Our FreeLynx telemetry device records high quality, wide bandwidth neural data and can be set to 3 different recording modes depending on your experiment needs: 

1. Wireless transmission directly to your acquisition computer running Cheetah 6.
2. Wireless transmission to a Digital Lynx SX acquisition system.
3. Onboard microSD: turn off wireless transmission at any time to use the FreeLynx as a data logger.

This TechTip contains a brief cost/benefit overview that may help you plan your next wireless electrophysiology experiment and explains the procedure for enabling/disabling recording to FreeLynx’s onboard microSD.

Mode #1: Connect-to-Cheetah Wireless Recording

This recording mode uses a single acquisition computer running Cheetah software connected via Ethernet cable to the FreeLynx wireless access point to communicate with one (1) FreeLynx wireless headstage. There are three primary benefits for using this recording mode rather than recording through a Digital Lynx SX acquisition system.

1. Easy Setup:
If your wireless access point, FreeLynx, and Cheetah computer came pre-configured from Neuralynx, getting started with Connect-to-Cheetah recording is nearly plug-and-play.

2. Reduced Cost:
If you don’t already own or have access to a DLSX, eliminating this equipment purchase may reduce your overall costs.

3. Additional Channels:
A DLSX system currently supports up to two (2) FreeLynx headstages with a maximum of 128 wirelessly-transmitted recording channels per headstage. If you need to wirelessly record more than 128 channels from each FreeLynx, the Connect-to-Cheetah mode supports up to a maximum of 256 wireless recording channels.

Note: Only one (1) FreeLynx headstage is supported by a Cheetah acquisition computer, regardless of channel count, and you will not have access to the additional capabilities made possible by the DLSX system.

Mode #2: Connect-to-SX Wireless Recording

This recording mode uses a Digital Lynx SX (DLSX) acquisition system consisting of the DLSX acquisition amplifier and computer running Cheetah software to communicate to your FreeLynx headstages. In this mode, the FreeLynx wireless access point is connected to the Ethernet port labeled “Wireless” on the back panel of the DLSX. (See Figure 1.)

Figure 1: The FreeLynx wireless access point connects to the Wireless Ethernet
port on the Digital Lynx SX. 

Benefits:
Two (2) FreeLynx headstages may be connected simultaneously to a single DLSX/Cheetah acquisition system. Additionally, the wireless data from FreeLynx is accessible using the DLSX’s Hardware Processing Platform (HPP) for closed loop processing. The DLSX may be used to conduct other electrophysiology recordings, including simultaneous synchronized data acquisition from tethered analog or digital multiplexing headstages.

Note: Each FreeLynx headstage may only record a maximum of 128 channels wirelessly in this mode. In Connect-to-SX mode, FreeLynx is not controlled using the Cheetah GUI but will receive commands sent to DLSX via configuration files or NetCom.

Mode #3: Onboard microSD Recording

Your FreeLynx headstage includes an approximately 0.5 g microSD card with a capacity of 64-256GB. At any time during either of the above two wireless recording modes, or as your default recording mode, you may use the FreeLynx as a data logger by disabling wireless transmission and recording data to the onboard memory card.

Benefits:
This may prolong battery life and allow the FreeLynx to continue operating during environmental WiFi interference or when exceeding the 10 meters of range between subject-mounted FreeLynx and wireless access point. Please note, however, that a wireless connection to DLSX or Cheetah is still needed to send commands to FreeLynx, synchronize time data, and receive status updates. If you are using the Connect-to-SX Wireless Recording Mode, switching to onboard microSD recording will allow you to record up to 256 channels. 

How to Toggle MicroSD Recording
If you are using Mode #1 (Connect-to-Cheetah Wireless Recording), toggle onboard microSD recording within Cheetah software by clicking View -> Hardware Properties and interacting with the FreeLynx Properties window. (See Figure 2.) 

Figure 2: Toggling microSD recording using Cheetah’s Hardware Properties panel.

If you are using Mode #2 (Connect-to-SX Wireless Recording), toggle onboard microSD recording by sending commands to DLSX through .cfg configuration files. The process for creating and executing these files is detailed below:

1. Use a plain text editor like Notepad to create a new document. Insert your commands using this format: -SendLynxSXCommand AcqSystem1 -WHSSetWiFiStreamEnable <1 or 2 for FreeLynx #1 or #2> <1 or 0 for Enabled or Disabled>
   -SendLynxSXCommand <Hardware Sub System Name> -WHSSetMicroSDrecordEnable <1 or 2 for FreeLynx #1 or #2> <1 or 0 for Enabled or Disabled>

In the following example commands we are telling a DLSX named “AcqSystem1” to disable wireless data transmission and enable microSD recording for connected FreeLynx #1.

-SendLynxSXCommand AcqSystem1 -WHSSetWiFiStreamEnable 1 0 
-SendLynxSXCommand AcqSystem1 -WHSSetMicroSDrecordEnable 1 1

1. Once we have completed the command syntax, save the file as “Enable microSD Recording.cfg”
   
   
2. To enable microSD recording in Cheetah, click File > Open Configuration File, and select the file “Enable microSD Recording.cfg.” It will be executed immediately, disabling wireless transmission and enabling microSD recording. This mode will be retained by FreeLynx, so it will continue recording to the microSD card, even after a power cycle, until you send the command to disable microSD recording. We recommend you save a second configuration file named “Disable microSD Recording.cfg” that will revert to wireless recording with, for example, the following commands:

-SendLynxSXCommand AcqSystem1 -WHSSetMicroSDrecordEnable 1 0
-SendLynxSXCommand AcqSystem1 -WHSSetWiFiStreamEnable 1 1

Retrieving Data from Onboard MicroSD
To retrieve data from the FreeLynx onboard microSD card you will need to remove the microSD card from the FreeLynx headstage and plug it into a computer. The microSD card is below the printed serial # of the FreeLynx on the side opposite from the implant interface. (See Figure 3). Press in the microSD card to unlatch it, then remove. A pen or tweezers may be necessary to depress the microSD card. Reading your data from a microSD card on a desktop computer typically requires either a microSD-to-SD Card Adapter and a SD-to-USB Card Reader or, less commonly, a microSD-to-USB Card Reader. 

Figure 3: MicroSD card location on a FreeLynx headstage.

Onboard recorded data is stored on a Linux Ext4 partition on the microSD card. If you have access to Ubuntu or a similar Linux distribution, accessing and copying the data to an exFAT, NTFS, or Mac formatted drive for analysis will be straightforward. However, Linux Ext4 drives are not accessible directly from a typical Windows or Mac operating system. To access the partition and retrieve your recorded data without a Linux operating system installed may require the use of a third-party application such as Linux Reader, Ext2Read, or extFS (for Mac or Windows).

Information in this TechTip is applicable to Cheetah version 6.4.1, FreeLynx firmware version 2.4, and Digital Lynx SX firmware version 2.3.