This chapter is copied from the DIGI_NED website which can be reached through the DIGI_NED portal at http://www.qsl.net/digi_ned
The APRS network very often uses digipeaters on high locations in rural areas or buldings in urban areas who cannot be entered easy due to owners restrictions or security policy's. In this case it is needed to be able to do some maintenance to the system without being there. Mantenance can vary from small parameter changes to updates of software.
In the situation of the DIGI_NED digi PI1APA, it was not possible te access the building during evening and night. So the remote access was required. The here discribed solution can be copied but needs adaption to your own specific configuration !
The basics of the DIGI_NED remote access are simple:
Starting the support program.
As the system boots the autoexec.bat runs the default sub from the menu. This DOS menu enables attended mantenance to boot without the digi software.
PROMPT DIGI_NED $p$g
ax25_mac.exe -poscc:158:5:4444 -b1200:1200:1200:1200 -L -F -C17 -BU50
if errorlevel 4 goto net_start
@echo type ctrl-c to exit
After DIGI_NED has stopped, the exit commando lets the batch-file select the next step. In our case exit code 4 starts the support software NETchl. All other exit codes makes the system reboot.
When NET is stopped the "autoexec.bat" runs a program named "boot" after a short wait program. this program, wait or pause, as you have available, enables the sysop to interfer with the normal programma loop as the system is attended.
The support software for example NETchl provides services for file transfer and to execute dos commands like copy and delete on the remote system.
As NETchl is a tcp/ip package for amateur use in a DOS environment it fits completely to our needs.
Due to complexity of the package the full functionality
will not bediscribed in this documentation. A full sample
configuration is available for download including doc's.
The available package at the DIGI_NED web-site is 800 Kbyte and contains some documentation.
Keep in mind that you need some experience of tcp/ip in combination with AX25 amateur packet radio !
The features used from the NETchl package are:
FTP, File Transfer Protocol must be clear. RCMD is a telnet session to a specific port in NETchl (459). This port uses 'Baycom authentification' from a text string in a file in "c:\net\rcmd\remote_host_name". After this the console prompt of the remote system is offerd to you.
It is also possible to use other packet-radio programs for this purpose. The minimum requrement is that you have to be able to reset the system remotely.
Isues on transferring data on APRS frequencys:
In the PI1APA system 2 ports are available. 1 port on VHF and 1 port on UHF. When in service mode, digi_ned is stopped and NETchl is running, we use the quiet UHF APRS frequency for up and downloading. It is good to have a separte frequency for up and downloading. Think of what happens when we load the APRS QRG with heavy tcip/ip up- or down-load traffic ! In such a case all resources will be used by the up- or down-load and nothing is left for the APRS users. Keep in mind that a wide commonly is placed at high altitude ! and has large coverage !
Practice learned that uploading digi_ned.exe at 1200 bps simplex takes about 30 minutes ! You can decrease required upload time by takin out all comments in the configuration files.
In case you do not have 2 or more ports available think seriously of some way to make your transmitter go QSY for the period required to do maintenance !
If you have more than one port it is also possible to
equip the APRS transmitter with both a 1200 bps AFSK modem and a 9600 bpq G3RUH
modem. It will decrease upload time and load on the APRS QRG !
As you can see there are many possible solutions. Probably you can think of more !.
Resetting the system and watchdogs. After the maintenance the system has to be reset to make the changes active. In NETchl a 'exit !' commando is available. Also the 'shell /c boot' command makes the system reboot.
In case the support software is not able to do so you have to reset the system by some other command. The packet radio node PI1VRZ and dx-cluster PI8DXW can be reset using a ZVEI tone code sequence ( sel-call ). It is even possible to use DTMF commands. On these topics you imagination is the limit !
To be sure the system not hangs we also use a watchdog. Some watchdog examples are available at the VrzApDxw web-site.
Due to the high flexibility of DIGI_NED on all items DIGI_NED is the solution in many cases. In the folowing cases we will discribe what DIGI_NED can do.