Create CDC ACM Applications

Create CDC ACM Applications explains how to program a USB Communication Device of Abstract Control Model type using the RL-USB Library. Communication applications control networks, serial and wireless communication interfaces, telecom devices, modems, printers, scanners.

Include into the project and configure the following RL-USB Device Source Files:

1. The library that matches the device core:
   USB_CM1.lib - for Cortex-M1 devices.
   USB_CM3.lib - for Cortex-M3 devices.
   USB_ARM_L.lib - for ARM7 or ARM9 devices.
2. usb_config.c - to configure the USB system.
3. board_name-vcom.inf - to configure the driver information file.
4. usbd_device family.c(.h) - to configure the device hardware layer.
5. usbd_user_cdc_acm.c - to adapt the code to the application needs.
6. USBD_Demo.c - to initialize and connect the USB Device from main().

   ..
   usbd_init();                         // USB Initialization
   usbd_connect(__TRUE);                // USB Connect
   while (!usbd_configured ())          // Wait for device to configure
   
                                        // Send message over USB Vitual COM Port
                                        // to the USB Host
   USBD_CDC_ACM_DataSend ("Send data over USB Virtual COM Port.", 36);
   
   ..
   

Applications can be created using existing µVision CDC ACM projects. The RL-USB communication examples use two simple functions that send the signals from the USB Virtual COM port to the boards Serial COM port and vice versa.

1. Copy all files from any folder \ARM\Boards\Vendor\BoardName\RL\USB\Device\CDC_ACM to a new folder and open the project *.uvproj with µVision. RTX projects are using the RTX-RTOS, whereas simple CDC projects work without an RTOS. However, the USB configuration does not differ.
2. Open the file usb_config.c and configure the USB device with the Configuration Wizard.
3. Enable USB Device and set the device characteristics.

   

4. Adapt the file board_name-vcom.inf whenever the Vendor ID and Product ID has been changed. (See picture above).
5. Enable Class Support and Communication Device (CDC) - Abstract Control Model (ACM) and set the characteristics.

   

6. Optionally, adapt the source file usbd_device family.c that contains hardware dependent code.
7. Modify the file usbd_user_cdc_acm.c to adapt the code to the application needs.

Note

• The options are explained in Communication Device (CDC) - Abstract Control Model (ACM) Options.