Tron Identity Disc upgrade.1

Upgrade a Tron Identity Disc with: RPI Zero, WS2812b LEDs, Sound, Gyro/Accel, USB storage/networking/charging, Wi-Fi, haptic feedback...

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The goal of this project is to research and develop next generation enhancements to upgrade the current Tron identity disc form factor.
Primary utility function factors: high capacity data storage with visual feedback, multi-frequency modulated photon emitters, increased power capacity, rechargeable.
Secondary subsystem goals include: processor core, wireless network co-processor, gesture input, haptic feedback, and speech synthesis.

Part 2
Part 3

End of Line

Last summer, my brother-in-law Wayne saw some videos of customized Tron discs -- and had the idea to upgrade a disc with lights and usb storage. A simple, usb thumb drive, arduino, EL-Wire, LEDs and AAA batteries were looking good -- until I picked up a Raspberry Pi Zero and found: WS2812b, LiPo, and ESP8266 SDIO WiFi.

Internal power, full brightness LED test:


SPI1 LED driver, solid colors and simple animation

py - 2.36 kB - 03/07/2017 at 04:38



Component overview

Portable Network Graphics (PNG) - 188.32 kB - 03/06/2017 at 05:59


  • 1 × Tron's Deluxe Identity Disc
  • 1 × Tools: rotary tool, knife, nibbler for cutting plastic
  • 1 × Tools: soldering iron, hot glue, heatshrink
  • 1 × Raspberry Pi Zero or now Zero W
  • 1 × Micro SD w Raspbian for RPI OS, and USB storage

View all 24 components

  • The I/O Tangle

    Dan Rogahn05/03/2017 at 05:22 1 comment

    Parts layout & wiring has made a lot of progress. Power switch is working. The halves still close.

    In the pic below:

    • button/speaker
    • audio amp
    • pager motor
    • battery
    • Using the LED common connections on the old main/switch board as a power bus.
    • charger is beneath the switch board
    • dual FET for main power switch and pager motor
    • battery door space for: RTC, accelerometer, external USB connector
    • RPI Zero (USB power, data, and SDIO wiring visible, other connections on the other side)
    • ESP8266 for SDIO WiFi
    • audio and button connectors, LED power

  • More RPI SPI/WS2812 problems, and USB

    Dan Rogahn04/29/2017 at 06:59 0 comments

    I investigated realtime and deadline schedulers to see if they could improve reliability of WS2812 LEDs connected to SPI1 on a RPI.

    In short: no.

    Additionally, the bcm2385 main & aux SPI drivers definitely need some work to support bit lengths other than 8.

    Surprisingly, I found that USB (or the USB network gadget) has a huge impact (I read USB on RPI makes use of a special high priority, fast interrupt).
    Activating the network, or a data transfer of several kB causes major glitches in the SPI/LED timing - until the traffic dies down.

    More details below...

    Read more »

  • The RPI SPI1 I/O Tower and WS2812b

    Dan Rogahn03/05/2017 at 11:18 0 comments

    First: Many Thanks to Tim's Blog for great work on Understanding the WS2812.

    Short version is, I now have a basic & good enough WS2812b SPI driver in Python, working with the RPI SPI1. But it was pretty rough. I ran into some really weird issues...

    Read more »

  • USB Gadget Networking & DHCP problems with Windows

    Dan Rogahn03/04/2017 at 21:30 1 comment

    Networking the PI through Windows isn't a primary goal of this project -- but not having network access (or even worse, having it intermittently) makes setting things up much, much harder. On top of that, a flaky network setup messes with Windows' cloud sync -- making some apps unresponsive, lock up, and possibly lose changes (bad if you're trying to take notes).

    The problem(s) appears to be mismatches between the linux dhclient and DHCP server in Windows Internet Connection Sharing (ICS), and a flaky RNDIS driver/implementation.
    This could be avoided in various ways, but ICS seems like a nice, simple way to go (if it worked better).

    The workaround version is:

    First boot: Wait at least 2-4 minutes for the PI to give up on dhcp and assume a link-local 169.254 address
    Repeat: down-up the interface / disconnect usb / reboot -- until dhcp succeds
    (it may succeed the 2nd time due to starting from the link local address & netmask?)
    (but may still take a couple minutes after the login prompt appears)
    Later boots: will probably still be slow because dhcp is intermittent, but it may fall back to the last saved dhcp reservation settings (if the address is not in use).

    More Details below:

    ---------- more ---------


    Setup usb gadget /boot/cmdline.txt :: dwc2,g_ether g_ether.host_addr=xx:xx... g_ether.dev_addr=xx:xx...
    Change device driver to RNDIS
    Setup ICS

    First: how to spot part of the problem in windows

    Open "View Network Connections" (typing in the start menu to search seems most consistent).
    Windows may disable the RPI network device driver: re-enabling will fail, networking will not work. Then the RPI must be disconnected from USB and rebooted. (if it's not disconnected, or if you tried to re-enable it -- then windows may also require a reboot)

    (the windows event log will show repeated 10400 NDIS "The network interface ... has begun restarting." -- "Reason: The network driver did not respond to an OID request in a timely fashion.")

    Second: getting the right commands, to trigger a dhcp request

    This first requires adding to /etc/network/interfaces
    (otherwise you will get an error "ifdown: interface usb0 not configured")

    allow-hotplug usb0
    iface usb0 inet dhcp

    Then, this command will restart dhcp on the interface

    sudo ifdown usb0 && sudo ifup usb0

    it will also show the output of dhclient. A typical result looks like this

    DHCPDISCOVER on usb0 to port 67 interval 5
    DHCPDISCOVER on usb0 to port 67 interval 12
    DHCPREQUEST on usb0 to port 67
    DHCPOFFER from
    DHCPREQUEST on usb0 to port 67
    DHCPDISCOVER on usb0 to port 67 interval 3
    DHCPDISCOVER on usb0 to port 67 interval 5
    DHCPDISCOVER on usb0 to port 67 interval 13
    DHCPDISCOVER on usb0 to port 67 interval 19
    DHCPREQUEST on usb0 to port 67
    DHCPOFFER from
    DHCPREQUEST on usb0 to port 67
    DHCPACK from
    bound to -- renewal in 236 seconds.

    Note: dhclient recieved two offers (from 137.1) but did not take the first one -- I've even seen it refuse 4 offers...
    Unless it works immediatley -- there always seems to be 4 discovers before a request...
    Where or how are the requests/offers lost or corrupted?
    Future: there is a tool called dhcpdump that logs all dhcp traffic on an interface

  • Checking Dimensions

    Dan Rogahn03/01/2017 at 07:07 0 comments

    Space inside the disc was roughly estimated by examining pictures and video, and similar projects.

    LED: The RPI can drive WS2812b LEDs with DMA
    This conflicts with PWM sound, but we have options:

    • No Sound / simple beeper
    • Disable LED updates while playing sound
    • Use existing disc chip sounds
    • square wave sound
    • I2S audio
    • "Upsample" audio to the shared PWM frequency?
    • Add a microcontroller for LED strip
      ESP8266: switch between sdio firmware & on board flash
      (using WiFi would disable LEDs)
    • SPI LED drive - previously dismissed because no DMA

    WiFi: The RPI has support for a 2nd SD / SDIO port, and the ESP8266 has a SDIO bootloader mode.
    The just released Pi Zero W (if/when you can get one) may make this redundant. But the ESP8266 may have future potential here as a scriptable WiFi/SPI/GPIO expander.

    Battery: The "Custom-Tron-Disc-Mod" project above stated AA would not fit but AAA would.
    But for this project, with more LEDs -- a LiPo can have a larger capacity (for more runtime and brighter lights), and fit more compactly (allowing more peripherals).
    Early plans were to fit the battery in the battery area - possibly removing the screw for the USB jack.
    But latest plans are to put the battery in the largest open area - to eliminate sharp corners that could puncture the LiPo.

    Other technical hurdles:

    • Organizing notes & plans: OneNote App has issues: slow to paste, flaky search, can totally hang up if network issues
    • RPI USB Ethernet Gadget trouble (device recognized, but no data transfer)
      • Has worked in the past
      • Always seemed flaky (maybe due to Win10 drivers and some OS corruption from multiple small disk failures)
      • Then worked on one machine but not another
      • Now not working anywhere: may be corrupt SD? (dmesg does show some errors)

View all 5 project logs

  • 1
    Step 1

    Disassemble the disc, remove and keep internal components.

    The top half has the C ring, the bottom half has the battery door.

    Trim the 6 wedges from inside the soft plastic ring - be careful to not damage the lip on the inner edge that holds the ring in place.

  • 2
    Step 2

    Make room for the outer LED ring on the top half of the disc:

    Completely trim away the 6 short spurs (by the screw posts)

  • 3
    Step 3

    On the bottom half of the disc, make room for the RPI and outer LED ring:

    The battery will be placed in the largest open area.
    For the RPI: trim down the post and screw mount where the bump sensor was.

    Cut a notch for the LED strip to go around the outside of the RPI.
    To help the RPI fit under the C ring: cut a few mm down into one rib.

    At the other end of the RPI, similarly trim down one rib of the screw support.
    Also trim down the inner side of the 4 ribs that stick up, to give the C ring more room.

View all 12 instructions

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