master.c

#include <stdio.h>
#include "driver/i2c_master.h"
#include "freertos/FreeRTOS.h"

void app_main(void)
{
    i2c_master_bus_config_t mcfg = {
        .i2c_port = 0,
        .scl_io_num = GPIO_NUM_15,
        .sda_io_num = GPIO_NUM_16,
        .clk_source = I2C_CLK_SRC_DEFAULT
    };

    i2c_master_bus_handle_t master_bus;
    ESP_ERROR_CHECK(i2c_new_master_bus(&mcfg, &master_bus));

    while (1) {
        int r = rand() & 0x7f;
        if (r != 106) {
            i2c_device_config_t dev_cfg = {
                .dev_addr_length = I2C_ADDR_BIT_LEN_7,
                .device_address = r,
                .scl_speed_hz = 400000,
                .scl_wait_us = 0
            };

            printf("trying to read from %d\n", r);
            i2c_master_dev_handle_t slave_dev;
            ESP_ERROR_CHECK(i2c_master_bus_add_device(master_bus, &dev_cfg, &slave_dev));
            uint8_t rb[10];
            i2c_master_receive(slave_dev, rb, sizeof(rb), 100);
            i2c_master_bus_rm_device(slave_dev);
        }
        vTaskDelay(150 / portTICK_PERIOD_MS);
    }
}