fifo

Functions for the inter-core FIFOs. More...

Functions
static bool	multicore_fifo_rvalid (void)
	Check the read FIFO to see if there is data available (sent by the other core) More...
static bool	multicore_fifo_wready (void)
	Check the write FIFO to see if it has space for more data. More...
void	multicore_fifo_push_blocking (uint32_t data)
	Push data on to the write FIFO (data to the other core). More...
bool	multicore_fifo_push_timeout_us (uint32_t data, uint64_t timeout_us)
	Push data on to the write FIFO (data to the other core) with timeout. More...
uint32_t	multicore_fifo_pop_blocking (void)
	Pop data from the read FIFO (data from the other core). More...
bool	multicore_fifo_pop_timeout_us (uint64_t timeout_us, uint32_t *out)
	Pop data from the read FIFO (data from the other core) with timeout. More...
static void	multicore_fifo_drain (void)
	Discard any data in the read FIFO. More...
static void	multicore_fifo_clear_irq (void)
	Clear FIFO interrupt. More...
static uint32_t	multicore_fifo_get_status (void)
	Get FIFO statuses. More...

Detailed Description

Functions for the inter-core FIFOs.

The RP2040 contains two FIFOs for passing data, messages or ordered events between the two cores. Each FIFO is 32 bits wide, and 8 entries deep. One of the FIFOs can only be written by core 0, and read by core 1. The other can only be written by core 1, and read by core 0.

Note

The inter-core FIFOs are a very precious resource and are frequently used for SDK functionality (e.g. during core 1 launch or by the lockout functions). Additionally they are often required for the exclusive use of an RTOS (e.g. FreeRTOS SMP). For these reasons it is suggested that you do not use the FIFO for your own purposes unless none of the above concerns apply; the majority of cases for transferring data between cores can be eqaully well handled by using a queue

Function Documentation

multicore_fifo_clear_irq()

static void multicore_fifo_clear_irq ( void  )

inlinestatic

Clear FIFO interrupt.

Note that this only clears an interrupt that was caused by the ROE or WOF flags. To clear the VLD flag you need to use one of the 'pop' or 'drain' functions.

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

See also

multicore_fifo_get_status

multicore_fifo_drain()

static void multicore_fifo_drain ( void  )

inlinestatic

Discard any data in the read FIFO.

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

multicore_fifo_get_status()

static uint32_t multicore_fifo_get_status ( void  )

inlinestatic

Get FIFO statuses.

Returns

The statuses as a bitfield

Bit	Description
3	Sticky flag indicating the RX FIFO was read when empty (ROE). This read was ignored by the FIFO.
2	Sticky flag indicating the TX FIFO was written when full (WOF). This write was ignored by the FIFO.
1	Value is 1 if this core’s TX FIFO is not full (i.e. if FIFO_WR is ready for more data)
0	Value is 1 if this core’s RX FIFO is not empty (i.e. if FIFO_RD is valid)

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

multicore_fifo_pop_blocking()

uint32_t multicore_fifo_pop_blocking

(

void

)

Pop data from the read FIFO (data from the other core).

This function will block until there is data ready to be read Use multicore_fifo_rvalid() to check if data is ready to be read if you don't want to block.

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

Returns

32 bit data from the read FIFO.

multicore_fifo_pop_timeout_us()

bool multicore_fifo_pop_timeout_us	(	uint64_t	timeout_us,
		uint32_t *	out
	)

Pop data from the read FIFO (data from the other core) with timeout.

This function will block until there is data ready to be read or the timeout is reached

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

Parameters

timeout_us	the timeout in microseconds
out	the location to store the popped data if available

Returns

true if the data was popped and a value copied into out, false if the timeout occurred before data could be popped

multicore_fifo_push_blocking()

void multicore_fifo_push_blocking

(

uint32_t

data

)

Push data on to the write FIFO (data to the other core).

This function will block until there is space for the data to be sent. Use multicore_fifo_wready() to check if it is possible to write to the FIFO if you don't want to block.

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

Parameters

data	A 32 bit value to push on to the FIFO

multicore_fifo_push_timeout_us()

bool multicore_fifo_push_timeout_us	(	uint32_t	data,
		uint64_t	timeout_us
	)

Push data on to the write FIFO (data to the other core) with timeout.

This function will block until there is space for the data to be sent or the timeout is reached

Parameters

data	A 32 bit value to push on to the FIFO
timeout_us	the timeout in microseconds

Returns

true if the data was pushed, false if the timeout occurred before data could be pushed

multicore_fifo_rvalid()

static bool multicore_fifo_rvalid ( void  )

inlinestatic

Check the read FIFO to see if there is data available (sent by the other core)

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

Returns

true if the FIFO has data in it, false otherwise

multicore_fifo_wready()

static bool multicore_fifo_wready ( void  )

inlinestatic

Check the write FIFO to see if it has space for more data.

See the note in the fifo section for considerations regarding use of the inter-core FIFOs

Returns

true if the FIFO has room for more data, false otherwise