Src-perl-Campbell::Comm

Campbell/Comm.pm

This module becomes part of a Perl program via the use or require keywords. It provides the machinery to connect and send/receive commands to/from a remote datalogger using Perl's object-oriented programming methodology. Individual methods are provided corresponding to some/most of the telecommunications commands documented in the Campbell Scientific CR10 family manuals.

Another Perl module is needed in order to interact with remote dataloggers, and that is Net::Telnet, which is included in the standard Perl distribution. This module allows automating the telnet protocol, but boils down to being able to send commands to the remote system and then wait for and handle responses -- or no response, if that's necessary.

Besides the nominal TCP/IP connections, Net::Telnet is capable of supporting interfaces using a direct serial or modem connection. This usage is implemented in the (or various...) open() methods.

A bug in Net::Telnet (this is my view; it may be considered a feature by the authors...) requires a patch; this should be represented in the Net::Telnet version included in the above tree. Specifically, Net::Telnet goes out of its way to handle timeouts using wall time (i.e., absolute time as measured on a wall clock) rather than relative inactivity time as used in the underlying select() system function. In our case the latter form is required due to the many levels and sources of latency in the communication system.

The Perl Expect module might provide a good alternative to Net::Telnet if Campbell::Comm were to be rewritten. Both provide the key functionality of being able to wait for and selectivly match on responses from the remote system.

Due to the specific need to communicate with dataloggers via FreeWave radios, the Campbell::Comm module was written with this capability perhaps too implicitly. A rewrite (anticipated) should remove any code not directly concerned with the Campbell dataloggers.