User guide

Charnwood Dynamics Ltd. Coda cx1 User Guide – Reference IV-6
CX1 USER GUIDE - COMPLETE.doc 26/04/04 160/162
DIGITAL EVENT INPUT-OUTPUT
Event Recording and Acquisition Triggering Outputs
The data channel type ‘Digital Event’ refers to digital data which can be acquired from the
standard digital I/O channels provided on the ADC-64 data acquisition unit. There are 15
digital I/O channels on the ADC-64 unit which is connected to the host PC via an ISA DSP32
interface card.
Codamotion Analysis may be configured to use the ADC-64 data acquisition unit in the
configuration file Codasys.cfg where the DSP interface board must be specified.
Four of the digital channels (5 - 8) have pre-programmed functionality (see below). At least
11 channels (1 – 4 and 9 – 15) are available as general-purpose inputs and/or trigger
outputs.
The 15 digital channels are bi-directional: they may be used both to record digital input
signals and to provide digital output (triggering) signals (see below). Digital input data is
acquired synchronously with ADC data (but with small phase advance).
The digital I/O channels are active low: they are held high (+5V) by internal 10k pull-up
resistors, and must be pulled low (grounded) to record a signal transition. When used as a
trigger output, the channel goes low (0V) when the trigger is ‘on’. Each output can sink a
current of up to 30mA. A digital channel should not be connected directly to 5V externally, as
the input current is not limited.
The Acquisition Setup dialogue (CODA: Acquisition Setup...) includes an ‘Acquire Digital
(ADC):’ check-box to activate digital data acquisition, and two ‘Trigger’ check-boxes to
activate digital output triggering (see below). When digital data is acquired, all 15 channels
are recorded, including those used for output triggering.
When digital data has been acquired, it may be shown on a graph by selecting the Digital
Channel data type in the Graph Add Plot dialogue (Views: New Graph View... Add
Plot...). Each digital channel may be selected individually. Digital data has a value of 0 or 1.
If several channels are plotted on the same graph, they may be separated by using the
Offset parameter (use 2 x channel number + 1).
Digital data channels may be named and assigned a colour in the same way as Marker
channels: Setup: Digital Event channels...
Real-time Display
The state of the digital channels may be displayed in real-time with the CODA: Display ADC
or CODA: Display EMG/Digital commands. This may be displayed at the same time as
real-time marker positions or real-time stick figure (CODA: Display Marker Positions or
CODA: Display Stick Figure commands). A real-time signal data view, (graphical scrolling
chart) of digital [analogue, or force plate] signals may be displayed with the CODA: Display
Input Signal Graphs command.