1 - Overview | LabJack
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App Notes

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1 - Overview

The LJM Library is a set of functions used to easily communicate with several of our devices using a simple Modbus interface.  The goal is to be easy to use and understand, yet flexible.

All important values & data from the device can be read and/or written by using the associated register(s).  Thus, the process for reading the serial number, an analog input, or a timer is all functionally the same, you simply provide a different address.  We have also included functionality so that values can be specified using a name instead of numerical value, such as "AIN6" to represent the register(s) that will read analog input number 6.


Begin with the open function.

Each device is represented by a handle which is obtained by using one of the open functions to open that device. That handle is passed to the other functions to specify that those functions should operate on that device.

More on Opening

Use the read/write functions.

The read/write functions provide a simple interface for reading/writing data by either specifying a name or an address.

More on Reading/Writing
Use the stream functions.

The stream functions allow data to be collected at a constant and/or fast rate.

More on streaming
More functions.

There are also utility functions provided to do things like debugging and making unit conversions easier, as well as a few functions that let you configure the library itself.

More on Other Functions
Error codes describe the problem.

A set of constants are defined for specific use within the library to represent various values, and a robust set of error codes that are returned when something goes wrong.

More on Error Codes