LabJack U3 - 2.8 Digital I;O

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power rails). If

±10, ±12, or ±15 volt supplies are available, consider using the LT1490A op-

1 can be adjusted to get the

esired gain. A fixed reference (such as 2.5 volts) could also be used instead of DAC1.

amp (linear.com), which can handle a supply span up to 44 volts.

A reference voltage is also required to provide the offset. In the following circuit, DAC1 is use

to provide a reference voltage. The actual value of DAC1 can be adjusted such that the circu

output is 0 volts at the DAC0 mid-scale voltage, and the value of R

Figure 2-7. ±10 Volt DAC Output Circuit

A two-point calibration should be done to determine the exact input/output relationship of this

circuit. Ref to application note SLOA097 from ti.com for further information about gain and

IO0-CIO3) are available on the DB15 connector. Each digital line

ured as input, output-high, or output-low. The digital I/O use 3.3 volt

olerant.

-15 EIO0-EIO7

ear on the built-in screw-terminals, while the 8 EIO and 4 CIO lines appear

nnector. See the DB15 Section of this User’s Guide for more information.

ll the digital I/O include an internal series resistor that provides overvoltage/short-circuit

of I/O

tolerant). When configured as output-high, a bit is

onnected to the internal 3.3 volt supply (through a series resistor). When configured as output-

low, a bit is connected to GND (through a series resistor).

offset design with op-amps.

2.8 Digital I/O

The LabJack U3 has up to 20 digital I/O channels. 16 are available from the flexible I/O lines,

and 4 dedicated digital I/O (C

can be individually config

logic and are 5 volt t

The LabJackUD driver uses the following bit numbers to specify all the digital lines:

0-7 FIO0-FIO7

16-19 CIO0-CIO3

The 8 FIO lines app

only on the DB15 co

protection. These series resistors also limit the ability of these lines to sink or source current.

Refer to the specifications in Appendix A.

All digital I/O on the U3 have 3 possible states: input, output-high, or output-low. Each bit

can be configured individually. When configured as an input, a bit has a ~100 kΩ pull-up

resistor to 3.3 volts (all digital I/O are 5 volt