System information
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Section 1. Introduction
This document outlines the structure for a fundamental subset of protocols and packet
types used to communicate directly with a single P
AKBUS® datalogger. The protocols and
packet types discussed in this document are collectively referred to as BMP5 and are used
to communicate with Campbell Scientific’s native PakBus dataloggers (CR200 Series,
CR1000, CR3000, etc.). This documentation assumes the communication link to the
datalogger has already been established. Therefore, packets are created, sent, and
received over a transparent link directly to and from a single datalogger.
While this document only discusses essential packet types that facilitate communication
with a single datalogger, the creation of these packets requires an understanding of packet-
switched protocols. With this understanding and through the use of this reference, a
developer should be able to send basic packets to and receive packets from a Campbell
Scientific CR200 or CR1000 type datalogger.
1.1 Communication Layers
Like other types of packet switched communication protocols such as TCP/IP,
transparent BMP5 communication relies on a low-level network protocol and
higher application level protocols. These different protocol layers exist to
facilitate communication between applications and nodes across a given
medium. The benefit of using protocol layers is that each layer becomes
responsible for a specific function that assists communication. Since these
functions are presented in manageable blocks, end-to-end communication is
easier because each layer focuses on a single responsibility.
The way a single layer handles a specific task internally can change as long as
communication to the protocol layer above and the protocol layer below
continues to function in the same manner. For example, the command to check
a datalogger clock may exist in the application layer while a separate layer
handles the connection. As long as these separate layers communicate with
each other, the information can be organized and sent across the network as a
complete packet.
The protocol types discussed in this document are the SerPkt Protocol used to
monitor the state of the communication link, the PakBus Control Protocol
(PakCtrl) used to facilitate PakBus network-level services, and the BMP5
Protocol used to send application messages. An understanding of these
message types and the packet structure for these protocols will be necessary to
send basic packets to and receive basic packets from a native PakBus
datalogger.