An I/O transaction is an operation that reads and/or writes multiple skill data points at once. Usually, this is done by sending one or more protocol specific commands to the device.

I/O transactions are provided by skills. Depending on the skill, an I/O transaction may be linked to a specific device, a specific communications bus, or it may be completely independent. The association between an I/O transaction and the skill data points it queries or writes is also skill specific. Usually, however, the skill data point will have some sort of configuration parameter to specify which I/O transaction it should be included in.

Here are some examples of what an I/O transaction may do:

Send a read or write command using a protocol like the Modbus protocol,
Scan the inputs of a physical I/O board installed on the computer,
Write to the outputs of a physical I/O board installed on the computer,
Execute a query to a relational database, or
Send a command to a cloud service using a web service interface like REST or SOAP

Executing I/O Transactions

I/O transactions must usually be triggered when the values of the skill data points need to be read or written. The I/O transaction will usually expose one or more tasks that allow you to query the data and/or send the commands as part of a timer, or in response to an event. The exact name or names of the tasks depend on the skill. Please refer to the documentation of the specific skill for details.