Assembly

IMU (Inertial Measurement Unit)

This guide is using the LSM6DSV IMU from Mofflab

When your IMUs arrive assuming they are LSM6DSVs ordered from Mofflab they will arrive connected like the following:

Tip

Avoid splitting your IMUs apart straight away. Leaving them connecting will help for the initial steps

Protective Taping

Applying tape

To protect the IMU that will be tightly stacked on top of the rest of our electronics we want to apply Kapton Tape to the back of the IMU to ensure that no contacts are shorted against the board underneath it

Tip

Try to line up the IMU with the left side of the tape as this will make trimming it down easier

Trimming down the tape

After applying your tape trim down the tape with scissors or a sharp craft knife so that it matches the size of the IMUs

Splitting IMUs

Now that you’ve taped your IMUs you can split them apart, I recommend running a sharp knife across the dividing lines to split the tape and loosen then bond before gently bending until it snaps off

Magnetometer soldering

The LSM6DSV chip has its magnetometer disabled out of the box through jumper pins, if you plan on using them you will need to connect these pins. If you don’t want to use the magnetometer you can skip this step.

Note

The power drain from connecting the magnetometer is negligible and can be freely enabled and disabled in software with a single if it doesn’t work well for you so I recommend connecting it anyway.

For more information on the difference between using a magnetometer (9 DOF) and not (6 DOF) you can continue reading Here

Some important snips from the above documentation:

“IMUs with a magnetometer, like a compass, use the Earth’s magnetic field as a reference point to reduce gyroscope drift, however they require a stable magnetic environment or else they will perform erratically.”

“IMUs without a magnetometer don’t require a stable magnetic environment, but are prone to gyroscope drift over time due to being unable to differentiate sensor noise from actual movement.”

“For SlimeVR’s purposes, neither is inherently better or worse than the other.”

To connect the magnetometer you must bridge pads 5, 6, 7, and 8 like so:

Pre-Soldering the IMU

This step has been designed by ibis-trackers to avoid damaging other components when connecting your IMU. This step uses the Soldering Cube model to assist with aligning and soldering pins.

Preparing Pins

Your MCU board should have come with set of pins, we will be using these to connect our MCU and IMU together.

Take your pins and split them into 6 + 6 + 1 (Each row should have 13 pins) like so:

Once you’ve split the pins you’ll need to push down the plastic covering till the pin is barely sticking out the bottom like so:

Preparing your solder cube

First place your IMU in the top of the soldering cube, the side with the most pins should be facing outwards towards the open side of the cube like so:

Next place the pins you cut so that they sit in the following holes on the soldering cube, the pins should line up with the outer slits on the IMU DO NOT place them through the holes on the IMU.

Only the last 6 pins should line up, skip the first pin on the left:

Solder the pins

You can now solder the pins to the pads on the IMU:

Remove the IMU from the soldering cube

Now that you’ve finished soldering the IMU you can remove it from the soldering cube and remove the plastic casing from the pins:

MCU (Microcontroller Unit)

The board used for this tracker is the SuperMini (ProMicro) nRF52840

Flashing Firmware

The firmware flashing guide has not been created yet

Pre-solder points

We are going to pre-solder some points ahead of time on your MCU in order to make things easier for later steps.

These points are:

• B+ & GND - Battery terminals
• 006 & GND - Button
• C3 - Wire mod (For improved signal)

Solder the button

Connect your button to the 006 and GND pins that you soldered in the previous step you can do this by the button ontop of the solder using a pair of pliers then heating the pins and the solder to push the button into the solder ball:

Combining

First side

You can now combine the IMU and the MCU. Place the IMU on top of your MCU placing its pins through holes 017 through to 100, the LSM6DSV label should be facing in the same direction as the USB-C port like below:

Push your IMU through the MCU holes until it is fit snug against the MCU:

Now you can flip the board over to the bottom:

And snip off the pins until they are flush with the bottom of the MCU:

Solder the snipped pins to the underside of the MCU:

Your tracker should now look like this:

Second side

Next we need to connect 002 on the MCU to the corresponding pin on the IMU

Bending the spare pin

Take the spare 1 pin from the pins that we split previously and create a 90deg bend at the top and remove the plastic from the bottom like so:

Solder the pin

Insert the pin through hole 002 on the MCU ensuring the bent portion connects with the IMU like so:

Then flip the tracker over and solder the pin from underneath the board, ensure the pin doesn’t rotate while you are flipping it or soldering it:

Once you’ve soldered the bottom solder the top portion to the IMU

Make sure you snip off the rest of the pin at the bottom so that its flush to the MCU, you may need to resolder hte bottom after making it flush.

Test

The testing guide has not been created yet, but at this point it would be a good idea to use a serial console with the tracker plugged into your computer to test that the tracker is detecting your IMU and Magnetometer

Wire mod

Cutting wire

Next to improve the signal strength of our MCU (“SuperMinis have horrendous signal strength by themselves”) we will cut a piece of wire to act as a antenna.

Cut around 33mm of your wire for however many trackers you need:

After cutting your wire strip ~1mm of the casing from the end of the wire

Now you can solder your wire to the MCU in the following spot:

Battery

Now all thats left to solder is your battery:

Connect the red wire from your battery to the B+ pin on the MCU that you’ve soldered previously and the black wire form your battery to the GND pin under the B+ like so:

Tip

Ensure you solder the wires angled to the left side of the IMU as shown in the photo as this is where the battery will sit within the case and your pins will not fit / will snap due to case clearance if you solder them to the right

Case

Your tracker is now complete you can stick it into your case now:

Important

Ensure that you route your power wires around the button, if they overlap with the button they can make it hard / impossible to push the button with the case lid on

All done

Now its time to Pair & Calibrate your trackers