Circular buffer for measurements. More...

Macros
#define	FRAM_BUFFER_START 0

#define	FRAM_BUFFER_END 1769

Functions
fram_status	fifo_put (const uint8_t *data, uint8_t num_bytes)
	Puts a measurement into the circular buffer.

fram_status	fifo_get (uint8_t data, uint8_t len)
	Reads a measurement from the queue.

fram_status	fifo_peek (size_t idx, uint8_t data, uint8_t len)
	Peeks at the next measurement in the buffer without removing it.

fram_status	fifo_drop (void)
	Drops the next measurement in the buffer.

uint16_t	fifo_buffer_len (void)
	Get the current number of measurements stored in the buffer.

fram_status	fifo_buffer_clear (void)
	Clears the buffer.

fram_status	fifo_save_buffer_state (void)
	Saves the buffer state (read address, write address, and buffer length) to FRAM.

fram_status	fifo_load_buffer_state (void)
	Loads the buffer state (read address, write address, and buffer length) from FRAM.

fram_status	fifo_init (void)
	Initializes the buffer.

int	fifo_size (void)
	Gets the total number of bytes in the buffer.

Detailed Description

Circular buffer for measurements.

A circular buffer is implemented on part of the memory space of the fram chip. The address space used can be modified with FRAM_BUFFER_START and FRAM_BUFFER_END depending on user needs.

Measurements are stored with a single uint8_t of their length followed by the serialized protobuf message. On reads, the length is first read, then the length number of bytes are read into RAM. Ensure the read buffer used is of sufficient size.

The buffer's implementation does not allow for overwriting of data. Once the buffer is full, indicated by FRAM_BUFFER_FULL, data needs to be removed by getting the next measurement or clearing the buffer entirely.

Todo:: Implement a clear pointer in the following

The buffer operates as a circular queue with three pointers:

Read Pointer: Points to the address of the next measurement to be uploaded.
Write Pointer: Points to the address where the next measurement will be stored.
Clear Pointer: Points to the last measurement that has been confirmed by the backend.

Unlike traditional circular buffers that maintain only read and write pointers with overflow protection, the ENTS design adds a clear pointer to track backend uplink confirmations. This pointer ensures that unacknowledged data is not overwritten by subsequent writes. The write pointer is allowed to wrap around but is restricted from advancing past the clear pointer. This constraint protects data integrity in field deployments where network failures may delay acknowledgment indefinitely.

Macro Definition Documentation

◆ FRAM_BUFFER_END

#define FRAM_BUFFER_END 1769

Ending address of buffer, which is INCLUSIVE

Definition at line 68 of file fifo.h.

◆ FRAM_BUFFER_START

#define FRAM_BUFFER_START 0

Starting address of buffer, which is INCLUSIVE

Definition at line 63 of file fifo.h.

Function Documentation

◆ fifo_buffer_clear()

fram_status fifo_buffer_clear ( void )

Clears the buffer.

Read and write addresses are set to their default values allowing for the buffer to be overwritten.

Definition at line 235 of file fifo.c.

References fifo_save_buffer_state(), FRAM_BUFFER_START, and FRAM_OK.

Referenced by fifo_init(), setUp(), test_fifo_buffer_clear(), test_fifo_drop(), test_fifo_load_buffer_state(), and test_fifo_peek().

◆ fifo_buffer_len()

uint16_t fifo_buffer_len ( void )

Get the current number of measurements stored in the buffer.

Returns: Number of measurements

Definition at line 233 of file fifo.c.

Referenced by main(), test_fifo_buffer_clear(), test_fifo_buffer_len(), test_fifo_drop(), test_fifo_peek(), test_fifo_put_ValidData(), and test_fifo_wraparound().

◆ fifo_drop()

fram_status fifo_drop ( void )

Drops the next measurement in the buffer.

Alternative to fifo_get when the data is not needed.

Returns: See fram_status

Definition at line 210 of file fifo.c.

References fifo_save_buffer_state(), FRAM_BUFFER_EMPTY, FRAM_OK, and fram_read().

Referenced by test_fifo_drop().

◆ fifo_get()

fram_status fifo_get	(	uint8_t *	data,
		uint8_t *	len
	)

Reads a measurement from the queue.

Parameters

data	Array to be read into
len	Length of data

Returns: See fram_status

Definition at line 102 of file fifo.c.

References data, fifo_save_buffer_state(), FRAM_BUFFER_EMPTY, FRAM_BUFFER_END, FRAM_OK, and fram_read().

Referenced by test_fifo_BufferEmpty(), test_fifo_drop(), test_fifo_load_buffer_state(), test_fifo_Sequential(), test_fifo_Sequential_BufferFull(), test_fifo_ValidData(), and test_fifo_wraparound().

◆ fifo_init()

fram_status fifo_init ( void )

Initializes the buffer.

Initializes the FIFO buffer by loading the buffer state (read address, write address, and buffer length) from FRAM. If the state cannot be loaded or is invalid, it initializes the buffer with default values.