This is the quick start guide for the USB Host Communication Device Class Module (UHI CDC) with step-by-step instructions on how to configure and use the modules in a selection of use cases.

The use cases highlights several code fragments. The code fragments in the steps for setup can be copied into a custom initialization function, while the steps for usage can be copied into, e.g., the main application function.

Basic Use Case

In this basic use case, the "USB Host CDC (Single Class support)" module is used.

The "USB Host CDC (Multiple Classes support)" module usage is described in Advanced Use Cases.

Setup Steps

As a USB host, it follows common USB host setup steps. Refer to USB Host Basic Setup.

Usage Steps

Example Code

Content of conf_usb_host.h:

#define USB_HOST_UHI        UHI_CDC
#define UHI_CDC_CHANGE(dev, b_plug) my_callback_cdc_change(dev, b_plug)
extern bool my_callback_cdc_change(uhc_device_t* dev, bool b_plug);
#define UHI_CDC_RX_NOTIFY() my_callback_cdc_rx_notify()
extern void my_callback_cdc_rx_notify(void);
#include "uhi_cdc.h" // At the end of conf_usb_host.h file

Add to application C-file:

static bool my_flag_cdc_available = false;
bool my_callback_cdc_change(uhc_device_t* dev, bool b_plug)
{
   if (b_plug) {
   // USB Device CDC connected
   my_flag_cdc_available = true;
   // Open and configure USB CDC ports
   usb_cdc_line_coding_t cfg = {
         .dwDTERate   = CPU_TO_LE32(115200),
         .bCharFormat = CDC_STOP_BITS_1,
         .bParityType = CDC_PAR_NONE,
         .bDataBits   = 8,
   };
   uhi_cdc_open(0, &cfg);
   } else {
   my_flag_cdc_available = false;
   }
}
void my_callback_cdc_rx_notify(void)
{
   // Wakeup my_task_rx() task
}
#define MESSAGE "Hello"
void my_task(void)
{
   static bool startup = true;
   if (!my_flag_cdc_available) {
      startup = true;
      return;
   }
   if (startup) {
      startup = false;
      // Send data on CDC communication port
      uhi_cdc_write_buf(0, MESSAGE, sizeof(MESSAGE)-1);
      uhi_cdc_putc(0,'\n');
      return;
   }
}
void my_task_rx(void)
{
   while (uhi_cdc_is_rx_ready(0)) {
      int value = uhi_cdc_getc(0);
   }
}

Workflow

Ensure that conf_usb_host.h is available and contains the following configuration which is the USB host CDC configuration:
#define USB_HOST_UHI UHI_CDC

Note
It defines the list of UHI supported by USB host.

#define UHI_CDC_CHANGE(dev, b_plug) my_callback_cdc_change(dev, b_plug)

extern bool my_callback_cdc_change(uhc_device_t* dev, bool b_plug);

Note
This callback is called when a USB device CDC is plugged or unplugged. The communication port can be opened and configured here.

#define UHI_CDC_RX_NOTIFY() my_callback_cdc_rx_notify()

extern void my_callback_cdc_rx_notify(void);

Note
This callback is called when a new data are received. This can be used to manage data reception through interrupt and avoid pooling.
The CDC data access functions are described in UHI CDC API Overview.

Advanced Use Cases

For more advanced use of the UHI CDC module, see the following use cases: