tone_cap.c File Reference

The phase tap's capture. More...

#include "tone_cap.h"
#include <string.h>
#include "hardware/clocks.h"
#include "hardware/dma.h"
#include "hardware/gpio.h"
#include "hardware/pio.h"
#include "pico/stdlib.h"
#include "tone_cap.pio.h"
#include "tone_svc.h"

Macros
#define	RING_BYTES   (TONE_RING_WORDS * 4u)
	16kB, on a 16kB boundary: the DMA wraps its write address on it.
#define	RING_BITS   14u

Functions
void	tone_cap_rest (uint8_t pin)
	The pin as an input with its pull-down on, driven by nothing: a tap that is off.
bool	tone_cap_start (uint8_t pin)
	Claim a state machine and a DMA channel, load the program, start the capture on pin.
bool	tone_cap_pause (void)
	Mark the capture not running, so the next order tells core 1 to read nothing from it; the state machine and the channel stay, and tone_cap_wr() and tone_cap_stalled() still read them for a pass already under way.
void	tone_cap_resume (void)
	Mark a paused capture running again, when core 1 did not acknowledge the pause and nothing was taken down.
void	tone_cap_stop (void)
	Stop the capture and give back what it claimed; the pin is left an input with its pull-down on.
bool	tone_cap_running (void)
	Whether the capture runs.
uint64_t	tone_cap_start_us (void)
	The microsecond timer when the counter began.
const uint32_t *	tone_cap_ring (void)
	The ring.
uint32_t	tone_cap_wr (void)
	The slot the DMA writes next; 0 when the capture does not run.
bool	tone_cap_stalled (void)
	Whether the state machine dropped a word (its FIFO was full) since the last call; clears the flag.

Variables
static uint32_t	s_ring [TONE_RING_WORDS]
static volatile bool	s_running
	Written by core 0 while the capture is stopped or starting, read by core 1: running is set last and cleared first.
static PIO	s_pio
static uint	s_sm
static uint	s_offset
static int	s_dma = -1
static volatile uint32_t	s_wr_base
static uint8_t	s_pin
static uint64_t	s_start_us

Detailed Description

The phase tap's capture.

See tone_cap.h.

SPDX-License-Identifier: MIT

Function Documentation

tone_cap_pause()

bool tone_cap_pause

(

void

)

Mark the capture not running, so the next order tells core 1 to read nothing from it; the state machine and the channel stay, and tone_cap_wr() and tone_cap_stalled() still read them for a pass already under way.

True when it was running. The first step of taking the capture down: tell core 1, wait for it to acknowledge, then tone_cap_stop().

Returns

true when it was running.

tone_cap_rest()

void tone_cap_rest

(

uint8_t

pin

)

The pin as an input with its pull-down on, driven by nothing: a tap that is off.

Not while the capture runs.

Parameters

pin	GPIO number of the phase input.

tone_cap_ring()

const uint32_t * tone_cap_ring

(

void

)

The ring.

Returns

The ring of edge words.

tone_cap_running()

bool tone_cap_running

(

void

)

Whether the capture runs.

Returns

true while the capture runs.

tone_cap_stalled()

bool tone_cap_stalled

(

void

)

Whether the state machine dropped a word (its FIFO was full) since the last call; clears the flag.

Called from core 1 only.

Returns

true when a word was dropped since the last call.

tone_cap_start()

bool tone_cap_start

(

uint8_t

pin

)

Claim a state machine and a DMA channel, load the program, start the capture on pin.

False, with nothing claimed, when no PIO block that reaches the pin has room for the program and a state machine, no DMA channel is free, or the system clock is not 150MHz.

Parameters

pin	GPIO number of the phase input.

Returns

true when the capture runs.

tone_cap_start_us()

uint64_t tone_cap_start_us

(

void

)

The microsecond timer when the counter began.

Returns

The microsecond timer value when the counter began.

tone_cap_stop()

void tone_cap_stop

(

void

)

Stop the capture and give back what it claimed; the pin is left an input with its pull-down on.

Safe when it is not running. Core 1 is not reading the ring or the channel at that moment (tone_cap_pause()).

tone_cap_wr()

uint32_t tone_cap_wr

(

void

)

The slot the DMA writes next; 0 when the capture does not run.

Returns

The slot the DMA writes next, 0 when the capture does not run.

Variable Documentation

s_pin

uint8_t s_pin

static

the capture pin, GPIO

s_start_us

uint64_t s_start_us

static

the capture's start, µs

s_wr_base

volatile uint32_t s_wr_base

static

the ring's address