8 Wiring P9
hut edited this page 5 months ago

How to wire up a Prototype 9?

Step 1: Start

Start with the bare boards:

photo 1

Step 2: Power

Take a cable with 3 plugs, choose one of the pin triplets on the power board that say "GND V+ Vref", and connect them with one of the same pin triplets on the first electrode board.

Don't push them in too hard, the plugs might break.

IMPORTANT: Make sure that the colors match up. E.g. if, on the power board, you use brown for GND, red for V+, and orange for Vref, then use the same colors for the same pins on the electrode module.

Then do the same with any other electrode modules you might have. The electrode modules have a second set of power pins, so you can chain them together, drawing power for the 2nd electrode module from the 1st, and so on. Doing so introduces more noise than using the power pins of the power module though, so unless you have more than 3 modules, it's recommended to use the power module's power pins only.

photo 2

Step 3: Signal connectors

Now, take a cable with as many plugs as the number of signals you want to use from the first electrode board. If the board is outfitted with the maximum number of 4 amplifier chips (the big black ones), then you can choose to use all 4 signals, otherwise you are limited to the signals that your electrode board provides.

Plug The cable into the connector on the electrode board that says "J3". Examples:

  • If you want to use all 4 signals, plug the cable into all 4 of the pins (see next photo)
  • If you want to signal 1 and 3 (which are the two electrode pairs on the left side,) then plug the cable into the first and the third pin of the J3 connector only

Then plug the other side of the cable into any of the pins on the power module that are labeled "A0" through "A7" (The "A" is for "analog", whereas the pins that start with a "D" are "digital" pins). It makes sense to plug the first plug into "A0", the second in "A1", and so on, but this is really up to you.

photo 3

Then repeat this with any other electrode modules you might have:

photo 4

You might notice that you can only use up to 8 signals. If you have more than 8 signal sources, you must select which ones you wish to record. Alternatively, you could use more than 8 signals by building an analog multiplexer board using the exposed digital pins on the power board, but this is not officially supported at the time of writing.

If you attempt to use signals that your electrode module doesn't provide, nothing bad will happen. The Arduino will just receive noise on that channel.

Step 4: Arduino

Plug in the "Arduino Nano 33 BLE Sense". Do not use a different type of Arduino, unless you verified that the pins are compatible. Make sure the Micro-USB connector of the Arduino points to the left, as shown on the photo:

photo 5

NOTE that the solder jumper with the label "3.3 V" on the backside of the Arduino needs to be cut, otherwise the Arduino will only accept power from the USB wire and not from PsyLink's battery. When cutting the solder jumper, use a small and sharp object very carefully to cut the thin connection between the two large pads. Please take care to not cut yourself and to not damage any other part of the Arduino.

photo 5.5

Step 5: Battery

Plug in the battery. Any AAA (mignon) battery with a voltage between 1V and 5V should theoretically work, but rechargeable 1.2V NiMH batteries are recommended.

Please pay attention to the polarity, the plus-side should go right.

photo 6

Step 6: Straps

Close the straps with the safety pins.

You may need to experiment which tightness works best for you. Please avoid hurting yourself by making the straps too tight.

photo 7

Step 7: Putting it on

First of all, do not use PsyLink on any living organisms. The following is just theoretical and anecdotal documentation and no instruction manual.

There's no one "right" way to wear the PsyLink. One way would be the following:

photo 8

Here, the power module rests in the middle of the radius bone and the electrode modules on the flexor digitorum superficialis muscle (the one that flexes your fingers.) This is an interesting setup, because most of the arm muscles produce movement of the PsyLink device itself, which can be picked up by the inertial measurement unit (gyroscope, accelerometer), but the finger movements can't be picked up by those instruments as easily. Placing all of the electrodes onto finger-controlling muscles then gives the biggest range of sensory data.

There are many other interesting places though, feel free to experiment. On non-living organisms, of course.

The author found it comfortable to put on the PsyLink by pushing the elastic straps apart with the fingers of the right hand, and then sliding the left hand and arm through the hole.

Please pay attention to not hurt yourself or damage your clothing with the exposed pins.

Note that some of the legs of the power module serve as "ground" electrode. You can tell by looking at which solder jumpers at JP4 through JP8 are closed. A firm connection between a ground pin and the skin results in better signals. If you use external electrodes instead of wearing the PsyLink directly, you may consider plugging an additional electrode on a Vref pin of the power board and use that as a ground electrode instead.

What now?

Once the PsyLink is properly wired, you need to establish a bluetooth connection with a Linux computer to receive the signals. This is described in the documentation on GNURadio.