> For the complete documentation index, see [llms.txt](https://docs.anthriq.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.anthriq.com/xbud/technical-guide.md). # Technical Guide xBud is a multimodal analog front-end (AFE) for biosignal acquisition. It conditions EEG, ECG, EMG, and EOG from dry electrodes and hands conditioned analog voltages to a data-acquisition device (DAQ), which digitises them. BXI Studio drives the acquisition, so the signal path is **electrodes → xBud → DAQ → host PC**. This guide covers the whole path: what shipped, power and safety, wiring, electrodes and montage, the BXI Studio workflow, choosing a visualization, recording and exporting data, programmatic access, and support. For parameter tables see [Specifications](/xbud/specifications.md); for a pictorial walkthrough of the same steps, see the illustrated setup guide. > **Applies to:** xBud hardware Rev A, with BXI Studio 1.0.0 or later. The screens here come from BXI Studio 1.0.145, and earlier 1.0.x builds differ in small details. > **Note:** xBud is for research and education. It is not a medical device and is not intended for diagnosis, treatment, or monitoring. ![xBud front-end wired to an NI DAQ and a laptop running BXI Studio, with an EEG interface alongside](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-d844c31e3db73e476fc66a6a3a9b4efa2c466ffc%2Fxbud_fulldevice.png?alt=media) ## Check what shipped | Item | Notes | | ------------------ | ------------------------------------------------------------------------- | | xBud AFE | In the channel variant you ordered: 4, 8, 12, or 16 channels | | Supported DAQ | NI USB-600x, NI mioDAQ (USB-6451), or NI cDAQ, with its USB cable | | xBud power adapter | The supplied adapter only | | Subject interfaces | The ones you ordered: EEG cap, EEG headband, EMG armband, ECG chest-strap | | Electrode contacts | Standard Ag/AgCl coated dry electrodes, comb and disc | | Marker box | Two buttons with LEDs, plus its cable | | Jumper wires | For the xBud-to-DAQ connection | | | | | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | ![xBud front-end unit](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-de447881da390d0364cd0de61a5954eda805bc5a%2Fxbud_isolated.png?alt=media) | ![NI mioDAQ unit](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-309fa2bcb3ecec92040e863d6df42f4595e0e297%2Fmio_isolated.png?alt=media) | ![xBud AC power adapter](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-81f67aab0cb91898eecddd2bf2e9bee581332b2e%2FAC_adaptor.png?alt=media) | | xBud AFE | Supported DAQ | Power adapter | | ![EEG cap with electrode holes and lead bundle](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-76caa6c1b9641a3b260395fc5e9bc30acb8c92a7%2FEEGcap_isolated.png?alt=media) | ![EEG headband](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-2f1258e1b07c76e19969e361c036fa284c4d75bb%2Fheadband_isolated.png?alt=media) | ![EMG armband](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-352ac8ee309f443da73b403cde34d02a4fd876ac%2Farmband_isolated.png?alt=media) | | EEG cap | EEG headband | EMG armband | You also need a host PC, the **NI-DAQmx** driver, and **BXI Studio**. If anything is missing or damaged, contact before powering on. ## Power and safety Read this section before connecting a subject. xBud runs from an external AC-DC adapter; the DAQ draws its own power, and the NI mioDAQ is USB-C bus-powered. | Item | Value | Notes | | ---------------------- | ----------------------------------------------------------------------------- | ----------------------------------------------------- | | xBud power adapter | 2-pin floating AC-DC adapter; 110–220 V AC in, 12 V DC / 2 A out, barrel jack | Use only the supplied adapter | | xBud power consumption | \~5 W | About 300 mA at ±5 V for the 4-channel, plus overhead | | DAQ power | Set by the DAQ | No external supply for the mioDAQ | ### Electrical isolation xBud is electrically isolated. A 3 kV barrier separates the subject side from the mains-powered supply, and the supplied 2-pin double-insulated adapter floats the low-voltage side with respect to earth. An isolation barrier is not the same as medical certification. xBud is not certified to IEC 60601-1 and is not characterised for patient leakage current, so it stays a teaching and research aid rather than a medical device. > **Warning:** Keep the subject clear of other mains-powered equipment while they are connected to xBud, such as laptop chargers, non-isolated desktop PCs, or bench supplies. Each additional mains-referenced path through the subject adds a fault route that xBud's barrier does not cover. > **Regulatory information:** For certifications, compliance declarations, and warranty terms, see . ### Operate safely * Inspect the electrode leads and the power adapter for damage before each session. * Power off xBud and the DAQ before wiring or rewiring terminals. * Keep electrodes off the subject during first power-on and testing. * Run sessions under the supervision of trained personnel. > **Warning:** Dry electrodes pressed against skin for long periods can cause irritation or pressure marks. Limit session duration and stop if the subject reports discomfort. > **Safety notice:** Follow all applicable local regulations when operating or modifying Anthriq hardware. Do not use outside the specified environmental conditions. ## Install the software Install the **NI-DAQmx** driver before connecting the DAQ for the first time, then install BXI Studio. Install the full NI-DAQmx runtime rather than NI MAX alone; without it the DAQ does not appear in BXI Studio. See [Install BXI Studio](/bxi-studio/installation.md). ## Wire the signal chain Each xBud analog output goes to a DAQ analog input through a jumper wire, along with the shared ground and the two marker lines. Power off both units first. | xBud output | DAQ terminal | Notes | | ----------- | --------------------- | ---------------------------------------------- | | EEG 0 | AI 0 | First conditioned channel | | EEG 1 | AI 1 | | | EEG *n* | AI *n* | Up to your channel count | | REF | AI *n*+1 | Optional; digitise the reference to inspect it | | AGND | The terminal marked ⏚ | Shared ground. Inputs are read against it | | Marker 1 | DI `port0/line0` | From the marker box, via the xBud chassis | | Marker 2 | DI `port0/line1` | | ![xBud rear panel showing the green screw-terminal header labelled GND, EEG0, EEG1, EEG2, REF, with lead wires attached](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-8a44097c088a3abe7048d65c477130f1e30cdb89%2Fxbud_powerplug.png?alt=media) Read the channels at the DAQ in RSE or pseudodifferential mode against the shared AGND. REF and DRL attach to the subject rather than the DAQ: xBud uses REF as the recording reference and drives DRL for common-mode cancellation. ![Jumper wires landing in the orange spring terminal blocks of the NI USB-6451](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-7dd27fcfa7d06e1f66f8c72327f673028a2eb194%2Fxbud_mio_pins.png?alt=media) Connect the marker box to the xBud chassis with its cable. Each button press drives its marker line high for one sample, and the DAQ records it time-aligned with the signal. ### Connect the DAQ to the host PC Plug the USB cable into the DAQ, tighten the retaining screw on the chassis, then plug the other end into the host PC. Connect the xBud power adapter last, and allow about a minute for the front-end to settle before judging a trace. | | | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ![USB cable secured to the NI DAQ chassis with its retaining screw](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-abc144f6ec2b13acdd6191bef948f28b49a4ee0c%2Fxbud_connect_mio1.png?alt=media) | ![The other end of the USB cable plugged into the host laptop](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-c9f31f7d19872b2c73df32724f24eaff66c7d274%2Fxbud_connect_mio2.png?alt=media) | | At the DAQ | At the host PC | ## Attach electrodes xBud uses dry Ag/AgCl coated electrodes, so contact pressure replaces conductive gel. Attach them after a bench signal check passes. 1. Choose the interface for the modality: the EEG cap or headband for EEG, the armband for surface EMG, the chest-strap for ECG. 2. Use comb contacts where hair is in the way and disc contacts on bare skin. 3. Fit the interface so every contact sits flat on skin. Snug, not tight. 4. For EEG, part the hair out from under the contacts so the combs reach the scalp. 5. Seat each electrode for firm, even contact, then confirm the live signal looks physiological. ![A subject wearing the xBud EEG cap with electrode leads routed to the back](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-f1e887b0ce5ea354c3eee7d26718e94d87601432%2Fxbus_wear_eeg_cap.png?alt=media) ### Montage Placement depends on the cap or band you ordered and the electrodes move, so treat this as a starting point. It is the montage the experiment guides use. | Signal | Site | Purpose | | ------ | ---- | --------------------------------------------- | | EEG 0 | O1 | Left occipital | | EEG 1 | O2 | Right occipital | | EEG 2 | Fpz | Frontal, a control site for occipital rhythms | | REF | Cz | Recording reference | | AGND | T7 | Analog ground, shared with the DAQ | | DRL | T8 | Driven right leg, common-mode cancellation | ![10-20 head map with O1, O2 and Fpz marked as recording sites, Cz as reference, and T7 and T8 as ground](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-673056498214f470445932786ec9c849387408cd%2Fmontage-10-20.svg?alt=media) Blue marks the recording sites, orange the reference, and rust the ground and DRL pair. The remaining 10-20 positions appear in grey for orientation. Placing AGND and DRL on the two mastoids instead works equally well. > **Tip:** Gel the AGND and DRL contacts. Neither carries a recorded signal, so gel there lowers the common-mode path impedance and reduces mains hum without affecting the dry recording sites. ### Record cleanly Movement and mains hum account for most poor recordings. Agreeing these points before the first block saves repeating it. | Do | Do not | | -------------------------------------------- | ------------------------------------------------------ | | Run the laptop on battery, charger unplugged | Record with the charger plugged in next to the subject | | Sit still, jaw and forehead relaxed | Talk, chew, or clench during a block | | Keep cables from swinging or rubbing | Touch the electrodes or leads mid-block | | Check the live trace before recording | Continue if the skin itches or reddens | ## Connect in BXI Studio Open BXI Studio and start the connect flow. Choose **Anthriq × NI mioDAQ** in **Select Device Family**. ![BXI Studio Select Device Family dialog listing Anthriq Instinct and Anthriq by NI mioDAQ](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-b7ef88a66f03bdce6b7c62ced5bc255c00a39bcd%2Fbxi_select_device.png?alt=media) BXI Studio scans the host and lists what it finds, each entry showing its name, model, maximum rate, and serial. Select **Connect** on yours. ![BXI Studio device discovery listing Dev1 USB-6451 and a simulated Dev4, each with a Connect button](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-a2c379e804090fa1dd279814e6cbf3cd52b75cbc%2Fbxi_connect_device_2.png?alt=media) > **Tip:** Tick **Show non-USB devices (PXI, cDAQ, …)** when pairing a cDAQ chassis rather than a USB DAQ, and select **Refresh** if the device does not appear. See [Device discovery](/bxi-studio/device-discovery.md). ### Configure the analog inputs BXI Studio walks through channel naming, signal settings, and a device-spec review. Set the voltage range, the terminal mode, and the sampling rate, then label each channel with its electrode site. Enter **100** as the external gain so displayed values read in electrode microvolts. See [Analog input configurations](/bxi-studio/configure/analog-input-configurations-xbud.md). > **Tip:** Choose the narrowest voltage range the signal allows. The fixed 100× gain puts a 100 µV EEG signal at about 10 mV, so ±2.5 V resolves it considerably better than ±10 V. Sampling rate belongs to the DAQ and is shared across the channels in a task, so the rate available per channel falls as channels are added. About 2 kS/s per channel is ample for EXG given the fixed 300 Hz low-pass. ### Set up markers Markers time-stamp events such as stimulus onset or eyes closing. BXI Studio prompts for a **Marker Library** before recording starts. ![BXI Studio Marker Library dialog with an Event Marker named Experiment Start bound to the U key, and Digital Marker rows with Link DI buttons](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-b2f2c7075374d90cd1fa2660974b336551c6b411%2Fbxi_select_markers2.png?alt=media) * **Event Marker** tags a single instant; **Epoch Marker** tags a span. Give each a name and a keybind, then press that key during the run. * **Digital Markers** fire from DI line edges and are device-scoped. Use **+ Link DI** to bind one to a digital input, which is how the marker-box buttons reach the recording. Naming markers before you start keeps the labels meaningful at analysis time. ## Choose a visualization BXI Studio offers four plot types, and the **Live Stream** view tiles several at once, each with its own plot type and source device. ![BXI Studio Live Stream with four tiles set to Real Time Plot, Fast Fourier Transform, Bandpower and Time Frequency Spectrogram](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-aa3117f8f5335a2c4c135ee15dc40b4ccf3f674d%2Fbxi_stream_4vi.png?alt=media) | Plot type | Answers | Use it for | | -------------------------- | --------------------------------------- | -------------------------------------- | | Real Time Plot | What is the signal doing now? | Contact checks, artefacts, ECG and EMG | | Fast Fourier Transform | Where is the power across frequency? | Alpha, SSVEP, any rhythm | | Bandpower | How much sits in each named EEG band? | Live band tracking, neurofeedback | | Time Frequency Spectrogram | How does the spectrum change over time? | Onsets, transitions, state changes | Running the Real Time Plot alongside one frequency view works well: the time trace shows whether the data is trustworthy, and the frequency view shows what is in it. ### Real Time Plot Amplitude against time. Use it to confirm contact by tapping an electrode, to spot mains hum as a thick 50 Hz band, and to watch events that are obvious in time such as ECG R-peaks and EMG bursts. Adjust the y-scale to zoom. > **Note:** EEG rhythms are rarely visible by eye here. A 10 µV alpha rhythm sits inside a trace that also carries drift and blinks, so use the Fast Fourier Transform to find it. ### Fast Fourier Transform Power against frequency over a sliding window. A resting spectrum falls smoothly as frequency rises, and what you look for is a departure from that curve: a bump at a particular frequency. | Setting | Effect | Choose | | ------------------ | --------------------------------------------------------------------- | ------------------------------------------------------ | | Window (s) | Longer windows resolve finer frequency detail but respond more slowly | Long enough to separate the rhythm from its neighbours | | Plot Frequency (s) | Shorter intervals refresh faster at the cost of stability | Fast for live demos, slower for a steady read | Frequency resolution and time resolution trade against each other: a window long enough to separate 10 Hz from 11 Hz spans several seconds, so it also smears anything changing within those seconds. > **Tip:** Compare two conditions rather than reading one spectrum. Eyes-open against eyes-closed on the same channel is far more informative than a single trace with a bump in it. ### Bandpower Power summed within each named EEG band, per channel. | Band | Range | Commonly associated with | | ----- | -------- | -------------------------------------------------------------- | | Delta | 0.5–4 Hz | Deep sleep; also where movement and sweat artefacts land | | Theta | 4–8 Hz | Drowsiness, memory tasks | | Alpha | 8–13 Hz | Relaxed wakefulness, eyes closed, occipital | | Beta | 13–30 Hz | Alert engagement; also EMG contamination from jaw and neck | | Gamma | >30 Hz | Cognitive load claims; heavily contaminated by muscle activity | This reduces a spectrum to a few numbers, which suits tracking change over minutes and neurofeedback. It hides where inside a band the power sits, so a shifted alpha peak and a stronger alpha peak look alike. > **Note:** Beta and gamma readings depend on the subject being still. Muscle activity from the jaw, neck, and forehead is broadband and overlaps both bands, so a jaw clench can raise apparent gamma power with no cortical change behind it. xBud's fixed 300 Hz low-pass also bounds the top of this range. ### Time Frequency Spectrogram Frequency against time with power as colour. Use it when *when* matters as much as *what*: alpha appearing within a second of the eyes closing, SSVEP onset locked to the stimulus, or signal quality drifting across a long recording. The spectrogram averages across the channels you select, so narrow the selection to occipital channels when looking for alpha. ### Filter before you judge All four views show what the filters leave behind. A sensible start for EEG is a bandpass of about 1–40 Hz with a 50 Hz bandstop. BXI Studio offers lowpass, highpass, bandpass, and bandstop, each with a cutoff and an order. * **High-pass** removes slow drift from electrode settling and sweat. * **Low-pass** removes high-frequency muscle activity and noise. * **Bandstop** removes mains interference at 50 Hz or 60 Hz. Raise the order only as far as the artefact requires: a higher order cuts more sharply but distorts the waveform near the cutoff, which matters when shape rather than power is the point. > **Note:** Filtering changes what you see rather than what the electrodes deliver. A 50 Hz bandstop hides mains hum, but the contact that caused it still degrades the rest of the signal, so it is worth reseating the electrode as well. ## Stream, record, and export ### Start a stream Open **Streams** and select **Start a New Stream**. ![BXI Studio Streams page with the Start a New Stream button, an Overview panel and an empty Recordings list](https://2761951758-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FhtBZnSGOC4EMhU3nc5oM%2Fuploads%2Fgit-blob-b7d1cb4a78999e4ec5cc71cbd41601ad6e41f749%2Fbxi_start_stream.png?alt=media) Select **Start Plotting** and watch the live trace. Tap an electrode and the trace should jump on that channel. A flat or railed trace points to a wiring, range, or contact problem: see [Maintenance and troubleshooting](/xbud/maintenance-and-troubleshooting.md). ### Record a session Select **Start Recording**, press the marker key or button at each event, then stop. BXI Studio saves the session and lists it under **Recordings** on the Streams page. See [Recording data](/bxi-studio/streams/recording-data.md). ### Export as CSV Open **Recordings**, select the session, and choose the download action. BXI Studio writes a CSV carrying the channel names you set and the marker columns, which any analysis tool reads: Python, MATLAB, R, or a spreadsheet. Convert to electrode microvolts by dividing each sample by the fixed 100× gain, unless you entered the external gain during configuration, in which case BXI Studio has already applied it. See [Exporting a dataset](/bxi-studio/streams/exporting-a-dataset.md). ## Read the DAQ programmatically BXI Studio is the supported interface for streaming, visualisation, and experiment orchestration. For programmatic access, read the DAQ directly through the NI-DAQmx APIs; xBud ships no separate SDK. | Tool | Purpose | | --------------------------- | ----------------------------------- | | NI-DAQmx Python (`nidaqmx`) | Read samples from the DAQ in Python | | NI-DAQmx C / C++ | Access the DAQ from native code | ```bash pip install nidaqmx ``` ```python import nidaqmx from nidaqmx.constants import AcquisitionType, TerminalConfiguration DEVICE = "Dev1" # the name shown in NI MAX, e.g. Dev1 (USB-6451) CHANNELS = ["ai0", "ai1", "ai2", "ai3"] SAMPLE_RATE = 250 # Hz; raise for higher-bandwidth modalities N_SAMPLES = 250 # one second at 250 Hz XBUD_GAIN = 100 # xBud's fixed front-end gain with nidaqmx.Task() as task: for ch in CHANNELS: task.ai_channels.add_ai_voltage_chan( f"{DEVICE}/{ch}", terminal_config=TerminalConfiguration.RSE, min_val=-10.0, max_val=10.0, ) task.timing.cfg_samp_clk_timing( SAMPLE_RATE, sample_mode=AcquisitionType.FINITE, samps_per_chan=N_SAMPLES, ) volts = task.read(number_of_samples_per_channel=N_SAMPLES) # Convert ADC volts to electrode microvolts microvolts = [[(v / XBUD_GAIN) * 1e6 for v in channel] for channel in volts] print(f"Read {len(microvolts)} channels x {len(microvolts[0])} samples") ``` > **Note:** Match the terminal mode and input range to your DAQ and wiring. This example uses `RSE` and ±10 V for the NI mioDAQ; set `min_val` and `max_val` to your DAQ's range, for example ±5 V on an NI USB-600x or cDAQ. To time-align events, add a digital input task on the two marker lines (`port0/line0` and `port0/line1`) and sample them alongside the analog channels. ## Get support **Need help?** Contact Anthriq support: * Email: Including this information speeds up a reply: 1. xBud channel variant and the DAQ model 2. BXI Studio version and host operating system 3. NI-DAQmx driver version 4. Acquisition settings: sampling rate, input range, terminal mode, external gain 5. What you expected, what happened, and any error text 6. A screenshot of the live trace or the spectrum, where relevant ## Next steps * [Specifications](/xbud/specifications.md): the full parameter tables * [Experiments](/xbud/experiments.md): guided recordings, starting with eyes-closed alpha * [Maintenance and troubleshooting](/xbud/maintenance-and-troubleshooting.md): when something looks wrong * [FAQ](/xbud/faq.md)