static void msc_data_rx_cb(usbd_device *usbd_dev, uint8_t ep)
{
	usbd_mass_storage *ms;
	struct usb_msc_trans *trans;
	int len, max_len, left;
	void *p;

	ms = &_mass_storage;
	trans = &ms->trans;

	/* RX only */
	left = sizeof(struct usb_msc_cbw) - trans->cbw_cnt;
	if (0 < left) {
		max_len = MIN(ms->ep_out_size, left);
		p = &trans->cbw.buf[0x1ff & trans->cbw_cnt];
		len = usbd_ep_read_packet(usbd_dev, ep, p, max_len);
		trans->cbw_cnt += len;

		if (sizeof(struct usb_msc_cbw) == trans->cbw_cnt) {
			scsi_command(ms, trans, EVENT_CBW_VALID);
			if (trans->byte_count < trans->bytes_to_read) {
				/* We must wait until there is something to
				 * read again. */
				return;
			}
		}
	}

	if (trans->byte_count < trans->bytes_to_read) {
		if (0 < trans->block_count) {
			if ((0 == trans->byte_count) && (NULL != ms->lock)) {
				(*ms->lock)();
			}
		}

		left = trans->bytes_to_read - trans->byte_count;
		max_len = MIN(ms->ep_out_size, left);
		p = &trans->msd_buf[0x1ff & trans->byte_count];
		len = usbd_ep_read_packet(usbd_dev, ep, p, max_len);
		trans->byte_count += len;

		if (0 < trans->block_count) {
			if (0 == (0x1ff & trans->byte_count)) {
				uint32_t lba;

				lba = trans->lba_start + trans->current_block;
				if (0 != (*ms->write_block)(lba,
							    trans->msd_buf)) {
					/* Error */
				}
				trans->current_block++;
			}
		}
/////////////////////ADD THIS//////////////////////////////////////////////////////////////////////////////////
		if (false == trans->csw_valid) {
			scsi_command(ms, trans, EVENT_NEED_STATUS);
			trans->csw_valid = true;
		}

		left = sizeof(struct usb_msc_csw) - trans->csw_sent;
		if (0 < left) {
			max_len = MIN(ms->ep_out_size, left);
			p = &trans->csw.buf[trans->csw_sent];
			len = usbd_ep_write_packet(usbd_dev, ms->ep_in, p,
					max_len);
			trans->csw_sent += len;
		}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	} else if (trans->byte_count < trans->bytes_to_write) {
		if (0 < trans->block_count) {
			if ((0 == trans->byte_count) && (NULL != ms->lock)) {
				(*ms->lock)();
			}

			if (0 == (0x1ff & trans->byte_count)) {
				uint32_t lba;

				lba = trans->lba_start + trans->current_block;
				if (0 != (*ms->read_block)(lba,
							   trans->msd_buf)) {
					/* Error */
				}
				trans->current_block++;
			}
		}

		left = trans->bytes_to_write - trans->byte_count;
		max_len = MIN(ms->ep_out_size, left);
		p = &trans->msd_buf[0x1ff & trans->byte_count];
		len = usbd_ep_write_packet(usbd_dev, ms->ep_in, p, max_len);
		trans->byte_count += len;
	} else {
		if (0 < trans->block_count) {
			if (trans->current_block == trans->block_count) {
				uint32_t lba;

				lba = trans->lba_start + trans->current_block;
				if (0 != (*ms->write_block)(lba,
							    trans->msd_buf)) {
					/* Error */
				}

				trans->current_block = 0;
				if (NULL != ms->unlock) {
					(*ms->unlock)();
				}
			}
		}
		if (false == trans->csw_valid) {
			scsi_command(ms, trans, EVENT_NEED_STATUS);
			trans->csw_valid = true;
		}

		left = sizeof(struct usb_msc_csw) - trans->csw_sent;
		if (0 < left) {
			max_len = MIN(ms->ep_out_size, left);
			p = &trans->csw.buf[trans->csw_sent];
			len = usbd_ep_write_packet(usbd_dev, ms->ep_in, p,
						   max_len);
			trans->csw_sent += len;
		}
	}
}

static void scsi_read_format_capacities(usbd_mass_storage *ms, struct usb_msc_trans *trans, enum trans_event event)
{
	if (EVENT_CBW_VALID == event) {

		trans->msd_buf[3] = 0x08;
		trans->msd_buf[4] = ms->block_count >> 24;
		trans->msd_buf[5] = 0xff & (ms->block_count >> 16);
		trans->msd_buf[6] = 0xff & (ms->block_count >> 8);
		trans->msd_buf[7] = 0xff & ms->block_count;

		trans->msd_buf[8] =  0x02;
		trans->msd_buf[9] = 0;
		trans->msd_buf[10] = 0x02;
		trans->msd_buf[11] = 0;
		trans->bytes_to_write = 9;
		set_sbc_status_good(ms);
	}
}

static void scsi_command(usbd_mass_storage *ms, struct usb_msc_trans *trans, enum trans_event event)
{
	if (EVENT_CBW_VALID == event) {
		/* Setup the default success */
		trans->csw_sent = 0;
		trans->csw.csw.dCSWSignature = CSW_SIGNATURE;
		trans->csw.csw.dCSWTag = trans->cbw.cbw.dCBWTag;
		trans->csw.csw.dCSWDataResidue = 0;
		trans->csw.csw.bCSWStatus = CSW_STATUS_SUCCESS;

		trans->bytes_to_write = 0;
		trans->bytes_to_read = 0;
		trans->byte_count = 0;
	}

	switch (trans->cbw.cbw.CBWCB[0]) {
	case SCSI_TEST_UNIT_READY:
	case SCSI_SEND_DIAGNOSTIC:
		/* Do nothing, just send the success. */
		set_sbc_status_good(ms);
		break;
	case SCSI_FORMAT_UNIT:
		scsi_format_unit(ms, trans, event);
		break;
	case SCSI_REQUEST_SENSE:
		scsi_request_sense(ms, trans, event);
		break;
	case SCSI_MODE_SENSE_6:
		scsi_mode_sense_6(ms, trans, event);
		break;
	case SCSI_READ_6:
		scsi_read_6(ms, trans, event);
		break;
	case SCSI_INQUIRY:
		scsi_inquiry(ms, trans, event);
		break;
	case SCSI_READ_CAPACITY:
		scsi_read_capacity(ms, trans, event);
		break;
	case SCSI_READ_10:
		scsi_read_10(ms, trans, event);
		break;
	case SCSI_WRITE_6:
		scsi_write_6(ms, trans, event);
		break;
	case SCSI_WRITE_10:
		scsi_write_10(ms, trans, event);
		break;
//////////////////ADD THIS///////////////////////////////////////////////////////////////////////////////////////////////////
	case SCSI_READ_FORMAT_CAPACITIES:
		scsi_read_format_capacities(ms, trans, event);
	 	break;
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	default:
		set_sbc_status(ms, SBC_SENSE_KEY_ILLEGAL_REQUEST,
					SBC_ASC_INVALID_COMMAND_OPERATION_CODE,
					SBC_ASCQ_NA);

		trans->bytes_to_write = 0;
		trans->bytes_to_read = 0;
		trans->csw.csw.bCSWStatus = CSW_STATUS_FAILED;
		break;
	}
}

static const uint8_t _spc3_inquiry_sn_response[20] = {
		0x00,
 		0x80,
 		0x00,
 		0x10, //количество символов в серийном номере. в нашем случае их 16 (third pin 123456)
 		't','h','i','r','d',' ','p','i','n',' ','1','2','3','4','5','6'
 };

static void scsi_inquiry(usbd_mass_storage *ms, struct usb_msc_trans *trans, enum trans_event event)
{
	if (EVENT_CBW_VALID == event) {
		uint8_t evpd;
		uint8_t *buf;

		buf = get_cbw_buf(trans);
		evpd = 1 & buf[1];

		if (evpd == 0) {
			size_t len;
			trans->bytes_to_write = sizeof(_spc3_inquiry_response);
			memcpy(trans->msd_buf, _spc3_inquiry_response,
			       sizeof(_spc3_inquiry_response));

			len = strlen(ms->vendor_id);
			len = MIN(len, 8);
			memcpy(&trans->msd_buf[8], ms->vendor_id, len);

			len = strlen(ms->product_id);
			len = MIN(len, 16);
			memcpy(&trans->msd_buf[16], ms->product_id, len);

			len = strlen(ms->product_revision_level);
			len = MIN(len, 4);
			memcpy(&trans->msd_buf[32], ms->product_revision_level,
			       len);

			trans->csw.csw.dCSWDataResidue =
				sizeof(_spc3_inquiry_response);

			set_sbc_status_good(ms);
		}
/////////////////////////////////ADD THIS/////////////////////////////////////////////////////////////////////////////
		else if (evpd == 1) {
			trans->bytes_to_write = sizeof(_spc3_inquiry_sn_response);
			memcpy(trans->msd_buf, _spc3_inquiry_sn_response,
					sizeof(_spc3_inquiry_sn_response));
			trans->csw.csw.dCSWDataResidue =
					sizeof(_spc3_inquiry_sn_response);

			set_sbc_status_good(ms);
		}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
		else {
			/* TODO: Add VPD 0x83 support */
			/* TODO: Add VPD 0x00 support */
		}
	}
}