Digital I/O (TTL Input and Output) Overview

The Cheetah Data Acquisition Software (DAS) is capable of reading transistor to transistor logic (TTL) input values and outputting TTL values via both dedicated add-on Digital I/O boards and through Neuralynx acquisition systems.  TTLs can either be on (voltage applied) or off (grounded).  The actual voltage value can vary from device to device but is usually either 3.3V or 5V.  Each TTL device has a specific number of physical TTL pins, otherwise known as bits, associated with it.  To allow for more flexibility in configuring how Cheetah utilizes your available TTL bits, each TTL device has their total number of bits divided into ports (groups of TTL bits).  You can then configure and use the bits on each port independently of the bits on other ports.  TTL values are timestamped along with all other data recorded by Cheetah DAS so they can be used during both offline and online analysis. To add additional TTL devices (available with 24, 48 or 96 TTL bits) to supplement the capabilities of your acquisition system, contact sales@neuralynx.com .

Supported Add-on Hardware

The following add-on Digital I/O boards are compatible with Cheetah.  For information on Digital I/O that is built into Neuralynx hardware, see the entry for your particular acquisition system in the Hardware Systems section of this guide.  The Cheetah Device Type is the value used when Cheetah assigns the device name used to reference the TTL device.

Device	Cheetah Device Type	Total TTL Bits	Number of Ports	Number of Bits per Port	Max Sampling Rate
Measurement Computing DIO-24	PCI-DIO24	24	3	8	1KHz*
Measurement Computing PCIe DIO-24	PCIe-DIO24	24	3	8	1KHz*
Measurement Computing DIO-48	PCI-DIO48H	48	6	8	1KHz*
Measurement Computing DIO-96	PCI-DIO96	96	12	8	1KHz*

*The maximum sampling rate is approximate, see the -SetDigitalIOInputScanDelay command for more information.

Hardware Installation

Upon receiving the DIO card, follow all of the included manufacturer’s installation and setup instructions before attempting to use it with Cheetah DAS.

Adding the TTL Board to Cheetah

After installation and setup is complete, Cheetah DAS will automatically detect your newly installed hardware and allow you to take advantage of your new TTL capabilities.

NOTE:  If Cheetah does not detect your hardware, it means one of the following has occurred:

1. The hardware is not supported by Cheetah
2. The hardware's driver is not correctly installed or configured
3. There is a physical problem with the hardware.
   

Configuring the TTL Board

Before the new TTL card can be of much use, you will need to define how the TTL bits will be used. Use the Digital IO Setup dialog in order to configure the board.

After the card has been added to the system, all TTL inputs will be recorded to event data files (NEV) just as those of your acquisition system’s built in TTL port.

Controlling the TTL Board

Cheetah has no user interface to directly control the output capabilities of Digital I/O devices, including those built into Neuralynx acquisition systems.  You will need to create a  NetCom program that sends commands or manually load a configuration file each time you want a sequence of commands to execute. The NetCom approach is much preferred for controlling an experiment as it will not interfere with Cheetah DAS’s normal operation. Many of our experiment control programs have the ability to send any command to Cheetah DAS.  For explanations of all control and status commands, see the Digital IO Commands section of this guide.

Add-on Digital I/O Board Limitations

There are a couple of limitations that the add-on Digital I/O boards have that the digital I/O built into the acquisition systems do not. First of all, the TTL values are not saved to a raw data file (RDF) during recording. So when the RDF is played back, you will not have any of the TTLs from the extra board show up.  Second,  the  sampling rate of the add-on boards  is set separately  from the sampling rate of the acquisition hardware.  Not all add-on boards will be able to have the same sampling rate as the acquisition hardware.  See the Supported Add-on Hardware section of this page for more information.

Additional TTL Input and Output Topics :

Digital I/O Setup
Digital IO Commands