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Reference Agent Ingress Protocols
There are also videos on how to develop adapters here Other Resources.
The adapters communicate with the MTConnect agent using a simple TCP sockets protocol. TCP is merely a convenient streaming character based protocol that has been around for over 30 years and is supported on every machine known to man (except for some manufacturing equipment!) The semantics were chosen as the simplest possible format to get data from a device to another process with minimal overhead, but still easily verifiable. The format is a pipe delimited line of data terminated with a <LF> or a <CR><LF>, both work. The format, commonly referred to as SHDR, is as follows:
2013-09-01T21:00:23.0123|name|value
The timestamp is in what is referred to as ISO 8601 format and it will always be given in UTC – MTConnect does no time zone conversions. The timestamp is optional and if it is not present the agent will supply its own time to the arriving data. A new feature has been added recently to handle clock skew and delta time, I'll cover that later. The format without a timestamp must begin with as | as follows:
|name|value
To make data collection more efficient, all data that changes at the same time can be represented on a single line as follows:
2013-09-01T21:00:23.0123|name1|value1|name2|value2|name3|value3
Each pair will get a separate sequence number, but they will all have the same timestamp. This save bandwidth having to repeat the timestamp multiple times. There are some exceptions to this rule; some data items require more than a single value, they have multiple arguments. These are: Alarm (deprecated), Condition, TimeSeries, and Message. Each of these require a themselves to be on a separate line.
A condition represents the state of an alarm or warning on the machine. The standard specifies there can be a lot of additional information passed through to represent a condition. These are:
time_stamp|name|level|native_code|native_severity|qualifier|error text
The level can be one of the following:
UNAVAILABLENORMALWARNINGFAULT
The native_code is whatever the controller call this alarm, usually a number or pneumonic representation. The native_severity is also controller defined and will be merely passed through. The qualifier can be currently HIGH or LOW and the error_text is just a pass through from the controller of the text from the controller.
The message is simply a |name|native_code|message where the native_code is similar to the condition and is just what the controller calls the alarm in a numeric or pneumonic form.
When time series data items are passed through, they must have two additional arguments (the second is optional since it can be defaulted, but an empty cell must be present. The time series is represented as follows:
2013-09-01T21:00:23.0123|name|count|rate|data...
as in
2013-09-01T21:00:23.0123|temp|10|10|18.2 18.4 18.3 18.9 19.0 19.2 19.1 19.3 19.4 19.7
Here we have ten samples at 10 hertz. If the 10 hertz was set as part of the data item, it can be omitted here:
2013-09-01T21:00:23.0123|temp|10||18.2 18.4 18.3 18.9 19.0 19.2 19.1 19.3 19.4 19.7
Since the release of Version 2.0 there are several additional ingress protocols available.
MQTT JSON Ingress Protocol Version 2.0
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