kst_line.c File Reference

The KST wire on one RP2350 pin. More...

#include "kst_line.h"
#include <string.h>
#include "hardware/clocks.h"
#include "hardware/dma.h"
#include "hardware/gpio.h"
#include "hardware/pio.h"
#include "hardware/timer.h"
#include "pico.h"
#include "kst_line.pio.h"

Macros
#define	IDLE_PC   1u
	The instruction the state machine stalls on between transactions.
#define	DMA_COUNT_MASK   0x0FFFFFFFu
	A transfer count's low 28 bits are the count; the rest is the mode.

Functions
static PIO	line_pio (const kst_line_t *l)
	Get the PIO block of a line.
static bool	line_idle (const kst_line_t *l)
	The state machine waits for a stream: it stalls on the first out, the FIFO is empty and the channel has handed over every word.
static void	line_restart (kst_line_t *l)
	Put the state machine at the start of the program with the pad driven low, whatever it was doing.
void	kst_line_init (kst_line_t *line)
	Mark line closed.
kst_line_err_t	kst_line_open (kst_line_t *line, unsigned pin)
	Claim the resources and take pin: from the return on the pad drives low.
void	kst_line_close (kst_line_t *line)
	Stop the state machine, give back what the open claimed and leave the pad an input with its pull-down on.
bool	kst_line_is_open (const kst_line_t *line)
	Check whether a line is open.
bool	kst_line_busy (const kst_line_t *line)
	A transaction runs: between a start() that returned true and the poll() that returns true.
uint32_t	kst_line_half_cell_ns (const kst_line_t *line)
	The transmit half-cell the system clock gives, in ns; 0 on a closed line.
bool	kst_line_start (void *ctx, const kst_frame_t *frame, uint32_t window_ns)
	The three functions of kst_driver_t; ctx is the kst_line_t.
bool	kst_line_poll (void *ctx, kst_capture_t *out)
	Poll a transaction; the second of the three driver functions.
uint32_t	kst_line_now_us (void *ctx)
	Read the microsecond clock; the third of the three driver functions.
kst_driver_t	kst_line_driver (kst_line_t *line)
	The driver for a session on line.

Detailed Description

The KST wire on one RP2350 pin.

See kst_line.h.

SPDX-License-Identifier: MIT

Function Documentation

kst_line_busy()

bool kst_line_busy

(

const kst_line_t *

line

)

A transaction runs: between a start() that returned true and the poll() that returns true.

Parameters

line	Line object.

Returns

true between a start that returned true and the poll that returns true.

kst_line_close()

void kst_line_close

(

kst_line_t *

line

)

Stop the state machine, give back what the open claimed and leave the pad an input with its pull-down on.

A transaction on the wire is cut. Safe on a closed line.

Parameters

line	Line object.

kst_line_driver()

kst_driver_t kst_line_driver

(

kst_line_t *

line

)

The driver for a session on line.

Parameters

line	Line object.

Returns

The driver for a session on the line.

kst_line_half_cell_ns()

uint32_t kst_line_half_cell_ns

(

const kst_line_t *

line

)

The transmit half-cell the system clock gives, in ns; 0 on a closed line.

Parameters

line	Line object.

Returns

The transmit half-cell in ns; 0 on a closed line.

kst_line_init()

void kst_line_init

(

kst_line_t *

line

)

Mark line closed.

Call once, before the first open.

Parameters

line	Line object to mark closed.

kst_line_is_open()

bool kst_line_is_open

(

const kst_line_t *

line

)

Check whether a line is open.

Parameters

line	Line object.

Returns

true when the line is open.

kst_line_now_us()

uint32_t kst_line_now_us

(

void *

ctx

)

Read the microsecond clock; the third of the three driver functions.

Parameters

ctx	The kst_line_t.

Returns

The microsecond clock.

kst_line_open()

kst_line_err_t kst_line_open	(	kst_line_t *	line,
		unsigned	pin )

Claim the resources and take pin: from the return on the pad drives low.

The caller has stopped every other use of the pin. On an error nothing stays claimed and the pin is not touched. An open line is closed first.

Parameters

line	Line object.
pin	GPIO number.

Returns

KST_LINE_OK, or the error that refused the open.

kst_line_poll()

bool kst_line_poll	(	void *	ctx,
		kst_capture_t *	out )

Poll a transaction; the second of the three driver functions.

Parameters

ctx	The kst_line_t.
out	Receives the capture when the transaction has ended.

Returns

true once, when the transaction has ended.

kst_line_start()

bool kst_line_start	(	void *	ctx,
		const kst_frame_t *	frame,
		uint32_t	window_ns )

The three functions of kst_driver_t; ctx is the kst_line_t.

Parameters

ctx	The kst_line_t.
frame	Frame to send.
window_ns	Capture end, in ns after the last edge.

Returns

true when the transaction started.

line_idle()

bool line_idle ( const kst_line_t * l )

static

The state machine waits for a stream: it stalls on the first out, the FIFO is empty and the channel has handed over every word.

A stream is 6 words or more and the FIFO and the shift register hold 5, so this is false from the start of a transfer to the end of the capture.