Device configuration

A device is configured through the configure commands (which sensors are enabled, their sampling rates and filtering, the memory mode, and more). This page explains when that configuration takes effect, what the settings do, the defaults SiFi Bridge applies when you don't specify a parameter, and the separate on-device configuration used by button-initiated acquisitions.

How configuration is applied

You stage configuration while connected with the configure commands, but it is only pushed to the device when you start an acquisition (start). Each configure command updates only the parameters you pass; everything else keeps its current staged value.

Any parameter you never set falls back to SiFi Bridge's default. These defaults are provided by SiFi Bridge itself. They are not read from the device. They are chosen to be suitable for most use cases, so you can start an acquisition without specifying every parameter.

Inspecting the applied configuration

Use info to see the configuration currently applied to a connected device. This is the source of truth for what your installed version actually applied.

Defaults

Default sampling rates applied by SiFi Bridge per sensor. EMG differs between devices: the SiFiBand carries an 8-channel EMG array, the BioPoint a single channel.

Sensor	Enabled by default	Default sampling rate (BioPoint)	Default sampling rate (SiFiBand)	Other configurations
ECG	Yes	500 Hz	500 Hz	0-30 Hz bandpass, 60 Hz notch, DC notch on
EMG	Yes	2000 Hz	1600 Hz	20-450 Hz bandpass, 60 Hz notch, DC notch on
EDA	Yes	50 Hz	50 Hz	0-5 Hz bandpass, 60 Hz notch, DC notch on
PPG	Yes	50 Hz	50 Hz	200 sps, 4 avg, all LEDs 9 mA
IMU	Yes	100 Hz	100 Hz	Bandwidth 170 Hz, Acceleration range ±2 g, Gyroscope range ±16 dps
Temperature	Yes	1 Hz	1 Hz	—

PPG has no --fs

Unlike the other sensors, PPG is not configured with --fs. Its optical front-end samples at a raw rate set by --sps, and consecutive samples are averaged in groups of --avg, so the effective output rate is --sps ÷ --avg. The defaults of 200 sps and 4 avg are what produce the 50 Hz shown above (200 ÷ 4). The effective rate is also reported live in each packet's sample_rate. See configure ppg for the accepted values.

Other defaults

Setting	Default	Notes
Memory mode	both	SiFiBand only supports streaming.
Low-latency mode	on	Enabled by default.
High gain	off	Applies to the ECG and EMG ADC.
BLE power	high
Night mode	off

What the settings do

The accepted values for every option live in the command reference. This section explains the settings whose effect or tradeoff isn't obvious from the name, so you can choose values deliberately.

Filtering (ECG, EMG, EDA)

The three biosignal sensors share the same filtering knobs, applied on-device:

• DC notch removes the constant DC offset and slow baseline drift, keeping the signal centred. Leave it on for most recordings; turn it off when you need the untouched baseline.
• Mains notch rejects powerline interference. Set it to your region's mains frequency — 60 Hz in North America, 50 Hz across much of Europe and Asia — or off if you reject mains downstream.
• Bandpass (with its low/high cutoffs) keeps only the frequency band of interest and discards the rest. The useful band differs per signal — narrow ECG (e.g. ~0.5–40 Hz) versus wide EMG (e.g. ~20–450 Hz).

The global configure filtering switch turns on-board filtering on or off; with it off, sensors report raw, unfiltered samples.

Gain and sensitivity

• High gain (high-gain) raises the ECG/EMG ADC gain: it resolves small signals more finely, at the cost of less headroom — large signals saturate (clip) sooner. Leave it off unless your signal is weak and you know it won't approach the rails.
• PPG sensitivity (--sens) is the analogous tradeoff for the optical front-end: higher sensitivity captures weaker reflected light but saturates sooner.

PPG LEDs

• The per-wavelength LED currents (--led-ir, --led-red, --led-green, --led-blue) set how hard each LED is driven. Raise them to recover signal on darker skin or a looser fit; lower them to avoid saturating the photodetector and to save power. Set a wavelength's current to 0 to disable it.
• PPG's output rate comes from --sps and --avg, not --fs — see the note above.

IMU ranges

• Accelerometer and gyroscope ranges (--acc-range, --gyro-range) set the full-scale measurement span. A smaller range gives finer resolution but clips during large or fast movements; pick the smallest range that won't saturate for your activity.

EDA excitation (--freq)

• Selects DC (0) versus an AC excitation frequency. Use DC for classic electrodermal activity / skin-conductance measurements, and a nonzero frequency for AC bioimpedance.

Link and runtime

• Low-latency mode packs samples from multiple sensors into a single BLE packet to minimise latency, at some cost in packet overhead. Typically always worth it unless limited by bandwidth.
• BLE power trades battery life for range and link reliability; raise it if you see dropouts at distance.
• Night mode disables the device's LEDs during an acquisition (e.g. for sleep studies).

On-device saved configuration

The defaults above, and any configure commands you issue, only apply to acquisitions started over the connection with start. Button-initiated acquisitions — started with the device's physical button rather than the start command — instead replay a configuration stored on the device.

To set that stored configuration, apply the configuration you want and start the acquisition with --set-default:

> start --set-default

Every subsequent button-initiated acquisition then uses that saved configuration. See start for details.