System and method for managing a serial port

• US 6,651,111 B2
• Filed: 02/16/2001
• Issued: 11/18/2003
• Est. Priority Date: 02/16/2001
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Shell, Scott R., Sherman, Roman
• Primary Examiner(s): Huynh, Kim
• Assistant Examiner(s): PEYTON, TAMMARA R
• Application Number:
  US09/788,125
• Publication Number:
  US 20020147853A1
• Time in Patent Office: 1,005 Days
• Field of Search: 710/12, 710/14, 710/29, 710/33, 710/52, 710/53, 709/200, 709/201, 709/310
• US Class Current: 710/14
• CPC Class Codes: G06F 13/102 where the programme performs an interfacing function, e.g. device driver G06F13/105 takes precedence; scheduling within device drivers G06F9/52; contention policies within device drivers G06F9/4881

Abstract

The present invention provides for a virtual serial port (VSP) situated between a serial port in a mobile electronic device, applications that require a serial port connection handle, and other applications that require command-mode access to the serial port. Data-communication applications (e.g. web browsing, e-mail, etc.) connect to the serial port through the VSP. The VSP creates a virtual connection handle that is returned to the application. Command-mode requests (e.g., short messaging requests) are received by the hardware abstraction layer, translated into command-mode messages (e.g., AT commands) and placed in a queue. The VSP multiplexes the serial port between the currently-open data communication session (data-mode) and command-mode messages by periodically suspending the currently-open connection and processing one or more command-mode messages that are in the queue. A buffer continually stores incoming data while the data communication session is suspended. The VSP uses a heuristic calculation to determine the maximum time interval for which the data-communication session can be interrupted. The heuristic calculation takes a percentage of a time-quantum (e.g. 0.5 seconds) based upon the ratio of an average bit rate for air communication (e.g. 7000 bits/sec) and a bit rate for the serial port (e.g. 152,000 bits/sec). This ensures that data-communications are not interrupted for a time interval long enough to result in lost data-packets. The parameter for the time quantum and other parameters may be statically or dynamically adjusted to account for a finite buffer size in the hardware.

Claims

1. A system for managing a port, comprising an interface that establishes a data-connection to the port, another interface that receives command-requests and stores command-messages in a buffer, and the interface periodically suspends the established data-connection with the port when command-messages are located in the buffer wherein the interface selectively sends command-messages from the buffer to the port and resumes the connection with the port within a prescribed time interval, wherein the prescribed time interval is determined by a heuristic calculation.

2. A system as in claim 1, wherein the heuristic calculation is based upon at least one of an effective air bit rate, a software-to-module bit rate, and a time quantum.

3. A system as in claim 1, wherein the heuristic calculation includes a time quantum that is dynamically adjusted.

4. A system as in claim 1, wherein the heuristic calculation is calculated at least during a power up condition.

5. A system as in claim 1, wherein the heuristic calculation is calculated at a predetermined time interval.

6. A system as in claim 1, wherein the interface selects command-messages from the buffer based upon one of a weighted priority that is associated with each entry in the buffer, a first-in first-out criteria, and a last-in first-out criteria.

7. A system method as in claim 1, wherein the port includes a receive buffer with a finite size, the receive buffer receiving data while the data-connection is suspended, and the heuristic calculation accounts for the finite size of the receive buffer.

8. A system as in claim 1, wherein the interface generates a virtual handle to the port when the data-connection is established, and data-communication is accomplished through the virtual handle.

9. A system as in claim 1, wherein the data-connection is suspended by setting a DTR control in the port low, and the data-connection is resumed by sending a command-message to the port.

10. A method of managing a port, comprising:

generating a virtual handle when a data-connection is established;

switching between a data-mode and a command-mode based upon a heuristic calculation;

routing data between the port and the virtual handle when the operating mode is the data-mode;

placing received command-messages in a buffer;

selecting at least one command-message from the buffer; and

sending the selected at least one command-message to the port when the operating mode is the command-mode.

11. The method of claim 10, wherein the data connection is active when the operating mode is a data-mode, and the data connection is suspended when the operating mode is a data-mode.

12. The method of claim 10, further comprising:

receiving a command-request from an application; and

formatting the command-request into a command-message.

13. The method of claim 10, further comprising:

receiving a reply-message from the port when the operating mode is the command-mode; and

sending the reply-message to an application when the operating mode is the command-mode.

14. The method of claim 10, further comprising:

receiving a reply-message from the port when the operating mode is the command-mode;

sending the reply-message to another buffer when the operating mode is the command-mode; and

switching from the command-mode to the data-mode after the reply-message is sent to the other buffer.

15. The method of claim 10, wherein the port is part of a portable electronic device.

16. A computer readable medium having computer executable instructions for managing a port connection, comprising:

activating a call-mode when a data-connection is established;

deactivating the call-mode when the data-connection is terminated;

determining a time interval based on a heuristic calculation;

routing data between an application and the port during the time interval when the operating mode is the call-mode;

suspending the data-connection at the end of the time interval when the operating mode is the call-mode;

activating a command-mode when the call-mode is deactivated;

activating the command-mode when the data-connection is suspended;

processing command-messages that are awaiting processing when the operating mode is the command-mode; and

resuming a suspended data connection after completing the processing of command messages when the call-mode is active.

17. A computer readable medium as in claim 16, wherein the heuristic calculation is based upon at least one of a data transfer speed associated with the port, a communication channel speed, a buffer length associated with the port, and a time quantum.

18. A computer readable medium as in claim 17, wherein the maximum time interval that an active call can be suspended is associated with a ratio between the data transfer speed and the communication channel speed.

19. A system for managing a serial port in a portable device, comprising:

means for activating a call-mode when a data-connection is established;

means for deactivating the call-mode when the data-connection is terminated;

means for receiving a command-request;

means for converting the command-request to a command-message;

means for sending the command-message to the serial port when operating in a command-mode;

means for routing data between an application and the serial port when operating in a data-mode;

means for selecting the command-mode when the call-mode is inactive;

means for selecting the data-mode when the call-mode is active; and

means for switching between the data-mode and the command-mode based on a heuristic calculation when the call-mode is active.

20. A system as in claim 19, wherein the means for switching, further comprising:

means for suspending the data-connection when the call mode is active and the command-mode is selected; and

means for resuming the suspended data-connection when the data-mode is selected, where the heuristic calculation determines a maximum time interval for which the data-connection can be suspended based on a ratio between an effective air bit rate and a software to module bit rate.