Final project notes

• Built a board for speaking TWI/I2C by bitbanging. Used Neil's serial bus board and adapted code from the accelerometer. Board failed in mysterious ways (see networking week); decided to revisit using native TWI.

• Designed a board for natively speaking TWI (using atmega328p).

  • Board design
  • Board had some manufacturing and design errors.
  • Manufacturing errors: some pins were subtly bridged (RESET and CLK).
  • Design errors: accidentally used pins that were not general-purpose I/O for some of the LEDs (most ADC pins are, but these weren't). Put placeholder 0 ohm resistors on the SCL and SDA lines, forgetting that if I needed pullup resistors, they'd need to be between the lines and Vcc, not on the lines themselves.
  • Mysteriously, serial i/o produces gibberish. Will need to use oscilloscope to determine
  • ! Emergent idea: Although I initially intended the LEDs to indicate status, I could also use one as an IR LED for testing the camera.

• Programmed the board.

  • I used Neil's hello.arduino.328p.blink code to test whether the board was programmable at all.
  • I borrowed a TWI library to test whether I could communicate with the camera. I intend to define my own API functions instead.
  • Initiating TWI worked once I fixed the solder bridge between reset and clk (which caused the board to reset every time the register was activated).
  • Sending a hello command to the camera worked — after many hours of debugging, I discovered that it was necessary to wait around 1sec before sending the first TWI command. I suspect the camera needs time to load.
  • Sending a read request to the camera worked — after a great mystery (the camera itself has very sparse, contradictory, flawed documentation written by various hobbyists), I found that you have to write a specific byte to the camera each time you want to request bytes from it.

• Fixed serial (Thursday)

  • I swapped which of TX and RX refered to in and out again. For reference, it's relative to the computer: Transmit is out, and Recieve is in. (To be absolutely sure, compare the board design and code for echo hello world and see which is which.)
  • Adapting the echo hello world code from attiny45 produced gibberish, suggesting timing errors.
  • I realized that the makefile for m328p.blink assumed a 20MHz crystal on the mega. So I changed F_CPU from 20000000 to 8000000, as 8MHz is the default clock speed for the m328p's internal clock.
  • Finally, the default echo hello world baud rate was too high. Given that there's no crystal, we need a lower baud rate.

• LED daughter boards

  • Using inkscape, made a triangular array.
  • Then experimented with a simpler design. You can add one or two leds (so, for example, one infrared and one visible).

• Board 2.0

  • Relocated all four LEDs to general i/o pins.
  • Added a status LED between vcc and gnd.
  • Added a 5V regulator to regulate power to the peripherals. This required one additional 0.1uF capacitor, because the datasheet recommended adding smoothing capacitors to both sides. (I already had a smoothing 1uF capacitor between unregulated power and ground, because this design is a descendant of one of Neil's.)
  • Added a 20MHz resonator — I expect the camera might require fast timing. Will remove if unneeded.

Saturday 8/Dec/2018

• Having milled four led daughter boards, stuffed. them.

• Used phone camera to check that the infrared leds were working. Turns out they work with 100Ω resistors rather than 500Ω resistors.

• Finally found documentation for the commands to send to the camera to make it activate. It works! (Todo later: simplify the code using subroutines and fundamental register commands instead of library commands.)

• By inserting appropriate delays, became able to request repeated reads from the camera without it blocking.

• Used Interface week's nodejs code to read from the serial output

• Wrote a bit-shifter to unpack the encoded data from the camera.

• Modified my synthetic-data-generating code to decode serial input and send it over web sockets (modification of Interface week's nodejs code.)

• ! Plotting of a single point works correctly. (Todo: test multiple points.)

• Plotting of multiple points works correctly. Experimented with various ways to deal with the event-based serial data spurts. Optimization using slice instead of repeated shift.

• Workflow:

  • Run node on ir-serial.js
  • Open a page like dxh.plot.infrared.html in the browser.

• wooden glasses (all one piece with flextured hinges!)

https://www.youtube.com/watch?v=2Nj167idFkQ

• Hinged all-wood glasses https://www.instructables.com/id/Laser-cut-foldable-wooden-glasses/

Sunday 9/Dec/2018

• Made a daughter board for converting 9V battery into regulated 5V using four pin connectors.
• Projection math

Monday 10/Dec/2018

• Began designing enclosure for pcb board; sketched plan to print a back part and lasercut a viewing screen.
• Brainstorming about ways to affix board to monitor like webcam.
• Lasercut a mounting place for the pcb board

Tuesday 11/Dec/2018

• Designed and lasercut draft version of visor; further iteration awaits.

Wed 12/Dec/2018

• Surface-mounted leds
• Designed and began printing chassis

Thu 13/Dec/2018

• Battery case screw holes. Two circles spaced apart. ~32mm outer distance, ~22mm inner distance.
• Safety glasses dimensions: 38mm from leg start to hinge, 70 from hinge to leg inflection, 45mm downturn, 6mm thick legs
• Battery case dimensions: 30mm x 54.5mm

Fri 14/Dec/2018

• Plan to make daughter boards with through-hole leds.

• Rivet diameters 1.0mm or 0.6mm inner-diameter rivets.

• ~ outer diameters: 1.5mm or 0.8mm, resp.

• Idea: since we're trying rivets, just print out the rivet part to confirm that it goes and to test the alignment process

  • front traces: just_holes_fcu.svg-traces
  • back traces: just_holes_fcu.svg-traces-reversed.png
  • edge cuts, including 8mm holes: just_holes_bcu-edges.png

• Origin: [40, 50, 15]

• For offsets: (1/32)" is 0.79375mm

• Failed, b/c 0.8mm holes were too small for 1/32" end mill

• Try again with 1mm holes.

• Riveting tool has different rivet applicators based on the inner diameter (here 1mm).

• Metric hex wrench

• In design file, increase drill diameter by 0.1mm larger than nominal

• Also, do holes first by reversing cut path

• New: traces:[20, 4, 17], edges:[20, 4, 16]

• Offset for tool width [20-0.79375, 4+0.79375, 16] = [19.20625, 4.79375, 16]

• Hairband dimensions:

  • Thickness: Squishy, somewhere between 4.6mm (uncompressed) down to <4mm (compressed).
  • band width: 7.5mm
  • band length: ?

• https://www.3dhubs.com/knowledge-base/how-design-snap-fit-joints-3d-printing

• http://fab.cba.mit.edu/classes/S62.12/people/vernelle.noel/Plastic_Snap_fit_design.pdf

• http://web.mit.edu/2.75/resources/random/Snap-Fit%20Design%20Manual.pdf

• https://www.slideshare.net/ankitsrivastava151/snap-fit-design-by-neeraj-kumar-jha

• https://choosemuse.com/

Sat 15/Dec/2018

• Milling 4x through hole

  • The image of the board is 13mm high (and 55mm wide). Adding 15mm buffer between to be safe.
  • Process: Mill all traces. Mill all outlines.
  • Trace 1: [10,6,18]
  • Trace 2: [10,21,18]
  • Trace 3: [10,36,18]
  • Trace 4: [10,51,18]
  • Trace Battery: [10, 66, 18]

X = 10-0.79375 = 9.20625 Y = 6+0.79375 = 6.79375 Z = 15

• What is a safe way to fixture flipped circuits?
• The infrared led works with external power. ¯\_(ツ)_/¯
• Clip works
• Rivets?
• Do we have access to machineable wax?

Sun 16/Dec/2018

• [X]

  Finish soldering leds

• [X]

  Test leds to ensure operation

• [X]

  Design a new enclosure for the leds.

  • Options include two snap pieces or one.
• [X]

  Laser cut a new window pane

• [X]

  Design battery attachment or enclosure (screws?)

• Consider straight led segments w/wires.
• Stretch: print a hexagonal camera enclosure for visual appeal.
• Stretch: redesign pcb to be half as wide (leave out the 2 resistor segment) Problem: will need to draw and mill and stuff two new double-sided boards
• Stretch: consider pure led and wire approach.

Monday 17/Dec/2018

• [X]

  Fix the 5V battery converter so the led lights up

• [ ]

  Affix bar to band

  • [ ] New strategy: use double-sided clip.
  • [ ] First clip prototype broke before being used — remaking sturdier.
  • [ ]
• [ ]

  Consult wii projection math to improve the fov calculation.

• [ ]

  Experiment with faster I2C rate?

• [ ]

  Do the writeup for the class.

  • [ ] Include pictures and files and so on.
• [ ]

  Design an immersive environment.

• [ ]

  Stretch: Remove I2C library from the code and just bit-bang

• [ ]

  Stretch: divide the 3D environment code into usable submodules.

• [ ]

  Stretch: Make the code a drop-in replacement for cameras in all threejs applications.

Button cell case + molding/casting glasses-like earhook on headband seems cool-looking but superfluous, given that it will take more than that to power the bright leds well.

Make: