Firmware Over the Air (FOTA) Update system. More...

Collaboration diagram for FOTA:

Classes
struct	FotaDatagramHeaderPacketPayload
	Structure representing the datagram header (In the payload) More...

struct	FotaDatagram
	Structure representing datagram. More...

struct	FotaPacket
	FOTA Packet structure. More...

struct	GpioAddress
	Port and pin data. More...

struct	UartSettings
	UART Settings. More...

struct	NetworkBuffer
	struct containing details of circular buffer More...

struct	PacketManager
	Packet manager context structure. More...

Macros
#define	FOTA_MAX_DATAGRAM_SIZE (8U * 256U)
	Maximum supported datagram size (2KB)

#define	FOTA_MAX_PACKETS_PER_DATAGRAM ((FOTA_MAX_DATAGRAM_SIZE / FOTA_PACKET_PAYLOAD_SIZE) + 1U)
	Maximum number of packets that can make up a datagram (8 data + 1 Header)

#define	NUM_FLASH_PAGES 128U
	256KB of memory / 2KB per page

#define	FOTA_PAGE_BYTES ((uint32_t)0x800U)
	2KB per flash page as per datasheet

#define	FOTA_PING_BYTES ((uint32_t)0x1000U)
	4KB max per ping

#define	FOTA_FLASH_WORD_SIZE 4U
	ARM32 Word size is 4 bytes.

#define	FOTA_ADDR_TO_PAGE(addr) (((uintptr_t)(addr) - (uintptr_t)APPLICATION_START_ADDRESS) / FOTA_PAGE_BYTES)
	Convert memory address to page number. More...

#define	FOTA_PAGE_TO_ADDR(page) ((uintptr_t)(page) * (uintptr_t)FOTA_PAGE_BYTES + (uintptr_t)APPLICATION_START_ADDRESS)
	Convert page number to memory address. More...

#define	LOG_FOTA_DEBUG(msg) printf("[FOTA DEBUG]: %s\n");
	Debug log.

#define	LOG_FOTA_WARNING(msg) printf("[FOTA WARNING]: %s\n");
	Warning log.

#define	LOG_FOTA_ERROR(msg) printf("[FOTA ERROR]: %s\n");
	Error log.

#define	FLASH_START_ADDRESS_LINKERSCRIPT ((uint32_t) & _flash_start)
	Flash start address as defined in the linkerscripts.

#define	FLASH_SIZE_LINKERSCRIPT ((size_t) & _flash_size)
	Flash size as defined in the linkerscripts.

#define	FLASH_PAGE_SIZE_LINKERSCRIPT ((size_t) & _flash_page_size)
	Flash page size as defined in the linkerscripts.

#define	APPLICATION_START_ADDRESS ((uint32_t) & _application_start)
	Application start address as defined in the linkerscripts.

#define	APPLICATION_SIZE ((size_t) & _application_size)
	Application size as defined in the linkerscripts.

#define	BOOTLOADER_START_ADDRESS ((uint32_t) & _bootloader_start)
	Bootloader start address as defined in the linkerscripts.

#define	BOOTLOADER_SIZE ((size_t) & _bootloader_size)
	Bootloader size as defined in the linkerscripts.

#define	SRAM_START_ADDRESS ((uint32_t) & _sram_start)
	SRAM start address as defined in the linkerscripts.

#define	SRAM_SIZE ((size_t) & _sram_size)
	SRAM size as defined in the linkerscripts.

#define	FOTA_PACKET_PAYLOAD_SIZE 256U
	FOTA packet payload size. More...

#define	FOTA_PACKET_SOF 0xAAU
	FOTA packet start of frame.

#define	FOTA_PACKET_EOF 0xBBU
	FOTA packet end of frame.

#define	FOTA_PACKET_MINIMUM_SIZE 14U
	FOTA packet minimum size.

#define	FOTA_TIMEOUT_MS 15000U

#define	UART_MAX_BUFFER_LEN 256U
	Maximum size permitted for a UART transaction.

#define	UART_TIMEOUT_MS 1U
	Maximum time permitted for a UART transaction.

#define	FOTA_UART_TIMEOUT_MS 10U
	Maximum time permitted for a FOTA UART transaction.

#define	NETWORK_BUFFER_SIZE 1024U

#define	FOTA_MAX_ACTIVE_DATAGRAMS 2U

Enumerations
enum	FotaDatagramType { FOTA_DATAGRAM_TYPE_FIRMWARE_METADATA , FOTA_DATAGRAM_TYPE_FIRMWARE_CHUNK , FOTA_DATAGRAM_TYPE_UPDATE_REQUEST , FOTA_DATAGRAM_TYPE_UPDATE_RESPONSE , FOTA_DATAGRAM_TYPE_VERIFICATION }
	Datagram types corresponding to different FOTA operations. More...

enum	FotaError { FOTA_ERROR_SUCCESS , FOTA_ERROR_RESOURCE_EXHAUSTED , FOTA_ERROR_INVALID_ARGS , FOTA_ERROR_INTERNAL_ERROR , FOTA_ERROR_CRC32_MISMATCH , FOTA_ERROR_CRC32_DATA_NOT_ALIGNED , FOTA_ERROR_FLASH_WRITE_FAILED , FOTA_ERROR_FLASH_WRITE_OUT_OF_BOUNDS , FOTA_ERROR_FLASH_WRITE_NOT_ALIGNED , FOTA_ERROR_FLASH_READ_FAILED , FOTA_ERROR_FLASH_ERASE , FOTA_ERROR_FLASH_VERIFICATION_FAILED , FOTA_ERROR_INVALID_PACKET , FOTA_ERROR_NO_MEMORY , FOTA_ERROR_NO_DATAGRAM_FOUND , FOTA_ERROR_JUMP_FAILED }
	FOTA Error code definitions. More...

enum	FotaJumpRequest { FOTA_JUMP_APPLICATION , FOTA_JUMP_BOOTLOADER , FOTA_JUMP_MIDSUN_BIOS }

enum	FotaPacketType { FOTA_PACKET_TYPE_DATA , FOTA_PACKET_TYPE_HEADER , FOTA_PACKET_TYPE_ACK , FOTA_PACKET_TYPE_NACK , FOTA_PACKET_TYPE_ERROR }
	FOTA Packet Type. More...

enum	UartPort { UART_PORT_1 = 0 , UART_PORT_2 , NUM_UART_PORTS , UART_PORT_1 = 0 , UART_PORT_2 , NUM_UART_PORTS }
	UART Port selection.

enum	UartFlowControl { UART_FLOW_CONTROL_NONE , UART_FLOW_CONTROL_RTS , UART_FLOW_CONTROL_CTS , UART_FLOW_CONTROL_RTS_CTS , UART_FLOW_CONTROL_NONE , UART_FLOW_CONTROL_RTS , UART_FLOW_CONTROL_CTS , UART_FLOW_CONTROL_RTS_CTS }
	UART Flow control selection. More...

enum	GpioPort { GPIO_PORT_A = 0 , GPIO_PORT_B , NUM_GPIO_PORTS , GPIO_PORT_A = 0 , GPIO_PORT_B , GPIO_PORT_C , GPIO_PORT_D , GPIO_PORT_E , GPIO_PORT_H , NUM_GPIO_PORTS }
	UART Settings. More...

enum	PacketReceiverState { PKT_STATE_WAITING_SOF , PKT_STATE_READING_HEADER , PKT_STATE_READING_PAYLOAD , PKT_STATE_READING_CRC , PKT_STATE_READING_EOF }
	State machine states for packet receiving. More...

Functions
FotaError	fota_init ()

void	fota_process (void)

FotaError	fota_datagram_init (FotaDatagram datagram, FotaDatagramType type, uint32_t datagram_id, uint8_t data, uint32_t length)
	Initialize a datagram structure. More...

FotaError	fota_datagram_to_packets (FotaDatagram datagram, FotaPacket packets, uint16_t *num_packets, uint16_t max_packets)
	Fragment a datagram into packets for transmission. More...

FotaError	fota_datagram_process_data_packet (FotaDatagram datagram, FotaPacket packet)
	Process a received packet and incorporate it into a datagram. More...

FotaError	fota_datagram_process_header_packet (FotaDatagram datagram, FotaPacket packet)
	Process a received header packet and incorporate it into a datagram. More...

bool	fota_datagram_is_complete (FotaDatagram *datagram)
	Check if a datagram has been completely received. More...

FotaError	fota_datagram_verify (FotaDatagram *datagram)
	Verify the integrity of a complete datagram. More...

FotaError	fota_encryption_init ()
	Initialize the encryption unit. More...

uint32_t	fota_calculate_crc32 (uint8_t *data, uint32_t length_words)
	Calculate the CRC32 for a given buffer of 4-byte aligned data. More...

FotaError	fota_verify_packet_encryption (FotaPacket *packet)
	Verify a FOTA packets encryption. More...

FotaError	fota_verify_datagram_encryption (FotaDatagram *datagram)
	Verify a FOTA datagrams encryption. More...

FotaError	fota_flash_write (uintptr_t address, uint8_t *buffer, uint32_t buffer_len)
	Write to flash memory. More...

FotaError	fota_flash_erase (uint8_t start_page, uint8_t num_pages)
	Erase some number of flash pages. More...

FotaError	fota_flash_read (uintptr_t address, uint8_t *buffer, uint32_t buffer_len)
	Read from flash memory. More...

FotaError	fota_verify_flash_memory (void)
	Verify that the flash memory is not erased. More...

FotaError	fota_jump (FotaJumpRequest jump_request)

FotaError	fota_packet_init (FotaPacket *packet, FotaPacketType type, uint8_t sequence, uint16_t length)
	Initialize a packet structure. More...

FotaError	fota_packet_set_crc (FotaPacket *packet)
	Calculate and set the CRC for a packet. More...

FotaError	fota_packet_serialize (FotaPacket packet, uint8_t buffer, uint32_t buf_size, uint32_t *bytes_written)
	Serialize packet into a buffer for transmission. More...

FotaError	fota_packet_deserialize (FotaPacket packet, uint8_t buffer, uint32_t buf_size)
	Deserialize packet from received data. More...

bool	fota_is_timed_out (void)
	Checks if FOTA has timed out, meaning no requests have been received. More...

FotaError	network_init (UartPort uart, UartSettings settings, NetworkBuffer network_buffer)
	Initialize UART instance, assuming standard 8 bits 1 stop bit. More...

FotaError	network_read (UartPort uart, uint8_t *data, size_t len)
	Read data from the network buffer. More...

FotaError	network_tx (UartPort uart, uint8_t *data, size_t len)
	Transmit data from the UART port. More...

bool	isTimeout (bool is_tx)
	Checks if tx or rx command has timed out. More...

FotaError	network_buffer_init (NetworkBuffer *network_buffer)
	Initalizes circular buffer for use, by initalizing assocated structs. More...

uint16_t	network_buffer_num_items (NetworkBuffer *network_buffer)
	Fetches the number of items in the network buffer. More...

uint16_t	network_buffer_num_empty_slots (NetworkBuffer *network_buffer)
	Fetches the number of empty slots in the network buffer. More...

bool	network_buffer_empty (NetworkBuffer *network_buffer)
	Checks if the network buffer is empty. More...

bool	network_buffer_full (NetworkBuffer *network_buffer)
	Checks if the network buffer is full. More...

FotaError	network_buffer_write (NetworkBuffer network_buffer, uint8_t data)
	Write data bytes. More...

FotaError	network_buffer_read (NetworkBuffer network_buffer, uint8_t data)
	Read data bytes. More...

FotaError	packet_manager_init (PacketManager manager, UartSettings uart2_settings, void(callback)(FotaDatagram datagram))
	Initialize the packet manager. More...

FotaError	packet_manager_process (PacketManager *manager)
	Process received data from the network buffer. More...

FotaError	packet_manager_send_datagram (PacketManager manager, FotaDatagram datagram, FotaError(send_func)(int8_t data, uint32_t length))
	Send a datagram by fragmenting it into packets. More...

FotaError	packet_manager_create_datagram (PacketManager manager, FotaDatagramType type, uint8_t data, uint32_t length, FotaDatagram *datagram)
	Create a new datagram for sending. More...

FotaError	packet_manager_get_datagram (PacketManager manager, uint32_t datagram_id, FotaDatagram *datagram)
	Get a pointer to a completed datagram. More...

FotaError	packet_manager_free_datagram (PacketManager *manager, uint32_t datagram_id)
	Free a datagram slot. More...

Variables
uint32_t	_flash_start

uint32_t	_flash_size

uint32_t	_flash_page_size

uint32_t	_accumulator_memory

uint32_t	_accumulator_memory_size

uint32_t	_application_start

uint32_t	_application_size

uint32_t	_bootloader_start

uint32_t	_bootloader_size

uint32_t	_bios_start

uint32_t	_bios_size

uint32_t	_sram_start

uint32_t	_sram_size

Detailed Description

Firmware Over the Air (FOTA) Update system.

Macro Definition Documentation

◆ FOTA_ADDR_TO_PAGE

#define FOTA_ADDR_TO_PAGE ( addr ) (((uintptr_t)(addr) - (uintptr_t)APPLICATION_START_ADDRESS) / FOTA_PAGE_BYTES)

Convert memory address to page number.

Parameters

addr	Address to be converted to page number

Returns: Page number

◆ FOTA_PACKET_PAYLOAD_SIZE

#define FOTA_PACKET_PAYLOAD_SIZE 256U

FOTA packet payload size.

FotaPacket Serialized Format:

+---------—+-------------—+---------------—+-------------—+----------------—+ | Field | Size (bytes) | Description | Example Value | Notes | +---------—+-------------—+---------------—+-------------—+----------------—+ | sof | 1 | Start of Frame | 0xAA | Always 0xAA | | packet_type| 1 | Packet Type Enum | 0x01 | Type identifier | | datagram_id| 4 | Datagram ID | 0x00000005 | Big/little endian | | sequence_num| 1 | Packet Index | 0x02 | 0–7 in a datagram | | payload_len| 2 | Payload Length | 0x0040 | In bytes | | payload | N (variable) | Payload Data | [...] | Up to defined max | | crc32 | 4 | CRC32 Checksum | 0xDEADBEEF | On payload | | eof | 1 | End of Frame | 0xBB | Always 0xBB | +---------—+-------------—+---------------—+-------------—+----------------—+

Total Size: 14 bytes of header/footer + N bytes payload

◆ FOTA_PAGE_TO_ADDR

#define FOTA_PAGE_TO_ADDR ( page ) ((uintptr_t)(page) * (uintptr_t)FOTA_PAGE_BYTES + (uintptr_t)APPLICATION_START_ADDRESS)

Convert page number to memory address.

Parameters

page	Page number

Returns: 32-bit address

Enumeration Type Documentation

◆ FotaDatagramType

enum FotaDatagramType

Datagram types corresponding to different FOTA operations.

Enumerator
FOTA_DATAGRAM_TYPE_FIRMWARE_METADATA	Firmware metadata information
FOTA_DATAGRAM_TYPE_FIRMWARE_CHUNK	Chunk of firmware data
FOTA_DATAGRAM_TYPE_UPDATE_REQUEST	Request to perform update
FOTA_DATAGRAM_TYPE_UPDATE_RESPONSE	Response to update request
FOTA_DATAGRAM_TYPE_VERIFICATION	Verification information

◆ FotaError

enum FotaError

FOTA Error code definitions.

Enumerator
FOTA_ERROR_SUCCESS	Success error code
FOTA_ERROR_RESOURCE_EXHAUSTED	Resource exhausted error code
FOTA_ERROR_INVALID_ARGS	Invalid arguments error code
FOTA_ERROR_INTERNAL_ERROR	Internal issue error code
FOTA_ERROR_CRC32_MISMATCH	CRC mismatch error code
FOTA_ERROR_CRC32_DATA_NOT_ALIGNED	Data not 4-byte aligned in CRC32 calculation

◆ FotaJumpRequest

enum FotaJumpRequest

Enumerator
FOTA_JUMP_APPLICATION	Jump to application memory
FOTA_JUMP_BOOTLOADER	Jump to bootloader memory
FOTA_JUMP_MIDSUN_BIOS	Jump to Midnight Sun BIOS

◆ FotaPacketType

enum FotaPacketType

FOTA Packet Type.

Enumerator
FOTA_PACKET_TYPE_DATA	Data packet
FOTA_PACKET_TYPE_HEADER	Header packet
FOTA_PACKET_TYPE_ACK	Acknowledgment packet
FOTA_PACKET_TYPE_NACK	Not Acknowledged packet
FOTA_PACKET_TYPE_ERROR	Error packet

◆ GpioPort

enum GpioPort

UART Settings.

TX Pin will transmit data. RX pin will receive data. The baudrate is the number of symbols sent per second. Both devices must agree on the baudrate with a tolerance of +-3%. Flow control is of type UartFlowControl.

Enumerator
GPIO_PORT_A	Gpio port A
GPIO_PORT_B	Gpio port B
NUM_GPIO_PORTS	Number of Gpio Ports
GPIO_PORT_A	GPIO Port A
GPIO_PORT_B	GPIO Port B
GPIO_PORT_C	GPIO Port C
GPIO_PORT_D	GPIO Port D
GPIO_PORT_E	GPIO Port E
GPIO_PORT_H	GPIO Port H
NUM_GPIO_PORTS	Number of GPIO Ports

◆ PacketReceiverState

enum PacketReceiverState

State machine states for packet receiving.

Enumerator
PKT_STATE_WAITING_SOF	Waiting for start of frame
PKT_STATE_READING_HEADER	Reading packet header
PKT_STATE_READING_PAYLOAD	Reading packet payload
PKT_STATE_READING_CRC	Reading CRC
PKT_STATE_READING_EOF	Reading end of frame

◆ UartFlowControl

enum UartFlowControl

UART Flow control selection.

Flow control is a method of synchronizing UART communication between 2 devices. For most applications, this can be set to UART_FLOW_CONTROL_NONE.

Enumerator
UART_FLOW_CONTROL_NONE	Disable flow control
UART_FLOW_CONTROL_RTS	Enable request-to-send flow control
UART_FLOW_CONTROL_CTS	Enable clear-to-send flow control
UART_FLOW_CONTROL_RTS_CTS	Enable both request-to-send and clear-to-send flow control
UART_FLOW_CONTROL_NONE	Disable flow control
UART_FLOW_CONTROL_RTS	Enable request-to-send flow control
UART_FLOW_CONTROL_CTS	Enable clear-to-send flow control
UART_FLOW_CONTROL_RTS_CTS	Enable both request-to-send and clear-to-send flow control

Function Documentation

◆ fota_calculate_crc32()

uint32_t fota_calculate_crc32	(	uint8_t *	data,
		uint32_t	length_words
	)

Calculate the CRC32 for a given buffer of 4-byte aligned data.

Parameters

data_start	Pointer to the start of the data
length_words	Size of the data in words

◆ fota_datagram_init()

FotaError fota_datagram_init	(	FotaDatagram *	datagram,
		FotaDatagramType	type,
		uint32_t	datagram_id,
		uint8_t *	data,
		uint32_t	length
	)

Initialize a datagram structure.

Parameters

datagram	Pointer to datagram to initialize
type	Type of datagram
datagram_id	Unique ID for this datagram
data	Data to include in datagram (can be NULL if building incrementally)
length	Length of data

Returns: FotaError Error code

◆ fota_datagram_is_complete()

bool fota_datagram_is_complete ( FotaDatagram * datagram )

Check if a datagram has been completely received.

Parameters

datagram Datagram to check

Returns: TRUE if datagram is complete FALSE otherwise

◆ fota_datagram_process_data_packet()

FotaError fota_datagram_process_data_packet	(	FotaDatagram *	datagram,
		FotaPacket *	packet
	)

Process a received packet and incorporate it into a datagram.

Parameters

datagram	Datagram being reconstructed
packet	Received packet

Returns: FotaError Error code

◆ fota_datagram_process_header_packet()

FotaError fota_datagram_process_header_packet	(	FotaDatagram *	datagram,
		FotaPacket *	packet
	)

Process a received header packet and incorporate it into a datagram.

Parameters

datagram	Datagram being reconstructed
packet	Received header packet

Returns: FotaError Error code

◆ fota_datagram_to_packets()

FotaError fota_datagram_to_packets	(	FotaDatagram *	datagram,
		FotaPacket *	packets,
		uint16_t *	num_packets,
		uint16_t	max_packets
	)

Fragment a datagram into packets for transmission.

Parameters

datagram	Datagram to fragment
packets	Array to store generated packets
num_packets	Pointer to store number of packets generated
max_packets	Maximum number of packets that can be stored in the array

Returns: FotaError Error code

◆ fota_datagram_verify()

FotaError fota_datagram_verify ( FotaDatagram * datagram )

Verify the integrity of a complete datagram.

Parameters

datagram Datagram to verify

Returns: FotaError Error code

◆ fota_encryption_init()

FotaError fota_encryption_init ( )

Initialize the encryption unit.

Returns: FOTA_SUCCESS if initialized succesfully FOTA_ERROR_INTERNAL_ERROR if initialization fails

◆ fota_flash_erase()

FotaError fota_flash_erase	(	uint8_t	start_page,
		uint8_t	num_pages
	)

Erase some number of flash pages.

Parameters

start_page	Initial page number to erase
num_pages	Number of pages to erase

Returns: FOTA_ERROR_SUCCESS if data is erased succesfully FOTA_ERROR_FLASH_ERASE if page is out of bounds OR erasing failed

◆ fota_flash_read()

FotaError fota_flash_read	(	uintptr_t	address,
		uint8_t *	buffer,
		uint32_t	buffer_len
	)

Read from flash memory.

Parameters

address	Base memory address to read from
buffer	Pointer to the data buffer
buffer_len	Length of the data buffer

Returns: FOTA_ERROR_SUCCESS if data is read succesfully FOTA_ERROR_FLASH_READ_FAILED if data read failed

◆ fota_flash_write()

FotaError fota_flash_write	(	uintptr_t	address,
		uint8_t *	buffer,
		uint32_t	buffer_len
	)

Write to flash memory.

Parameters

address	Base memory address to write to
buffer	Pointer to the data buffer
buffer_len	Length of the data buffer

Returns: FOTA_ERROR_SUCCESS if data is written succesfully FOTA_ERROR_FLASH_WRITE_FAILED if HAL flash fails FOTA_ERROR_FLASH_WRITE_OUT_OF_BOUNDS if address is out of bounds FOTA_ERROR_FLASH_WRITE_NOT_ALIGNED if data is not aligned

◆ fota_is_timed_out()

bool fota_is_timed_out ( void )

Checks if FOTA has timed out, meaning no requests have been received.

Returns: TRUE if a timeout event has occurred FALSE if no timeout has occurred

◆ fota_packet_deserialize()

FotaError fota_packet_deserialize	(	FotaPacket *	packet,
		uint8_t *	buffer,
		uint32_t	buf_size
	)

Deserialize packet from received data.

Parameters

packet	Output packet structure
buffer	Input buffer containing serialized packet
buf_size	Size of input buffer

Returns: FotaError Error code

◆ fota_packet_init()

FotaError fota_packet_init	(	FotaPacket *	packet,
		FotaPacketType	type,
		uint8_t	sequence,
		uint16_t	length
	)

Initialize a packet structure.

Parameters

packet	Pointer to the packet to initialize
type	Type of packet
sequence	Sequence number
length	Payload length

Returns: FotaError Error code

◆ fota_packet_serialize()

FotaError fota_packet_serialize	(	FotaPacket *	packet,
		uint8_t *	buffer,
		uint32_t	buf_size,
		uint32_t *	bytes_written
	)

Serialize packet into a buffer for transmission.

Parameters

packet	Packet to serialize
buffer	Output buffer
buf_size	Size of output buffer
bytes_written	Number of bytes written

Returns: FotaError Error code

◆ fota_packet_set_crc()

FotaError fota_packet_set_crc ( FotaPacket * packet )

Calculate and set the CRC for a packet.

Parameters

packet Pointer to packet

Returns: FotaError Error code

◆ fota_verify_datagram_encryption()

FotaError fota_verify_datagram_encryption ( FotaDatagram * datagram )

Verify a FOTA datagrams encryption.

Parameters

datagram Pointer to the encrypted datagram

Returns: FOTA_SUCCESS if encryption is decoded succesfully and the datagram is valid

◆ fota_verify_flash_memory()

FotaError fota_verify_flash_memory ( void )

Verify that the flash memory is not erased.

This checks the entire application flash memory to ensure it is not entirely erased

Returns: FOTA_ERROR_SUCCESS if the memomry is valid FOTA_ERROR_FLASH_ERR if the memory is corrupt

◆ fota_verify_packet_encryption()

FotaError fota_verify_packet_encryption ( FotaPacket * packet )

Verify a FOTA packets encryption.

Parameters

packet Pointer to the encrypted packet

Returns: FOTA_SUCCESS if encryption is decoded succesfully and the datagram is valid

◆ isTimeout()

bool isTimeout ( bool is_tx )

Checks if tx or rx command has timed out.

Subtracts the difference of current clock time and clock time when command started

Parameters

is_tx if it is checking timeout for a tx or an rx command

Returns: true if time elapsed is greater than FOTA_UART_TIMEOUT_MS false if time elapsed is less than FOTA_UART_TIMEOUT_MS