only used to send stream data from the U3 to the host.
2.2 - Status LED
There is a green status LED on the LabJack U3. This LED blinks on reset, and then remains steadily lit. Other LED behavior is
generally related to flash upgrade modes ("Section 1.2":/support/u3/users-guide/1.2).
Normal Power-Up Status LED Behavior:
When the USB cable is connected to the U3, the Status LED blinks 5-6 times over 2
seconds and then remains solid on.
LED blinking continuously at about 4 Hz, even with no software running:
This indicates that the U3 is in flash mode. See
Section 1.2 and reprogram the device.
2.3 - GND and SGND
The GND connections available at the screw-terminals and DB connectors provide a common ground for all LabJack functions. All
GND terminals are the same and connect to the same ground plane. This ground is the same as the ground line on the USB
connection, which is often the same as ground on the PC chassis and therefore AC mains ground.
SGND is located near the upper-left of the device. This terminal has a self-resetting thermal fuse in series with GND. This is often
a good terminal to use when connecting the ground from another separately powered system that could unknowingly already share
a common ground with the U3.
See the AIN, DAC, and Digital I/O Sections for more information about grounding.
2.4 - VS
The Vs terminals are designed as outputs for the internal supply voltage (nominally 5 volts). This will be the voltage provided from
the USB cable. The Vs connections are outputs, not inputs. Do not connect a power source to Vs in normal situations. All Vs
terminals are the same.
2.5 - Flexible I/O (FIO/EIO)
The FIO and EIO ports on the LabJack U3 can be individually configured as digital input, digital output, or analog input. This is
FIO0-EIO7 on the U3-LV (16 lines), or FIO4-EIO7 on the U3-HV (12 lines). In addition, up to 2 of these lines can be configured as
timers, and up to 2 of these lines can be configured as counters. If a line is configured as analog, it is called AINx according to the
following table:
AIN0
FIO0
AIN8
EIO0
AIN1
FIO1
AIN9
EIO1
AIN2
FIO2
AIN10
EIO2
AIN3
FIO3
AIN11
EIO3
AIN4
FIO4
AIN12
EIO4
AIN5
FIO5
AIN13
EIO5
AIN6
FIO6
AIN14
EIO6
AIN7
FIO7
AIN15
EIO7
Table 2.5-1. Analog Input Pin Locations
On the U3-HV, compared to the -LV, the first four flexible I/O are fixed as analog inputs (AIN0-AIN3) with a nominal ±10 volt input
range. All digital operations, including analog/digital configuration, are ignored on these 4 fixed analog inputs.
Timers and counters can appear on various pins, but other I/O lines never move. For example, Timer1 can appear anywhere from
FIO4 to EIO1, depending on TimerCounterPinOffset and whether Timer0 is enabled. On the other hand, FIO5 (for example), is
always on the screw terminal labeled FIO5, and AIN5 (if enabled) is always on that same screw terminal.
The first 8 flexible I/O lines (FIO0-FIO7) appear on built-in screw terminals. The other 8 flexible I/O lines (EIO0-EIO7) are available
on the DB15 connector.
Many software applications will need to initialize the flexible I/O to a known pin configuration. That requires calls to the low-level
functions ConfigIO and ConfigTimerClock. Following are the values to set the pin configuration to the factory default state:
Byte #
6
WriteMask
15
Write all parameters
8
TimerCounterConfig
0
No Timers/Counters. Offset = 4
9
DAC1 Enable
0
DAC1 Disabled. (Ignored on HW 1.3)
10
FIOAnalog
0
FIO all digital.
11
EIOAnalog
0
EIO all digital.
Table 2.5-2. ConfigIO Factory Default Values
Byte #
8
TimerClockConfig
130
Set clock to 48MHz.
9
TimerClockDivisor
0
Divisor = 0.
Table 2.5-3. ConfigTimerClock Factory Default Values
When using the high-level LabJackUD driver, this could be done with the following requests:
ePut (lngHandle, LJ_ioPUT_CONFIG, LJ_chNUMBER_TIMERS_ENABLED, 0, 0);
ePut (lngHandle, LJ_ioPUT_CONFIG, LJ_chTIMER_COUNTER_PIN_OFFSET, 4, 0);
ePut (lngHandle, LJ_ioPUT_CONFIG, LJ_chTIMER_CLOCK_BASE, LJ_tc48MHZ, 0);
ePut (lngHandle, LJ_ioPUT_CONFIG, LJ_chTIMER_CLOCK_DIVISOR, 0, 0);
ePut (lngHandle, LJ_ioPUT_COUNTER_ENABLE, 0, 0, 0);
ePut (lngHandle, LJ_ioPUT_COUNTER_ENABLE, 1, 0, 0);
ePut (lngHandle, LJ_ioPUT_DAC_ENABLE, 1, 0, 0); //Ignored on hardware rev 1.30+.
ePut (lngHandle, LJ_ioPUT_ANALOG_ENABLE_PORT, 0, 0, 16);
… or with a single request to the following IOType created exactly for this purpose:
ePut (lngHandle, LJ_ioPIN_CONFIGURATION_RESET, 0, 0, 0);
2.6 - AIN
The LabJack U3 has up to 16 analog inputs available on the flexible I/O lines (FIO0-FIO7 and EIO0-EIO7). Single-ended
measurements can be taken of any line compared to ground, or differential measurements can be taken of any line to any other
line.
Analog input resolution is 12-bits. The range of single-ended analog inputs is normally about 0-2.44, and there is a “special” 0-3.6
volt range available. The range of differential analog inputs is typically ± 2.4 volts, but is pseudobipolar, not true bipolar. The
difference (positive channel minus negative channel) can be -2.4 volts, but neither input can have a voltage less than -0.3 volts to
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