diff --git a/sysmoOCTSIM/usb/usb_protocol.c b/sysmoOCTSIM/usb/usb_protocol.c
new file mode 100644
index 0000000..9f6323e
--- /dev/null
+++ b/sysmoOCTSIM/usb/usb_protocol.c
@@ -0,0 +1,161 @@
+/**
+ * \file
+ *
+ * \brief USB protocol implementation.
+ *
+ * This file contains the USB definitions and data structures provided by the
+ * USB 2.0 specification.
+ *
+ * Copyright (c) 2015-2018 Microchip Technology Inc. and its subsidiaries.
+ *
+ * \asf_license_start
+ *
+ * \page License
+ *
+ * Subject to your compliance with these terms, you may use Microchip
+ * software and any derivatives exclusively with Microchip products.
+ * It is your responsibility to comply with third party license terms applicable
+ * to your use of third party software (including open source software) that
+ * may accompany Microchip software.
+ *
+ * THIS SOFTWARE IS SUPPLIED BY MICROCHIP "AS IS". NO WARRANTIES,
+ * WHETHER EXPRESS, IMPLIED OR STATUTORY, APPLY TO THIS SOFTWARE,
+ * INCLUDING ANY IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY,
+ * AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT WILL MICROCHIP BE
+ * LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE, INCIDENTAL OR CONSEQUENTIAL
+ * LOSS, DAMAGE, COST OR EXPENSE OF ANY KIND WHATSOEVER RELATED TO THE
+ * SOFTWARE, HOWEVER CAUSED, EVEN IF MICROCHIP HAS BEEN ADVISED OF THE
+ * POSSIBILITY OR THE DAMAGES ARE FORESEEABLE.  TO THE FULLEST EXTENT
+ * ALLOWED BY LAW, MICROCHIP'S TOTAL LIABILITY ON ALL CLAIMS IN ANY WAY
+ * RELATED TO THIS SOFTWARE WILL NOT EXCEED THE AMOUNT OF FEES, IF ANY,
+ * THAT YOU HAVE PAID DIRECTLY TO MICROCHIP FOR THIS SOFTWARE.
+ *
+ * \asf_license_stop
+ */
+
+#define CONF_NO_ASSERT_CHECK
+
+#include "usb_protocol.h"
+
+#ifdef CONF_NO_ASSERT_CHECK
+#define _param_error_check(cond)
+#define _desc_len_check()                                                                                              \
+	if (usb_desc_len(desc) < 2) {                                                                                      \
+		/* Encounter an invalid descriptor. */                                                                         \
+		return NULL;                                                                                                   \
+	}
+#else
+#define _param_error_check(cond) ASSERT(cond)
+#define _desc_len_check() ASSERT(usb_desc_len(desc) >= 2)
+#endif
+
+uint8_t *usb_find_desc(uint8_t *desc, uint8_t *eof, uint8_t type)
+{
+	_param_error_check(desc && eof && (desc < eof));
+
+	while (desc < eof) {
+		_desc_len_check();
+		if (type == usb_desc_type(desc)) {
+			return desc;
+		}
+		desc = usb_desc_next(desc);
+	}
+	return NULL;
+}
+
+uint8_t *usb_find_iface_after(uint8_t *desc, uint8_t *eof, uint8_t iface_n)
+{
+	_param_error_check(desc && eof && (desc < eof));
+
+	while (desc < eof) {
+		_desc_len_check();
+		if (USB_DT_INTERFACE == usb_desc_type(desc)) {
+			if (iface_n != desc[2]) {
+				return desc;
+			}
+		}
+		desc = usb_desc_next(desc);
+	}
+	return eof;
+}
+
+uint8_t *usb_find_ep_desc(uint8_t *desc, uint8_t *eof)
+{
+	_param_error_check(desc && eof && (desc < eof));
+
+	while (desc < eof) {
+		_desc_len_check();
+		if (USB_DT_INTERFACE == usb_desc_type(desc)) {
+			break;
+		}
+		if (USB_DT_ENDPOINT == usb_desc_type(desc)) {
+			return desc;
+		}
+		desc = usb_desc_next(desc);
+	}
+	return NULL;
+}
+
+uint8_t *usb_find_cfg_desc(uint8_t *desc, uint8_t *eof, uint8_t cfg_value)
+{
+	_param_error_check(desc && eof && (desc < eof));
+
+	desc = usb_find_desc(desc, eof, USB_DT_CONFIG);
+	if (!desc) {
+		return NULL;
+	}
+	while (desc < eof) {
+		_desc_len_check();
+		if (desc[1] != USB_DT_CONFIG) {
+			break;
+		}
+		if (desc[5] == cfg_value) {
+			return desc;
+		}
+		desc = usb_cfg_desc_next(desc);
+	}
+	return NULL;
+}
+
+uint8_t *usb_find_othspdcfg_desc(uint8_t *desc, uint8_t *eof, uint8_t cfg_value)
+{
+	_param_error_check(desc && eof && (desc < eof));
+
+	desc = usb_find_desc(desc, eof, USB_DT_OTHER_SPEED_CONFIG);
+	if (!desc) {
+		return NULL;
+	}
+	while (desc < eof) {
+		_desc_len_check();
+		if (desc[1] != USB_DT_OTHER_SPEED_CONFIG) {
+			break;
+		}
+		if (desc[5] == cfg_value) {
+			return desc;
+		}
+		desc = usb_cfg_desc_next(desc);
+	}
+	return NULL;
+}
+
+uint8_t *usb_find_str_desc(uint8_t *desc, uint8_t *eof, uint8_t str_index)
+{
+	uint8_t i;
+
+	_param_error_check(desc && eof && (desc < eof));
+
+	for (i = 0; desc < eof;) {
+		desc = usb_find_desc(desc, eof, USB_DT_STRING);
+		if (desc) {
+			_desc_len_check();
+			if (i == str_index) {
+				return desc;
+			}
+			i++;
+			desc = usb_desc_next(desc);
+		} else {
+			return NULL;
+		}
+	}
+	return NULL;
+}