How to output 2.048MHz clock on any pin on the ESP32

You can use the LEDC timer (typically used for PWM) to output a 50% duty cycle clock with 3.3V P-P amplitude on any output-capable GPIO pin.

First,

#include <driver/ledc.h>

then setup the timer. You only need to do this once on startup, no code in your loop function is required.

/**
 * Setup 2.048MHz clock output on GPIO33
 */
ledc_timer_config_t ledc_timer = {
    .speed_mode = LEDC_HIGH_SPEED_MODE,
    .bit_num    = LEDC_TIMER_2_BIT,
    .timer_num  = LEDC_TIMER_0,
    .freq_hz    = 2048000
};
ledc_channel_config_t ledc_channel = {
    .gpio_num   = GPIO_NUM_33,
    .speed_mode = LEDC_HIGH_SPEED_MODE,
    .channel    = LEDC_CHANNEL_0,
    .timer_sel  = LEDC_TIMER_0,
    .duty       = 2
};
ledc_timer_config(&ledc_timer);
ledc_channel_config(&ledc_channel);