knob.c File Reference

The poll transactions and the angle steps of the rotary knob, see knob.h. More...

#include "knob.h"
#include <stddef.h>

Functions
uint16_t	knob_decode (uint8_t hi, uint8_t lo)
	The datasheet's angle, 0..16383, rising counter-clockwise seen from the chip's top: hi read from KNOB_REG_ANGLE_HI, lo from KNOB_REG_ANGLE_LO.
uint16_t	knob_clockwise (uint16_t angle)
	angle mirrored, rising clockwise seen from the top: 0 stays 0.
bool	knob_attach (knob_t *k, unsigned addr)
	Take addr as the sensor's address and forget the reference.
int	knob_poll_addr (const knob_t *k)
	The address the next poll reads, or -1 for a knob that is not attached: then no transaction is made.
bool	knob_poll_probe_first (const knob_t *k)
	Whether the next poll probes the address before its reads: an attached knob with no reference.
void	knob_reset (knob_t *k)
	Forget the reference: the next usable reading moves nothing.
int	knob_feed (knob_t *k, bool usable, uint16_t raw)
	Feed one poll.
int	knob_poll_done (knob_t *k, bool answered, const uint8_t bytes[KNOB_POLL_READS])
	End one poll.
float	knob_span_fraction (int steps, int scale_deg)
	Fraction of a slider's span that steps moves it when the span is scale_deg degrees of knob.

Variables
const uint8_t	knob_poll_regs [KNOB_POLL_READS]

Detailed Description

The poll transactions and the angle steps of the rotary knob, see knob.h.

SPDX-License-Identifier: MIT

Function Documentation

knob_attach()

bool knob_attach	(	knob_t *	k,
		unsigned	addr )

Take addr as the sensor's address and forget the reference.

An address the panel board answers at (panel_i2c.h) is refused: the knob stays detached, knob_poll_addr() names no address and nothing is ever sent for it. Returns whether the address was taken.

Parameters

k	The knob to attach.
addr	The 7-bit sensor address.

Returns

true when the address was taken.

knob_clockwise()

uint16_t knob_clockwise

(

uint16_t

angle

)

angle mirrored, rising clockwise seen from the top: 0 stays 0.

Parameters

angle

The angle, 0 to 16383.

Returns

The mirrored angle, 0 to 16383.

knob_decode()

uint16_t knob_decode	(	uint8_t	hi,
		uint8_t	lo )

The datasheet's angle, 0..16383, rising counter-clockwise seen from the chip's top: hi read from KNOB_REG_ANGLE_HI, lo from KNOB_REG_ANGLE_LO.

Bits 1 and 0 of lo are ignored.

Parameters

hi	The byte read from KNOB_REG_ANGLE_HI.
lo	The byte read from KNOB_REG_ANGLE_LO.

Returns

The 14-bit angle, 0 to 16383.

knob_feed()

int knob_feed	(	knob_t *	k,
		bool	usable,
		uint16_t	raw )

Feed one poll.

usable false (no answer) forgets the reference. Returns the signed steps since the last usable reading, positive for a rising raw, taking the short way across 16383 to 0; zero for the first reading after a reset, and for a step over KNOB_MAX_STEP, which becomes the new reference.

Parameters

k	The knob.
usable	false for no answer, which forgets the reference.
raw	The angle, 0 to 16383.

Returns

The signed steps since the last usable reading.

knob_poll_addr()

int knob_poll_addr

(

const knob_t *

k

)

The address the next poll reads, or -1 for a knob that is not attached: then no transaction is made.

Parameters

k

The knob.

Returns

The address, or -1 for a knob that is not attached.

knob_poll_done()

int knob_poll_done	(	knob_t *	k,
		bool	answered,
		const uint8_t	bytes[KNOB_POLL_READS] )

End one poll.

answered: every read of knob_poll_regs answered, and bytes[i] is what knob_poll_regs[i] gave. Returns the steps, positive clockwise seen from the top; a poll that was not answered, or a knob that is not attached, returns 0 and forgets the reference. A poll whose two 0x03 bytes differ returns 0 and keeps the reference.

Parameters

k	The knob.
answered	true when every read of knob_poll_regs answered.
bytes	The bytes read, one per knob_poll_regs entry.

Returns

The steps, positive clockwise seen from the top; 0 when the poll is not answered.

knob_poll_probe_first()

bool knob_poll_probe_first

(

const knob_t *

k

)

Whether the next poll probes the address before its reads: an attached knob with no reference.

A probe that is not acknowledged ends the poll as not answered, with no read made.

Parameters

k

The knob.

Returns

true when the next poll probes the address first.

knob_reset()

void knob_reset

(

knob_t *

k

)

Forget the reference: the next usable reading moves nothing.

Parameters

k	The knob to reset.

knob_span_fraction()

float knob_span_fraction	(	int	steps,
		int	scale_deg )

Fraction of a slider's span that steps moves it when the span is scale_deg degrees of knob.

scale_deg outside the setting's range is clamped to it.

Parameters

steps	The signed steps moved.
scale_deg	Degrees of knob per full slider span.

Returns

The fraction of the slider span that steps moves it.

Variable Documentation

knob_poll_regs

const uint8_t knob_poll_regs[KNOB_POLL_READS]

Initial value:

                             = {
    KNOB_REG_ANGLE_HI,      
    KNOB_REG_ANGLE_LO,
    KNOB_REG_ANGLE_HI,      
}