patch-2.1.7 linux/drivers/char/README.baycom

• Lines: 165
• Date: Thu Jan 1 02:00:00 1970
• Orig file: v2.1.6/linux/drivers/char/README.baycom
• Orig date: Sat May 18 11:15:09 1996

diff -u --recursive --new-file v2.1.6/linux/drivers/char/README.baycom linux/drivers/char/README.baycom
@@ -1,164 +0,0 @@
-		    LINUX DRIVER FOR BAYCOM MODEMS
-
-	     Thomas M. Sailer <hb9jnx@radio.amiv.ethz.ch>
-
-This document describes the Linux Kernel Driver for simple Baycom style
-amateur radio modems. The driver supports the following modems:
-
-ser12: This is a very simple 1200 baud AFSK modem. The modem consists only
-       of a modulator/demodulator chip, usually a TI TCM3105. The computer
-       is responsible for regenerating the receiver bit clock, as well as
-       for handling the HDLC protocol. The modem connects to a serial port,
-       hence the name. Since the serial port is not used as an async serial
-       port, the kernel driver for serial ports cannot be used, and this
-       driver only supports standard serial hardware (8250, 16450, 16550)
-
-par96: This is a modem for 9600 baud FSK compatible to the G3RUH standard.
-       The modem does all the filtering and regenerates the receiver clock.
-       Data is transferred from and to the PC via a shift register.
-       The shift register is filled with 16 bits and an interrupt is signalled.
-       The PC then empties the shift register in a burst. This modem connects
-       to the parallel port, hence the name. The modem leaves the 
-       implementation of the HDLC protocol and the scrambler polynomial to
-       the PC.
-
-par97: This is a redesign of the par96 modem by Henning Rech, DF9IC. The modem
-       is protocol compatible to par96, but uses only three low power ICs
-       and can therefore be fed from the parallel port and does not require
-       an additional power supply.
-
-All of the above modems only support half duplex communications. However,
-the driver supports the KISS (see below) fullduplex command. It then simply
-starts to send as soon as there's a packet to transmit and does not care
-about DCD, i.e. it starts to send even if there's someone else on the channel.
-This command is required by some implementations of the DAMA channel 
-access protocol.
-
-
-The Interface of the driver
-
-The driver interfaces to the AX25 stack via a KISS interface. The driver
-can be accessed as a character device with major 60. Major 60 is the first
-number of the local/experimental range. I did no steps to coordinate a
-major number for this driver, but I plan to do so in the near future.
-The driver supports multiple modems (currently four, as defined with
-NR_PORTS). It therefore responds to minor numbers 0 to 3. I recommend
-to access the driver via the special device files /dev/bc[0-3], which
-can be created with 'make bc'.
-
-
-Compiling and installing the driver
-
-First unpack the source files into a directory. Then enter the following: (you
-must be root to do it)
-
-  make dep
-  make
-
-This will create the files baycom.o and setbaycom. baycom.o is as well copied
-to /lib/modules/`uname -n`/misc. If you plan to use kerneld, do the following:
-
-  depmod -a
-
-Do not forget to create the device special files if you install the driver the
-first time. This can be done with:
-
-  make bc
-
-You are now ready to use the driver. You can now activate the driver manually
-by entering
-
-  insmod baycom
-
-or leave this task to kerneld (if installed). Add the following line to
-/etc/conf.modules
-
-  alias char-major-60 baycom
-
-
-
-Configuring the driver
-
-Every time the driver is inserted into the kernel, it has to know which
-modems it should access at which ports. This can be done with the setbaycom
-utility. If you are only using one modem, you can also configure the
-driver from the insmod command line (or by means of an option line in
-/etc/conf.modules).
-
-Examples:
-  insmod baycom modem=1 iobase=0x3f8 irq=4 options=1
-  setbaycom -i /dev/bc0 -p ser12 0x3f8 4 1
-
-Both lines configure the first port to drive a ser12 modem at the first
-serial port (COM1 under DOS). options=1 instructs the driver to use
-the software DCD algorithm (see below).
-
-  insmod baycom modem=2 iobase=0x378 irq=7 options=1
-  setbaycom -i /dev/bc0 -p par96 0x378 7 1
-
-Both lines configure the first port to drive a par96 or par97 modem at the
-first parallel port (LPT1 under DOS). options=1 instructs the driver to use
-the software DCD algorithm (see below).
-  
-The channel access parameters must be set through KISS parameter frames. The
-AX25 stack may be used to generate such frames. KA9Q NET derivatives such
-as WAMPES or TNOS offer the 'param' command for this purpose.
-
-
-
-Hardware DCD versus Software DCD
-
-To avoid collisions on the air, the driver must know when the channel is
-busy. This is the task of the DCD circuitry/software. The driver may either
-utilise a software DCD algorithm (options=1) or use a DCD signal from
-the hardware (options=0).
-
-ser12: if software DCD is utilised, the radio's squelch should always be
-       open. It is highly recommended to use the software DCD algorithm,
-       as it is much faster than most hardware squelch circuitry. The
-       disadvantage is a slightly higher load on the system.
-
-par96: the software DCD algorithm for this type of modem is rather poor.
-       The modem simply does not provide enough information to implement
-       a reasonable DCD algorithm in software. Therefore, if your radio
-       feeds the DCD input of the PAR96 modem, the use of the hardware
-       DCD circuitry is recommended.
-
-par97: as far as I know it is in this respect equivalent to par96.
-
-
-
-Compatibility with the rest of the Linux kernel
-
-The tty interface gave me some headaches. I did not find a reasonable
-documentation of its interfaces, so I'm not particularly sure if I implemented
-it the way I should. Perhaps someone with a more profound knowledge about
-tty drivers could check the interface routines.
-The driver produces a rather high interrupt load. par96/par97 generates 600
-interrupts per second, ser12 1200 while transmitting and 2400 if hardware
-DCD is used, 3600 otherwise. If other device drivers disable interrupts
-too long, the performance of the driver drops (the packet loss rate increases),
-especially with the ser12 modem.
-There were also reports that under rather high load situations the driver
-drops frames. This might be either an interrupt problem, or an AX25 stack
-running in user mode might not get enough CPU time to process the packets
-before the drivers internal buffers overflow. There is no way to throttle
-the other radio stations from this layer, throttling must be done in the
-AX25 layer.
-
-The serial driver, the line printer (lp) driver and the baycom driver compete
-for the same hardware resources. Of course only one driver can access a given
-interface at a time. The serial driver grabs all interfaces it can find at
-startup time. Therefore the baycom driver subsequently won't be able to
-access a serial port. You might therefore find it necessary to release
-a port owned by the serial driver with 'setserial /dev/ttyS# uart none', where
-# is the number of the interface. The baycom driver does not reserve any
-port at startup, unless one is specified on the 'insmod' command line. Another
-method to solve the problem is to compile all three drivers as modules and
-leave it to kerneld to load the correct driver depending on the application.
-
-
-
-vy 73s de
-Tom Sailer, hb9jnx@radio.amiv.ethz.ch
-hb9jnx @ hb9w.ampr.org