WO2012150267A1

WO2012150267A1 - Data communication via usb mass storage interface

Info

Publication number: WO2012150267A1
Application number: PCT/EP2012/058040
Authority: WO
Inventors: Markus Münzer
Original assignee: Testo Ag
Priority date: 2011-05-02
Filing date: 2012-05-02
Publication date: 2012-11-08
Also published as: DE102011075096A1

Abstract

The invention relates to a system for continuously transmitting data between a terminal and a computer. The system comprises the following: a USB bus; a terminal which continuously generates data during operation and which continuously makes said data available on a USB bus in accordance with the USB mass storage class standard; and a computer which is connected to the USB bus, which comprises a USB device driver that operates in accordance with the USB mass storage class standard, and which comprises an application program designed to receive the data that is continuously generated by the measuring device from the USB bus using the device driver.

Description

Data communication via USB mass storage interface

The invention relates to a type of data communication via USB (Universal Serial Bus), in particular to a continuous data transmission, in particular in real time, from a terminal, such as a meter, to a computer using a protocol that the USB Mass Storage Class (USB-MSC) specification.

In order to transfer data from a terminal to a computer, or control commands from the computer to the terminal, there are various possibilities. The following example uses data communication between a meter and a computer, sending meter data from the meter to the computer and control data from the computer to the meter. It is a common and frequently used way to connect the meter to a personal computer (PC) using the Universal Serial Bus (USB). To avoid a separate driver being required for each device, the USB standard defines various device classes that can be addressed by generic drivers, ie controlled. Such drivers are already installed on common operating systems. An example of this is the USB mass storage class (see, for example, "Universal Serial Bus Mass Storage Class Specification Overview", Rev. 1 .4, Feb. 19, 2010, available online at: www.usb.org/developers/). devclass_docs), which standardizes the behavior of mass storage devices connected to the PC via USB (eg USB sticks, external hard disks, digital cameras, etc.) on the USB bus and their communication with a PC. For communication with USB devices that comply with this USB mass storage class, no special driver from the manufacturer is required on the PC because the standard driver (mass storage driver) can be used. Static measurement data, which is usually stored on the side of the measuring device in a file system (ie in folders and files), can thus be copied to the PC with the existing mass storage driver without prior driver installation, in a manner such as, for example, pictures of a digital camera ra be downloaded to a PC. Often, however, it is desirable or necessary to transmit, in addition to the static measurement data stored in files, data and / or control commands continuously generated by the measurement device (eg measurement start / stop commands). This is particularly the case when the measurement data in real time ("on-line") are to be displayed on the screen of the PC, or when the measured data received from the PC is to be reacted immediately (eg in a control loop). For this purpose, a specially developed for the respective device driver is required, which must be installed on the PC. For example, so-called CDC drivers (communication device class drivers) or, for transporting the data according to the USB mass storage class bulk-only transport protocol, so-called bulk drivers are used. Such a driver has to be developed and deployed, sometimes even developing several driver versions is necessary for different types and derivatives of common operating systems. For the user, the installation of new drivers is expensive and takes time.

The object of the invention is, in addition to static data in the form of files also control commands and other data "on-line" on the same, on the PC standard existing USB mass storage class driver to transport, so that the additional installation of additional drivers is no longer necessary.

This object is achieved by a system according to claim 1, by a method according to claim 7, and a terminal according to claim 8. Exemplary embodiments and further developments of the invention are the subject of the dependent claims.

A system for the on-going transmission of data between a terminal and a computer is described. The system comprises: a USB bus; a terminal that continuously generates data in operation and provides it continuously on a USB bus in accordance with the USB Mass Storage Class standard; a computer connected to the USB bus with a USB device driver that operates according to the USB Mass Storage Class standard and an application program designed to to continuously receive data generated by the meter from the USB bus using the device driver.

Further described is a method of continuously transmitting data in real time between a terminal and a computer connected to the terminal via a USB bus, the computer having a USB device driver operating in accordance with the USB Mass Storage Class standard , The method includes the steps of: invoking SCSI commands using an I / O Ctri system call provided by the device driver; Transfer the real-time data or commands via the USB device driver using SCSI commands provided by the device driver that are not needed to transfer folders and files. A terminal with a USB interface is also described, which is designed to be connected to a computer via a USB bus and to continuously transmit data to and / or receive control data from it according to the above-mentioned method. Previously additionally required CDC or bulk drivers for transmitting the real-time data are no longer needed with a solution according to the above-mentioned examples of the invention. USB devices are assigned to different classes according to the USB standard. Devices belonging to the same class use the same device driver. The measuring device according to the invention is assigned to the USB mass storage device class, also known as USB MSC or UMS. The Mass-Sto rage protocol emulates a running on the SCSI (SCSI Small Computer System Interface) standard mass storage device. The necessary PC drivers for the most common operating systems Windows, MAC OS, Linux and BSD are standard components of the respective operating systems.

How mass storage devices behave on the USB bus is described in various USB mass storage class specifications supported by the USB Mass Storage Class (CWG) Working Group (CWG). The title of one of these Specifications are "USB Mass Storage Class, Control / Bulk / Interrupt Transport" (Rev. 1 .1 available at:

www.usb.org/developers/devclass_docs/usb_msc_cbi_1 .1 .pdf). For the solution described below, the data is preferably made available according to this specification on the USB bus.

The following figures and further description are intended to help to better understand the invention. Further details, variants and further developments of the inventive concept will be explained with reference to the figures. The elements in the figures are not necessarily to be construed as limiting, rather value is placed to represent the principle of the invention. In the pictures show:

FIG. 1 shows, by way of example, the general data transmission principle from a measuring device to a computer;

FIG. 2 shows by way of example the data transmission from a measuring device to a computer according to an example of the invention; and FIG. 3 shows the example from FIG. 2 with more details.

The example described below relates to the continuous transmission of real-time data between a meter and a computer. Continuous transmission in this context means the continuous, regular transmission of data at predetermined (not necessarily equidistant) intervals, so that the data can not easily be summarized in completed files before they are transmitted.

The method according to the invention for the continuous transmission of measured data in real time between a measuring device and a computer involves several steps. Initially, SCSI commands are invoked via an IoO system call that is implemented by the device driver. SCSI commands originally came from a protocol for devices that use the used parallel small-computer system interface (SCSI). The standardized SCSI instruction set provides a system to obtain information about a storage device and to write data blocks to the storage medium and read data.

Storage media using other hardware interfaces, including USB, also use the SCSI instruction set (or at least parts of it) to perform the above functions. The SCSI commands cover a large number of device types and functions. Most devices need only support a small number of SCSI commands to read from or write to mass storage. Different specifications for the SCSI commands used by mass storage devices can be found in a variety of sources. The INCITS Technical Committee T10 defines the following specifications, among others:

SCSI Primary Commands (SPC): Defines commands that are used on all SCSI devices. The current version is SPC-3.

SCSI Block Commands (SBC): Defines commands used by hard drives, mass storage devices, and other direct access devices (Block Command Specification). The current version is SBC-3.

Each device issues a command set to a SCSI INQUIRY command, which defines the commands required for communication. A device that provides an INQUIRY command PERIPHERAL DEVICE TYPE = 00h (direct ac- cess device) and VERSION = 05h (SPC-3) should use all commands specified in the SPC-3 specification, as well as in a block diagram. Command specification such as the SBC-2 or SBC-3 specified as mandatory are implemented. The commands required for the operation of USB mass storage devices (see also online: www.t10.org/lists/opnumber.htm): INQUIRY,

READ CAPACITY (10),

READ (10)

REQUEST SENSE,

TEST UNIT READ,

WRITE (10) (for writable devices).

There are also additional, optional commands. These are not required for USB mass storage operation, but can also be called up on the computer via an appropriate I / O control system call (ioctl system call).

These optional commands include, for example: WRITE BUFFER (SCSI operation code 3B), and READ BUFFER (SCSI operation code 3C). Both the static data and the real-time data are transmitted in the inventive solution via USB mass storage. However, a distinction is made as to whether a USB mass storage packet or a special (eg WRITE BUFFER) packet is being transmitted. This distinction takes place in the USB stack. The USB stack is the component that enables communication between USB devices and the corresponding drivers. The heart of the USB stack is the USB device manager, which can be used as a portal and manages both the connected USB devices and the USB drivers. With him, a driver can register with the responsible product and manufacturer ID. When a new device is plugged in, it is enumerated, checked for sufficient power, the descriptors read, and finally the driver that was registered to that device. When loading, the driver gets the information about the enumerated device that he needs to address it. In a WRITE BUFFER command an additional channel number is inserted in the data part of this telegram. This number can be used in the USB stack to distinguish what kind of package it is. The data comes, so to speak, from different branches, channels according to the invention and are bundled for transmission from the USB stack. The branches must be implemented accordingly in the USB stack. The multiplexing of the channels can then take place in the application code of a special application software.

The data is accessed on the computer side via a file system interface. This programming interface (also referred to as API, application programming interface) is used e.g. addressed via the normal file system calls fopen, fclose, fread, fwrite. On the PC, application software (application software, in short: app) is required to receive the data (real-time data) continuously generated by the measuring device. This application software executes the file system calls and other system calls (File Access and Directory System Calls) to perform and control data exchange with the meter.

Using the commands specified as required, static data in the form of files and directories can be exchanged between the PC and the meter. If, as described above, optional SCSI commands not required for the file transfer are used, the real-time data and control commands can additionally be "tunneled" through the SCSI protocol, as described, whereby a continuous exchange of data between the measuring device takes place "on-line" and PC is enabled.

FIG. 1 shows the principle of data transmission between a computer and a conventional USB mass storage device, for example a USB stick. The static measurement data are usually stored in a file system (ie in folders and files of a FAT32 file system), stored in the data memory and can be saved with the aid of the mass storage driver for USB mass storage devices (USB sticks, USB Hard disks, etc.) are transmitted to the computer. A separate driver installation by the user is in most cases not necessary, since generic USB mass storage drivers are already included in almost all common operating systems. Because continuous transfer of data (in real time, so to speak) via USB with the available standardized USB Mass Storage Class device driver is not readily possible, separate drivers must be provided and installed on the computer. Usually CDC (Communication Device Class) or bulk drivers are used here. The drivers have to be specially developed for this purpose and delivered with the measuring device to the customer, whereby here also several versions may be necessary for different operating system derivatives (eg Windows XP, Windows Vista, Windows 7).

FIG. 2 shows an example of the difference between the data transmission according to the invention and the manner described in FIG. The possibility of transmitting static data (files and folders) is unchanged. These are further combined in folders and files, stored in a data system (referred to as "file system" in FIG. 1) and then transmitted to the computer by means of the common USB Mass Storage Class device drivers. In contrast to the example of FIG. 1, however, the real-time data is transmitted to the computer by means of the identical USB mass storage driver. Installation of additional CDC or bulk drivers is therefore no longer necessary. For continuous (real-time) data transmission (referred to as "specific communication" in FIGS. 1 and 2), as already explained, SCSI commands provided by the device driver are used, which are not required for the exchange of files and folders. however, are included in the standard SCSI instruction set.

In Figure 3, the inventive method for transmitting the real-time data on the present on the operating system USB mass storage driver is shown in more detail. On the instrument side, two branches (ChanneM, Channel_2) are indicated, whereby the static (Channel_2) and specific (real-time) data (ChanneM) are transmitted via one of the branches. In the USB stack, as well as in the meter corresponding channels must be implemented for this purpose. SCSI commands are sent via the PC's I / O Control system call. In the SCSI commands used in the SBC-2 and the SBC-3 Block Commands specification is specified as optional for USB communication, additional channel numbers are included. The channel numbers can then be used to distinguish whether static data or specific data is transmitted. SCSI commands are 3B WRITE

BUFFER and 3C READ BUFFER.

Access to the data occurs on the computer side via a file system interface (i.e., a corresponding API of the operating system). This programming interface is e.g. addressed via the normal file system calls fopen, fclose, fread, fwrite.

The USB stack provides communication between the meter and the driver being used and processes the sent packets at a low-level level. The inventively implemented channels are bundled in the USB stack. Based on the additionally introduced channel numbers, the channel can distinguish which type of packet it is and how a sent packet should be further processed.

Preferably, the data to be sent as real-time data is present only in a working memory. File-based storage on the data storage would generally take too much time to ensure real-time transfer.

Claims

claims

1 . A system for the continuous transmission of data between a terminal and a computer; the system includes:

a USB bus;

a terminal that continuously generates data in operation and provides it continuously on a USB bus in accordance with the USB Mass Storage Class standard;

a computer connected to the USB bus with a USB device driver operating in accordance with the USB Mass Storage Class standard, and

an application program, which is designed to receive the data continuously generated by the meter using the device driver from the USB bus.

2. System according to claim 1, wherein

the continuous transmission of data from the terminal to the computer takes place in particular in real time and in which

Continuous data transfer occurs using SCSI commands provided by the device driver, which are not required for transferring folders and files.

3. System according to claim 2, wherein the continuous data transmission in particular by means of the SCSI commands "3D WRITE BUFFER" and "3C READ

BUFFER "takes place.

4. System according to claim 1, 2 or 3, wherein the user program and terminal are adapted to continuously in both directions data using provided by the device driver SCSI commands, in particular the SCSI commands "3D WRITE BUFFER" or "3C READ BUFFER", exchange.

A system according to any one of claims 1, 2 or 3, wherein the SCSI commands are invoked via an I / O control system call of the device driver.

6. System according to one of claims 1 to 5, wherein the terminal at least two channels are provided, wherein one of the channels for the continuous transmission of data is provided in real time.

A system according to claim 7, wherein a channel is selected by means of the SCSI commands used for real-time transmission.

A method of continuously transmitting data in real time between a terminal and a computer connected to the terminal via a USB bus, the computer having a USB device driver operating in accordance with the USB Mass Storage Class standard; The procedure comprises the following steps:

Invoking SCSI commands using an I / O Ctri system call provided by the device driver;

Transfer real-time data or commands using a known mass-storage driver, using SCSI commands provided by the device driver, which are not needed to transfer folders and files.

The method of claim 8, further comprising:

Selection of a channel in the terminal by means of a SCSI command.

10. A method according to claim 8 or 9, wherein the continuous data exchange in both directions using SCSI commands provided by the device driver, in particular the SCSI commands "3D WRI-TE BUFFER" or "3C READ BUFFER", he follows.

1 1. Terminal with USB interface, which is designed to be connected to a computer via a USB bus and to which it is continuously connected. according to a method according to claim 8 to 10 and / or to receive control data from the latter.

12. Terminal with USB interface according to claim 1 1, which has at least two channels, one of which for the continuous transmission of data in

Real time is provided.

13. The terminal with USB interface according to claim 1 1, which has at least two channels, one of which is provided for the transmission of files and folders and at least one for the continuous transmission of the data in real time.

14. Terminal with USB interface according to claim 1 1, 12 or 13, wherein the channels are bundled in the USB stack, so that the data transmitted can be distinguished on the basis of the channel number.