea_print_hex

(

const nmea_msg_t *

msg

)

Print NMEA message.

Primarily for debug purposes. Will print string generated by nmea_string_hex() to stdout.

Parameters

[in]

*msg

Input message

Definition at line 188 of file NMEAMessages.c.

nmea_set_checksum()

void nmea_set_checksum

(

nmea_msg_t *

msg

)

Set checksum bytes for NMEA message.

Simple wrapper around nmea_calc_checksum() to update the checksum bytes within the structure.

Parameters

[in,out]

msg

Message to update

Definition at line 74 of file NMEAMessages.c.

nmea_string_hex()

char* nmea_string_hex

(

const nmea_msg_t *

msg

)

Return NMEA message as string.

Allocates a character array and fills with hexadecimal character pairs representing the message content.

As we're dealing with ASCII anyway, this just wraps nmea_flat_array and adds a null terminator

Character array must be freed by caller.

Parameters

[in]

msg

Input message

Returns

Pointer to character array

Definition at line 174 of file NMEAMessages.c.