1# USB Host CDC-ACM Class Driver
2
3This directory contains an implementation of a USB CDC-ACM Host Class Driver that is implemented on top of the [USB Host Library](https://docs.espressif.com/projects/esp-idf/en/latest/esp32s2/api-reference/peripherals/usb_host.html).
4
5## Supported Devices
6
7The CDC-ACM Host driver supports the following types of CDC devices:
8
91. CDC-ACM devices
102. CDC-like vendor specific devices (usually found on USB to UART bridge devices)
11
12### CDC-ACM Devices
13
14The CDC-ACM Class driver supports CDC-ACM devices that meet the following requirements:
15- The device class code must be set to the CDC class `0x02` or implement Interface Association Descriptor (IAD)
16- The CDC-ACM must contain the following interfaces:
17    - A Communication Class Interface containing a management element (EP0) and may also contain a notification element (an interrupt endpoint). The driver will check this interface for CDC Functional Descriptors.
18    - A Data Class Interface with two BULK endpoints (IN and OUT). Other transfer types are not supported by the driver
19
20### CDC-Like Vendor Specific Devices
21
22The CDC-ACM Class driver supports CDC-like devices that meet the following requirements:
23- The device class code must be set to the vendor specific class code `0xFF`
24- The device needs to provide and interface containing the following endpoints:
25    - (Mandatory) Two Bulk endpoints (IN and OUT) for data
26    - (Optional) An interrupt endpoint (IN) for the notification element
27
28For CDC-like devices, users are responsible for ensuring that they only call APIs (e.g., `cdc_acm_host_send_break()`) that are supported by the target device.
29
30
31## Usage
32
33The following steps outline the typical API call pattern of the CDC-ACM Class Driver
34
351. Install the USB Host Library via `usb_host_install()`
362. Install the CDC-ACM driver via `cdc_acm_host_install()`
373. Call `cdc_acm_host_open()`/`cdc_acm_host_open_vendor_specific()` to open a target CDC-ACM/CDC-like device. These functions will block until the target device is connected
384. To transmit data, call `cdc_acm_host_data_tx_blocking()`
395. When data is received, the driver will automatically run the receive data callback
406. An opened device can be closed via `cdc_acm_host_close()`
417. The CDC-ACM driver can be uninstalled via `cdc_acm_host_uninstall()`
42
43## Examples
44
45- For an example with a CDC-ACM device, refer to [cdc_acm_host](../../cdc_acm_host)
46- For an example with a CDC-like device, refer to [cdc_acm_host_bg96](../../cdc_acm_bg96)
47