diff --git a/main/usb_cdc.c b/main/usb_cdc.c
new file mode 100644
--- /dev/null
+++ b/main/usb_cdc.c
@@ -0,0 +1,86 @@
+//
+// usb-cdc
+//
+
+#include "usb_cdc.h"
+
+#include "tinyusb.h"
+#include "tusb_cdc_acm.h"
+#include "sdkconfig.h"
+#include "esp_log.h"
+
+
+// Private variables
+static const char *TAG = "main";
+
+
+// ------------------------ USB CDC ----------------------------------------
+static uint8_t buf[CONFIG_TINYUSB_CDC_RX_BUFSIZE + 1];
+
+void tinyusb_cdc_rx_callback(int itf, cdcacm_event_t *event)
+{
+    /* initialization */
+    size_t rx_size = 0;
+
+    /* read */
+    esp_err_t ret = tinyusb_cdcacm_read(itf, buf, CONFIG_TINYUSB_CDC_RX_BUFSIZE, &rx_size);
+    if (ret == ESP_OK) {
+        ESP_LOGI(TAG, "Data from channel %d:", itf);
+        ESP_LOG_BUFFER_HEXDUMP(TAG, buf, rx_size, ESP_LOG_INFO);
+    } else {
+        ESP_LOGE(TAG, "Read error");
+    }
+
+    /* write back */
+    tinyusb_cdcacm_write_queue(itf, buf, rx_size);
+    tinyusb_cdcacm_write_flush(itf, 0);
+}
+
+void tinyusb_cdc_line_state_changed_callback(int itf, cdcacm_event_t *event)
+{
+    int dtr = event->line_state_changed_data.dtr;
+    int rts = event->line_state_changed_data.rts;
+    ESP_LOGI(TAG, "Line state changed on channel %d: DTR:%d, RTS:%d", itf, dtr, rts);
+}
+
+
+void usb_cdc_init(void)
+{
+    ESP_LOGI(TAG, "USB initialization");
+    const tinyusb_config_t tusb_cfg = {
+        .device_descriptor = NULL,
+        .string_descriptor = NULL,
+        .external_phy = false,
+        .configuration_descriptor = NULL,
+    };
+
+    ESP_ERROR_CHECK(tinyusb_driver_install(&tusb_cfg));
+
+    tinyusb_config_cdcacm_t acm_cfg = {
+        .usb_dev = TINYUSB_USBDEV_0,
+        .cdc_port = TINYUSB_CDC_ACM_0,
+        .rx_unread_buf_sz = 64,
+        .callback_rx = &tinyusb_cdc_rx_callback, // the first way to register a callback
+        .callback_rx_wanted_char = NULL,
+        .callback_line_state_changed = NULL,
+        .callback_line_coding_changed = NULL
+    };
+
+    ESP_ERROR_CHECK(tusb_cdc_acm_init(&acm_cfg));
+    /* the second way to register a callback */
+    ESP_ERROR_CHECK(tinyusb_cdcacm_register_callback(
+                        TINYUSB_CDC_ACM_0,
+                        CDC_EVENT_LINE_STATE_CHANGED,
+                        &tinyusb_cdc_line_state_changed_callback));
+
+#if (CONFIG_TINYUSB_CDC_COUNT > 1)
+    acm_cfg.cdc_port = TINYUSB_CDC_ACM_1;
+    ESP_ERROR_CHECK(tusb_cdc_acm_init(&acm_cfg));
+    ESP_ERROR_CHECK(tinyusb_cdcacm_register_callback(
+                        TINYUSB_CDC_ACM_1,
+                        CDC_EVENT_LINE_STATE_CHANGED,
+                        &tinyusb_cdc_line_state_changed_callback));
+#endif
+
+    ESP_LOGI(TAG, "USB initialization DONE");
+}
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