Homage Tektronix Circuit Computer: Laser Printed Scales

Given the proper command-line options, GCMC can produce an SVG image and, after some Bash fiddling and a bank shot off Inkscape, the same GCMC program I’ve been using to plot Homage Tektronix Circuit Computer decks can produce laser-printed decks:

Tek CC - laser - detail
Tek CC – laser – detail

Pen-plotting on yellow Astrobrights paper showed how much ink bleeds on slightly porous paper, but laser-printing the same paper produces crisp lines:

Tek CC - laser - yellow detail
Tek CC – laser – yellow detail

Laser printing definitely feels like cheating, but, for comparison, here’s a Genuine Tektronix Circuit Computer:

Tek CC - genuine - detail
Tek CC – genuine – detail

Plotting the decks on hard mode was definitely a learning experience!

Obviously, my cursor engraving hand remains weak.

KeyboardIO Atreus: LED Diffuser

After staring at the RGB LED I installed in my Atreus keyboard for a while, I converted the stub of a ¼-20 nylon screw into a light diffuser:

Atreus keyboard - LED diffuser
Atreus keyboard – LED diffuser

It stands slightly proud of the surface plate so I can extract it without dismantling the whole keyboard again:

Atreus keyboard - LED diffuser installed
Atreus keyboard – LED diffuser installed

I’ll eventually make a better-looking diffuser from a recently arrived translucent acrylic rod, but this will reduce the accumulation of fuzz inside the keyboard until the matching Round Tuit arrives.

KeyboardIO Atreus: RGB LED Firmware

Having wired a WS2812 RGB LED into my KeyboardIO Atreus, lighting it up requires some QMK firmware configuration. It’s easiest to set up a “new” keymap based on the QMK Atreus files, as described in the QMK startup doc:

qmk new-keymap -kb keyboardio/atreus -km ednisley

Obviously, you’ll pick a different keymap name than I did. All the files mentioned below will reside in the new subdirectory, which starts out with only a keymap.c file copied from the default layout.

The rules.mk file enables RGB Lighting, as well as Auto Shift and Tap Dance:

AUTO_SHIFT_ENABLE = yes			# allow automagic shifting
TAP_DANCE_ENABLE = yes			# allow multi-tap keys

RGBLIGHT_ENABLE = yes			# addressable LEDs

If you had different hardware, you could specify the driver with a WS2812_DRIVER option.

QMK can also control single-color LEDs with PWM (a.k.a. backlighting), and per-key RGB LEDs (a.k.a. RGB Matrix). These functions, their configuration / controls / data, and their documentation overlap and intermingle to the extent that I spent most of my time figuring out what not to include.

Some configuration happens in the config.h file:

#define RGB_DI_PIN B2
#define RGBLED_NUM 1

// https://github.com/qmk/qmk_firmware/blob/master/docs/ws2812_driver.md
//#define WS2812_TRST_US 280


#define NO_DEBUG
#define NO_PRINT

The first two lines describe a single WS2812 RGB LED wired to pin B2 (a.k.a. MOSI) of the Atmel 32U4 microcontroller. The default Reset duration and Byte Order values work for the LED I used

Protip: swapping the order from GRB to RGB is a quick way to discover if the firmware actually writes to the LED, even before you get anything else working: it’ll be red with the proper setting and green with the wrong one.

Dialing the maximum intensity down works well with a bright LED shining directly at your face from a foot away.

Turning on RGBLIGHT_LAYERS is what makes this whole thing happen. The RGBLIGHT_EFFECT_RGB_TEST option enables a simple test animation at the cost of a few hundred bytes of code space; remove that line after everything works.

The last two lines remove the debugging facilities; as always with microcontroller projects, there’s enough room for either your code or the debugger required to get it running, but not both.

With those files set up, the keymap.c file does the heavy lifting:

// Modified from the KeyboardIO layout
// Ed Nisley - KE4ZNU


enum layer_names {

// Tap Dance

enum {

qk_tap_dance_action_t tap_dance_actions[] = {

// Layer lighting

// Undefine this to enable simple test mode
// Also put #define RGBLIGHT_EFFECT_RGB_TEST in config.h

#define LED_LL

#ifdef LED_LL

const rgblight_segment_t PROGMEM ll_0[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_WHITE} );
const rgblight_segment_t PROGMEM ll_1[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_MAGENTA} );
const rgblight_segment_t PROGMEM ll_2[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_CYAN} );
const rgblight_segment_t PROGMEM ll_3[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_BLUE} );
const rgblight_segment_t PROGMEM ll_4[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_GREEN} );
const rgblight_segment_t PROGMEM ll_5[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_RED} );
const rgblight_segment_t PROGMEM ll_6[] = RGBLIGHT_LAYER_SEGMENTS( {0,1,HSV_YELLOW} );

const rgblight_segment_t* const PROGMEM ll_layers[] = RGBLIGHT_LAYERS_LIST(


void keyboard_post_init_user(void) {

#ifdef LED_LL
    rgblight_layers = ll_layers;
    rgblight_set_layer_state(0, 1);
//    rgblight_mode_noeeprom(RGBLIGHT_MODE_BREATHING + 3);


#ifdef LED_LL

layer_state_t layer_state_set_user(layer_state_t state) {
    for (uint8_t i=0 ; i < _NLAYERS; i++)
        rgblight_set_layer_state(i, layer_state_cmp(state, i));

    return state;

// Key maps

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
  [_BASE] = LAYOUT(                             // base layer for typing
    KC_Q,    KC_W,    KC_E,    KC_R,    KC_T,                      KC_Y,    KC_U,    KC_I,    KC_O,    KC_P    ,
    KC_A,    KC_S,    KC_D,    KC_F,    KC_G,                      KC_H,    KC_J,    KC_K,    KC_L,    KC_SCLN ,
    KC_Z,    KC_X,    KC_C,    KC_V,    KC_B,    KC_GRV,  KC_LALT, KC_N,    KC_M,    KC_COMM, KC_DOT,  KC_SLSH ,

  [_SHIFTS] = LAYOUT(                           // shifted chars and numpad
    KC_EXLM, KC_AT,   KC_UP,   KC_DLR,  KC_PERC,                  KC_PGUP, KC_7,    KC_8,   KC_9, KC_HOME,
    KC_LPRN, KC_LEFT, KC_DOWN, KC_RGHT, KC_RPRN,                  KC_PGDN, KC_4,    KC_5,   KC_6, KC_END,

  [_FUNCS] = LAYOUT(                            // function keys
    KC_INS,  KC_HOME, KC_UP,   KC_END,  KC_PGUP,                   KC_UP,   KC_F7,   KC_F8,   KC_F9,   KC_F10  ,
    KC_DEL,  KC_LEFT, KC_DOWN, KC_RGHT, KC_PGDN,                   KC_DOWN, KC_F4,   KC_F5,   KC_F6,   KC_F11  ,
    KC_NO,   KC_VOLU, KC_NO,   KC_NO,   RESET,   _______, _______, KC_NO,   KC_F1,   KC_F2,   KC_F3,   KC_F12  ,

Undefine LED_LL to enable the test mode, compile, flash, and the LED should cycle red / green / blue forever; you also need the RGB_TEST option in the config.h file.

Define LED_LL and layer lighting should then Just Work™, with the LED glowing:

  • White for the basic layer with all the letters
  • Magenta with the Fun key pressed
  • Cyan with the Esc key pressed

The key map code defines colors for layers that don’t yet exist, but it should get you started.

For convenience, I wadded all three QMK files into a GitHub Gist.

The LED is kinda subtle:

Atreus keyboard - LED installed
Atreus keyboard – LED installed

As you might expect, figuring all that out took much longer than for you to read about it, but now I have a chance of remembering what I did.

KeyboardIO Atreus: RGB LED Installation

Having scouted out the territory inside the KeyboardIO Atreus, adding an LED requires taking it completely apart to drill a hole in the aluminum faceplate:

Atreus keyboard - panel drilling
Atreus keyboard – panel drilling

Reattaching the plate to the PCB with only three screws allows marking the hole position on the PCB, which is much easier than pretending to derive the position from first principles:

Atreus keyboard - LED marking
Atreus keyboard – LED marking

Despite appearances, I traced the hole with a mechanical pencil: black graphite turns shiny silvery gray against matte black soldermask. Also, the PCB trace is off-center, not the hole.

Overlay the neighborhood with Kapton tape to protect the PCB from what comes next:

Atreus keyboard - Kapton tape

Snip a WS2812 RGB LED from a strip, stick it in place with eyeballometric alignment over the target, and wire it up:

Atreus keyboard - LED wiring
Atreus keyboard – LED wiring

Despite the terrible reliability of WS2812 RGB LEDs mounted on PCB carriers, a different set on a meter of high-density flex tape have worked reasonably well when not thermally stressed, so I’ll assume this one arrived in good order.

Aligning the LED directly under the hole required a few iterations:

Atreus keyboard - LED positioning
Atreus keyboard – LED positioning

The iridescent green patch is a diffraction pattern from the controller chip’s internal circuitry.

The data comes from MOSI, otherwise known as B2, down in the lower left corner:

Atmel 32U4 - JTAG pins
Atmel 32U4 – JTAG pins

Actually lighting the LED now becomes a simple matter of software QMK firmware.

Straightening Armature Wire

Although I was blithely unaware when I bought some useful-looking surplus, it turns out 1/16 inch armature wire works really well to seal our homebrew masks around our noses. Mary added a narrow passage along the top edge of her slightly reshaped Fu Mask pattern to retain the wire and I provided 4.5 inch lengths of straightened wire:

Armature wire - stock vs. straightened
Armature wire – stock vs. straightened

The wire comes off the roll in dead-soft condition, so I can straighten (and slightly harden) it by simply rolling each wire with eight fingertips across the battered cutting board. The slightly wavy wire shows its as-cut condition and the three straight ones are ready for their masks.

Although nearly pure aluminum wire doesn’t work-harden quickly, half a year of mask duty definitely takes its toll. This sample came from my biking mask after the edges wore out:

Armature wire - work-hardened
Armature wire – work-hardened

We initially thought using two wires would provide a better fit, but more metal just made adjusting the nose seal more difficult after each washing. The wire has work-hardened enough to make the sharper bends pretty much permanent; they can be further bent, but no longer roll out under finger pressure.

Although we’re not yet at the point where we must reuse wires, I took this as an opportunity to improve my annealing hand: heat the wire almost to its melting point, hold it there for a few seconds, then let it cool slowly. The usual technique involves covering the aluminum with something like hand soap or permanent marker ink, heat until the soap / marker burns away, then let it air-cool. Unlike steel, there’s no need for quenching or tempering.

Blue Sharpie worked surprisingly well with a propane torch:

Armature wire - annealed straightened
Armature wire – annealed straightened

As far as I can tell after a few attempts, the pigment vanishes just below the annealing temperature and requires another pass to reach the right temperature. Sweep the flame steadily, don’t pause, and don’t hold the wire over anything melt-able.

Those wires (I cut the doubled wire apart) aren’t quite as soft as the original stock, but they rolled straight and are certainly good enough for our simple needs; they’re back in the Basement Laboratory Warehouse for future (re)use.

Makergear M2: New Filament Drive and Guide Tube Adapter

After replacing the M2’s nozzle, I also installed a spare filament drive:

Makergear M2 filament drive R3 - installed
Makergear M2 filament drive R3 – installed

That’s the V4 R3 version, although I bought it from Makergear rather than fight with all the support required to get a proper bearing opening.

The long M4 screw and spring apply a constant force to the filament against the drive gear, rather than the constant position from the default (and much shorter) stock screw. The lever arm does have some springiness, but not much travel, so IMO the spring works better with the fine teeth in the drive gear.

This drive has a 5 mm hole at the top for the stock PTFE guide tube, which I long ago replaced with ¼ inch OD HDPE tubing to reduce the friction required to get the filament off the spool and into the hot end. The rather hideous hot-melt glue blob holding a ¼ inch ID tube onto the previous drive never failed enough to bother me, but a little lathe action produced a much better adapter:

Makergear M2 filament drive R3 - guide adapter
Makergear M2 filament drive R3 – guide adapter

It’s a chunk of ⅜ inch = 9.5 mm Delrin rod with a 2.4 mm hole through that 5 mm spigot for easy extraction of a gear-mashed 1.75 mm filament. The other end has a 6.5 mm hole drilled 20 mm deep to hold the guide tube.

Looks downright dressy, it does!