Host signal processor modem and telephone

• US 5,940,459 A
• Filed: 07/09/1996
• Issued: 08/17/1999
• Est. Priority Date: 07/09/1996
• Status: Expired due to Term

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: PC-TEL Incorporated
• Inventors: Hsu, Wen-Liang, Hsu, Tseng Jan
• Primary Examiner(s): Vu, Huy D.
• Assistant Examiner(s): Corrielus, Jean B.
• Application Number:
  US08/677,485
• Time in Patent Office: 1,134 Days
• Field of Search: 375/222, 375/377, 375/220, 375/372, 375/259, 455/73, 455/75, 395/872, 395/889, 395/890, 379/67, 379/88, 370/468, 370/505
• US Class Current: 375/377
• CPC Class Codes: G06F 3/162 Interface to dedicated audio devices, e.g. audio drivers, interface to CODECs
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Abstract

A host signal processor (HSP) modem has a software interface between HSP modem hardware and native audio hardware in a host computer. No hard wire connections between modem hardware and audio hardware are required for synchronization. Instead, a software clock recovery system matches a transfer rate of the HSP modem hardware and a transfer rate of the audio hardware by duplicating or deleting samples. The software interface allows the native audio hardware to make audible the handshaking sequence during modem connections which eliminates the need for a speaker and speaker drivers in the modem hardware. The combination of HSP modem hardware, audio hardware, and software executed by the host computer also allows the HSP modem to perform voice communication such as telephone or speakerphone functions.

Claims

1. A communication system comprising:

a host computer which includes native audio hardware capable of generating audible output from the host computer, wherein the audio hardware processes digital samples according to a first sampling clock;

a communication device comprising;

an interface coupled to the host computer; and

an analog-to-digital converter coupled to the interface, the analog-to-digital converter converting an analog signal from an input line to digital samples accessible by the host computer through the interface, wherein the communication device processes digital samples according to a second sampling clock which is asynchronous to the first sampling clock; and

software executed by the host computer, the software transferring the digital samples from the communication device to the native audio hardware which plays the digital samples, the software comprising a procedure which transfers digital samples from the communication device to a buffer in a memory of the host computer, wherein the procedure duplicates or deletes samples to equalize a data transfer rate from the communication device and a data transfer rate to the audio hardware, wherein;

samples from the communication device are transferred to a location the buffer, indicated by a first index;

samples are transferred to the audio hardware from a location in the buffer, indicated by a second index; and

the procedure compares the first index to the second index and determines from a difference between the first and second indices whether to duplicate or delete samples being transferred to the buffer.

2. The communication system of claim 1, wherein:

the communication device further comprises a digital-to-analog converter coupled to the interface, the digital-to-analog converter converting digital samples from the interface into an analog signal transmitted on an output line; and

the software further comprises a second procedure which transfers digital samples from a second buffer in the memory of the host computer to the communication device, wherein the second procedure duplicates or deletes samples to equalize a data transfer rate to the communication device and a data transfer rate from the audio hardware.

3. The communication system of claim 1, wherein:

the communication device further comprises a digital-to-analog converter coupled to the interface, the digital-to-analog converter converting digital samples from the interface into a transmitted analog signal on an output line; and

the software transfers digital samples from the audio hardware to the communication device for conversion to transmitted analog signal.

4. The communication system of claim 1, wherein the software provides voice communications when operated in a first mode during which digital samples are transferred between the audio hardware and the communication device and provides modem functions when operated in a second mode during which digital samples are converted according to a modem protocol to generate data.

5. The communication system of claim 4, wherein the input line is a telephone line, and the communication system provides voice and modem communications through the communication device.

6. A host signal processor modem comprising:

a communication device comprising an interface for connection to a host computer, and an analog-to-digital converter which converts analog signals from an input line to digital samples accessible to the host computer through the interface; and

software executed by the host computer, the software including a procedure which during a handshake sequence for the host signal processor modem, transfers digital samples from the communication device to audio hardware native to the host computer, the audio hardware playing the digital samples to allow user monitoring of the handshake sequence, wherein;

samples from the communication device are transferred to a location in a buffer, indicated by a first index;

samples are transferred to the audio hardware from a location in the buffer, indicated by a second index; and

the procedure compares the first index to the second index and determines from a difference between the first and second indices whether to delete or duplicate samples being transferred to the buffer, whereby the software deletes or duplicates digital samples being transferred, as necessary to equalize a transfer rate from the communication device and a transfer rate to the audio hardware.

7. The host signal processor modem of claim 6, wherein the communication device generates an audible modem handshake sequence solely through audio hardware native to the host computer.

8. The host signal processing modem of claim 6, wherein for voice communications, the procedure transfers digital samples from the communication device to the audio hardware native to the host computer.

9. The host signal processing modem of claim 8, wherein the input line is a telephone line.

10. The host signal processing modem of claim 6, wherein the procedure transfers digital samples from the communication device to a modem unit for conversion according to a protocol for modem communications.

11. A host signal processor modem comprising:

a communication device comprising an interface for connection to a host computer, and an analog-to-digital converter which converts analog signals from an input line to digital samples accessible to the host computer through the interface;

software executed by the host computer, the software including a procedure which during a handshake sequence for the host signal processor modem, transfers digital samples from the communication device to audio hardware native to the host computer, the audio hardware playing the digital samples to allow user monitoring of the handshake sequence; and

a buffer in a memory of the host computer, wherein samples from the communication device are transferred from the communication device to a location in the buffer, indicated by a first index and samples are transferred to the audio hardware from a location in the buffer, indicated by a second index, wherein;

the audio hardware processes digital samples according to a first sampling clock;

the communication device processes digital samples according to a second sampling clock which is asynchronous to the first sampling clock; and

the software comprises a procedure that compares the first index to the second index and determines from a difference between the first and second indices whether to duplicate or delete digital samples.

12. The host signal processor modem of claim 11, wherein the communication device generates an audible modem handshake sequence solely through audio hardware native to the host computer.

13. The host signal processing modem of claim 11, wherein for voice communications, the procedure transfers digital samples from the communication device to the audio hardware native to the host computer.

14. The host signal processing modem of claim 13, wherein the input line is a telephone line.

15. The host signal processing modem of claim 11, wherein the procedure transfers digital samples from the communication device to a modem unit for conversion according to a protocol for modem communications.

16. A method for operating a host signal processor modem, comprising:

transferring digital samples from an analog-to-digital converter in a hardware portion of the host signal processor modem to a buffer in a host computer which executes a software portion of the host signal processor modem; and

using audio hardware native to the host computer to play the digital samples from the buffer, wherein transferring the digital samples comprises;

transferring samples from the hardware portion of the host signal processor modem to a location in the buffer, indicated by a first index;

transferring samples to the audio hardware from a location in the buffer, indicated by a second index; and

determining from a difference between the first and second indices whether to duplicate samples being transferred; and

duplicating digital samples from the hardware portion of the host signal processor modem to increase a data transfer rate to the buffer and match a rate at which the audio hardware plays the digital samples from the buffer.

17. The method of claim 16, wherein the digital samples represent an analog signal input to the host signal processor during a handshake sequence.

18. A method for operating a host signal processor modem, comprising:

transferring digital samples from an analog-to-digital converter in a hardware portion of the host signal processor modem to a buffer in a host computer which executes a software portion of the host signal processor modem; and

using audio hardware native to the host computer to play the digital samples from the buffer, wherein transferring the digital samples comprises;

transferring samples from the hardware portion of the host signal processor modem to a location in the buffer, indicated by a first index;

transferring samples to the audio hardware from a location in the buffer, indicated by a second index; and

determining from a difference between the first and second indices whether to skip transfer of some digital samples; and

skipping transfer of some digital samples from the hardware portion of the host signal processor modem to decrease a data transfer rate to the buffer and match a rate at which the audio hardware plays the digital samples from the buffer.

19. The method of claim 18, wherein the digital samples represent an analog signal input to the host signal processor during a handshake sequence.