JP4924472B2 - Host device - Google Patents

Description

  The present invention reduces the processing load on a host device while quickly reading data stored in the USB serial converter when transferring data between the serial device and the host device using a USB serial converter. Regarding technology.

  2. Description of the Related Art Conventionally, electronic devices such as printers and modems that are connected to a host device such as a personal computer are known. Such an electronic device has an interface such as RS-232C or Centronics, for example, is connected to a host device via a predetermined cable, and operates according to control from the host device.

  In recent years, USB (Universal Serial Bus) is increasing as an interface standard adopted for host devices. This USB is supported by a general OS (Operating System) installed in the host device, and can be connected while the power of the electronic device is turned on. It is characterized by plug and play that can be automatically set (see, for example, Patent Document 1). There are many opportunities to use a mixture of an electronic device having a conventional interface such as the above-mentioned RS-232C and an electronic device having the latest interface such as USB. At that time, both are connected using a so-called USB serial converter.

  This USB serial converter has an additional serial terminal by connecting to a host device such as a personal computer, and uses a conventional serial API for access from the application layer of the host device. Also, the USB serial converter driver maintains compatibility at the API level by simulating the conventional serial driver. With such a mounting method, communication software for serial communication can be used even if a USB serial converter is used.

  In the data transfer in the serial standard, data transfer is performed bi-directionally and asynchronously. On the other hand, in the data transfer in the USB standard, frame structure packet transfer is performed. For this reason, a data exchange protocol between the USB serial converter and the host device becomes a problem. That is, when a USB serial converter receives a bit string from RxD, the received data is byte-converted and held in a buffer. In this case, since the capacity of the buffer inside the USB serial converter is generally set to be small, it is necessary for the host device to read the data stored in the buffer before the buffer has no free space.

  Therefore, the host device generally performs interrupt transfer or periodically performs bulk transfer (polling) to check whether data is stored in the buffer of the USB serial converter.

  However, when the host device performs an interrupt transfer, the transfer cycle is determined and a fixed amount of packets are always transferred. Therefore, there is a problem that the USB bus is occupied by a certain width even when data is not stored in the buffer. . Also, when the host device performs bulk transfer, the host device periodically issues a control command, and the USB serial converter repeats the process of returning data in response to this, and in this case as well, There is a problem that the USB bus is occupied by a certain width even when data is not stored in the buffer. In other words, in the data transfer in the serial system, the frequency of occurrence of data to be transferred is low, and there are many periods in which there is no data to be transferred. The burden on the USB serial converter is increasing.

As described above, the transfer cycle when performing interrupt transfer or bulk transfer must have a margin for the maximum transfer rate (generally 115200 bps) when data transfer is performed in a serial manner. For example, in the case of “FT232R” manufactured by FTDI (Future Technology Devices International Ltd.), for example, the capacity of the data reception buffer of the control LSI of the UBS serial converter is about 256 bytes, so the transfer cycle is 22 msec or less. For example, interrupt transfer is performed and bulk transfer is performed at a cycle of 22 msec or less.
JP 2002-197048 (second page, FIG. 2)

  However, in the data transfer method between the serial device and the host device using such a USB serial converter, compared to the case where data transfer with the serial device is performed via a conventional serial communication driver, There is a problem that the processing load of the CPU provided in the host device increases. The reason is that the USB host controller LSI provided in the host device has three types of “OHCI”, “EHCI”, and “UHCI” as PCI bus connections. In either case, the USB standard receives one packet. This is because it is necessary to perform the interrupt processing once for each, and therefore it is necessary to perform the interrupt processing in the transfer cycle. By the way, when transferring data with a serial device via a conventional serial driver, the above interrupt processing is performed only when transferring data, so the frequency with which data to be transferred is generated. In data transfer with a low-speed serial device, the frequency of interrupt processing is extremely low, and even if the cycle of interrupt processing is short, the load of processing actually performed by the CPU included in the host device is small.

  In addition, among serial devices, there are many devices that transfer data of, for example, several bytes per several minutes, such as sensor devices and operation terminals, and devices that have a large variation in processing load. Furthermore, in USB standard data transfer, it is not possible in the standard to issue a transfer trigger from a USB serial converter. Therefore, in the USB serial converter, since the host device needs to read the data stored in the buffer before the buffer runs out of space, the load on the CPU of the host device increases when performing bulk transfer. The transfer cycle is set as short as possible. In other words, despite the low frequency with which data to be transferred is generated, the presence or absence of data stored in the buffer is frequently checked.

  The present invention has been made in view of such a problem, and an object of the present invention is to use a USB serial converter when performing data transfer between a serial device and a host device using the USB serial converter. It is an object to provide a technique for reducing the processing load on a host device while quickly reading data stored in the host device.

  In order to solve the above-described problems, a host device according to claim 1 includes a device driver capable of transmitting / receiving USB standard data to / from a USB serial converter, and a communication application.

  The USB serial converter relays data transfer between a “serial device” that is an electronic device that can process serial standard data and a “USB device” that is an electronic device that can process USB standard data. It has a function. Specifically, when the USB serial converter is connected between the serial device and the USB device, the USB serial converter temporarily stores the serial standard data transmitted from the serial device to the USB device and stores the data in the USB. The data is converted into standard data and transmitted to the USB device in response to a request from the USB device. On the other hand, the USB standard data transmitted from the USB device to the serial device is converted into serial standard data and then transmitted to the serial device. The time for converting the serial standard data to the USB standard data may be before the data is stored in the buffer or after the data stored in the buffer is read.

  The device driver can transmit / receive USB standard data to / from the USB serial converter as described above, can issue various commands to the USB serial converter, and can store the data stored in the buffer. A confirmation command for confirming the presence or absence is issued to the USB serial converter at a preset cycle. The preset period is set in advance according to the capacity of the buffer and the maximum data transfer amount per unit time when performing data transfer with the USB serial converter.

  The communication application issues a read command to the USB serial converter via the device driver. Note that the read command is a command for reading data stored in the buffer of the USB serial converter, and is issued at a cycle set so that the free space of the buffer of the USB serial converter is not lost.

  Then, the device driver described above measures the period at which the communication application issues the read command, and changes the period at which the confirmation command is issued from the preset period to the measured period. The data stored in the USB serial converter is transferred from the USB serial converter to the host device every time the communication application issues a read command.

Note that the host device functions as a USB device by the functions of the device driver and the communication application as described above.
In this case, since the cycle in which the communication application issues the read command is longer than the cycle in which the device driver issues the confirmation command, the cycle in which the changed confirmation command is issued becomes longer than before the change. Note that the data stored in the buffer of the USB serial converter is transferred from the USB serial converter to the host device every time the communication application issues a read command, so that the buffer free capacity is not lost. . Therefore, it is possible to reduce the processing load on the host device while quickly reading the data stored in the USB serial converter.

  In addition, it is conceivable to change the period for issuing the above confirmation command from a preset period to a period corresponding to the data transfer rate set by the communication application. Specifically, as described in claim 2, the RS232C serial communication speed, that is, the data transfer amount per unit time when the communication application performs data transfer with the serial device, that is, the baud rate (bps: Bits Per). Second) can be set, and it is conceivable that the device driver calculates a period corresponding to the baud rate set by the communication application, and changes the period for issuing the confirmation command from the preset period to the calculated period. .

  In this way, the baud rate is smaller than the “maximum data transfer amount per unit time” used when calculating the preset period, so the period for issuing the confirmation command after the change is less than before the change. become longer. As described above, the data stored in the buffer of the USB serial converter is transferred from the USB serial converter to the host device every time the communication application issues a read command. There is no loss of capacity. Therefore, it is possible to reduce the processing load on the host device while quickly reading the data stored in the USB serial converter.

  It is also conceivable to stop issuing the above confirmation command. Specifically, as in claim 3, an input unit for inputting that the issuance of the confirmation command is stopped is provided, and when the input unit is inputted to stop the issuance of the confirmation command, the device It is possible that the driver stops issuing confirmation commands. As a method for inputting to the input means to stop issuing the confirmation command, there are manual input by the user, command issuance by the host device, and the like. As described above, the data stored in the buffer of the USB serial converter is transferred from the USB serial converter to the host device every time the communication application issues a read command. There is no loss of capacity. Therefore, it is possible to reduce the processing load on the host device while quickly reading the data stored in the USB serial converter.

Embodiments of the present invention will be described below with reference to the drawings.
[First embodiment]
FIG. 1 is an explanatory diagram showing an example in which a host device and a serial device are connected using a USB serial converter. FIG. 2 is a hardware block diagram showing the configurations of the host device and the USB serial converter. FIG. 3 is a software block diagram showing the configuration of the host device. The USB device is an electronic device capable of processing USB standard data, and the serial device is an electronic device capable of processing serial standard data.

[Description of Configuration of USB Serial Converter 20]
The USB serial converter 20 includes a USB (B) connector 21 to which a USB device can be connected, a USB serial conversion LSI 22, and a serial connector 23 to which a serial device can be connected. In the USB serial converter 20, a USB (B) connector 21 and a USB device controller circuit block 22 a (described later) of the USB serial conversion LSI 22 are connected, and a serial circuit block 22 c (described later) of the USB serial conversion LSI 22 is serially connected. The connector 23 is connected.

  The USB serial conversion LSI 22 includes a microcomputer CPU circuit block 22b that executes various processes, and a USB device controller circuit that mediates data exchange between the microcomputer CPU circuit block 22b and a USB device connected to the USB (B) connector 21. And a serial circuit block 22c that mediates data exchange between the microcomputer CPU circuit block 22b and a serial device connected to the serial connector 23.

  The USB serial converter 20 configured as described above has a function of relaying data transfer between the serial device and the USB device. Specifically, the USB serial converter 20 is temporarily connected to a buffer (not shown) containing serial standard data transmitted from the serial device to the USB device when connected between the serial device and the USB device. Is converted to USB standard data and transmitted to the USB device in response to a request from the USB device. On the other hand, the USB standard data transmitted from the USB device to the serial device is converted into serial standard data and then serialized. Send to device. The time for converting the serial standard data to the USB standard data may be before the data is stored in the buffer or after the data stored in the buffer is read.

[Description of Configuration of Host Device 10]
The host device 10 connects a CPU 11 that executes processes based on a plurality of software in parallel in a time division manner, a PC chip set 12, a USB host controller LSI 13 that executes various processes as a host for the USB device, and a USB device. A USB (A) connector 14 and a serial connector 15 to which a serial device can be connected are provided, and functions as a USB device. Note that the host device 10 of the present embodiment includes four USB (A) connectors 14 and one serial connector 15.

  In the host device 10, the CPU 11 and the PC chip set 12 are connected, and the PCI bus bridge circuit block 12 b (described later) of the PC chip set 12 and the USB host controller LSI 13 are connected via the PCI bus, and the PC chip. A serial circuit block 12a (described later) of the set 12 and a serial connector 15 are connected, and a USB host controller LSI 13 and a USB (A) connector 14 are connected.

  The PC chip set 12 includes a serial circuit block 12a that mediates data exchange between the CPU 11 and the serial device, and a PCI bus that mediates data exchange between the CPU 11 and various components connected to the PCI bus. A bridge circuit block 12b and the like are mounted.

  Also, the USB host controller LSI 13 is controlled by the CPU 11 to generate USB standard data, and outputs the generated data to the USB device connected to the USB (A) connector 14 via the USB (A) connector 14. At the same time, a communication signal transmitted from the USB device via the USB (A) connector 14 is received, and the received data is input to the CPU 11.

  Further, as shown in FIG. 3, the host device 10 includes a communication application 101 in the application layer, a serial API 102 in the API layer, a USB serial converter device driver 103, a 16550 serial device driver 104 in the device driver layer, and A USB host controller device driver 105 is provided. Various application software provided in the host device 10 is executed by the CPU 11, the PC chip set 12, and the USB host controller LSI 13 described above.

  The USB serial converter device driver 103 as a device driver can send and receive USB standard data to and from the USB serial converter 20 via the USB host controller device driver 105. Further, the USB serial converter device driver 103 can issue various commands to the USB serial converter 20, and a confirmation command (polling) for checking the presence or absence of data accumulated in the buffer of the USB serial converter 20. ) Is issued to the USB serial converter 20 at a preset cycle. The preset period is set in advance according to the capacity of the buffer and the maximum data transfer amount per unit time when performing data transfer with the USB serial converter 20, and in the present embodiment, 16 msec. Set to

[Other configuration of host device 10]
Since other configurations of the host device 10 according to the present embodiment are in accordance with known techniques, detailed description thereof is omitted here.

[Description of Data Transmission / Reception Process Between Conventional Host Device 10 and Serial Device 30]
Next, a conventional process for transmitting and receiving data between the host device 10 and the serial device 30 by connecting the host device 10 and the serial device 30 using the USB serial converter 20 is described as follows: (1) OPEN command The order of issue, (2) READ command issue, (3) WRITE command issue, and (4) CLOSE command issue will be described in this order. FIG. 4 is a sequence diagram for explaining a data transmission / reception process between the conventional host device 10 and the serial device 30.

(1) OPEN command issuance When starting transmission / reception of data between the communication application 101 and the USB serial converter 20, the communication application 101 issues an OPEN command. That is, when the communication application 101 issues an OPEN command to start transmission / reception of data with the USB serial converter 20, the OPEN command is transmitted to the USB serial converter device driver 103 via the serial API 102. When the USB serial converter device driver 103 receives the OPEN command, it issues an OPEN return value. This OPEN return value is transmitted to the communication application 101 via the serial API 102. The USB serial converter device driver 103 issues a command to the USB serial converter 20. This command is transmitted to the USB serial converter 20 via the USB host controller device driver 105. When the USB serial converter 20 receives a command, it issues a command reply interrupt. The command reply interrupt is transmitted to the USB serial converter device driver 103 via the USB host controller device driver 105. Through the above process, data transmission / reception is started between the communication application 101 and the USB serial converter 20.

  The USB serial converter device driver 103 that has received the command reply interrupt starts polling at a predetermined cycle. Specifically, the USB serial converter device driver 103 issues a command for confirming that data is stored in the buffer of the USB serial converter 20. This command is transmitted to the USB serial converter 20 via the USB host controller device driver 105. The USB serial converter 20 checks whether data is stored in the buffer and issues a command (command reply interrupt) indicating the check result. The command reply interrupt is transmitted to the USB serial converter device driver 103 via the USB host controller device driver 105.

  When the USB serial converter 20 receives the data transmitted from the serial device and accumulates the received data in the buffer, it waits for the communication application 101 to issue the READ command and accumulates it. Data is transmitted to the communication application 101.

In the present embodiment, the initial value of the polling cycle is set to 16 msec, and thereafter polling is executed in this cycle.
(2) READ command issuance The communication application 101 is set to issue a READ command at a predetermined cycle, and issues a READ command at this cycle. The READ command is a command for reading data stored in the buffer of the USB serial converter 20, and is issued at a cycle set so that the free capacity of the buffer of the USB serial converter 20 is not lost. . Note that this cycle is set by the communication application 101.

  First, when the communication application 101 issues a READ command to read data stored in the buffer of the USB serial converter 20, the READ command is transmitted to the USB serial converter device driver 103 via the serial API 102. When the USB serial converter device driver 103 receives the READ command, it issues a READ return value. This READ return value is transmitted to the communication application 101 via the serial API 102. The USB serial converter device driver 103 issues a command to the USB serial converter 20. This command is transmitted to the USB serial converter 20 via the USB host controller device driver 105. When the USB serial converter 20 receives the command and stores data in the buffer, the USB serial converter 20 transmits the stored data to the USB serial converter device driver 103 via the USB host controller device driver 105. The USB serial converter device driver 103 converts the received data into the USB standard and then transmits the data to the communication application 101 via the serial API 102 or the like. In the communication application 101, the received data is temporarily stored in a buffer and processed according to an instruction from an application that requires the data.

(3) WRITE command issuance When data is transmitted to a serial device according to an instruction from another application, the communication application 101 issues a WRITE command to write data to the buffer of the USB serial converter 20. That is, when the communication application 101 issues a WRITE command to write data to the buffer of the USB serial converter 20, the WRITE command is transmitted to the USB serial converter device driver 103 via the serial API 102. On the other hand, when the USB serial converter device driver 103 receives the WRITE command, it issues a WRITE return value. This WRITE return value is transmitted to the communication application 101 via the serial API 102. Then, the communication application 101 transmits data to be written to the buffer of the USB serial converter 20 to the USB serial converter 20 via the serial API 102 or the like. The USB serial converter 20 temporarily stores the received data in a buffer, converts it into a serial standard, and transmits it to a serial device.

(4) CLOSE command issuance When the transmission / reception of data between the communication application 101 and the USB serial converter 20 is completed, the communication application 101 issues a CLOSE command. That is, when the communication application 101 issues a CLOSE command to end data transmission / reception with the USB serial converter 20, the CLOSE command is transmitted to the USB serial converter device driver 103 via the serial API 102. On the other hand, when receiving the CLOSE command, the USB serial converter device driver 103 stops the polling that has been periodically performed and issues a CLOSE return value. This CLOSE return value is transmitted to the communication application 101 via the serial API 102.

[Description of polling cycle change processing (1)]
Hereinafter, the procedure (1) of the polling cycle changing process executed by the USB serial converter device driver 103 will be described with reference to the flowchart of FIG. 5 and FIG. FIG. 6 is a sequence diagram for explaining the polling cycle changing process (1).

This polling cycle changing process (1) is repeatedly executed independently of other processes when the host device 10 is activated.
First, when a driver call that is a command issue by the USB serial converter device driver 103 is started, a function branch is performed according to the type of the driver call. In this embodiment, (A) when the type of driver call is an OPEN command, (B) when the type of driver call is a CLOSE command, (C) when the type of driver call is a READ command, (D) A case where the type of the driver call is a WRITE command and (E) the type of the driver call is a baud rate setting command will be described.

(A) When the type of the driver call is an OPEN command In this process, an initialization command for instructing to initialize the setting contents is issued. When the initialization command is issued, the timer processing settings are initialized. In the present embodiment, the polling period is set to 16 msec. Then, the driver call ends.

  Note that when the timer activation process, which is one of the functions of the OS installed in the host device 10, is executed, the above-described timer process is started, and in the present embodiment, the above-described READ command is issued every 250 msec. Then, the timer process ends.

(B) When the type of driver call is a CLOSE command In this process, the timer process setting is canceled. As a result, the timer process is not executed and the READ command is not issued thereafter. Also, polling is stopped by issuing the CLOSE command as described above. Then, the driver call ends.

(C) When Driver Call Type is READ Command In this process, an output process of READ data is executed. Specifically, data is read from a buffer in the USB serial converter device driver 103. The read data is processed according to an instruction from an application that requires the data. Furthermore, the timer process is reset. Specifically, each time a process is executed, the processing time record stored in a built-in memory (not shown) is referred to, and the calculation result obtained by calculating the time from the previous processing time to the current processing time is newly polled. Set as period. As an example, when the time from the time when the READ command is issued to the time when the READ command is issued is 250 msec, the polling period is set to 250 msec. Then, the driver call ends.

  Note that the data stored in the buffer in the USB serial converter device driver 103 is read by the READ data output process as described above, and is also read when the command completion interrupt process is started. Specifically, when the command completion interrupt process is started, the data stored in the buffer in the USB serial converter device driver 103 is read, and the read data is transferred to the USB serial converter 20. The The USB serial converter 20 stores the transferred data in a buffer. The data stored in the buffer is transmitted from the USB standard to the serial standard and then transmitted to the serial device. Command completion interrupt processing ends.

(D) When the type of the driver call is a WRITE command In this process, a WRITE data input process is executed. Specifically, data is written to a buffer in the USB serial converter device driver 103 and also written to a buffer of the USB serial converter 20. Then, a WRITE command is issued to reset the timer process as described above. Then, the driver call ends.

(E) When the type of driver call is a baud rate setting command In this process, a baud rate setting command is issued. The baud rate (bps: Bits Per Second) is an RS232C serial communication speed, and is a data transfer amount per unit time when data is transferred to and from the serial converter 30. This baud rate is set by the communication application 101. Then, the driver call ends.

[Effect of the first embodiment]
(1) As described above, according to the host device 10 of the first embodiment, the calculation result obtained by calculating the interval for issuing the READ command is set as a new polling cycle. The polling cycle calculated in this way is a polling preset in accordance with the buffer capacity of the USB serial converter 20 and the maximum data transfer amount per unit time when data is transferred to and from the USB serial converter 20. Since the period is longer than the initial value, the polling period after the change becomes longer than before the change. The data accumulated in the buffer of the USB serial converter 20 is transferred from the USB serial converter 20 to the host device 10 every time the communication application 101 issues a READ command. There is no loss of free buffer space. Therefore, the processing load on the host device 10 can be reduced while quickly reading the data stored in the USB serial converter 20.

[Other Embodiments]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, It is possible to implement in the following various aspects.

  (1) In the above embodiment, the calculation result obtained by calculating the interval at which the READ command is issued is set as a new polling cycle. However, the present invention is not limited to this. For example, the cycle corresponding to the baud rate set by the communication application 101 is set as a new polling cycle. You may set as a period. 7 is a flowchart showing the polling cycle changing process (2), and FIG. 8 is a sequence diagram for explaining the polling cycle changing process (2). Specifically, as illustrated in FIGS. 7 and 8, when the type of the driver call is a baud rate setting, the timer process is reset after issuing a baud rate command. At this time, a cycle corresponding to the baud rate set by the communication application 101 is set as a new polling cycle. In this case, the timer process is executed after the READ data output process is executed when the driver call type is the READ command, and after the WRITE command is issued when the driver call type is the WRITE command. The processing for calculating the interval for issuing the READ command at the resetting is not performed. Since the polling period calculated in this way is longer than the initial value of the preset polling period as described above, the polling period after the change becomes longer than before the change. The data stored in the buffer of the USB serial converter 20 is transferred from the USB serial converter 20 to the host device 10 every time the communication application 101 issues a READ command as described above. The free space of the buffer of the USB serial converter 20 is not lost. Therefore, the processing load on the host device 10 can be reduced while quickly reading the data stored in the USB serial converter 20.

  A specific example of setting a new polling cycle with a numerical value (FIG. 7, polling cycle X (ms)) corresponding to the baud rate set by the communication application 101 by resetting the timer processing described above will be described below. . Here, “SET” is a communication speed (baud rate: bps) set by the communication application 101. Data (transfer data) transferred by RS232C with respect to data (valid data) 8 bits sent by the communication application 101 includes an RS232C start bit (START-bit) and a stop bit (STOP-bit) in addition to the valid data. Therefore, the RS232C transfer data when valid data 8 bits (1 byte) is sent is (8 bits + 1 bit + 1 bit). Note that the buffer capacity of the USB serial converter 20 (for example, FT232R) in this embodiment is 256 (bytes). Therefore, the polling cycle X is X (sec) = 1 / (SET / (8 + 1 + 1) / 256). If the unit is converted from seconds to milliseconds, X * 1000 = 1 / (SETbps / (8 + 1 + 1) / 256) = X (ms).

  (2) Polling may be stopped after issuing an OPEN command. FIG. 9 is a sequence diagram for explaining the polling cycle changing process (3). Specifically, as illustrated in FIG. 9, the communication application 101 uses a manual trigger to stop polling according to an instruction from a user or an instruction from another application to the keyboard of the host device 10 as an input unit. Issue a mode change command to change the mode. That is, when the communication application 101 issues a mode change command, the mode change command is transmitted to the USB serial converter device driver 103 via the serial API 102. On the other hand, when receiving the mode change command, the USB serial converter device driver 103 stops polling that has been performed regularly and issues a mode change return value. This mode change return value is transmitted to the communication application 101 via the serial API 102. The data stored in the buffer of the USB serial converter 20 is transferred from the USB serial converter 20 to the host device 10 every time the communication application 101 issues a READ command as described above. The free space of the buffer of the USB serial converter 20 is not lost. Therefore, the processing load on the host device 10 can be reduced while quickly reading the data stored in the USB serial converter 20.

It is explanatory drawing which shows the example which connects a host apparatus and a serial apparatus using a USB serial converter. It is a hardware block diagram which shows the structure of a host apparatus and a USB serial converter. It is a software block diagram which shows the structure of a host apparatus. It is a sequence diagram explaining the data transmission / reception process of the conventional host device and a serial device. It is a flowchart which shows a polling period change process (1). It is a sequence diagram explaining a polling period change process (1). It is a flowchart which shows a polling period change process (2). It is a sequence diagram explaining a polling period change process (2). It is a sequence diagram explaining a polling period change process (3).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Host apparatus, 11 ... CPU, 12 ... PC chip set, 12a ... Serial circuit block, 12b ... PCI bus bridge circuit block, 13 ... USB host controller LSI, 14 ... USB (A) connector, 15 ... Serial connector, 20 ... USB serial converter, 21 ... USB (B) connector, 22 ... USB serial conversion LSI, 22a ... USB device controller circuit block, 22b ... Microcomputer CPU circuit block, 22c ... Serial circuit block, 23 ... Serial connector, 30 ... Serial Device 101 Communication application 102 Serial API 103 USB serial converter device driver 104 Serial device driver 105 USB host controller device driver

Claims (3)

The serial device transmitted to the USB device when connected between a serial device that is an electronic device capable of processing serial standard data and a USB device that is an electronic device capable of processing USB standard data Standard data is temporarily stored in a built-in buffer, converted to USB standard data and transmitted to the USB device in response to a request from the USB device, while the USB device transmits to the serial device USB standard data is converted to serial standard data and then transmitted to the serial device, and USB standard data is transmitted and received between the serial device and the USB serial converter that relays data transfer between the serial device and the USB device. A confirmation command for confirming the presence or absence of data accumulated in the buffer. And the device driver issuing into the USB serial converter at preset periods according to the maximum data transfer amount per unit time for data transfer in and between the USB serial converter,
A communication application for issuing a read command for reading data stored in the buffer of the USB serial converter to the USB serial converter via the device driver;
A host device that functions as the USB device,
The host device is characterized in that the device driver measures a cycle in which the communication application issues the read command, and changes a cycle in which the confirmation command is issued from a preset cycle to the measured cycle. The serial device transmitted to the USB device when connected between a serial device that is an electronic device capable of processing serial standard data and a USB device that is an electronic device capable of processing USB standard data Standard data is temporarily stored in a built-in buffer, converted to USB standard data and transmitted to the USB device in response to a request from the USB device, while the USB device transmits to the serial device USB standard data is converted to serial standard data and then transmitted to the serial device, and USB standard data is transmitted and received between the serial device and the USB serial converter that relays data transfer between the serial device and the USB device. A confirmation command for confirming the presence or absence of data accumulated in the buffer. And the device driver issuing into the USB serial converter at preset periods according to the maximum data transfer amount per unit time for data transfer in and between the USB serial converter,
A communication application for issuing a read command for reading data stored in the buffer of the USB serial converter to the USB serial converter via the device driver;
A host device that functions as the USB device,
The communication application can set a baud rate, which is a data transfer amount per unit time when performing data transfer with the serial device,
The host device calculates a period corresponding to a baud rate set by the communication application, and changes a period for issuing the confirmation command from a preset period to the calculated period. The serial device transmitted to the USB device when connected between a serial device that is an electronic device capable of processing serial standard data and a USB device that is an electronic device capable of processing USB standard data Standard data is temporarily stored in a built-in buffer, converted to USB standard data and transmitted to the USB device in response to a request from the USB device, while the USB device transmits to the serial device USB standard data is converted to serial standard data and then transmitted to the serial device, and USB standard data is transmitted and received between the serial device and the USB serial converter that relays data transfer between the serial device and the USB device. A confirmation command for confirming the presence or absence of data accumulated in the buffer. And the device driver issuing into the USB serial converter at preset periods according to the maximum data transfer amount per unit time for data transfer in and between the USB serial converter,
A communication application for issuing a read command for reading data stored in the buffer of the USB serial converter to the USB serial converter via the device driver;
A host device that functions as the USB device,
An input means for inputting that the issuance of the confirmation command is stopped;
The host device, wherein the device driver stops issuing the confirmation command when the input means inputs an instruction to stop issuing the confirmation command.