For the connection script to work properly, your Raspbian installation needs a few prerequisite packages. The most important of these is the PPP daemon “pppd” and IP Tables to route packets.
sudo apt-get update sudo apt-get install ppp iptables
In the next chapter we will download and install vmodem onto your Raspberry linux box!
sudo mkdir /boot/vmodem sudo wget http://www.steptail.com/_export/code/guides:virtual_modem:script?codeblock=0 -O /boot/vmodem/vmodem.sh sudo wget http://www.steptail.com/_export/code/guides:virtual_modem:script?codeblock=1 -O /boot/vmodem/1.sh sudo wget http://www.steptail.com/_export/code/guides:virtual_modem:script?codeblock=2 -O /boot/vmodem/ppp.sh
sudo chmod 770 /boot/vmodem/vmodem.sh sudo chmod 770 /boot/vmodem/1.sh sudo chmod 770 /boot/vmodem/ppp.sh
The VModem script has been preconfigured to use ttyUSB0 as the default serial port name. Typically Raspbian will call its first serial port adapter ttyUSB0 when using USB to Serial converters, and you won't need to modify this script. However, if the name is something different, such as ttyAMA0, you may need to update the script to point to the correct serial port name. The following section described how to double-check your serial port name:
To confirm your serial port name, do the following:
/dev/ttyUSB0listed, you will need to update the script with the correct serial port. Visit this page to update the script with the correct serial port.
/dev/ttyUSB0listed, continue on!
This would be a good time to test your network to eliminate any future headaches.
Over SSH run the command:
To test VModem, you should be able to simply run the script. Test it first over SSH to see it's output:
cd /boot/vmodem sudo ./vmodem.sh
If you wish to share a wireless connection on serial instead of a wired connection, you will need to edit the line “etherp=eth0” in vmodem.sh to “etherp=wlan0”.
Now you can proceed to check out the system specific guides on how to interface different vintage computers and devices with VModem. Once you are done, return back to this guide!
Make sure vmodem.sh is running on the Raspberry Pi first before attempting connection!
After you have verified that the VModem works properly on the console, and you have tested that you are able to connect to your network, you can make VModem run automatically as a background process after the Raspberry Pi is powered on. It will run as a background process so you won't see it's output, so it's highly recommended to thoroughly test the script first.
exit 0. Now add the following lines ABOVE it.
# Start serial port and simulate a modem cd /boot/vmodem/ /boot/vmodem/vmodem.sh &
Beware the ampersand “&” at the end of the line. Without it, the boot process may not complete correctly (or at all).
You can now proceed to connect your retro machine to the Internet using Virtual modem.
After dialing in, system is disconnected immediately
Make sure you are using the latest version of the Virtual Modem script. An early version had an issue where the serial connection would be cut before the network connection was established. Also, be sure to make sure your serial baud settings are correct, and they match the virtual modem script. Finally, try turning off Flow Control from the Modem Settings under Advanced Settings.
After dialing in, system reports connected, but no network is available
Make sure you have updated the network device in vmodem.sh to reflect the correct network interface. By default it is eth0. If you are using Raspberry on WIFI, you may need to change this to wlan0.