eGet can be handy for very simple scripts, but when doing a number of different requests, it is much better to use the AddRequest() / GoOne() / GetResult() functions. So, if we wanted to read channels 1 through 3 we could do:
eGet(0, LJ_ioGET_AIN, 1, @val1, 0)
eGet(0, LJ_ioGET_AIN, 2, @val2, 0)
eGet(0, LJ_ioGET_AIN, 3, @val3, 0)
or we could do:
AddRequest(0, LJ_ioGET_AIN, 1, 0, 0, 0)
AddRequest(0, LJ_ioGET_AIN, 2, 0, 0, 0)
AddRequest(0, LJ_ioGET_AIN, 3, 0, 0, 0)
GoOne(0)
GetResult(0, LJ_ioGET_AIN, 1, @val1)
GetResult(0, LJ_ioGET_AIN, 2, @val2)
GetResult(0, LJ_ioGET_AIN, 3, @val3)
OK, you may think that eGet looks much easier since its only three lines of code vs. seven, and it is easier on a basic level, but with ease you lose flexibility and efficiency. Using the second method is more efficient internally as the LabJack driver only makes a single call to the device. The second method also allows you to do error handling easier using the GetNextError() function. With error handling, the eGet code ends up looking like this:
err = eGet(0, LJ_ioGET_AIN, 1, @val1, 0)
if (err)
... error!
endif
err = eGet(0, LJ_ioGET_AIN, 2, @val2, 0)
if (err)
... error!
endif
err = eGet(0, LJ_ioGET_AIN, 3, @val3, 0)
if (err)
... error!
endif
But the Add / Go / Get looks like this:
AddRequest(0, LJ_ioGET_AIN, 1, 0, 0, 0)
AddRequest(0, LJ_ioGET_AIN, 2, 0, 0, 0)
AddRequest(0, LJ_ioGET_AIN, 3, 0, 0, 0)
GoOne(0)
GetResult(0, LJ_ioGET_AIN, 1, @val1)
GetResult(0, LJ_ioGET_AIN, 2, @val2)
GetResult(0, LJ_ioGET_AIN, 3, @val3)
while (GetNextError(1,@io,@ch,@err)
... error!
endwhile
As you can see the second method is much cleaner and easier to read. The eGet() version would get worse and worse as you added more function calls. Using the second method also allows you to create a single error handler for the entire block, or as shown in the section on error handling, you can create a single function to do all your error handling for all your scripts.
Note: variable declarations are not shown in the above examples, but would be required. Likewise, ... error! would need to be replaced with script to actually do something in the case of an error.
