usb_descriptors.c

#include "tusb.h"

#define STRING_DESC_MANUFACTURER 1
#define STRING_DESC_PRODUCT 2
#define STRING_DESC_SERIAL 3
#define STRING_DESC_XX 4

#define CONFIG_TOTAL_LEN                                                       \
  (TUD_CONFIG_DESC_LEN + CFG_TUD_CDC * TUD_CDC_DESC_LEN +                      \
   CFG_TUD_VENDOR * TUD_VENDOR_DESC_LEN)
uint8_t const desc_configuration[] = {
    // Config number, interface count, string index, total length, attribute,
    // power in mA
    TUD_CONFIG_DESCRIPTOR(1, 1, 0, CONFIG_TOTAL_LEN, 0, 100),

    TUD_VENDOR_DESCRIPTOR(0, STRING_DESC_XX, 2, 0x80 + 1, 32),
};

uint8_t const *tud_descriptor_configuration_cb(uint8_t index) {
  return desc_configuration;
}

tusb_desc_device_t const desc_device = {
    .bLength = sizeof(tusb_desc_device_t),
    .bDescriptorType = TUSB_DESC_DEVICE,
    .bcdUSB = 0x0200, // Supported USB standard (2.1)
    .bDeviceClass = TUSB_CLASS_MISC,
    .bDeviceSubClass = MISC_SUBCLASS_COMMON,
    .bDeviceProtocol = MISC_PROTOCOL_IAD,
    .bMaxPacketSize0 = CFG_TUD_ENDPOINT0_SIZE, // Endpoint 0 packet size
    .idVendor = 0x1209,                        // Vendor identifier
    .idProduct = 0x2323,                       // Product identifier
    .bcdDevice = 0x0100,                       // Protocol version
    .iManufacturer =
        STRING_DESC_MANUFACTURER,        // Index of manufacturer name string
    .iProduct = STRING_DESC_PRODUCT,     // Index of product name string
    .iSerialNumber = STRING_DESC_SERIAL, // Index of serial number string
    .bNumConfigurations = 0x01           // Number of configurations supported
};
uint8_t const *tud_descriptor_device_cb(void) {
  return (uint8_t const *)&desc_device;
}

char const *string_desc_arr[] = {
    (const char[]){0x09, 0x04}, // 0: is supported language is English (0x0409)
    "D",                        // 1: Manufacturer
    "rp2040-can",               // 2: Product
    "123456",                   // 3: Serials, should use chip ID
    "CDC",                      // 4: CDC Interface
    "CDC",                      // 4: CDC Interface
};

static uint16_t _desc_str[32];
uint16_t const *tud_descriptor_string_cb(uint8_t index, uint16_t langid) {
  uint8_t chr_count;

  if (index == 0) {
    memcpy(&_desc_str[1], string_desc_arr[0], 2);
    chr_count = 1;
  } else {

    if (!(index < sizeof(string_desc_arr) / sizeof(string_desc_arr[0]))) {
      return NULL;
    }

    const char *str = string_desc_arr[index];

    // Cap at max char
    chr_count = (uint8_t)strlen(str);
    if (chr_count > 31)
      chr_count = 31;

    // Convert ASCII string into UTF-16
    for (uint8_t i = 0; i < chr_count; i++) {
      _desc_str[1 + i] = str[i];
    }
  }

  // first byte is length (including header), second byte is string type
  _desc_str[0] = (uint16_t)((TUSB_DESC_STRING << 8) | (2 * chr_count + 2));
  return _desc_str;
}