USB CDC-ACM Interface

The USB CDC-ACM (Communications Device Class - Abstract Control Model) component enables supported devices to function as USB virtual serial ports. When connected to a host computer, the microcontroller will appear as one or more serial/COM ports, allowing serial communication with the application running on the microcontroller.

You must have TinyUSB in your device’s configuration to use this component.

The following ESP32 microcontroller variants are currently supported:

ESP32-P4
ESP32-S2
ESP32-S3

# Example minimal configuration entry
usb_cdc_acm:

Configuration variables

rx_buffer_size (Optional, int): Size of the USB receive buffer in bytes. Range: 1-65535. Defaults to 256.
tx_buffer_size (Optional, int): Size of the USB transmit buffer in bytes. Range: 1-65535. Defaults to 256.
interfaces (Optional, list): List of CDC-ACM interface instances. Up to two are supported; at least one is required. Defaults to a single-item list which defines a single interface only.

Interface configuration variables

Each interface in the interfaces list consists of the following:

id (Optional, ID): The ID to use for this interface instance. This is used to refer to the interface in other components, platforms or lambdas.

Multiple Interface Example

The USB CDC-ACM component supports up to two simultaneous virtual serial port interfaces on a single device. This allows you to create multiple independent communication channels over a single physical USB connection.

# Example configuration with two interfaces
usb_cdc_acm:
  interfaces:
    - id: cdc_acm_1
    - id: cdc_acm_2

In this configuration, the device will appear as two separate serial/COM ports to the host computer. Each interface operates independently with its own data buffers.

Buffer Size Considerations

The buffer sizes determine how much data can be temporarily stored during USB transfers:

Small buffers (256 bytes, default): Suitable for low-bandwidth applications and conserves RAM
Large buffers (512-1024 bytes): Recommended for high-throughput applications or when handling bursts of data

Increase buffer sizes if you experience data loss or need to handle larger data packets without frequent polling.