USB OTG

The ESP32-P4 includes a USB 2.0 OTG controller capable of operating in both host and device modes at High Speed (480 Mbps). The board provides two USB connectors and a jumper for mode selection.

USB ports on the board

Connector	Type	Purpose
USB-A	Standard Type-A socket	HOST mode — connect USB peripherals (keyboards, flash drives, etc.)
Type-C USB (OTG)	Type-C receptacle	DEVICE mode — board acts as a USB device to a host computer
Type-C UART	Type-C receptacle	Programming and serial debug (not part of USB OTG)

Jumper configuration

The mode-switching jumper (J1) controls which USB port is active for the OTG controller.

Jumper position	Active port	Mode	Use case
HOST	USB-A socket	Host	Connect external USB devices
DEVICE	Type-C OTG port	Device	Board appears as USB device to your computer

Power off the board before changing the jumper position.
Locate jumper J1 near the USB connectors.
Move the jumper to the desired position:
- HOST: Pins toward the USB-A connector
- DEVICE: Pins toward the Type-C OTG connector
Power the board back on. The selected USB port is now active.

Host mode

In host mode, the ESP32-P4 can enumerate and communicate with standard USB devices through the USB-A port.

Supported device classes

The ESP-IDF USB Host library supports several standard device classes:

HID: Keyboards, mice, gamepads
MSC: USB flash drives, external storage
CDC-ACM: Serial devices, modems
Custom: Vendor-specific protocols via raw transfers

Host mode example (MSC — USB flash drive)

#include "usb/usb_host.h"
#include "usb/msc_host.h"

void app_main(void)
{
    // Install USB Host library
    usb_host_config_t host_config = {
        .skip_phy_setup = false,
        .intr_flags = ESP_INTR_FLAG_LEVEL1,
    };
    usb_host_install(&host_config);

    // Initialize MSC host driver
    msc_host_driver_config_t msc_config = {
        .create_backround_task = true,
        .task_priority = 5,
        .stack_size = 4096,
    };
    msc_host_install(&msc_config);

    // The driver will detect and mount USB flash drives automatically.
    // Access files via standard VFS paths once mounted.
}

Device mode

In device mode, the board presents itself as a USB device when connected to a host computer via the Type-C OTG port.

Common device class implementations

CDC-ACM: Virtual serial port (useful for custom communication protocols)
MSC: Present the microSD card or flash as a mass storage device
HID: Emulate a keyboard or mouse
DFU: Device firmware update over USB

Device mode example (CDC-ACM — virtual serial port)

#include "tinyusb.h"
#include "tusb_cdc_acm.h"

void app_main(void)
{
    tinyusb_config_t tusb_cfg = {
        .device_descriptor = NULL,  // Use default
        .configuration_descriptor = NULL,
    };
    tinyusb_driver_install(&tusb_cfg);

    tinyusb_config_cdcacm_t acm_cfg = {
        .usb_dev = TINYUSB_USBDEV_0,
        .cdc_port = TINYUSB_CDC_ACM_0,
        .callback_rx = NULL,  // Set your RX callback
    };
    tusb_cdc_acm_init(&acm_cfg);

    // The board now appears as a COM port on the host computer
}

Troubleshooting

Symptom	Cause	Fix
USB device not detected (host mode)	Jumper not set to HOST	Power off, move J1 to HOST position
Board not recognized by computer (device mode)	Jumper not set to DEVICE	Power off, move J1 to DEVICE position
”Device not recognized” on Windows	Missing TinyUSB driver	Install the WinUSB driver via Zadig
USB flash drive not mounting	Insufficient power	Some drives draw too much current; try a powered hub
Intermittent disconnections	Poor cable quality	Use a short, high-quality USB cable