task_tlv.h

Task-based TLV (TTLV) communication module for ATmega microcontrollers. Also supports the INM (Inter-Node Messaging) protocol. Uses the task_sched.h task scheduler to perform communication asynchronously.

Summary

task_tlv.h	Task-based TLV (TTLV) communication module for ATmega microcontrollers.
Configuration Macros
Macros
TTLV_XMIT_BFR_SIZE	Size in bytes of the TTLV transmit buffer.
TTLV_RECV_BFR_SIZE	Size in bytes of the TTLV receive buffer.
Protocol Constants
Macros
TTLV_MAX_MESSAGE_ID	Largest valid TTLV message ID.
TTLV_MAX_MESSAGE_ADR	Largest valid INM address.
TTLV_LOCAL_ADR	Special INM address representing the local node.
TTLV_BROADCAST_ADR	Special INM address used for broadcast messages.
TTLV_MIN_TYPE_NUM	Smallest valid TTLV message type number for standard messages.
TTLV_MAX_TYPE_NUM	Largest valid TTLV message type number for standard messages.
TTLV_MAX_MESSAGE_LEN	Maximum TTLV message length for standard messages.
TTLV_PROTOCOL_TYPE_NUM	TTLV message type number reserved for protocol messages.
TTLV_MIN_LARGE_TYPE_NUM	Smallest valid TTLV message type number for large messages.
TTLV_MAX_LARGE_TYPE_NUM	Largest valid TTLV message type number for large messages.
TTLV_MAX_LARGE_MESSAGE_LEN	Maximum TTLV message length for large messages.
Data Types
Enumerations
TTLV Module State/Result Codes	NOTE: The error codes are those with names starting with “TTLV_E_”.
TTLV Mode Flags
TTLV Byte Parity Codes
Variables
ttlv_mode	The type of mode flags for the TTLV module.
ttlv_state	The type of state codes for the TTLV module.
Macros
TTLV_HEADER_BYTES_TLV	Size in bytes of a TLV header.
TTLV_HEADER_BYTES_INM	Combined size in bytes of an INM header and a TLV header.
TTLV_MAX_LEN_TLV	Maximum TLV length of a plain TLV message handled by the TTLV module.
TTLV_MAX_LEN_INM	Maximum TLV length of an INM message handled by the TTLV module.
ttlv_s_inm_header	Specifies the byte format of an INM message header.
Variables
msg_id	Identification number of the INM message.
dstadr	INM address of the destination node.
srcadr	INM address of the source node.
ttlv_inm_header	Provides byte access to the ttlv_s_inm_header struct h via the byte array b.
ttlv_s_header	Specifies the byte format of a TLV header.
Variables
type	TLV type identifier field.
length	TLV length field.
ttlv_header	Provides byte access to the ttlv_s_header struct h via the byte array b.
API Variables
Variables
ttlv_mode_flags	Contains a set of mode flags that represent the current operation mode of the TTLV module.
ttlv_xmit_task_cats	Contains a set of task category bit flags.
ttlv_recv_task_cats	Contains a set of task category bit flags.
ttlv_xmit_state	Contains a state code representing the current state of the TTLV transmitter.
ttlv_xmit_inm_header	Contains the INM header to transmit.
ttlv_xmit_header	Contains the TLV header to transmit.
ttlv_recv_state	Contains a state code representing the current state of the TTLV receiver.
ttlv_recv_inm_header	Contains the most recently received INM header.
ttlv_recv_header	Contains the most recently received TLV header.
Helper Macros
Macros
BAUD_TO_UBRR	Converts a baud rate to an UBRR register value that can be passed to ttlv_init.
TTLV_HAS_MESSAGE	Evaluates to a true value if and only if at least one complete received message is currently pending.
TTLV_HAS_HEADER	Evaluates to a true value if and only if at least one received message header (TLV header only in TLV mode, INM+TLV header in INM mode) is currently pending.
TTLV_IS_ERROR	Evaluates to a true value if and only if the argument is a TTLV error code.
TTLV_CHECK_TL	Evaluates to a true value and only if the specified TLV message type identifier and length match the ones currently stored in ttlv_recv_header.
TTLV_PTR	Converts a pointer to an arbitrary type into a pointer to another arbitrary type, without triggering compiler warnings.
TTLV_CPTR	Converts a pointer to an arbitrary type into a pointer to a constant instance of another arbitrary type, without triggering compiler warnings.
TTLV_DATA_PTR	Converts a pointer to an arbitrary type into a pointer to uint8_t, without triggering compiler warnings.
TTLV_DATA_CPTR	Converts a pointer to an arbitrary type into a pointer to const uint8_t, without triggering compiler warnings.
API Functions
Functions
ttlv_init	Initializes the TTLV communication module.
ttlv_put_byte	Appends a data byte to the sequence of outgoing bytes in the transmit buffer.
ttlv_put_bytes	Appends data bytes to the sequence of outgoing bytes in the transmit buffer.
ttlv_unput_bytes	Removes uncommitted data bytes from the end of the sequence of outgoing bytes in the transmit buffer.
ttlv_try_put_bytes	Attempts to append all the specified data bytes to the sequence of outgoing bytes in the transmit buffer.
ttlv_begin_xmit	Initiates message transmission.
ttlv_try_begin_xmit	Initiates message transmission or clears the transmit buffer.
ttlv_xmit	Initiates transmission of a specified message or clears the transmit buffer.
ttlv_get_bytes	Retrieves data bytes from the start of the sequence of incoming bytes in the receive buffer.
ttlv_finish_recv	Finishes message reception.
ttlv_recv	Retrieves the data bytes of a received message and finishes message reception.
ttlv_shutdown	Shuts down the TTLV communication module.

Configuration Macros

Summary

Macros
TTLV_XMIT_BFR_SIZE	Size in bytes of the TTLV transmit buffer.
TTLV_RECV_BFR_SIZE	Size in bytes of the TTLV receive buffer.

Macros

TTLV_XMIT_BFR_SIZE

Size in bytes of the TTLV transmit buffer. Configuration macro.

Default value: 32

TTLV_RECV_BFR_SIZE

Size in bytes of the TTLV receive buffer. Configuration macro.

Default value: 32

Protocol Constants

Summary

Macros
TTLV_MAX_MESSAGE_ID	Largest valid TTLV message ID.
TTLV_MAX_MESSAGE_ADR	Largest valid INM address.
TTLV_LOCAL_ADR	Special INM address representing the local node.
TTLV_BROADCAST_ADR	Special INM address used for broadcast messages.
TTLV_MIN_TYPE_NUM	Smallest valid TTLV message type number for standard messages.
TTLV_MAX_TYPE_NUM	Largest valid TTLV message type number for standard messages.
TTLV_MAX_MESSAGE_LEN	Maximum TTLV message length for standard messages.
TTLV_PROTOCOL_TYPE_NUM	TTLV message type number reserved for protocol messages.
TTLV_MIN_LARGE_TYPE_NUM	Smallest valid TTLV message type number for large messages.
TTLV_MAX_LARGE_TYPE_NUM	Largest valid TTLV message type number for large messages.
TTLV_MAX_LARGE_MESSAGE_LEN	Maximum TTLV message length for large messages.

Macros

TTLV_MAX_MESSAGE_ID

Largest valid TTLV message ID. Constant macro.

TTLV_MAX_MESSAGE_ADR

Largest valid INM address. Constant macro.

TTLV_LOCAL_ADR

Special INM address representing the local node. Constant macro.

TTLV_BROADCAST_ADR

Special INM address used for broadcast messages. Constant macro.

TTLV_MIN_TYPE_NUM

Smallest valid TTLV message type number for standard messages. Constant macro.

TTLV_MAX_TYPE_NUM

Largest valid TTLV message type number for standard messages. Constant macro.

TTLV_MAX_MESSAGE_LEN

Maximum TTLV message length for standard messages. Constant macro.

CAUTION: The actual maximum message length this module can handle is less than this general upper limit. See TTLV_MAX_LEN_TLV and TTLV_MAX_LEN_INM.

TTLV_PROTOCOL_TYPE_NUM

TTLV message type number reserved for protocol messages. Constant macro.

TTLV_MIN_LARGE_TYPE_NUM

Smallest valid TTLV message type number for large messages. Constant macro.

TTLV_MAX_LARGE_TYPE_NUM

Largest valid TTLV message type number for large messages. Constant macro.

TTLV_MAX_LARGE_MESSAGE_LEN

Maximum TTLV message length for large messages. Constant macro.

Data Types

Summary

Enumerations
TTLV Module State/Result Codes	NOTE: The error codes are those with names starting with “TTLV_E_”.
TTLV Mode Flags
TTLV Byte Parity Codes
Variables
ttlv_mode	The type of mode flags for the TTLV module.
ttlv_state	The type of state codes for the TTLV module.
Macros
TTLV_HEADER_BYTES_TLV	Size in bytes of a TLV header.
TTLV_HEADER_BYTES_INM	Combined size in bytes of an INM header and a TLV header.
TTLV_MAX_LEN_TLV	Maximum TLV length of a plain TLV message handled by the TTLV module.
TTLV_MAX_LEN_INM	Maximum TLV length of an INM message handled by the TTLV module.

Enumerations

TTLV Module State/Result Codes

NOTE: The error codes are those with names starting with “TTLV_E_”. These all have numeric values greater than or equal to TTLV_E_UNSPECIFIED.

TTLV_SUCCESS	operation or function finished successfully
TTLV_DISABLED	module is disabled
TTLV_READY	module is idle and ready to transmit or receive
TTLV_ACTIVE	module is currently transmitting or receiving data
TTLV_INM_HEADER	module has an incoming INM header buffered, but not a TLV header
TTLV_HEADER	module has an incoming TLV header buffered, but not a complete message
TTLV_VALUE	module is currently transmitting a TLV value in streaming mode
TTLV_VALUE_DONE	module has a complete incoming message buffered
TTLV_E_UNSPECIFIED	unspecified error
TTLV_E_PARITY	parity error in USART receiver
TTLV_E_OVERRUN	data overrun error in USART receiver
TTLV_E_FRAME	frame error in USART receiver
TTLV_E_DROP	data overrun error in TTLV receive buffer
TTLV_E_LENGTH	TLV length error (message too large)
TTLV_E_STATE	attempted operation not allowed in current module state
TTLV_E_BUFFER	data buffering error (too few or too many buffered bytes)

TTLV Mode Flags

TTLV_MODE_INM	Specifies that INM message headers should be used.
TTLV_MODE_STREAM	Specifies that stream I/O should be enabled.

TTLV Byte Parity Codes

TTLV_PARITY_NONE	no byte parity
TTLV_PARITY_EVEN	even byte parity
TTLV_PARITY_ODD	odd byte parity

Variables

ttlv_mode

typedef uint8_t ttlv_mode

The type of mode flags for the TTLV module.

ttlv_state

typedef uint8_t ttlv_state

The type of state codes for the TTLV module.

Macros

TTLV_HEADER_BYTES_TLV

Size in bytes of a TLV header. Constant macro.

TTLV_HEADER_BYTES_INM

Combined size in bytes of an INM header and a TLV header.

TTLV_MAX_LEN_TLV

Maximum TLV length of a plain TLV message handled by the TTLV module.

TTLV_MAX_LEN_INM

Maximum TLV length of an INM message handled by the TTLV module.

ttlv_s_inm_header

typedef struct __attribute__ ( (__packed__) ) ttlv_s_inm_header

Specifies the byte format of an INM message header.

Summary

Variables
msg_id	Identification number of the INM message.
dstadr	INM address of the destination node.
srcadr	INM address of the source node.

Variables

msg_id

uint16_t msg_id

Identification number of the INM message. These are generated independently by each source node.

dstadr

uint8_t dstadr

INM address of the destination node.

srcadr

uint8_t srcadr

INM address of the source node.

ttlv_inm_header

typedef union ttlv_inm_header

Provides byte access to the ttlv_s_inm_header struct h via the byte array b.

ttlv_s_header

typedef struct __attribute__ ( (__packed__) ) ttlv_s_header

Specifies the byte format of a TLV header.

Summary

Variables
type	TLV type identifier field.
length	TLV length field.

Variables

type

uint8_t type

TLV type identifier field. The type identifiers are application-defined.

length

uint8_t length

TLV length field. Specifies the size in bytes of the TLV value field that follows.

ttlv_header

typedef union ttlv_header

Provides byte access to the ttlv_s_header struct h via the byte array b.

API Variables

Summary

Variables
ttlv_mode_flags	Contains a set of mode flags that represent the current operation mode of the TTLV module.
ttlv_xmit_task_cats	Contains a set of task category bit flags.
ttlv_recv_task_cats	Contains a set of task category bit flags.
ttlv_xmit_state	Contains a state code representing the current state of the TTLV transmitter.
ttlv_xmit_inm_header	Contains the INM header to transmit.
ttlv_xmit_header	Contains the TLV header to transmit.
ttlv_recv_state	Contains a state code representing the current state of the TTLV receiver.
ttlv_recv_inm_header	Contains the most recently received INM header.
ttlv_recv_header	Contains the most recently received TLV header.

Variables

ttlv_mode_flags

extern ttlv_mode ttlv_mode_flags

Contains a set of mode flags that represent the current operation mode of the TTLV module.

CAUTION: Do not update this variable in external code, unless you know what you’re doing.

ttlv_xmit_task_cats

extern sched_catflags ttlv_xmit_task_cats

Contains a set of task category bit flags. Tasks in the indicated categories will be notified in response to certain events in the TTLV transmitter.

The following transmitter events will trigger task notification

Additional transmit buffer space becomes available while a message is being transmitted in streaming mode.

ttlv_recv_task_cats

extern sched_catflags ttlv_recv_task_cats

Contains a set of task category bit flags. Tasks in the indicated categories will be notified in response to certain events in the TTLV receiver.

The following receiver events will trigger task notification

A complete INM header is received in INM mode.
A complete TLV header is received.
A complete message is received.
Additional data bytes become available while a message is being received in streaming mode.
A communication error is detected by the TTLV receiver.

ttlv_xmit_state

extern ttlv_state ttlv_xmit_state

Contains a state code representing the current state of the TTLV transmitter.

CAUTION: Do not update this variable in external code, unless you know what you’re doing.

ttlv_xmit_inm_header

extern ttlv_inm_header ttlv_xmit_inm_header

Contains the INM header to transmit.

When the TTLV module is used in INM mode, the srcadr field of this struct MUST be set to an appropriate value by external code before any function that initiates transmission of a message is called. Once set, the same value may be used for several messages.

NOTE: In INM mode, the msg_id field of this struct is incremented by the TTLV transmitter each time an INM header has been committed for transmission.

ttlv_xmit_header

extern ttlv_header ttlv_xmit_header

Contains the TLV header to transmit.

ttlv_recv_state

extern ttlv_state ttlv_recv_state

Contains a state code representing the current state of the TTLV receiver.

CAUTION: Do not update this variable in external code, unless you know what you’re doing.

ttlv_recv_inm_header

extern ttlv_inm_header ttlv_recv_inm_header

Contains the most recently received INM header.

CAUTION: Do not update this struct in external code, unless you know what you’re doing.

ttlv_recv_header

extern ttlv_header ttlv_recv_header

Contains the most recently received TLV header.

CAUTION: Do not update this struct in external code, unless you know what you’re doing.

Helper Macros

Summary

Macros
BAUD_TO_UBRR	Converts a baud rate to an UBRR register value that can be passed to ttlv_init.
TTLV_HAS_MESSAGE	Evaluates to a true value if and only if at least one complete received message is currently pending.
TTLV_HAS_HEADER	Evaluates to a true value if and only if at least one received message header (TLV header only in TLV mode, INM+TLV header in INM mode) is currently pending.
TTLV_IS_ERROR	Evaluates to a true value if and only if the argument is a TTLV error code.
TTLV_CHECK_TL	Evaluates to a true value and only if the specified TLV message type identifier and length match the ones currently stored in ttlv_recv_header.
TTLV_PTR	Converts a pointer to an arbitrary type into a pointer to another arbitrary type, without triggering compiler warnings.
TTLV_CPTR	Converts a pointer to an arbitrary type into a pointer to a constant instance of another arbitrary type, without triggering compiler warnings.
TTLV_DATA_PTR	Converts a pointer to an arbitrary type into a pointer to uint8_t, without triggering compiler warnings.
TTLV_DATA_CPTR	Converts a pointer to an arbitrary type into a pointer to const uint8_t, without triggering compiler warnings.

Macros

BAUD_TO_UBRR

Converts a baud rate to an UBRR register value that can be passed to ttlv_init. Function-like macro.

CAUTION: This macro depends on the F_CPU macro deing defined as a long integer expression representing the master clock frequency of the target ATmega controller.

Parameters

B	A positive integer baud rate. B MUST be less than or equal to F_CPU / 16 (F_CPU / 8 if X is true).
X	A Boolean flag indicating whether the double-speed mode of the ATmega USART will be used.

Returns

A nonnegative integer UBRR clock divisor value that may be passed to ttlv_init.

TTLV_HAS_MESSAGE

Evaluates to a true value if and only if at least one complete received message is currently pending. Expression macro.

TTLV_HAS_HEADER

Evaluates to a true value if and only if at least one received message header (TLV header only in TLV mode, INM+TLV header in INM mode) is currently pending. Expression macro.

TTLV_IS_ERROR

Evaluates to a true value if and only if the argument is a TTLV error code. Function-like macro.

CAUTION: This macro may evaluate true if the argument is not a valid TTLV result code.

Parameters

S	A ttlv_state result code.

Returns

True if and only if S is a TTLV error code.

TTLV_CHECK_TL

Evaluates to a true value and only if the specified TLV message type identifier and length match the ones currently stored in ttlv_recv_header. The type identifier is tested for equality, while the message length is tested for being less than or equal to the one in ttlv_recv_header. Function-like macro.

Parameters

T	A TLV message type identifier.
L	A TLV message length.

Returns

True if and only if the arguments match the current ttlv_recv_header.

TTLV_PTR

Converts a pointer to an arbitrary type into a pointer to another arbitrary type, without triggering compiler warnings. Function-like macro.

Parameters

T	A type name. The macro will evaluate to a pointer to an instance of this type.
P	A pointer. The macro will evaluate to a pointer containing the same address as this pointer.

Returns

A pointer to T, containing the same address as P.

TTLV_CPTR

Converts a pointer to an arbitrary type into a pointer to a constant instance of another arbitrary type, without triggering compiler warnings. Function-like macro.

Parameters

T	A type name. The macro will evaluate to a pointer to a constant instance of his type.
P	A pointer. The macro will evaluate to a pointer containing the same address as this pointer.

Returns

A pointer to const T, containing the same address as P.

TTLV_DATA_PTR

Converts a pointer to an arbitrary type into a pointer to uint8_t, without triggering compiler warnings. Function-like macro.

Parameters

P	A pointer. The macro will evaluate to a pointer containing the same address as this pointer.

Returns

A pointer to uint8_t, containing the same address as P.

TTLV_DATA_CPTR

Converts a pointer to an arbitrary type into a pointer to const uint8_t, without triggering compiler warnings. Function-like macro.

Parameters

P	A pointer. The macro will evaluate to a pointer containing the same address as this pointer.

Returns

A pointer to const uint8_t, containing the same address as P.

API Functions

Summary

Functions
ttlv_init	Initializes the TTLV communication module.
ttlv_put_byte	Appends a data byte to the sequence of outgoing bytes in the transmit buffer.
ttlv_put_bytes	Appends data bytes to the sequence of outgoing bytes in the transmit buffer.
ttlv_unput_bytes	Removes uncommitted data bytes from the end of the sequence of outgoing bytes in the transmit buffer.
ttlv_try_put_bytes	Attempts to append all the specified data bytes to the sequence of outgoing bytes in the transmit buffer.
ttlv_begin_xmit	Initiates message transmission.
ttlv_try_begin_xmit	Initiates message transmission or clears the transmit buffer.
ttlv_xmit	Initiates transmission of a specified message or clears the transmit buffer.
ttlv_get_bytes	Retrieves data bytes from the start of the sequence of incoming bytes in the receive buffer.
ttlv_finish_recv	Finishes message reception.
ttlv_recv	Retrieves the data bytes of a received message and finishes message reception.
ttlv_shutdown	Shuts down the TTLV communication module.

Functions

ttlv_init

void ttlv_init( uint8_t task_num_cat,
uint16_t ubrr,
uint8_t parity,
uint8_t u2x,
ttlv_mode mode,
sched_catflags xmit_task_cats,
sched_catflags recv_task_cats )

Initializes the TTLV communication module.

CAUTION: This function MUST be called before any other API function of the TTLV module is called.

Parameters

task_num_cat	A TCSB value containing the task instance and category numbers that should be used by the TTLV receiver/transmitter task. (The SLP bit of the argument is ignored.)
ubrr	A nonnegative clock divisor value that determines the baud rate of the ATmega USART. The BAUD_TO_UBRR macro may be used to convert a baud rate to a corresponding UBRR value. Note that this conversion is approximate, i.e. the baud rate produced by the resulting UBRR value may be slightly different from the one given to the macro.
parity	A value that specifies the type of byte parity checking to be used by the ATmega USART. This should be one of the TTLV_PARITY_x enum constants.
u2x	A value that specifies whether double-speed mode should be used by the ATmega USART. This should be either 0 (false) or 1 (true). The double-speed reception mode doubles the baud rate for a given UBRR value.
mode	A set of bit flags specifying the mode the TTLV module should operate in,
xmit_task_cats	A set of bit flags specifying task categories whose members should be notified in response to certain events in the TTLV transmitter. See ttlv_xmit_task_cats for details.
recv_task_cats	A set of bit flags specifying task categories whose members should be notified in response to certain events in the TTLV receiver. See ttlv_recv_task_cats for details.

ttlv_put_byte

uint8_t ttlv_put_byte( uint8_t data )

Appends a data byte to the sequence of outgoing bytes in the transmit buffer. If a message is being transmitted in streaming mode, the appended byte will immediately be committed for transmission.

Parameters

data	A data byte to append to the outgoing data.

Returns

The number of bytes appended (1 if successful, 0 if there was a problem).

ttlv_put_bytes

uint8_t ttlv_put_bytes( uint8_t n,
const uint8_t * data_p )

Appends data bytes to the sequence of outgoing bytes in the transmit buffer. If a message is being transmitted in streaming mode, the appended bytes will immediately be committed for transmission.

Parameters

n	Number of data bytes to append to the outgoing data.
data_p	Pointer to data bytes to append to the outgoing data.

Returns

The number of bytes appended. If an error occurred or there was insufficient buffer space, this number will be less than n.

ttlv_unput_bytes

uint8_t ttlv_unput_bytes( uint8_t n )

Removes uncommitted data bytes from the end of the sequence of outgoing bytes in the transmit buffer.

NOTE: To remove all uncommitted bytes, give the argument TTLV_XMIT_BFR_SIZE.

Parameters

n	Maximum number of data bytes to remove from the outgoing data.

Returns

The number of bytes removed.

ttlv_try_put_bytes

uint8_t ttlv_try_put_bytes( uint8_t n,
const uint8_t * data_p )

Attempts to append all the specified data bytes to the sequence of outgoing bytes in the transmit buffer. If a message is being transmitted in streaming mode, the appended bytes will immediately be committed for transmission. If this function cannot append all the specified bytes, it will remove ALL uncommitted data bytes from the transmit buffer.

NOTE: This is intended to work as a fire-and-forget output function that will either successfully deliver data bytes for transmission or leave the transmit buffer cleared and ready to begin transmission of another, unrelated message.

Parameters

n	Number of data bytes to append to the outgoing data.
data_p	Pointer to data bytes to append to the outgoing data.

Returns

A true value iff all the specified bytes were appended to the outgoing data.

ttlv_begin_xmit

ttlv_state ttlv_begin_xmit( void )

Initiates message transmission. Message headers will be copied into the transmit buffer from the ttlv_xmit_inm_header and ttlv_xmit_header structs. Any uncommitted data bytes in the transmit buffer will be committed for transmission.

Returns

An integer result code, which will be an error code if and only if the attempt to initiate transmission failed.

ttlv_try_begin_xmit

ttlv_state ttlv_try_begin_xmit( void )

Initiates message transmission or clears the transmit buffer. Message headers will be copied into the transmit buffer from the ttlv_xmit_inm_header and ttlv_xmit_header structs. Any uncommitted data bytes in the transmit buffer will either be committed for transmission or, if the attempt to initiate transmission fails, removed from the buffer.

NOTE: This is intended to work as a fire-and-forget output function that will either successfully initiate message transmission or leave the transmit buffer cleared and ready to begin transmission of another, unrelated message.

Returns

An integer result code, which will be an error code if and only if the attempt to initiate transmission failed.

ttlv_xmit

ttlv_state ttlv_xmit( uint8_t dstadr,
uint8_t type,
uint8_t length,
const uint8_t * data_p )

Initiates transmission of a specified message or clears the transmit buffer. The header field arguments will be used to update ttlv_xmit_inm_header and ttlv_xmit_header, which will then be copied into the transmit buffer. The specified data bytes will be copied into the transmit buffer and then either committed for transmission or, if the attempt to initiate transmission fails, removed from the buffer.

NOTE: This is intended to work as a fire-and-forget output function that will either successfully initiate transmission of a complete message or leave the transmit buffer cleared and ready to begin transmission of another, unrelated message.

Parameters

dstadr	INM destination address of the message to transmit. If not in INM mode, the ttlv_xmit_inm_header field will still be updated.
type	TLV type identifier of the message to transmit.
length	TLV length of the message to transmit.
data_p	Pointer to the data bytes (TLV value) of the message to transmit.

Returns

An integer result code, which will be an error code if and only if the attempt to initiate transmission failed.

ttlv_get_bytes

uint8_t ttlv_get_bytes( uint8_t n,
uint8_t * data_p )

Retrieves data bytes from the start of the sequence of incoming bytes in the receive buffer. Each retrieved byte will be removed from the buffer.

Parameters

n	Maximum number of data bytes to retrieve.
data_p	Pointer to memory to copy the retrieved data bytes into.

Returns

The number of bytes retrieved. If an error occurred or there was an insufficient number of bytes available in the buffer, this number will be less than n.

ttlv_finish_recv

ttlv_state ttlv_finish_recv( void )

Finishes message reception. If any of the data bytes of the message that was being received remain in the receive buffer, they will be removed from the buffer. When this function returns, the TTLV receiver will be ready to begin processing of the next incoming message.

CAUTION: Once a complete message has been received, processing of incoming messages will be paused until this function or ttlv_recv is called by external code. This means that to prevent receive buffer overruns, programs that use the TTLV module MUST respond to each incoming message by calling one of those functions within a message reception interval, even if the received message itself is not of interest.

Returns

An integer result code, which will be an error code if and only if the attempt to finish reception failed.

ttlv_recv

ttlv_state ttlv_recv( uint8_t * data_p )

Retrieves the data bytes of a received message and finishes message reception. When this function returns, the TTLV receiver will be ready to begin processing of the next incoming message.

CAUTION: Once a complete message has been received, processing of incoming messages will be paused until this function or ttlv_finish_recv is called by external code. This means that to prevent receive buffer overruns, programs that use the TTLV module MUST respond to each incoming message by calling one of those functions within a message reception interval, even if the received message itself is not of interest.

Parameters

data_p

Pointer to memory to copy the data bytes of the received message into. The specified block of memory MUST be large enough to store all the data bytes of the received message (as indicated by the length field of the ttlv_recv_header struct).

Returns

An integer result code, which will be an error code if and only if the attempt to retrieve data bytes and finish reception failed.

ttlv_shutdown

void ttlv_shutdown( void )

Shuts down the TTLV communication module. Erases all current transmit and receive operations, aborting them first if they are still pending.