/*
 * i2c_bus — single owner of the board's I2C bus.
 *
 * SDA 38 / SCL 39, shared by the PCF8574 expander (0x21) and the CST826 touch
 * controller (0x15). The I2C connector on the case brings the same bus out, so
 * anything added later lands here too.
 */
#pragma once

#include "driver/i2c_master.h"
#include "esp_err.h"

#define I2C_BUS_SDA_GPIO    38
#define I2C_BUS_SCL_GPIO    39
#define I2C_BUS_FREQ_HZ     400000

/* Initialise the bus. Safe to call more than once. */
esp_err_t i2c_bus_init(void);

/* Add a device to the shared bus. */
esp_err_t i2c_bus_add_device(uint8_t addr, i2c_master_dev_handle_t *out);

/*
 * Probe every address and log what answers.
 *
 * PRD 8.1: this is the cheap sanity check that tells you the board is alive
 * and the I2C pins are right, independently of the display. Expect 0x21 and
 * 0x15. Returns the number of devices found.
 */
int i2c_bus_scan(void);