CR Single-Cable Project North Star Variant Kit

Purchases of this kit will help fund development of a mass production North Star derivative. 

This is a new Single-cable (USB Type-C) Project North Star variant kit, cost-optimized with an example of lightweight and modular headset design.. The use of a single cable and its modularity are the biggest differences with the previous version. The individual parts are as follows: 

Electronics

Display Driver Board

• USB-C with DisplayPort Alt-Mode (Not all USB-C host ports support DisplayPort; please make sure in advance that your intended host device has at least one that does.)
• Using same 3.5” 1440 x 1600 VS035ZSM-NW0-69P0 displays from BOE (Grade B*)
• LT7911D display controller (good relationship with manufacturer, good support, and a stable supply)
• The D variant of the LT7911 series has two MIPI outputs, while together the displays have four. We’re pushing the limit of what a single 4-channel MIPI port can handle, with the benefit of using 25-pin ribbon cables with only half the pins of their predecessors.
• Low-cost alternative to original board, but with 85 – 90Hz maximum stable refresh rate
• Support for audio output
• USB 2 (High-Speed) passthrough to downstream hub or direct peripheral connection
• Backlight brightness control (can be switched off entirely) with non-volatile settings. When you plug in headset, it has the same brightness as when you unplugged it. You can use a microcontroller to adjust the brightness, but you don’t need one connected for the display and backlight circuitry to work.
• 8-pin ribbon connector for future I2S stereo audio output breakout board

USB Hub

•  Connects to display driver board and doesn’t require any additional external cables
•  4-port USB 2 High Speed Hub with FE1.1 controller IC.
•  1A integrated fuse with 1.5A cutoff
•  3x 6-pin ribbon connectors for USB 2
• 1x 12-pin ribbon connector for USB 2 with passthrough connection to display driver board’s backlight brightness control pins and one GPIO pin connection for switching power to one of the 6-pin ports (for resetting any finicky sensors with enumeration issues like the T261.)

Note: We’re including a 12Pin breakout board, users can connect an arduino board to adjust the display's brightness. (Power output on the hub’s 12-pin USB header is 5v, so it should be connected to the VREG / RAW input of any 3.3v or 1.8v microcontroller boards.) Future plans include a purpose-built microcontroller board that will be purchasable separately.

Our new North Star Combiner!

Mechanical Design

Introduction about Modularity

Electronics Modularity

• Driver board: Breakout Audio ports and Brightness controlling pins
• Adapters, the kit includes several USB adapters so that you can connect it to a variety of different sensors that are in use in the North Star community:
  - USB-C male connector supporting USB 2 High Speed, with both 6-pin and 12-pin ribbon connectors for direct connection to the Display Driver board or to one of the 6-pin connectors on the PNS Hub board.
  - MicroUSB male connector with upstream 6-pin connector; similar to and compatible with the MicroUSB adapter included with our older kits. Works with PNS Hub board.
  - Ultraleap SIR170 / Rigel adapter with upstream 6-pin connector for use with our PNS Hub board.
  - T261 USB2 High Speed adapter with 6-pin connector. (Note, with USB2 bandwidth, you won’t be able to stream video from the T261 when used concurrently with an Ultraleap or Leap Motion hand-tracking module. You can, however, get a low-latency stream of the 6DOF tracking data generated onboard the device.) The Realsense T261 has been discontinued by Intel, but can still be found. We include this adapter mainly for the convenience of those North Star builders who already have this module.
• Planned microcontroller board (to be sold separately):
  - Brightness control
  - Eye-tracking (Experimental and in development)
  - Additional sensors (like 3DOF with IMU or ambient light sensor)
  - User interface (like configuration buttons)
  - Compatibility with planned magnetically-coupled module connectors
  - Mechanical Modularity
  - Easily removable and swappable core electronics bay and sensor pods
  - Snap-together / snap-apart design

 

Mechanical Modularity

• Easily removable and swappable core electronics bay and sensor pods
• Snap-together / snap-apart design

Main parts specifications:

• Input Interface: USB-C DisplayPort Alt-Mode (requires host port compatibility; a full-featured USB-C 3.2, Thunderbolt 3 or better, or spec-compliant USB 4 are all safe bets)
• Displaying Resolution: 2880x1600 pixels (2x 1600x1440 Displays)
• Frame Rate: 85-90Hz
• Support Brightness control by adjusting digital potentiometer (Microchip MCP4021T-503E/MC)
• Driver board Board dimensions: 
• USB hub speed: Max 20-30MB/s
• Max useable USB2.0 high speed downstream ports: 4
• 4 Downstream ports, 3 with 6P Connector, 1 port with power switch controlled via the 4th port(12 Pin Connector)
• USB Hub board dimension: 

• Considerations re: open sourcing display driver board files
  Our display driver board is marked with a Creative Common License, and we fully intended, and still intend to publish the full KiCAD design files for this PCB. Unfortunately, since having the PCBs fabricated, we had to turn to one of the IC suppliers for support and non-public documentation. This entailed signing an agreement that currently precludes the publication of anything derived from what we’ve received from them. We’re working on a redacted version of the files, and hope in the future to be able to release at least the full layout files. At the moment, we think that pushing to release the files would compromise our relationship with the vendor and lead to them withholding future support while still leaving us bound by the terms of the agreement we signed. The agreement does allow us to publish materials with their permission, but pushing for that permission needs to wait until we’ve demonstrated that we can sell enough units to place larger component orders, and support our users directly without creating a load on the IC vendors support team. We realize the inherent paradox in this, which is that we can’t provide support by way of documentation, which is exactly what might cause user’s to contact the chip vendor directly. Please don’t. The board works, we believe we’ll be able to provide firmware updates in the future and, for now, it is what it is. If we haven’t resolved this by the time we produce new PCBs, we’ll remove the CC-BY-SA license marking from the board. It is not our intent to mislead members of our community, and are fully aware that the current situation is not in keeping with the ethos of Project North Star. We apologize, and will update the community here and on the PNS Discord server if there is progress on this front. We do not, however, believe that we are currently in technical violation of the Creative Commons CC-BY-SA 3.0 license.
  Our display ribbon adapter, hub and usb adapters are all open source, with published KiCAD files.
  
  
• Disclaimer about condition of grade B displays
  The displays included with our kits are not in new or perfect condition. This is why we’re able to offer them at this price. Almost all of them have minor bruising of the LCD in the location pictured here, and many have small additional imperfections. We tested an insanely large number of these so-called “Grade B” displays by hand, and rejected at least half of them. The ones we accepted are the ones that we believe can be used in a Project North Star headset without it significantly affecting the quality of experience that is possible with the headset, but it was a process that involved subjective judgment. We did not accept any displays with what we considered to be major blemishes, many blemishes, or blemishes at the center of the viewing area. Because of the nature of these displays, they are sold without warranty and are not returnable. Please see the product page for the individual displays for pictures of the kind of imperfections that you might see. For the price of a single new “Grade A” display, you can buy at least five of these.
  
  
• RTFM!
  Do not plug in your display driver board without first full-reading and understanding the assembly guide. Both the 6-pin and 25-pin connections are capable of permanently damaging your hardware if not connected properly. We are not liable for replacement of items damaged in this way.

Links: 

• Project North Star Discord Server
• Project North Star Assembly Guide
• Source files on Github
• Project North Star Leap Motion Github
• Project North Star Sensor Selection Guide