Chapter 6
Digital I/O
©
National Instruments Corporation
6-3
Increasing Current Drive on USB-6210/6211/6215/6218 Devices
The total internal c
u
rrent limit for digital o
u
tp
u
ts and power drawn from the
+5 V terminals is 50 mA. Yo
u
can increase this internal c
u
rrent limit by
s
u
pplying an ex5 V s
u
pply. Refer to the
section of Chapter 3,
Connecting Digital I/O Signals on USB-6210/6211/6215/6218 Devices
The DI and DO signals, P0.<0..7> and P1.<0..7> are referenced to D GND.
Digital inp
u
t applications incl
u
de receiving TTL signals and sensing
external device states, s
u
ch as the state of the switch shown in the fig
u
re.
Digital o
u
tp
u
t applications incl
u
de sending TTL signals and driving
external devices, s
u
ch as the LED shown in Fig
u
Figure 6-2.
USB-6210/6211/6215/6218 Digital I/O Connections
Caution
Exceeding the maxim
u
m inp
u
t voltage ratings, which are listed in the
NI USB-621x Specifications
, can damage the DAQ device and the comp
u
ter. NI is
not
liable for any damage res
u
lting from s
u
ch signal connections.
+5 V
LED
TTL
S
ign
a
l
+5 V
S
witch
I/O Connector
D GND
U
S
B-6210/6211/6215/6218 Device
P0.<0..
3
>
P1.<0..
3
>
Digit
a
l
I
s
ol
a
tor
s
I
s
ol
a
tion
B
a
rrier
(U
S
B-6215
a
nd U
S
B-6218
device
s
only)
When
us
ing
a
U
S
B-6215/6218,
yo
u
m
us
t connect
D GND
a
nd/or AI GND
to the loc
a
l gro
u
nd
on yo
u
r
s
y
s
tem.
