Fundamental Concepts - LTT -184-8ch Referenzhandbuch

Fundamental concepts

The API is designed to manage one or a group of LTT devices in an efficient manner. The
most important design goals are stability and performance. The calls are described in
STDCALL calling convention. It's also possible to access the API-calls with CDECL calling
convention. You must add only CDECL to every function call:
__stdcall LTTInit()
...
The use of the API is divided in several steps:
Initialization:
The call LTTInit must be the first call to the API. With this call the internal
resources are initialised and the system is scanned for connected LTT devices.
Note: This function should be used only once at the beginning.
Setup:
The devices can now be configured with a certain setup, as turn on several
channels, select its input type and range or select a trigger. Also the amount of
data has to be specified. These calls don't communicate directly with the devices.
Instead, all setup calls build up a certain configuration which is passed to the
devices with LTTUploadParameters. This call does an integrity check to see if the
configuration is a valid one.
Transfer:
The devices will be started with LTTStart, which basically means that the trigger
will be active or in the case of no trigger, the measurement process of the devices
begins.
Now the transfer of the data from the devices to the RAM-buffer/File can be done
in two ways. In both cases the transfer is invoked with LTTTransfer2Buffers.
BLOCKED_MODE:
The call LTTTransfer2Buffers returns when the transfer of the data to the RAM-
buffer/File is completed. This is the easiest way, and the most used one.
NONE_BLOCKED_MODE:
The call LTTTransfer2Buffers returns immediately after invoking the transfer.
Now the transfer to the RAM-buffer/File needs the cooperation of the application.
The transfer must be monitored with LTTTransferStatus to catch when the
transfer is completed or interrupted.
In STREAM-mode the internally used buffer is mostly smaller then the requested
transfer amount of data, so this buffer is used like a ring-buffer. To avoid the
overwriting of already in the buffer transferred data, the application must read out
blocks of already transferred data. If the call LTTTransferStatus signals that there
is an amount of data ready for read-out, then the start index and the length of the
block inside the buffer must be obtained with LTTData_GetBlock. When the
processing of the block is finished, LTTData_BlockDone must be called. Now go
back to monitoring the transfer with LTTTransferStatus.
Deinitialization:
To close all internal resources, call LTTDeInit.
Other calls:
Beschreibung der DLL LTT2API
== > __cdecl LTTInitCDECL()
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