The Linux Modem-HOWTO

David S.Lawyer mailto:dave@lafn.org

1. Introduction

• 1.1 DSL, Cable, and ISDN Modems in other HOWTOs
• 1.2 Also not covered: PCMCIA Modems, PPP
• 1.3 Copyright, Disclaimer, Trademarks, & Credits
• 1.4 Contacting the Author
• 1.5 New Versions of this HOWTO
• 1.6 New in this Version
• 1.7 What is a Modem ?
• 1.8 Quick Install

2. Modems for a Linux PC

• 2.1 External vs. Internal
• 2.2 External Modems
• 2.3 Internal Modems
• 2.4 Software (Internal) Modems (mostly winmodems)
• 2.5 PCI Modems
• 2.6 Which Internal Modems might not work with Linux

3. Modem Pools, Digital Modems

• 3.1 Analog Modem Pools, Multiport Modem Cards
• 3.2 Digital Modems

4. Modem & Serial Port

• 4.1 Modem Converts Digital to Analog (and conversely)
• 4.2 What is a Serial Port ?
• 4.3 IO Address & IRQ
• 4.4 Names: ttyS0, ttyS1, etc.
• 4.5 Interrupts
• 4.6 Data Compression (by the Modem)
• 4.7 Error Correction
• 4.8 Data Flow (Speeds)
• 4.9 Flow Control
• 4.10 Data Flow Path; Buffers
• 4.11 Modem Commands
• 4.12 Serial Software: Device Driver Module

5. Configuring Overview

6. Configuring the Serial Port

• 6.1 PCI Bus Support Underway
• 6.2 Configuring Overview
• 6.3 Common mistakes made re low-level configuring
• 6.4 I/O Address & IRQ: Boot-time messages
• 6.5 What is the current IO address and IRQ of my Serial Port ?
• 6.6 Choosing Serial IRQs
• 6.7 Choosing Addresses --Video card conflict with ttyS3
• 6.8 Set IO Address & IRQ in the hardware (mostly for PnP)
• 6.9 Giving the IRQ and IO Address to Setserial
• 6.10 Other Configuring

7. Modem Configuration (excluding serial port)

• 7.1 Finding Your Modem
• 7.2 AT Commands
• 7.3 Init Strings: Saving and Recalling
• 7.4 Other Modem Commands

8. Serial Port Devices /dev/ttyS2, etc.

• 8.1 Serial Port Device Names & Numbers
• 8.2 Link ttySN to /dev/modem ?
• 8.3 The cua Device

9. Interesting Programs You Should Know About

• 9.1 What is setserial ?
• 9.2 What is isapnp ?
• 9.3 What is wvdialconf ?
• 9.4 What is stty ?

10. Trying Out Your Modem (Dialing Out)

• 10.1 Are You Ready to Dial Out ?
• 10.2 Dialing Out with Minicom
• 10.3 Dialing Out with Kermit

11. Dial-In

• 11.1 Overview
• 11.2 Getty
• 11.3 What Happens when Someone Dials In ?
• 11.4 Why Manual Answer is Best
• 11.5 Callback
• 11.6 Voice Mail

12. Uugetty for Dial-In (from the old Serial-HOWTO)

• 12.1 Installing getty_ps
• 12.2 Setting up uugetty
• 12.3 Customizing uugetty

13. What Speed Should I Use with My Modem?

• 13.1 Speed and Data Compression
• 13.2 Where do I Set Speed ?
• 13.3 Can't Set a High Enough Speed
• 13.4 Speed Table

14. Communications Programs And Utilities

• 14.1 Minicom vs. Kermit
• 14.2 List of Communication Software
• 14.3 SLiRP and term

15. What Are UARTs? How Do They Affect Performance?

• 15.1 Introduction to UARTS
• 15.2 Two Types of UARTs
• 15.3 FIFOs
• 15.4 UART Model Numbers

16. Troubleshooting

• 16.1 My Modem is Physically There but Can't be Found
• 16.2 I can't get near 56k on my 56k modem
• 16.3 Uploading (downloading) files is broken/slow
• 16.4 For Dial-in I Keep Getting "line NNN of inittab invalid"
• 16.5 I Keep Getting: ``Id "S3" respawning too fast: disabled for 5 minutes''
• 16.6 My Modem is Hosed after Someone Hangs Up, or uugetty doesn't respawn
• 16.7 uugetty Still Doesn't Work
• 16.8 The following subsections are in both the Serial and Modem HOWTOs:
• 16.9 My Serial Port is Physically There but Can't be Found
• 16.10 Extremely Slow: Text appears on the screen slowly after long delays
• 16.11 Somewhat Slow: I expected it to be a few times faster
• 16.12 The Startup Screen Show Wrong IRQs for the Serial Ports.
• 16.13 "Cannot open /dev/ttyS?: Permission denied"
• 16.14 "Operation not supported by device" for ttyS?
• 16.15 "Cannot create lockfile. Sorry"
• 16.16 "Device /dev/ttyS? is locked."
• 16.17 "/dev/ttyS?: Device or resource busy"
• 16.18 Troubleshooting Tools

17. Flash Upgrades

18. Other Sources of Information

• 18.1 Misc
• 18.2 Books
• 18.3 HOWTOs
• 18.4 Usenet newsgroups
• 18.5 Web Sites

19. Appendix A: How Analog Modems Work (technical) (unfinished)

• 19.1 Modulation Details
• 19.2 56k Modems (v.90)
• 19.3 Full Duplex on One Circuit
• 19.4 Echo Cancellation

20. Appendix B: Digital Modem Signal Processing (not done)

21. Appendix C: "baud" vs. "bps"

• 21.1 A simple example
• 21.2 Real examples

22. Appendix D: Terminal Server Connection

23. Appendix E: Other Types of Modems

• 23.1 Digital-to-Digital "Modems"
• 23.2 ISDN "Modems"
• 23.3 Digital Subscriber Line (DSL)
• 23.4 56k Digital-Modems
• 23.5 Leased Line Modems

24. Appendix F: Fax pixels (dots)