49 lines
2.6 KiB
Markdown
49 lines
2.6 KiB
Markdown
# USB Host CDC-ACM Class Driver
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[](https://components.espressif.com/components/espressif/usb_host_cdc_acm)
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This 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).
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## Supported Devices
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The CDC-ACM Host driver supports the following types of CDC devices:
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1. CDC-ACM devices
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2. CDC-like vendor specific devices (usually found on USB to UART bridge devices)
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### CDC-ACM Devices
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The CDC-ACM Class driver supports CDC-ACM devices that meet the following requirements:
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- The device class code must be set to the CDC class `0x02` or implement Interface Association Descriptor (IAD)
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- The CDC-ACM must contain the following interfaces:
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- 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.
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- A Data Class Interface with two BULK endpoints (IN and OUT). Other transfer types are not supported by the driver
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### CDC-Like Vendor Specific Devices
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The CDC-ACM Class driver supports CDC-like devices that meet the following requirements:
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- The device class code must be set to the vendor specific class code `0xFF`
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- The device needs to provide and interface containing the following endpoints:
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- (Mandatory) Two Bulk endpoints (IN and OUT) for data
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- (Optional) An interrupt endpoint (IN) for the notification element
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For 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.
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## Usage
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The following steps outline the typical API call pattern of the CDC-ACM Class Driver
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1. Install the USB Host Library via `usb_host_install()`
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2. Install the CDC-ACM driver via `cdc_acm_host_install()`
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3. 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
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4. To transmit data, call `cdc_acm_host_data_tx_blocking()`
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5. When data is received, the driver will automatically run the receive data callback
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6. An opened device can be closed via `cdc_acm_host_close()`
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7. The CDC-ACM driver can be uninstalled via `cdc_acm_host_uninstall()`
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## Examples
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- For an example with a CDC-ACM device, refer to [cdc_acm_host](../../cdc_acm_host)
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- For an example with a CDC-like device, refer to [cdc_acm_host_bg96](../../cdc_acm_bg96)
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