The headset will not only be in charge of showing you the image and relaying back rotation data from it's internal IMU, but it will also be in charge of receiving the RF Controller data and sending it back to the computer. Another thing that can be integrated into the headset is an USB Sound Card, that way it'll also have an integrated Microphone and a headphone jack for you to plug your headphones in. Though it's not mandatory.
I plan on eventually making a custom pcb for the headset that includes a 2 port USB hub, an audio interface for headphones and microphone integration, and maybe a couple other goodies like an attempt at backlight strobing to reduce screen blur.
For the shell you can use any "Phone VR" enclosure, they come in very different qualities but all of them should do the trick (even the carboard ones). Keep in mind the enclosure will dictate your max fov and that you can always modify the shell to allow for a wider fov.
You could also 3d print the shell, like the guys over at Relativty did. Keep in mind you'll also need to source your own lenses with the correct focal length and head strap.
As the main microcontroller I suggest sticking to stuff that supports the Arduino HID library. That means:
- Arduino Leonardo
- Arduino Pro micro
- Arduino DUE (code might require some modification since it doesn't support EEPROM.)
An ideal candidate is the Arduino Pro Micro since it's based on the Atmega32u4 which is the microcontroller used on the Arduino Leonardo and it's fairly small.
Also needed are:
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An MPU9250 to gather rotation data (though you could use any IMU that's fast enough and can output rotation data to quaternions if you modify the code a bit to allow for that).
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An NRF24L01 to receive the controller data from both controllers*
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A 5v to 3.3v voltage regulator to power the NRF24 module*
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A High brightness LED that's a different colour from the ones used on the controllers (I suggest green) and a resistor for that LED for blob tracking (also needed is a white ping pong ball to put the LED into)**
*: Only needed if you're also building the controllers. **: Only needed for 6dof tracking.
There's a couple different displays you can use for this headset, anything from 4.5 to 6 inches should work just fine. As of right now, using a phone with ALVR or RiftCat or whatever isn't supported though.
You can find these screens on Aliexpress, but make sure what you're getting is what you think you're getting. Ask the seller if the screen AND the driver board support the resolution and refresh rate they advertise.
Most of these screens come with a Blue driver board based around the Toshiba TC358870XBG, be skeptical of these boards since they support a huge multitude of displays at different refresh rates and resolutions, some sellers even claim they can drive two displays at 90hz.
There's a couple different versions of these blue driver boards, the most common one based around the TOSHIBA chip, the other one based on a clone of said chip.
Some screen options are:
With this option you'll have to purchase the display and board separately. Make sure you choose the right display to go with the right board (LS055R1SX04 lcd won't work with LS055R1SX03 board) and make sure the display has a backlight before purchasing since these are usually used for resin 3d printers.
These screens are 1440x2560(vertical), they officially support up to 60Hz but with the board linked below they can be pushed to around 72hz without artifacts.
The board is meant to run the display at 60hz but it can easily do 72hz if you create a custom resolution in nvidia control panel or amd's driver settings thing.
These screens are 1440x2560(vertical), they officially support up to 60Hz but depending on the driver board they can be pushed to around 65hz without artifacts (this depends on the driver board).
These are reasonably cheap since they're commonly used in resin 3d printers and can be found for around 50USD.
You can find these boards by searching with the terms "5.5 LCD MIPI"
These screens are 1080x1200 per eye (2160x1200) and they claim to run at 90Hz. They use the Blue driver board and the screens are 3.81 inches each and use AMOLED displays.
These are a lot more expensive than the last one and can be found for around 170USD for the pair of screens + driver board You can find these boards by searching with the terms "90Hz VR LCD"
These screens are 1440x1440 per eye (2880x1440) and run at 120hz. The use a different driver board that uses DisplayPort as a video input and the displays are 2.9 inch IPS LCD.
These go for around 180USD for the pair of screens and driver board, making them a better purchase than the dual AMOLED if you're looking for high refresh rate.
You can find these boards by searching with the terms "120Hz VR LCD"
Circuit pins for the Arduino pro micro are as follows:
⚠️ IMPORTANT: YOU NEED A 5V TO 3.3V REGULATOR TO POWER THE NRF24 MODULE, THE PRO MICRO DOES NOT SUPPLY 3.3V ON ANY OF ITS PINS
To upload the firmware you will need to have the FastIMU (also available on the Arduino library manager) and the RF24 Arduino Library installed in your Arduino IDE.
You can download the required library using the Libraries manager from within the Arduino IDE. The rest of the used libaries are already included in the firmware folder.
The steps to upload the firmware are as follows:
- Open Headset.ino inside the Software/Firmware/Headset folder
- Select "Arduino Leonardo" as the board if you're using an Arduino Pro Micro
- Select the correct COM port for the board
- Press the Upload button, if all goes well, you can move to setting the correct COMPort.
To configure the driver you will need the VID and PID values from the board you're using. The easiest way of getting them is going to the Arduino IDE, clicking on tools and clicking on get board info with the HMD plugged in:
Do note these values are in HEX so to use them in the driver config file you'll need to convert them to decimal numbers. to do that you can use websites like Rapidtables, just input your VID and PID values one at a time and convert them to decimal numbers.
Once done, you'll get values like these and then all you have to do is load them up in your driver config file. For more details on driver configuration, check out the driver configuration docs
