Low-level HDLC framing: flag bytes, byte stuffing, and CRC. More...

Classes
struct	hdlc_ll_init_t
	Structure describes configuration of lowest HDLC level Initialize this structure by 0 before passing to hdlc_ll_init() function. More...

Typedefs
typedef struct hdlc_ll_data_t *	hdlc_ll_handle_t
	Handle for HDLC low level protocol.

Enumerations
enum	hdlc_ll_reset_flags_t { HDLC_LL_RESET_BOTH = 0x00, HDLC_LL_RESET_TX_ONLY = 0x01, HDLC_LL_RESET_RX_ONLY = 0x02 }
	Flags for hdlc_ll_reset function.

Functions
int	hdlc_ll_init (hdlc_ll_handle_t handle, hdlc_ll_init_t init)
	Initializes hdlc level and returns hdlc handle or NULL in case of error. More...

int	hdlc_ll_close (hdlc_ll_handle_t handle)
	Shutdowns all hdlc activity. More...

void	hdlc_ll_reset (hdlc_ll_handle_t handle, uint8_t flags)
	Resets hdlc state. More...

int	hdlc_ll_run_rx (hdlc_ll_handle_t handle, const void data, int len, int error)
	Processes incoming data. More...

int	hdlc_ll_run_tx (hdlc_ll_handle_t handle, void *data, int len)
	If hdlc protocol has some data to send it will full data with This function returns either if no more data to send, or specified buffer is filled completely. More...

int	hdlc_ll_put (hdlc_ll_handle_t handle, const void *data, int len) __attribute__((deprecated))
	Puts next frame for sending. More...

int	hdlc_ll_put_frame (hdlc_ll_handle_t handle, const void *data, int len)
	Puts next frame for sending. More...

int	hdlc_ll_get_buf_size (int mtu)
	Returns minimum buffer size, required to hold hdlc low level data for desired payload size. More...

int	hdlc_ll_get_buf_size_ex (int mtu, hdlc_crc_t crc_type, int rx_window)
	Returns minimum buffer size, required to hold hdlc low level data for desired payload size. More...

typedef struct hdlc_ll_data_t	hdlc_ll_data_t
	Structure describes configuration of lowest HDLC level Initialize this structure by 0 before passing to hdlc_ll_init() function.

#define	HDLC_MIN_BUF_SIZE(mtu, crc) (sizeof(hdlc_ll_data_t) + (int)(crc) / 8 + (mtu) + TINY_ALIGN_STRUCT_VALUE - 1)
	low level HDLC protocol function - only framing More...

#define	HDLC_BUF_SIZE_EX(mtu, crc, window) (sizeof(hdlc_ll_data_t) + ((int)(crc) / 8 + (mtu)) * (window) + TINY_ALIGN_STRUCT_VALUE - 1)
	Macro calculating buffer size required for specific packet size in bytes, and window.

Detailed Description

Low-level HDLC framing: flag bytes, byte stuffing, and CRC.

This module implements low-level HDLC framing according to RFC 1662 and ISO 3309-1979. It handles:

Frame delimiters (0x7E)
Byte stuffing / transparency (0x7D escape sequences)
CRC calculation and validation (8-bit, FCS-16, FCS-32, or none)

This is a stateless framing layer — it does not implement acknowledgments, sequence numbers, or retransmission. For reliable delivery, use the Full-Duplex protocol (Tiny Full Duplex API functions).

The hdlc_ll functions do not use any synchronization primitives (mutexes, etc.), making them completely platform-independent and safe for use in interrupt context (with care).

Macro Definition Documentation

◆ HDLC_MIN_BUF_SIZE

#define HDLC_MIN_BUF_SIZE	(	mtu,
		crc
	)	(sizeof(hdlc_ll_data_t) + (int)(crc) / 8 + (mtu) + TINY_ALIGN_STRUCT_VALUE - 1)

low level HDLC protocol function - only framing

this group implements low level HDLC functions, which implement framing only according to RFC 1662: 0x7E, 0x7D, 0x20 (ISO Standard 3309-1979). Macro calculating minimum buffer size required for specific packet size in bytes

Function Documentation

◆ hdlc_ll_close()

int hdlc_ll_close ( hdlc_ll_handle_t handle )

Shutdowns all hdlc activity.

Parameters

handle hdlc handle

◆ hdlc_ll_get_buf_size()

int hdlc_ll_get_buf_size ( int mtu )

Returns minimum buffer size, required to hold hdlc low level data for desired payload size.

Note: This function calculates required buffer size based on CRC32

Parameters

mtu	size of desired max payload in bytes

Returns: size of the buffer required

◆ hdlc_ll_get_buf_size_ex()

int hdlc_ll_get_buf_size_ex	(	int	mtu,
		hdlc_crc_t	crc_type,
		int	rx_window
	)

Returns minimum buffer size, required to hold hdlc low level data for desired payload size.

Parameters

mtu	size of desired max payload in bytes
crc_type	type of crc validation to use for the protocol
rx_window	number of RX frames in the RX ring buffer

Returns: size of the buffer required

◆ hdlc_ll_init()

int hdlc_ll_init	(	hdlc_ll_handle_t *	handle,
		hdlc_ll_init_t *	init
	)

Initializes hdlc level and returns hdlc handle or NULL in case of error.

Parameters

handle	pointer to hdlc handle variable
init	pointer to hdlc_ll_struct_t structure, which defines user-specific configuration

Returns: -1 if error 0 if success

◆ hdlc_ll_put()

int hdlc_ll_put	(	hdlc_ll_handle_t	handle,
		const void *	data,
		int	len
	)

Puts next frame for sending.

Deprecated: use hdlc_ll_put_frame() instead. hdlc_ll_put() function will not wait or perform send operation, but only pass data pointer to hdlc state machine. In this case, some other thread needs to or in the same thread you need to send data using hdlc_ll_get_tx_data().

Parameters

handle	hdlc handle
data	pointer to new data to send
len	size of data to send in bytes

Returns: TINY_ERR_BUSY if TX queue is busy with another frame. TINY_ERR_INVALID_DATA if len is zero. TINY_SUCCESS if data is successfully sent

Warning: buffer with data must be available all the time until data are actually sent to tx hw channel. That is you need to use callback to understand, when buffer is not longer needed at hdlc low level. Or you can use hdlc_ll_reset() to reset hdlc tx state and to stop using passed buffer.

Note: TINY_ERR_BUSY and TINY_ERR_INVALID_DATA refer to putting new frame to TX hdlc queue.

◆ hdlc_ll_put_frame()

int hdlc_ll_put_frame	(	hdlc_ll_handle_t	handle,
		const void *	data,
		int	len
	)

Puts next frame for sending.

hdlc_ll_put_frame() function will not wait or perform send operation, but only pass data pointer to hdlc state machine. In this case, some other thread needs to or in the same thread you need to send data using hdlc_ll_run_tx().

Parameters

handle	hdlc handle
data	pointer to new data to send
len	size of data to send in bytes

Returns: TINY_ERR_BUSY if TX queue is busy with another frame. TINY_ERR_INVALID_DATA if len is zero. TINY_SUCCESS if data is successfully sent

Warning: buffer with data must be available all the time until data are actually sent to tx hw channel. That is you need to use callback to understand, when buffer is not longer needed at hdlc low level. Or you can use hdlc_ll_reset() to reset hdlc tx state and to stop using passed buffer.

Note: TINY_ERR_BUSY and TINY_ERR_INVALID_DATA refer to putting new frame to TX hdlc queue.

◆ hdlc_ll_reset()

void hdlc_ll_reset	(	hdlc_ll_handle_t	handle,
		uint8_t	flags
	)

Resets hdlc state.

Use this function, if hw error happened on tx or rx line, and this requires hardware change, and cancelling current operation.

Parameters

handle	hdlc handle
flags	HDLC_LL_RESET_TX_ONLY, HDLC_LL_RESET_RX_ONLY, HDLC_LL_RESET_BOTH

◆ hdlc_ll_run_rx()

int hdlc_ll_run_rx	(	hdlc_ll_handle_t	handle,
		const void *	data,
		int	len,
		int *	error
	)

Processes incoming data.

Implementation of reading data from hw is user responsibility. If hdlc_ll_run_rx() returns value less than size of data passed to the function, then hdlc_ll_run_rx() must be called later second time with the pointer to and size of not processed bytes.

If you don't care about errors on RX line, it is allowed to ignore all error codes except TINY_ERR_FAILED, which means general failure.

if hdlc_ll_run_rx() returns 0 bytes processed, just call it once again. It is guaranteed, that at least second call will process bytes.

Note: this API can be used in interrupt context, but please implement on_frame_read callback carefully.

This function will return the following codes in error field:

TINY_ERR_DATA_TOO_LARGE if receiving data fails to fit incoming buffer
TINY_ERR_FAILED if generic failure happened
TINY_ERR_WRONG_CRC if crc field of incoming frame is incorrect
TINY_SUCCESS if operation completed successfully

Parameters

handle	hdlc handle
data	pointer to incoming data to process
len	size of received data in bytes
error	pointer to store error code. If no error, 0 is returned. this argument can be NULL.

Returns: number of processed bytes from specified data buffer. Never returns negative value

◆ hdlc_ll_run_tx()

int hdlc_ll_run_tx	(	hdlc_ll_handle_t	handle,
		void *	data,
		int	len
	)

If hdlc protocol has some data to send it will full data with This function returns either if no more data to send, or specified buffer is filled completely.

Parameters

handle	hdlc handle
data	pointer to buffer to fill with data
len	length of specified buffer

Returns: number of bytes written to specified buffer

Classes

Typedefs

Enumerations

Functions

Detailed Description

Macro Definition Documentation

◆ HDLC_MIN_BUF_SIZE

Function Documentation

◆ hdlc_ll_close()

◆ hdlc_ll_get_buf_size()

◆ hdlc_ll_get_buf_size_ex()

◆ hdlc_ll_init()

◆ hdlc_ll_put()

◆ hdlc_ll_put_frame()

◆ hdlc_ll_reset()

◆ hdlc_ll_run_rx()

◆ hdlc_ll_run_tx()