knob_task.c File Reference

The knob's I2C bus, its sensor's registration and the task that polls it. More...

#include "knob_task.h"
#include <stdatomic.h>
#include <stddef.h>
#include "board_pins.h"
#include "driver/i2c_master.h"
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "knob.h"

Macros
#define	KNOB_I2C_TIMEOUT_MS   5
	The longest one transaction waits, in milliseconds.

Functions
static bool	knob_read (uint8_t reg, uint8_t *byte)
static void	knob_task (void *arg)
	The polling task: one poll every KNOB_POLL_MS while the sensor answers, every KNOB_POLL_IDLE_MS while it does not or the setting is off.
void	knob_task_attach (void)
	Set up the knob's bus and register the sensor on it.
void	knob_task_start (void)
void	knob_task_set_enabled (bool on)
int	knob_task_take (void)

Variables
static const char *	TAG = "knob"
static atomic_bool	s_on
static atomic_int	s_steps
static i2c_master_bus_handle_t	s_bus
	The knob's own bus; NULL when it did not come up.
static i2c_master_dev_handle_t	s_dev
static knob_t	s_knob

Detailed Description

The knob's I2C bus, its sensor's registration and the task that polls it.

SPDX-License-Identifier: MIT

Macro Definition Documentation

KNOB_I2C_TIMEOUT_MS

#define KNOB_I2C_TIMEOUT_MS   5

The longest one transaction waits, in milliseconds.

The bus is the knob's alone, so a transaction waits for nothing else. The three transactions of one poll take about 0.3ms at 400kHz. A failed one costs more: the driver resets the controller and clears the bus, which waits up to 50ms (I2C_CLR_BUS_TIMEOUT_MS) while SDA is held low.

Function Documentation

knob_task()

void knob_task ( void * arg )

static

The polling task: one poll every KNOB_POLL_MS while the sensor answers, every KNOB_POLL_IDLE_MS while it does not or the setting is off.

Logs one line when the sensor first answers and one when it stops answering after that: a change, not a poll.

Parameters

arg

Unused.

knob_task_attach()

void knob_task_attach

(

void

)

Set up the knob's bus and register the sensor on it.

Call once, before knob_task_start(). Sends nothing. A bus or a device that does not come up is logged; the task then reads nothing.

knob_task_set_enabled()

void knob_task_set_enabled

(

bool

on

)

Poll the sensor (true) or leave the bus alone (false).

knob_task_start()

void knob_task_start

(

void

)

Create the task. Call once, after knob_task_attach().

knob_task_take()

int knob_task_take

(

void

)

The steps turned since the last call, signed; clears the count.