I am using a U3 (LV) in a Unix environment with the exodriver to acquire signals from a number of analogue sensors. All works well but... alas, if the power is interrupted and restored the FIO lines default to outputs and the FIOs are driven to a non-zero voltage. This causes havoc with connected instruments until the software is restarted as the connected instruments are expecting the FIOs to be inputs (i.e. not driven).
Is there a way of changing the power-on default configuration of FIO lines on a U3(LV)?
Apologies if this has already been covered elsewhere.
-Scott
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The easiest way to configure the reboot defaults is using LJControlPanel on Windows. If that is not an option for you let us know and I will have someone else help.
The default from the factory is input, and you can make sure you are using factory defaults by powering up with a jumper securely installed from FIO6 to SPC:
https://labjack.com/support/datasheets/u3/hardware-description/spc
All digital I/O on the T7 have 3 possible states: input, output-high, or output-low. When configured as an input, a bit has a ~100 kO pull-up resistor to 3.3 volts. When configured as output-high, a bit is connected 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).
If a DIO terminal is at about 3.3 volts, and you are not sure if it is set to input or output-high, a couple ways to tell are:
1. Look for a slight change on a terminal with nothing connected except a DMM. For example, a DMM measurement of an input might show 3.30V whereas that same terminal as output-high reads 3.31V.
2. Add a load resistor. If you add a 100k from FIO7 to GND, the terminal should measure about 1.6V for input and 3.3V for output-high.
Thank you for the support and detailed explanation.
LJControlPanel did the trick and the power on default behavior in the Unix environment is now as desired.