FreeLynx Acquisition Device

Hardware Overview

The FreeLynx Acquisition Device is a stand alone acquisition system. The FreeLynx Acquisition Device consists of an analog front end (AFE) connected to a transceiver. The total number of channels available in the AFE are 64 or 128. The signal is digitized and then formatted and sent wirelessly to the acquisition PC.

Hardware Sub System Interface

In order to retrieve data from the FreeLynx, a hardware sub system (HWSS) must be created.  A hardware sub system is an object in __prod_name that controls the acquisition of data from a specified piece of hardware, in this case the FreeLynx Acquisition Device.  The hardware sub system has a set of properties that control how data is retrieved and processed.   The creation and properties of a sub system can only be accessed using the configuration file commands.   

The -CreateHardwareSubSystem command is used to create a new hardware sub system.  As part of the creation command, a name must be given to the sub system.  The name must be unique and is used to report errors or to set the properties of the sub system.

Once a sub system is set up, its first responsibility is to retrieve data from the hardware and store it in a buffer.  In some instances, buffers may fill up faster than the data in them can be processed by the rest of the system.  If this occurs, we have what's called a buffer overrun error and some data will be lost.

The user has the option to save the unfiltered data coming from the hardware sub system to a raw data file.  This file must be specified by the user, __prod_name will only save data to this file if it has been requested.

The next step is to process the data that resides in our buffers.  When data is acquired by the FreeLynx Acquisition Device, it is packed into a record and then sent over the wireless network to __prod_name.  The data now has to be unpacked and its validity checked.  The first step is to find a valid record, this is called hunting.  A couple things are checked during the hunting process to determine if a record is valid.  The first thing is to check to see if the id associated with the record is valid.  The next thing is to see if the record size is valid.  The record size is determined by the number of channels in the FreeLynx Acquisition Device.  The last thing that is done is a check to make sure the data has not been corrupted.   If any of these checks fail, then a hunt error is reported to the System Status Dialog.  Now that we know we have a valid record, the timestamp is checked to make sure it is incrementing.  If it is not incrementing, the record may be reordered based on its timestamp or an error is generated.

The record has now been validated.  The last step is to unpack the data from the record and store it into a buffer where the DSP filters will process the samples.  The hardware sub system will continue to process records until acquisition is turned off.

TTL Input and Output

The FreeLynx has built in support for bidirectional TTL use. The direction of the TTL port can be changed in the Digital IO Setup.  The FreeLynx may have two digital IO boards (the Base device and Analog Front End). Each board on the device will be assigned a reference TTL device name by __prod_name.  For more information, see the Digital I/O Overview.

Port Label	Board Name	Total TTL Bits	Number of Ports	Number of Bits per Port	Port Direction
TTL Port	Base	4	1 or 4	4 or 1	Bidirectional
TTL Port	AFE	4	1 or 4	4 or 1	Bidirectional

Each board (Base, AFE) can operate as 1 port with 4 bits (default) or 4 ports with 1 bit each. This can be changed using the -SetDigitalIOBitsPerPort command. See Digital I/O Commands for how to use this command.

FreeLynx Acquisition Device Topics :

FreeLynx Acquisition Device Properties Dialog
FreeLynx Acquisition Device Commands