Device Support

XClock supports various data acquisition (DAQ) devices for clock generation. This page provides device-specific information, wiring diagrams, and configuration details.

Supported Devices

LabJack T4

The LabJack T4 is the primary supported device for XClock. It’s a USB-based data acquisition device with excellent timing precision.

Specifications:

• Base clock frequency: 80 MHz

• Available output channels: 8 flexible I/O (FIO0-7) + 4 extended I/O (EIO0-3)

• Trigger input: DIO4

• Maximum clock frequency: Limited by divisor calculations

• Minimum clock frequency: ~1 Hz

Advantages:

• Affordable and widely available

• USB-powered, no external power needed

• Cross-platform support (Windows, macOS, Linux)

• Precise internal clock

• Multiple simultaneous outputs

Wiring Diagram

Recommended Wiring:

• Clock Outputs: FIO0, FIO1, FIO2, FIO3 (first 4 channels recommended)

• Trigger Input: DIO4 (for external trigger start)

• Ground: GND (connect to equipment ground)

• Power: USB (no additional power needed)

Pin Configuration

Pin Name	Function	Type	Description
FIO0-7	Clock Output	Output	Flexible I/O, can be used for clock signals
EIO0-3	Clock Output	Output	Extended I/O, additional clock channels
DIO4	Trigger Input	Input	External trigger for synchronized start
GND	Ground	-	Common ground reference
VS	Power Out	Output	5V output (USB power)

Available Channels

Query available channels in Python:

from xclock.devices import LabJackT4

t4 = LabJackT4()
output_channels = t4.get_available_output_clock_channels()
print(f"Clock outputs: {output_channels}")
# Output: ('FIO0', 'FIO1', 'FIO2', 'FIO3', 'EIO0', 'EIO1', 'EIO2', 'EIO3')

trigger_channels = t4.get_available_input_start_trigger_channels()
print(f"Trigger inputs: {trigger_channels}")
# Output: ('DIO4',)

Clock Frequency Limitations

The LabJack T4 uses a divisor-based system for generating clocks from the 80 MHz base clock. Not all frequencies are achievable exactly.

Achievable frequencies:

• Frequency = 80,000,000 Hz / (divisor × roll_value)

• Divisor: 1, 2, 4, 8, 16, 32, 64, 256

• Roll value: 1-65536

XClock automatically calculates the closest achievable frequency:

channel = t4.add_clock_channel(clock_tick_rate_hz=100, ...)
print(f"Requested: 100 Hz")
print(f"Actual: {channel.actual_sample_rate_hz} Hz")

Example: Basic LabJack T4 Usage

from xclock.devices import LabJackT4

# Initialize
t4 = LabJackT4()

# Add two synchronized clocks
t4.add_clock_channel(
    clock_tick_rate_hz=60,
    channel_name="FIO0",
    duration_s=10.0,
)

t4.add_clock_channel(
    clock_tick_rate_hz=100,
    channel_name="FIO1",
    duration_s=10.0,
)

# Start and wait
t4.start_clocks(wait_for_pulsed_clocks_to_finish=True)
t4.close()

Troubleshooting LabJack T4

Device not found:

• Install LabJack LJM software

• Check USB connection

• Test with Kipling software (included with LJM)

Permission errors (Linux):

• Set up udev rules for USB access (see Installation)

Unexpected frequencies:

• Check actual_sample_rate_hz to see achieved frequency

• Try different target frequencies

• Some frequencies may not be exactly achievable

Dummy DAQ Device

A software-only device for testing and development without hardware.

Features:

• Simulates all XClock functionality

• No hardware required

• Same API as real devices

• Useful for unit tests and development

Limitations:

• No actual output signals

• Timestamps are simulated

• Cannot trigger external equipment

Example: Using Dummy Device

from xclock.devices import DummyDaqDevice

# Initialize dummy device
dummy = DummyDaqDevice()

# Use exactly like a real device
dummy.add_clock_channel(clock_tick_rate_hz=100, duration_s=5.0)
dummy.start_clocks(wait_for_pulsed_clocks_to_finish=True)
dummy.close()

Use cases:

• Testing code without hardware

• Development and debugging

• Automated testing

• Learning XClock API

Device Comparison

Feature	LabJack T4	Dummy Device
Hardware required	Yes	No
Actual outputs	Yes	No (simulated)
Timestamp accuracy	High (ns)	Simulated
Cost	~$200	Free
Platform support	All	All
Max channels	12	Unlimited
Trigger input	Yes	Simulated

Connection Examples

Single Camera Synchronization

Connect one camera trigger input to LabJack FIO0:

LabJack T4          Camera
---------          --------
FIO0     ------>   Trigger In
GND      ------>   Ground

Multi-Camera Setup

Connect multiple cameras to different channels:

LabJack T4          Devices
---------          --------
FIO0     ------>   Camera 1 Trigger
FIO1     ------>   Camera 2 Trigger
FIO2     ------>   DAQ System Trigger
GND      ------>   Common Ground

External Trigger Start

Use external signal to start all clocks simultaneously:

Trigger Source     LabJack T4          Cameras
--------------     ----------          -------
Trigger Out ----> DIO4
                   FIO0      ------>   Camera 1
                   FIO1      ------>   Camera 2
                   GND       ------>   Common Ground

Electrical Specifications

LabJack T4 Output

• Logic level: 3.3V (TTL compatible)

• High level: ~3.3V

• Low level: ~0V

• Output current: Max 6 mA per pin

• Rise/fall time: ~20 ns

Warning

Do not exceed maximum output current. Use buffer circuits if driving high-current loads.

Signal Buffering

For driving long cables or multiple devices, use a buffer:

LabJack FIO0 --> 74HCT244 Buffer --> Camera Triggers (multiple)

Recommended buffer ICs:

• 74HCT244 (non-inverting)

• 74HCT541 (non-inverting)

• SN74LVC244A (low voltage)

Device-Specific Best Practices

LabJack T4

Do:

• Use FIO0-3 first (most reliable for clocks)

• Keep cables short (<2m) for best signal integrity

• Connect grounds between all devices

• Test frequencies with short pulses first

• Monitor actual_sample_rate_hz for frequency accuracy

Don’t:

• Exceed 6 mA output current per pin

• Apply voltages >3.6V to any pin

• Use extremely long USB cables (>5m)

• Hot-plug while clocks are running

General

Do:

• Always call close() when done

• Use with statements for automatic cleanup (if supported)

• Check available channels before adding clocks

• Validate wiring before starting clocks

• Record timestamps for critical synchronization

Don’t:

• Add more clocks than available channels

• Mix continuous and pulsed clocks without planning

• Ignore actual vs. requested frequencies

• Share ground connections with noisy equipment

Performance Characteristics

Timing Accuracy

LabJack T4:

• Base clock: 80 MHz ± 20 ppm

• Jitter: <1 µs

• Channel-to-channel skew: <100 ns

• Long-term drift: <50 ppm/°C

Timestamp Resolution

When recording timestamps:

• Resolution: 1 ns (nanosecond)

• Accuracy: Limited by base clock accuracy

• Format: 64-bit signed integer

Future Device Support

Planned support for additional devices:

• National Instruments DAQ: USB-6001, USB-6008, USB-6343

• LabJack T7: Higher precision version of T4

• Arduino-based: Low-cost alternative

• Raspberry Pi GPIO: Software-timed clocks

Note

See Adding New Device Support for information on adding support for new devices.

See Also

• Installation - Installing device drivers

• Quick Start Guide - Basic usage examples

• Adding New Device Support - Adding new device support

• Devices API Reference - Device API reference