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(Last edited by Mhavela on 5 Jan 2011.)

Requirements

Install alpine-2.1.3 or newer (see these notes if you are unsure how to do it).
And do basic setup (run 'setup-alpine').

Hardware

Choose what ttyS port to use. (In below examples replace ttyS? with the ttyS? that applies for your needs)

/dev/ttyS0 is same as COM1
/dev/ttyS1 is same as COM2
(and so on...)

Install packages

Configure repository

When this article was written, some of the packages was still in 'testing'. So we need to add testing to repository.

echo "http://dl-3.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repository
apk update

Install packages

Install required packages

apk add ppp
apk add setserial

Modules

Load some needed modules and make sure they get automatically loaded at next reboot

modprobe ppp
echo "ppp" >> /etc/modules

Configure

Create configfiles

/etc/ppp/peers/serialmodem

debug
/dev/ttyS0
115200
modem
crtscts
asyncmap 0
defaultroute
noipdefault
lock
connect '/usr/sbin/chat -f /etc/ppp/chat-serialmodem'

/etc/ppp/chat-serialmodem

'ABORT' 'BUSY'
'ABORT' 'ERROR'
'ABORT' 'NO ANSWER'
'ABORT' 'NO CARRIER'
'ABORT' 'NO DIALTONE'
'ABORT' 'Invalid Login'
'ABORT' 'Login incorrect'
'REPORT' 'CONNECT'
'TIMEOUT' '60'
'' 'ATZ'
'OK' 'ATDT{phonenumber}'
'CONNECT' ''
'ogin:' '{login_id}'
'sword:' '{your_password}'

Note: Replace above words {login_id}, {your_password} and {phonenumber} with what you received from your ISP.

See this link for more details.

Start/Stop

Start connection

pon serialmodem

Stop connection

poff serialmodem

If something goes wrong...

Check if process is running

ps | grep pppd

Logfile would also give you information on what happened

grep pppd /var/log/messages

Check nic information

ifconfig ppp0

pppd seems to have some pppstats function

pppstats

Check and set serial speed

Check your ttyS settings

setserial -ga /dev/ttyS1

You should see something like this:

/dev/ttyS1, Line 1, UART: 16550A, Port: 0x02f8, IRQ: 3
    Baud_base: 115200, close_delay: 50, divisor: 0
    closing_wait: 3000
    Flags: spd_normal skip_test