configure BioEra for the E-wiz

This is an introductory description. The full description of Wiz devices can be found under the Manuals tab.

The E-wiz is a two channel ExG bio-signal acquisition device, where ExG refers to EEG, ECG, EMG and SCP Modalities. It is equally a wireless and USB-direct device. As wireless, two AA batteries are to be inserted and a wireless kit is to be separately purchased. As a USB-direct device, batteries are optional. If batteries are inserted then power is not drawn from the USB port. This means when teamed with a tablet or smartphone, the E-wiz does not drain the batteries of those devices. The choice of wireless or USB-direct is automatic: if the E-wiz receives power from the USB port then it will transmit over the USB -direct link. If not, it will commence transmitting wirelessly. The Transmit link is steady on when not transmitting wirelessly, and will blink when wireless is active. The number of blinks indicate the wireless channel number and this must be matched by the wireless dongle receiver.

The E-wiz supports continuous electrode impedance measurement and electrode offset voltage measurement. ExG signals can be AC or DC coupled, and the two electrode references can be electronically linked

The E-wiz has an 8-LED array which reflects the state of EEG channel 1 at any instant.  This can be particularly useful when the device is in wireless operation.

Functions on the E-wiz are controlled by a Power button and two configuration buttons: a Mode button and a Link/Freeze button. Note however that all functions, indeed some additional functions as well, can be controlled from the Application, whether that application be BioExplorer, BioEra, EEGer, or Wiz Central. In general, it is easier to command the Wiz from the Application rather than navigate many functions applied to just two buttons. As a consequence this introduction will focus on commanding the Wiz from the Application. Information on using the buttons on the Wiz can be found in the User Manual.

“Mode” refers to the characteristics of the channels used to transport the bio-signals from the Wiz to the Application. Mode defines the sampling rate and the number of channels. “Modality”, on the other hand,  refers to the different types of bio- signals supported, such as EEG, EMG, and ECG. Different modalities place different demands on the channel supporting them, thus for example, SCP can be supported on a low sampling rate channel and EMG demands a high sampling rate channel. The Wiz provides different Modes to optimally support different Modalities on up to four slots available for sending bio-signals to the Application.

Since the Wiz remembers certain parameters including Mode, in the most common usage scenario of  single channel & single modality, operation reduces to

  • connect the sensors,Ewiz_layout01
  • turn on the Wiz, and
  • hit the play button on the Application.

The Modes available are listed below. The Mode light on the Wiz will blink once for Mode 1, etc.

 

E-wiz Modes

<Mode 0> program mode – used to upload new firmware or interrogate firmware version number

<Mode 1> 2ch x 32sps – (EEG protocol processing – future)

<Mode 2> 2ch x 128sps – Hi resolution EEG

<Mode 3> 2ch x 512sps – EMG, ECG, Othmer and SCP  – higher bandwidth, lower sensitivity.

<Mode 4a> 4 slots x 256sps – ch 3 & 4 used for electrode impedance of ch 1 & 2

<Mode 4b> 4 slots x 256sps – ch 3 & 4 used for electrode offset of ch 1 & 2 – invoked by command from the Application

In each Mode, the content on the two/four slots being sent to the Application depends on which sensors are active (ie plugged into the Wiz). In general, the design controlling the Application trains a particular Modality and therefore expects a particular Mode. The Mode expected should constitute part of the name of the design. The user should then set the Wiz to the Mode expected by the design. The table below is provided for reference.

configurationSlot 1Slot 2Slot 3Slot 4Comment
Mode 1/2/3
EEG1EEG2
Mode 4a
EEG1EEG2EIM1EIM2continuous electrode impedance measurement
Mode 4b
EEG1EEG2Offset 1Offset 2continuous electrode offset measurement

The lights on the Wiz can be used to confirm that commands sent from the Application have been received:

Indicator 
Transmit (blue)
On steadysending to Application via USB
On blinksending wirelessly
Off blinknot transmitting to Application (ie Program Mode)
4 blinksacknowledging command received for Application
No of blinkswireless channel number
Mode/Good (green)
Onno EEG lead off, and/or nIR full signal strength, and/or pIR valid reading
OffEEG pair off, or nIR not full strength, or pIR reading out of range
Fast BlinkEEG single electrode off
No of blinksMode 0/1/2/3/4 = Program/32sps(2ch)/128sps(2ch)/512sps(2ch)/256sps(4ch)
Link/Freeze(blue/green)
On blueEEG baseline frozen (DC coupled)
Off blueDC removal - EEG low frequency response ~0.2Hz
On greenEEG References linked - only one Reference electrode required
Off greenEEG References independent - two References required for 2 eeg channel operation

BioEra and BioExplorer interface to the Wiz somewhat differently. Whereas BioExplorer has a pop-up window with a list of commands, BioEra has the functions built into the PN_Wiz element which is embedded in the design. These are treated like other Properties in BioEra elements – they may be set manually at design time and be constants, or be under the control of “events” (like pressing buttons) at run-time.

This leads to two separate approaches to creating BioEra designs for the Wiz:

  • allow the user to configure the Wiz via buttons and menus in BioEra  –  reference the “GP” (general purpose) illustrative designs
  • have the BioEra design automatically sned commands to configure the Wiz as is appropriate for the design  – reference most other illustrative designs

In the latter case, the name of the design will include the Mode which it forces.

Note that the PN_Wiz element is the super-set of Wiz capabilities, so some Properties will be ignored by some models – the design does not know which model it is connected to, but since the Mode that the design expects is built into the design name, the user is tasked with ensuring a design is relevent to the Wiz model being used. Properties also have a “No change” setting which means for that Property no commands are sent at start-up.

PN_Wiz PropertiesWiz_Command_BioEra_Design

  • Power – turn Wiz on & off
  • Link EEG References – electronically connect the two eeg reference electrodes
  • Freeze : EEG DC coupled – instantly directly couple the ExG signal, DC offset removal is inhibited
  • HEG Baseline – initiate search for the HEG nominal value of 100
  • Mode
    • Program – Mode 0:  set this mode to update firmware or interrogate version number
    • 2ch HEG – Mode 1:  not applicable
    • 2ch EEG – Mode 2: set this mode for EEG and minimum load on the PC processor
    • 2ch ExG – Mode 3: set this mode for ECG. EMG, SCP and Othmer protocols, hi bandwidth and reduced sensitivity, Also set “Freeze” for SCP, Othmer & possibly ECG
    • 4ChEEG – Mode 4: not applicable, ignored
    • EEG+Impedance – Mode 4a: 2ch EEG and continuous electrode impedance measurement in ch 3 & 4
    • EEG+Offset – Mode 4b: 2ch EEG and continuous electrode voltage offset measurement in ch 3 & 4
  • Helper functions used occasionallyPN_Wiz_Properties
    • None – revert back to normal mode
    • Impedance Check – interrupt the eeg signals to test for electrode impedance
    • Offset Check – interrupt the eeg to test for electrode offset voltage
    • Self-Test – initiates start-up self-test
    • SigGen – continuous Test Tone
    • HEG Test Mode – not applicable, ignored
    • No Electrode-off sense – turn of the current used to sense electrodes falling off to improve accuracy of DC coupling
  • Radio channel [1-8]
    • USB Only – turn off wireless
    • 1…8 – turn on simultaneous USB and wireless, the latter allows monitoring of the eeg by a monitoring station
  • Buzzer – not applicable
  • TLC 4C Assess – not applicable
  • Debug Command
    • Off
    • Q-wiz force HEG – allow HEG testing without HEG heabdands connected
  • EEG Cap Setup chart – not applicable, ignored

PN_Wiz Advanced PropertiesPN_Wiz_Properties_Advanced

  • Firmware file path – Wiz firmware can up upgraded (see the “update” tab on PN home page
  • Firmware  – after selecting the firmware update file, initiate firmware update here (allow 45 seconds to execute)
  • Current rate – reflects current sampling rate in samples per second
  • Current range – reflects maximum value that can be measured (after DC bias is removed) in +_uVolts
  • Current Mode – reflects current Mode [0..4]
  • Command delay – ensures a nominal 35mSec separates multiple commands. Increase if some commands are being ignored on your machine (processor dependant)
  • Set rectangle size – vary if you are having difficulty selecting sites on the Cap setup chart

 

Interfacing the PN_Wiz element to a USB port

To run a BioEra_For_Android design in Windows (or a BioEra_For_Windows design in Windows), the PN_wiz element gets connected to a “Serial Port” element. In that element you need to set the baud rate to 38400 and set the COM port to the port assigned by windows when the Wiz was first plugged in and a Windows driver installed (see here for details). If the driver was successfully installed you will see the COM port assignment in Windows Device Manager under COM ports. All other setting in the Serial Port element can be left as the defaults.

For a BioEra_For_Android design that will run on an Android device, the PN_Wiz element gets connected to a “FTDI serial port” element. In this element you need to set the VID & PID (USB vendor & product ID) to 0403 & E958 respectively, and set the baud rate to 38400.

This again makes the Android tablet solution relatively straight forward, since

  • in Windows, the User needs toadvise the design of the COM port assigned when the driver is installed
  • in Android, there is no driver and the information needed by the operating system (ie PID, VID & baud rate) is embedded in the design

Modifying or Creating your own designs in BioEra_For_Windows

This is only briefly discussed here since at initial installation, modifying designs is not a priority.

In BioEra_For_Windows, initiate a new “Android Design”. BioEra will then provide to the designer only that subset of elements that are applicable to Android. The design can generally be tested on the host Windows machine or the target Android machine, however note the discussion above about using either the Serial Port element or the FTDI serial port” element to interface to the USB port depending whether the design is running on Windows or Android respectively.

To test on the target Android device, the designer must advise BioEra_For_Windows the IP address of the Android target device. Knowing this, BioEra_For_Windows can download the test design to BioEra_For_Android over the LAN or internet.

To find the IP address of the Android machine, either use the function provided in BioEra_For_Android, namely Overflow Button (upper right corner) | Other Options |Show Device Info, which will display “Android Host: 192.168.1.23” or similar, or go into the Android Settings | WiFi | [currently active wLAN], and it too will display the IP address.

Enter the IP address of the target Android device into BioEra_For_Windows | Android | Connection settings. The “Android Device Port” field does not need to be changed.

Checking the validity of bio-signals

There are a few things in the Wiz to enable you to check it’s health.

  • for ExG  (applicable to EEG, ECG, EMG and SCP)

First item is the “Test Tone”  Helper function. This is available in the Wiz window in BioExplorer under Helper functions:  Test Tone.

If ExG is active, the Test Helper function injects a tone right at the input of the Wiz, so in general, if the Test function is working, then the Wiz is working. If the Test signal is fine, but the EEG is flat-lined, then the first thing to check is that “Freeze” blue light is off. Freeze is switched on for working with SCP (& ERPs), Othmer low frequency protocols, and possibly ECG. Activating the Freeze function puts the Wiz into its DC-coupled mode. This means that the offset removal that is normally in place, acting to return the EEG signal to an average of 0 microVolt is deactivated. If Freeze is switched-on whilst the EEG is out of range, not yet having fully restored itself to an average of 0 microVolt, then it will stay out of range indefinitely. That is, the EEG will be flat-lined. For this reason the Freeze state is not remembered by the Wiz – each time the Wiz is started, it starts with Freeze off.

Also, if using one-channel EEG designs, you must use Channel 1 (aks 1+/1-, aka Left). If you use Channel 2 (or 3 or 4) without using Channel 1, then the feature of actively suppressing 50/60Hz interference is lost.

If these conditions are satisfied, then one should look to problems with the electrodes themselves.

In relation to electrode performance there are several layers of defense.

  • First, the Red/Green information in the Status Bar of BioExplorer, give “electrode off” indications. This will actually identify which electrode has fallen off using the following code
    • steady red light – both electrodes are off (or that channel is not in use)
    • flashing red light – one of the pair of electrodes is dislodged

Linking reference electrodes can then distinguish which of the pair of electrodes is dislodged

    • if the flashing red light persists when electrodes are linked, then it is the active electrode that has dislodged
    • if the flashing red light goes steady green, then it is the reference electrode that has dislodged.
  • Second, there are two Helper functions related to checking electrodes:
    • “Impedance Check” and
    • “Offset Check”.

Electrode impedance is a measure of the goodness of the contact of the electrode with the skin. Poor contact will result in a noisy EEG and quite possibly a large increase in 50/60Hz power line interference which too can lead to flat-lining. EIM is a measure of the impedance of an electrode pair, not a single electrode. So values under 20kOhm can be considered good and up to 50kOhm is quite serviceable. Offset Check is a measure of the voltage generated by the metal electrode together with an electrolyte  (the paste) onto the skin. All metals will generate this voltage with Ag/AgCl electrodes having the lowest voltage. EEG systems are designed to tolerate this relatively large voltage, however gold-plated electrodes, when the gold plating wears or is otherwise compromised, exposing a different base metal, produces a particularly severe offset voltage that can cause the EEG to intermittently flat-line. Gold electrodes are not recommended. The Wiz can tolerate offset voltages +-250mV and so should not be an issue if gold electrodes are not used.

Mode 4a and 4b allow EIM and Offset respectively, to be monitored continuously. However if not in either of these Modes, for instance if using Mode 4 for 4ch EEG, then EIM and Offset measurement (in this case for 4 channels) is invoked by selecting the Helper function Check Impedance and Check Offset. Once the measure is obtained, then Helper functions are set to Off, and the normal ExG operation is restored.