knob.h

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#pragma once
 
#include <stdbool.h>
#include <stdint.h>
 
#include "panel_i2c.h"
 
#ifdef __cplusplus
extern "C" {
#endif

#define KNOB_I2C_ADDR        0x06
 
_Static_assert(!PANEL_I2C_RESERVED(KNOB_I2C_ADDR),
               "the knob's address is one the panel board answers at");

#define KNOB_REG_ANGLE_HI    0x03
#define KNOB_REG_ANGLE_LO    0x04

#define KNOB_POLL_READS      3
extern const uint8_t knob_poll_regs[KNOB_POLL_READS];

#define KNOB_COUNTS          16384

#define KNOB_POLL_MS         10
#define KNOB_POLL_IDLE_MS    100

#define KNOB_MAX_STEP        (KNOB_COUNTS / 4)

#define KNOB_SCALE_DEG_DEFAULT 270
#define KNOB_SCALE_DEG_MIN     90
#define KNOB_SCALE_DEG_MAX     720

uint16_t knob_decode(uint8_t hi, uint8_t lo);

uint16_t knob_clockwise(uint16_t angle);

typedef struct {
    bool     attached;    
    uint8_t  addr;        
    bool     have_ref;                  
    uint16_t ref;
} knob_t;

bool knob_attach(knob_t *k, unsigned addr);

int knob_poll_addr(const knob_t *k);

bool knob_poll_probe_first(const knob_t *k);

void knob_reset(knob_t *k);

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

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

float knob_span_fraction(int steps, int scale_deg);
 
#ifdef __cplusplus
}
#endif