USB Peripheral Communications Device Class (r_usb_pcdc)

This module provides a USB Peripheral Communications Device Class Driver (PCDC). It implements the USB PCDC Interface.

Functions

Refer to USB (r_usb_basic) for the common API (r_usb_basic) to be called from the application.

Detailed Description

Overview

The r_usb_pcdc module combines with the r_usb_basic module to provide a USB Peripheral Communications Device Class (PCDC) driver. The PCDC driver conforms to Abstract Control Model of the USB Communications Device Class (CDC) specification and enables communication with a CDC host device.

Features

The r_usb_pcdc module has the following key features:

• Data transfer to and from a USB host
• Response to CDC class requests
• Supports CDC notifications

Configuration

Build Time Configurations for r_usb_pcdc

The following build time configurations are defined in fsp_cfg/r_usb_pcdc_cfg.h:

Configuration	Options	Default	Description
Bulk In Pipe	USB PIPE1 USB PIPE2 USB PIPE3 USB PIPE4 USB PIPE5	USB PIPE1	Select the USB pipe to use for bulk input transfers.
Bulk Out Pipe	USB PIPE1 USB PIPE2 USB PIPE3 USB PIPE4 USB PIPE5	USB PIPE2	Select the USB pipe to use for bulk output transfers.
Interrupt Out Pipe	USB PIPE6 USB PIPE7 USB PIPE8 USB PIPE9	USB PIPE6	Select the USB pipe to use for interrupts.

Configurations for Connectivity > USB PCDC driver on (r_usb_pcdc)

This module can be added to the Stacks tab via New Stack > Connectivity > USB PCDC driver on (r_usb_pcdc).

Configuration	Options	Default	Description
Name	Name must be a valid C symbol	g_pcdc0	Module name.

Note

Refer to the USB (r_usb_basic) module for hardware configuration options.

Clock Configuration

Refer to the USB (r_usb_basic) module.

Pin Configuration

Refer to the USB (r_usb_basic) module.

Usage Notes

Abstract Control Model Overview

The Abstract Control Model subclass of CDC is a technology that bridges the gap between USB devices and earlier modems (employing RS-232C connections), enabling use of application programs designed for older modems.

Class Requests (Host to Peripheral)

This driver notifies the application when receiving the following class requests:

Request	Code	Description
SetLineCoding	0x20	Sets communication line settings (bitrate, data length, parity, and stop bit length)
GetLineCoding	0x21	Acquires the communication line setting state
SetControlLineState	0x22	Set communication line control signals (RTS, DTR)

Note

For details concerning the Abstract Control Model requests, refer to Table 11 "Requests - Abstract Control Model" in the "USB Communications Class Subclass Specification for PSTN Devices", Revision 1.2.

Data Format of Class Requests

The data format of supported class requests is described below:

bmRequestType	bRequest	wValue	wIndex	wLength	Data
0x21	SET_LINE_CODING (0x20)	0x0000	0x0000	0x0007	usb_pcdc_linecoding_t
0xA1	GET_LINE_CODING (0x21)	0x0000	0x0000	0x0007	usb_pcdc_linecoding_t
0x21	SET_CONTROL_LINE_STATE (0x22)	usb_pcdc_ctrllinestate_t	0x0000	0x0000	None

Class Notifications (Peripheral to Host)

The following class notifications are supported:

Notification	Code	Description
SERIAL_STATE	0x20	Notification of serial line state

The data types returned are as follows:

bmRequestType	bRequest	wValue	wIndex	wLength	Data
0xA1	SERIAL_STATE (0x20)	0x0000	0x0000	0x0002	usb_serial_state_bitmap_t

Note

The host is notified with SERIAL_STATE whenever a change in the UART port state is detected. This driver will automatically detect overrun, parity and framing errors. A state notification is performed when a transition from normal to error state is detected.

Virtual COM-port Usage

When connected to a PC the CDC device can be used as a virtual COM port. After enumeration, the CDC class requests GetLineCoding and SetControlLineState are executed by the target, and the CDC device is registered in Windows Device Manager as a virtual COM device.

Registering the CDC device as a virtual COM-port in Windows Device Manager enables data communication with the CDC device via a terminal app such as PuTTY. When changing settings of the serial port in the terminal application, the UART setting is propagated to the firmware via the class request SetLineCoding.

Data input (or file transmission) from the terminal app window is transmitted to the board using endpoint 2 (EP2); data from the board side is transmitted to the PC using EP1.

When the last packet of data received is the maximum packet size, and the terminal determines that there is continuous data, the received data may not be displayed in the terminal. If the received data is smaller than the maximum packet size, the data received up to that point is displayed in the terminal.

Limitations

• This module must be incorporated into a project using r_usb_basic and does not provide any public APIs.
• This driver does not support Low-speed.

Examples

USB PCDC Loopback Example

The main functions of the PCDC loopback example are as follows:

1. Receives virtual UART configuration data from the host terminal
2. Loops all other received data back to the host terminal

Example Operating Environment

Main Loop processing (Echo mode)

void usb_basic_example (void)
{
    usb_event_info_t event_info;
    usb_status_t     event;

    g_usb_on_usb.open(&g_basic0_ctrl, &g_basic0_cfg);


    while (1)
    {

        /* Get USB event data */
        g_usb_on_usb.eventGet(&event_info, &event);


        /* Handle the received event (if any) */
        switch (event)
        {
            case USB_STATUS_CONFIGURED:
            case USB_STATUS_WRITE_COMPLETE:


                /* Initialization complete; get data from host */
                g_usb_on_usb.read(&g_basic0_ctrl, g_buf, DATA_LEN, USB_CLASS_PCDC);

                break;

            case USB_STATUS_READ_COMPLETE:


                /* Loop back received data to host */
                g_usb_on_usb.write(&g_basic0_ctrl, g_buf, event_info.data_size, USB_CLASS_PCDC);

                break;

            case USB_STATUS_REQUEST:   /* Receive Class Request */
                if (USB_PCDC_SET_LINE_CODING == (event_info.setup.request_type & USB_BREQUEST))
                {
                    /* Configure virtual UART settings */
                    g_usb_on_usb.periControlDataGet(&g_basic0_ctrl, (uint8_t *) &g_line_coding, LINE_CODING_LENGTH);
                }
                else if (USB_PCDC_GET_LINE_CODING == (event_info.setup.request_type & USB_BREQUEST))
                {
                    /* Send virtual UART settings back to host */
                    g_usb_on_usb.periControlDataSet(&g_basic0_ctrl, (uint8_t *) &g_line_coding, LINE_CODING_LENGTH);
                }
                else
                {
                    /* ACK all other status requests */
                    g_usb_on_usb.periControlStatusSet(&g_basic0_ctrl, USB_SETUP_STATUS_ACK);
                }

                break;

            case USB_STATUS_SUSPEND:
            case USB_STATUS_DETACH:
                break;

            default:
                break;
        }
    }
}

Descriptor

A template for PCDC descriptors can be found in ra/fsp/src/r_usb_pcdc/r_usb_pcdc_descriptor.c.template. Also, please be sure to use your vendor ID.