> 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/specifications.md).

# Specifications

xBud is a multi-channel analog front-end (AFE) that conditions EEG, ECG, EMG, and EOG signals and feeds a data-acquisition device (DAQ) for digitisation. This page lists the platform specifications. xBud is DAQ-agnostic; the NI mioDAQ (USB-6451) values below are the reference example.

> **Applies to:** xBud hardware Rev A, with BXI Studio 1.0.0 or later.

> **Note:** xBud is for research, education, and prototyping only. It is not a medical device and is not intended for diagnosis, treatment, or monitoring. See [Power and safety](/xbud/technical-guide.md#power-and-safety).

> **Note:** Specifications marked *To be confirmed* are pending final hardware characterisation. All electrical figures carry their test conditions where measured.

## Key features

* Multi-channel EXG amplifier: 4, 8, 12, or 16 channels, plus dedicated REF, AGND, and DRL
* Multimodal acquisition of EEG, ECG, EMG, and EOG from one front-end
* Dry Ag/AgCl electrode support across four subject interfaces: EEG cap, headband, armband, and chest-strap
* Fixed front-end conditioning: 100× gain, 300 Hz low-pass, 0.5 Hz AC-coupled high-pass
* Active noise cancellation with a driven-right-leg (DRL) circuit
* DAQ-agnostic: tested with NI USB-600x, NI mioDAQ, and NI cDAQ
* Digitisation resolution and sampling rate set by the DAQ you pair with
* Two digital marker lines via a two-button marker box

## System architecture

```
   Subject            xBud (Stage 1)               DAQ (Stage 2)            Host PC
 ┌──────────┐  EXG   ┌──────────────────────┐ cond.┌────────────────────┐   ┌────────────┐
 │ dry EXG  ├───────►│ instrumentation amp  ├─────►│ analog inputs      │   │            │
 │electrodes│ µV–mV  │ + fixed gain (100×)  │  ±V  │ ADC, 12–24-bit,    │USB│ BXI Studio │
 │ REF / DRL│        │ + fixed 300 Hz LPF   │      │ rate set by the DAQ├──►│            │
 └──────────┘        │ + active noise canc. │      │                    │   └────────────┘
 ┌──────────┐ cable  │ + DRL drive          │      │ digital inputs     │
 │marker box├───────►│ 2 digital marker outs├─────►│  (marker lines)    │
 │ 2 buttons│        └──────────────────────┘      └────────────────────┘
 └──────────┘          xBud analog + marker outputs → DAQ terminals (jumper-wired)
                       DAQ examples: NI USB-600x, NI mioDAQ (USB-6451), NI cDAQ
```

## Capabilities and applications

| Capability                               | Application                                         |
| ---------------------------------------- | --------------------------------------------------- |
| Multimodal acquisition (EEG/ECG/EMG/EOG) | Biomedical instrumentation teaching                 |
| Fixed, characterised gain and bandwidth  | Biosignal and digital signal processing labs        |
| Active noise cancellation and DRL        | Brain–computer interface (BCI) prototyping          |
| Stimulus marker and triggering           | Cognitive and attention studies                     |
| Up to 24-bit digitisation, DAQ-dependent | Evoked-response studies (SSVEP, AEP, somatosensory) |
| Real-time streaming pipelines            | Surface-EMG gesture classification                  |

## Electrical: xBud analog front-end

| Parameter                       | Value                               | Conditions                                                                           |
| ------------------------------- | ----------------------------------- | ------------------------------------------------------------------------------------ |
| EXG channels                    | 4 / 8 / 12 / 16, + REF + AGND + DRL | Variant-dependent                                                                    |
| Electrode type                  | Dry Ag/AgCl                         |                                                                                      |
| Gain                            | 100×                                | Fixed. Not user-adjustable                                                           |
| Low-pass cutoff                 | 300 Hz                              | Fixed. Not user-adjustable                                                           |
| High-pass coupling              | AC-coupled, 0.5 Hz                  |                                                                                      |
| Noise floor                     | < 10 µV                             | Measured over 0.5–45 Hz                                                              |
| Active noise cancellation       | DRL-based common-mode suppression   |                                                                                      |
| Minimum detectable signal (EEG) | \~10 µV                             | Comparable to the noise floor; averaging or spectral methods recover smaller signals |
| Input impedance                 | *To be measured*                    | At DC and in-band                                                                    |
| CMRR                            | *To be measured*                    | At 50/60 Hz                                                                          |
| Channel crosstalk               | *To be measured*                    |                                                                                      |
| Weight                          | 300 g                               |                                                                                      |

## Supported DAQs

xBud is DAQ-agnostic. The same front-end (4/8/12/16 channels + 2 digital marker lines) pairs with any supported DAQ; resolution, input range, and terminal mode are set by the DAQ you choose. BXI Studio handles acquisition for the devices below, and the list grows over time.

| DAQ                  | Resolution  | Input range | Practical rate                          | Notes                                  |
| -------------------- | ----------- | ----------- | --------------------------------------- | -------------------------------------- |
| NI USB-600x          | 12 / 14-bit | ±5 V        | \~1.2 kHz per channel across 4 channels | Entry-level multifunction USB DAQ      |
| NI mioDAQ (USB-6451) | 16 / 20-bit | ±10 V       | 4–5 kHz per channel                     | Reference device for this sheet        |
| NI cDAQ              | 24-bit      | ±5 V        | Up to 10 kHz per channel                | Modular CompactDAQ; highest resolution |

All three read in pseudodifferential or RSE mode against the shared AGND.

> **Note:** Sampling rate belongs to the DAQ, not to xBud. On multiplexing DAQs the maximum is an aggregate figure shared across the channels in the task, so the rate available per channel falls as you add channels. Size the DAQ to the channel count and bandwidth your experiment needs.

The table below lists the NI mioDAQ as the reference example.

## Electrical: reference DAQ (NI mioDAQ USB-6451)

| Parameter             | Value                                                                 |
| --------------------- | --------------------------------------------------------------------- |
| Model                 | NI USB-6451                                                           |
| ADC resolution        | 20-bit                                                                |
| Input voltage range   | ±2.5 / ±5 / ±10 V (software-selectable)                               |
| Analog input channels | 16 single-ended / 8 differential                                      |
| Sampling rate         | Up to 1 MS/s aggregate; about 4–5 kHz per channel in typical xBud use |
| Digital I/O           | Digital inputs accept the two marker lines                            |
| Connectivity / power  | USB-C, bus-powered                                                    |

> **Note:** These are the values the xBud workflow relies on. For the complete and authoritative mioDAQ specifications and compliance declarations, see the [NI USB-6451 specifications](https://www.ni.com/docs/en-US/bundle/usb-6451-specs/page/specs.html).

## System (end-to-end)

| Parameter                             | Value             | Notes                                                                                   |
| ------------------------------------- | ----------------- | --------------------------------------------------------------------------------------- |
| Recommended acquisition rate (EEG)    | >500 Hz           | User-configurable up to the DAQ maximum                                                 |
| End-to-end input-referred noise       | *To be confirmed* | xBud + DAQ, electrodes shorted. The < 10 µV front-end figure is measured over 0.5–45 Hz |
| Effective resolution at the electrode | \~191 nV/LSB      | mioDAQ ±10 V, 20-bit, ÷ the fixed 100× gain. \~95 nV/LSB on the ±5 V range              |
| System bandwidth (−3 dB)              | *To be confirmed* | Set by the xBud filters                                                                 |

> **Note:** Resolution example: the mioDAQ resolves ±10 V across 20 bits, about 19 µV per LSB at the ADC. At the fixed 100× gain that is about 191 nV per LSB referred to the electrode.

> **Tip:** Set the DAQ to the narrowest input range the signal allows. The fixed 100× gain puts a 100 µV EEG signal at about 10 mV, which uses roughly 0.1% of a ±10 V range. Selecting ±2.5 V instead recovers two bits of effective resolution. Surface EMG at a few millivolts is comfortable on any range.

## Mechanical and physical

### xBud

| Parameter                   | Value                                                                                                                 |
| --------------------------- | --------------------------------------------------------------------------------------------------------------------- |
| Dimensions (L × W × H)      | 110 × 170 × 30 mm (4-channel; larger variants to be confirmed)                                                        |
| Weight                      | 300 g                                                                                                                 |
| Enclosure material / finish | *To be confirmed*                                                                                                     |
| Electrode connector         | Standard EXG electrode connectors for dry Ag/AgCl electrodes (comb contacts through hair, disc contacts on bare skin) |
| Analog output connector     | Standard jumper-wire header to the mioDAQ terminals                                                                   |
| Indicators                  | Three LEDs: two for digital markers, one for system power                                                             |
| Controls                    | None. Gain and bandwidth are fixed in hardware                                                                        |

### xBud signal map

| Signal              | Count           | Description                                                                                           | Routed to mioDAQ                          |
| ------------------- | --------------- | ----------------------------------------------------------------------------------------------------- | ----------------------------------------- |
| EXG channel outputs | 4 / 8 / 12 / 16 | Conditioned biopotential, post-gain                                                                   | AI0…AI(n−1), read against AGND            |
| AGND                | 1               | Analog ground, shared between xBud and mioDAQ                                                         | AI GND                                    |
| REF                 | 1               | Recording reference electrode on the subject (for example, Cz for EEG); used within xBud conditioning | Not separately digitised                  |
| DRL                 | 1               | Driven-right-leg electrode for common-mode noise cancellation                                         | Subject only (not digitised)              |
| Marker lines        | 2               | Driven by the two-button marker box, which cables to the xBud chassis                                 | DAQ digital inputs (e.g. `port0/line0–1`) |

> **Note:** xBud amplifies every electrode, including REF, differentially against AGND, then amplifies the EEG electrodes against REF. The common-mode signal drives the DRL electrode for noise cancellation. Read the channels at the DAQ in RSE or pseudodifferential mode against the shared AGND.

> **Note:** Markers can be triggered in hardware (the two-button marker box) or in software (a BXI Studio keypress).

### NI mioDAQ (USB-6451)

| Parameter         | Value                                                             |
| ----------------- | ----------------------------------------------------------------- |
| Form factor       | Terminal block with spring terminals and back-shell strain relief |
| Weight            | 598 g                                                             |
| Connector to host | USB-C (locking, 2 m cable supplied)                               |
| Terminal access   | Spring terminals; NI screwdriver supplied                         |
| Dimensions        | *To be confirmed* (from the NI USB-6451 datasheet)                |

## Power

| 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 (the NI mioDAQ is USB-C bus-powered)                           |                                                       |

> **Warning:** xBud carries a 3 kV power isolation barrier, but it is not certified to IEC 60601-1 and is not characterised for patient leakage current. It is a teaching aid, not a medical device. Read [Power & Safety](/xbud/technical-guide.md#power-and-safety) before connecting any subject.

## Environmental

| Parameter             | Value                 |
| --------------------- | --------------------- |
| Operating temperature | Not yet characterised |
| Operating humidity    | Not yet characterised |
| Storage temperature   | Not yet characterised |
| Altitude              | Not yet characterised |
| Pollution degree      | Not yet characterised |

## Regulatory and safety

| Item                          | Status                                                                                                                          |
| ----------------------------- | ------------------------------------------------------------------------------------------------------------------------------- |
| Intended use                  | Research, education, and prototyping only, not a medical device                                                                 |
| Diagnostic use                | Prohibited                                                                                                                      |
| Electrical isolation          | 3 kV barrier in the power supply. Not certified to IEC 60601-1. See [Power & Safety](/xbud/technical-guide.md#power-and-safety) |
| Certifications and compliance | See the regulatory portal link below                                                                                            |

## Ordering information

| Variant         | Channels              | Typical use                        |
| --------------- | --------------------- | ---------------------------------- |
| xBud 4-channel  | 4 EXG + REF/AGND/DRL  | Entry: ECG, EMG, single-region EEG |
| xBud 8-channel  | 8 EXG + REF/AGND/DRL  | Intermediate multimodal            |
| xBud 12-channel | 12 EXG + REF/AGND/DRL | Multi-region EEG                   |
| xBud 16-channel | 16 EXG + REF/AGND/DRL | Advanced BCI and dense montage     |

### Subject interfaces

Order any or all of the four interfaces with any channel variant. The interface determines where electrodes sit on the body, not what the front-end does.

| Interface       | Modality                  | Contact type                                           |
| --------------- | ------------------------- | ------------------------------------------------------ |
| EEG cap         | EEG, full montage         | Comb contacts through hair, disc contacts on bare skin |
| EEG headband    | EEG, frontal or occipital | Comb and disc contacts                                 |
| EMG armband     | Surface EMG               | Disc contacts                                          |
| ECG chest-strap | ECG                       | Disc contacts                                          |

### What's in the box

* xBud AFE in the selected channel variant
* Standard Ag/AgCl coated dry electrode set (comb and disc contacts) and lead cables
* The subject interfaces ordered: EEG cap, EEG headband, EMG armband, ECG chest-strap
* xBud line-power adapter
* Marker box (two buttons with LEDs) and connecting cable
* A supported DAQ (NI USB-600x, NI mioDAQ, or NI cDAQ) with its cable and terminal accessories
* Jumper wires for the xBud-to-DAQ connection
* BXI Studio software access

## Software

| Tool                          | Purpose                                                           |
| ----------------------------- | ----------------------------------------------------------------- |
| BXI Studio                    | Primary acquisition and visualisation                             |
| NI-DAQmx driver               | Required runtime; install before BXI Studio can detect the mioDAQ |
| NI-DAQmx APIs (Python, C/C++) | Programmatic access to the mioDAQ                                 |

See [SDK & Dev Resources](/xbud/technical-guide.md#read-the-daq-programmatically) for code examples.