An Inexpensive High Speed Modem for the Universal SerialBus (USB)

Thomas Sailer, HB9JNX/AE4WA,and

Johannes Kneip, DG3RBU

August 3, 1999

Abstract

This article describes a simple and inexpensive modem intended to link end users at 76.8kBit/s tothe high speed backbone network. The modem can be connected to standard PC’s using the UniversalSerial Bus (USB).

1 Introduction

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3 DESIGN CONSIDERAT/ONS

2 Design Goals

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3 Design Consi

3.1 Microcontroller selection

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3 DESIGN CONSIDERATIONS

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3.2 Power Supply Considerations

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3.3 Firm ware Download

3.3 Firmware Download

3.4 The FSK Mode

3 DESIGN CONSIDERATIONS

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3.5 The AFSK Mode

3.6 Modification of the analog circuitry for AFSK demodulation

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3.6 Modification of the analog circuitry for AFSK demodulation

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3 DESIGN CONSIDERATIONS

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3.7 The Demodulator

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3.7 The Demodulator

5 STATE OF THE PROJECT

3.8 The Modulator

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3.9 Microcontroller Interface

4 The Analog IO mode

5 State of the Project

6 Conclusion

7 Outlook

112

REFERENCES

References

[lo] Hblger l%ka& DEQIQ h!kmdm& m 7h.l?fW?3K-Trmceiver 77F

[ll] Nimpalenxp, Iv3NWy YetA?wtkr9k6ilBmkrnhttp://j~iter.~host~g,cam/-Ilicopal/~/

[12] Janus C chndy, an&Gabor C Tm, C%erxznpZing~~for~dL)/A Ccwtversion, IEEE?Circuits and System society, 1992, ISBNO-87942-285-8

113