looks like you are attempting ESP32S3 OTG Host serial (Virtual COM Port)
the ESP32S3 File>Examples>USB all appear to be OTG device examples (composite, serial, etc)
there is a ESP-IDF ESP32S3 OTG VCP example - see USB CDC-ACM Virtual COM Port example
I adapted it to connect to a Quectel Mini PCIe EVB Kit (with Quectel EC21-E modem) via RS232
// ESP32-S3-DevKitC-1 USB CDC-ACM Virtual COM Port example
// adapted from https://github.com/espressif/esp-idf/blob/master/examples/peripherals/usb/host/cdc/cdc_acm_vcp/README.md
/*
* SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: CC0-1.0
*/
#include <stdio.h>
#include <string.h>
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "usb/cdc_acm_host.h"
#include "usb/vcp_ch34x.hpp"
#include "usb/vcp_cp210x.hpp"
#include "usb/vcp_ftdi.hpp"
#include "usb/vcp.hpp"
#include "usb/usb_host.h"
#include "esp_task_wdt.h"
using namespace esp_usb;
// Change these values to match your needs
#define EXAMPLE_BAUDRATE (9600)//115200)
#define EXAMPLE_STOP_BITS (0) // 0: 1 stopbit, 1: 1.5 stopbits, 2: 2 stopbits
#define EXAMPLE_PARITY (0) // 0: None, 1: Odd, 2: Even, 3: Mark, 4: Space
#define EXAMPLE_DATA_BITS (8)
namespace {
static const char *TAG = "VCP example";
static SemaphoreHandle_t device_disconnected_sem;
/**
* @brief Data received callback
*
* Just pass received data to stdout
*
* @param[in] data Pointer to received data
* @param[in] data_len Length of received data in bytes
* @param[in] arg Argument we passed to the device open function
* @return
* true: We have processed the received data
* false: We expect more data
*/
static bool handle_rx(const uint8_t *data, size_t data_len, void *arg)
{
printf("\e[0;33m%.*s", data_len, data);
return true;
}
/**
* @brief Device event callback
*
* Apart from handling device disconnection it doesn't do anything useful
*
* @param[in] event Device event type and data
* @param[in] user_ctx Argument we passed to the device open function
*/
static void handle_event(const cdc_acm_host_dev_event_data_t *event, void *user_ctx)
{
switch (event->type) {
case CDC_ACM_HOST_ERROR:
ESP_LOGE(TAG, "CDC-ACM error has occurred, err_no = %d", event->data.error);
break;
case CDC_ACM_HOST_DEVICE_DISCONNECTED:
ESP_LOGI(TAG, "Device suddenly disconnected");
xSemaphoreGive(device_disconnected_sem);
break;
case CDC_ACM_HOST_SERIAL_STATE:
ESP_LOGI(TAG, "Serial state notif 0x%04X", event->data.serial_state.val);
break;
case CDC_ACM_HOST_NETWORK_CONNECTION:
default: break;
}
}
/**
* @brief USB Host library handling task
*
* @param arg Unused
*/
static void usb_lib_task(void *arg)
{
while (1) {
// Start handling system events
uint32_t event_flags;
usb_host_lib_handle_events(portMAX_DELAY, &event_flags);
if (event_flags & USB_HOST_LIB_EVENT_FLAGS_NO_CLIENTS) {
ESP_ERROR_CHECK(usb_host_device_free_all());
}
if (event_flags & USB_HOST_LIB_EVENT_FLAGS_ALL_FREE) {
ESP_LOGI(TAG, "USB: All devices freed");
// Continue handling USB events to allow device reconnection
}
}
}
}
/**
* @brief Main application
*
* This function shows how you can use Virtual COM Port drivers
*/
extern "C" void app_main(void)
{
printf("\n\nESP32-S3-DevKitC-1 OTG Host VCP serial test\n");
device_disconnected_sem = xSemaphoreCreateBinary();
assert(device_disconnected_sem);
// Install USB Host driver. Should only be called once in entire application
ESP_LOGI(TAG, "Installing USB Host");
usb_host_config_t host_config = {};
host_config.skip_phy_setup = false;
host_config.intr_flags = ESP_INTR_FLAG_LOWMED;
ESP_ERROR_CHECK(usb_host_install(&host_config));
// Create a task that will handle USB library events
BaseType_t task_created = xTaskCreate(usb_lib_task, "usb_lib", 4096, NULL, 10, NULL);
assert(task_created == pdTRUE);
ESP_LOGI(TAG, "Installing CDC-ACM driver");
ESP_ERROR_CHECK(cdc_acm_host_install(NULL));
// Register VCP drivers to VCP service
VCP::register_driver<FT23x>();
VCP::register_driver<CP210x>();
VCP::register_driver<CH34x>();
// Do everything else in a loop, so we can demonstrate USB device reconnections
while (true) {
const cdc_acm_host_device_config_t dev_config = {
.connection_timeout_ms = 5000, // 5 seconds, enough time to plug the device in or experiment with timeout
.out_buffer_size = 512,
.in_buffer_size = 512,
.event_cb = handle_event,
.data_cb = handle_rx,
.user_arg = NULL,
};
// You don't need to know the device's VID and PID. Just plug in any device and the VCP service will load correct (already registered) driver for the device
ESP_LOGI(TAG, "Opening any VCP device...");
auto vcp = std::unique_ptr<CdcAcmDevice>(VCP::open(&dev_config));
if (vcp == nullptr) {
ESP_LOGI(TAG, "Failed to open VCP device");
continue;
}
vTaskDelay(10);
ESP_LOGI(TAG, "Setting up line coding");
cdc_acm_line_coding_t line_coding = {.dwDTERate = EXAMPLE_BAUDRATE,
.bCharFormat = EXAMPLE_STOP_BITS, .bParityType = EXAMPLE_PARITY, .bDataBits = EXAMPLE_DATA_BITS,
};
ESP_ERROR_CHECK(vcp->line_coding_set(&line_coding));
printf("\n\nenter text to transmit over VCP serial\n");
// loop reading characters from keyboard and serial and displaying
while(1) {
vTaskDelay(10); // cleat WDT
char ch;
ch=fgetc(stdin); // read character from keyboard?
if(ch!=0xFF) {
if(ch>=' ' || ch=='\n'){ // character read if OK
if(ch=='\n')ch='\r'; // \r is line terminator
printf("\e[0;32m%c",ch); // print character and transmit over serial
ESP_ERROR_CHECK(vcp->tx_blocking((uint8_t*) &ch, sizeof(ch)));
ESP_ERROR_CHECK(vcp->set_control_line_state(true, true));
}
}
}
// We are done. Wait for device disconnection and start over
ESP_LOGI(TAG, "Done. You can reconnect the VCP device to run again.");
xSemaphoreTake(device_disconnected_sem, portMAX_DELAY);
}
}
the ESP-IDF Powershell monitor displays (transmitted characters blue received characters yellow)
test setup
note that GPIO19 and 20 are used for USB D- and USB D+ respectively therefore you cannot use them as general GPIO
note to enable USB host 5V you have to solder a link on the rear of the PCB
