Category: goatee-stroking musing, or something

tiny guard piece to stop croc clips / alligator clips shorting out on your micro:bit. Designed entirely from the Kitronik mechanical drawings, as the official ones are useless.

All the other designs like this on Thingiverse that I tried were really hard to print. Apart from a small amount of bridging (which any printer should be able to handle) this one should be easier.

Thingiverse link: micro:bit croc clip keeper by scruss

On thingiverse: IKEA TERTIAL tripod mount

Dupont connectors — the little doohickeys at the end of jumper wires — are great if you never have to build them yourself. You’ll probably attempt it once with the wrong tools, and while the scars are healing you’ll vow never to do it again.

I recently bought a cheap crimp kit to build the MidTBot ESP32 plotter. My first attempts were, one might say, crap. But I wanted to clean up some of the cables from my desk, and one of them was a horrible taped-together set of jumper wires to use with a ST-LINK V2 compatible In-Circuit Programmer. Surely I could do better than my first try?

I did — thanks to this Instructable: Make a Good Dupont Pin-Crimp EVERY TIME!. Yes, it’s very long. Yes, it’s all about the only way to do it. Curiously, though, it’s actually right: I got all 8 connectors made while only wasting one.

The absolutely golden detail that improved my success was making the connector jig out of a little bit of pin header. This made the process mostly repeatable and quite a bit faster. And the guide has some really helpful failure matrices:

I wouldn’t go out of my way to make Dupont connectors now — they’re still fiddly and slow — but now I have the tools, parts and skills to make less of a mess of them.

Updated: here’s a better one. Who knew that hp2xx had a gcode mode built in?

hp2xx -t -m nc -z 0 -Z 5 -f - file.hpgl | grep -v '^M0.' | sed 's/^G01/G0/;' | awk 'BEGIN {print "G21\nG90";} END {print "G0 Z5";} {print;}' > file.gcode

Aah, no: forget the stuff below.

hp2xx -t -m hpgl -f - phweeen.hpgl | sed 's/;/\n/g;' | grep -v '^SP' | grep -v PA | awk -F, 'BEGIN {print "G0X0Y0Z5";} /^PU/ {sub(/PU/, "", $1); printf("G0Z5\nG0X%fY%f\n", $1/40.0, $2/40.0);} /^PD/ {sub(/PD/, "", $1); printf("G0Z0\nG0X%fY%fZ0\n", $1/40.0, $2/40.0);} END {print "G0Z5";}' > ~/Desktop/phweeen.gcode

1. likely targets a MidTBot a little too much
2. ignores pen changes
3. assumes pen up means tool Z=5 and pen down means tool Z=0
4. only understands PU (move) and PD (draw) commands
5. requires hp2xx
6. tested with trivially few sample files exported as HP-GL from Inkscape
7. doesn’t care about paper size; your plotter does, though.

More details: Three-colour Penrose P2 tiles by scruss – Thingiverse.

I like Arduino Nanos. They’re cheap. They work. They’re small. But they’re a bit fiddly, what with their breadboard legs and tiny pin labels. Wouldn’t it be nicer to use them as self-contained units, with Dupont wires coming from the pins?

This is where nspohrer’s Arduino Nano case with completely accessible pins comes in:

Flip it over, label the pins, and you’ve got a polished little microcontroller in a box. And do I have just the right label for you …

I’ve even included the original SVG so you can make custom versions. Please ignore the “micro” in the name … they are really for the Nano.

And PDF files, for ease of printing:

How many CPU hours did I burn in the early 1990s rendering bits of the Mandelbrot Set? A lot, mainly because I was doing it in BASIC on an unexpanded 8 MHz Commodore Amiga A500. The image below that Fraqtive rendered in almost no time would have taken me days:

But it turns out that the first rendering of what we now call the Mandelbrot set wasn’t produced by Benoit Mandelbrot, but by Brooks & Matelski a year or two earlier:

What I’ve done – and mostly thanks to tweaks by commenter nobody below – is create period-appropriate code to reproduce that graphic. Since the paper was presented in 1978, there’s a fair chance that the authors had access to a machine running FORTRAN-77 or a near equivalent. FORTRAN’s particularly good for this:

• it has a built-in COMPLEX type that extends regular mathematical functions;
• it has just good enough string handling to output a line of spaces/asterisks. I would not have wanted to write this in FORTRAN-66, as that language had no string manipulation facilities at all.

So here’s the code. It should compile on any Fortran compiler:

      PROGRAM BRKMTF
!     GENERATE FIGURE FROM BROOKS-MATELSKI PAPER C.1978
!     THAT EVENTUALLY BECAME KNOWN AS THE MANDELBROT SET
!     - SCRUSS, 2022-05
!     REF: BROOKS, ROBERT, AND J. PETER MATELSKI.
!     "THE DYNAMICS OF 2-GENERATOR SUBGROUPS OF PSL (2, C)."
!     RIEMANN SURFACES AND RELATED TOPICS: PROCEEDINGS OF THE
!     1978 STONY BROOK CONFERENCE,
!     ANN. OF MATH. STUD. VOL. 97. 1981: FIG. 2, P. 81

      REAL MAP, CR, CI
      INTEGER I, J, K, M, ROWS, COLS, MAXIT
      COMPLEX C, Z
      PARAMETER (ROWS=31, COLS=71, MAXIT=200)
      CHARACTER*80 OUT
      CHARACTER CH*1

      DO J=1,ROWS
         CI=MAP(REAL(J), 1.0, REAL(ROWS), -0.8715, 0.8715)
         DO I=1,COLS
            CR=MAP(REAL(I), 1.0, REAL(COLS), -1.975, 0.475)
            C=CMPLX(CR, CI)
            Z=CMPLX(0.0, 0.0)
            CH='*'
            DO 100, K=1,MAXIT
               Z = Z**2 + C
               IF (ABS(Z) .GT. 2) THEN
                  CH=' '
                  GO TO 101
               END IF
 100        CONTINUE
 101        OUT(I:I)=CH
         END DO
         WRITE(*,*)OUT
      END DO
      END

      REAL FUNCTION MAP(X, XMIN, XMAX, YMIN, YMAX)
      REAL X, XMIN, XMAX, YMIN, YMAX
      MAP = YMIN + (YMAX - YMIN) * ((X - XMIN) / (XMAX - XMIN))
      END

The results are spot-on:

Maybe Brooks & Matelski had access to an Apple II and wrote something in BASIC? I could be entirely period-accurate and write something in PDP-8 BASIC on my SBC6120, but not today.

It really is much easier using a language with complex number support when working with the Mandelbrot set. Here’s the same program in Python3, which bears more of a resemblance to FORTRAN-77 than it might admit:

#!/usr/bin/python3
# brkmtf - Brooks-Matelski proto ASCII Mandelbrot set - scruss, 2022-05
# -*- coding: utf-8 -*-

def valmap(value, istart, istop, ostart, ostop):
    return ostart + (ostop - ostart) * ((value - istart) / (istop - istart))

rows = 31
cols = 71
maxit = 200

for y in range(rows):
    ci = valmap(float(y + 1), 1.0, float(rows), -0.8715, 0.8715)
    for x in range(cols):
        cr = valmap(float(x + 1), 1.0, float(cols), -1.975, 0.475)
        c = complex(cr, ci)
        z = complex(0.0, 0.0)
        ch = '*'
        for k in range(maxit):
            z = z**2 + c
            if (abs(z) > 2.0):
                ch = ' '
                break
        print(ch, end='')
    print()

I found out about the Brooks-Matelski paper from this article: Who Discovered the Mandelbrot Set? – Scientific American. It’s none too complimentary towards Benoit Mandelbrot.

Update: see the comment from one of the authors of the original paper below.

I’ve extended the MicroPython examples for the BrainPad Classic so that all of the devices work: scruss/brainpad-micropython: Micropython examples for the BrainPad Classic (BP2) from GHI Electronics.

The ones that already worked in the original examples repo are:

• buttons
• accelerometer
• LEDs
• light sensor
• OLED screen

I’ve added:

• temperature sensor: although my calibration may be a bit off on the MCP9701a used on the board
• timer blink example: STM32 Timers are cool and we should use them
• PWM RGB LED example: floating-point silliness with HSV(ish) Colour Wheel in Python
• buzzer: simple tones plus tunes (in RTTTL) via dhylands / upy-rtttl
• servos: I may have forgotten to put the example in there, but the standard Servo(1) code should work.

Yes, it would be nice to have a slick unified library like the BBC micro:bit does. For later, though.

Other resources:

• BrainPad Classic/BP2 Schematic
• STM32F401RE summary and datasheet: because sometimes you need to know what Timer talks to which Pin …

Using ansicolors:

#!/usr/bin/python3
# -*- coding: utf-8 -*-
# colourshen.py - stdin to rainbow stdout
# scruss, 2020-06

from colors import *            # see https://pypi.org/project/ansicolors/
import sys
wheel_pos = 0


def cos_wheel(pos):
    # Input a value 0 to 255 to get a colour value.
    # scruss (Stewart Russell) - 2019-03 - CC-BY-SA
    from math import cos, pi
    if pos < 0:
        return (0, 0, 0)
    pos %= 256
    pos /= 255.0
    return (int(255 * (1 + cos(pos * 2 * pi)) / 2),
            int(255 * (1 + cos((pos - 1 / 3.0) * 2 * pi)) / 2),
            int(255 * (1 + cos((pos - 2 / 3.0) * 2 * pi)) / 2))


def hex_wheel(pos):
    rgb = cos_wheel(pos)
    return('#%02x%02x%02x' % rgb)


def wheel_print(s):
    global wheel_pos
    incr = int(256/(1+len(s)))-1
    if incr < 1:
        incr = 1
    for c in s:
        print(color(c, fg=hex_wheel(wheel_pos)), end='')
        wheel_pos = (wheel_pos+incr) % 256
    print()


for txt in sys.stdin:
    wheel_print(txt.rstrip())

(fixed a very obvious ahem! in the code, hope no-one noticed …)

Long ago, the was a thing that called itself SimStapler©. It was a very early clicker game: every ten times you clicked on the virtual stapler, you got bonus audio. That was all it did.

A couple of days ago, lee posted a video with reminded me so much of that virtual stapler:

Today is a stapler switch pic.twitter.com/RkjHWT0Qyn

lee cyborg 🦞🔭 (@Leeborg_) April 22, 2020

Since I have the hardware and for various reasons my social calendar isn’t what it was, I set out on the bold plan to make Sim-SimStapler©… or SimStapler© Simulator … or RealStapler … or … look, I’ve spent more effort in trying to come up with a name for this than I did making the thing, so call it what you want.

You’ll need a Circuit Playground Express, a couple of alligator clip test leads, and a stapler. And maybe some tape and a paperclip, too

The important thing about a switch is that it has two electrically isolated parts that come together to close a circuit. And that’s exactly what the Swingline® 747® stapler doesn’t have: its entire metal body and mechanism is electrically conductive. So we have to rig something up …

Did I say take the staples out yet? No? Take the staples out of the stapler. Possibly even before doing anything else.

The code we’re going to run on the Circuit Playground Express is very simple:

• Set up pin 1 (helpfully named A7 on the board) as an input. Turn off all the LEDs
• If pin 1 is shorted to ground, increase a counter and light successive numbers of LEDs round the CPX’s face
• If the counter reaches 10, play the sample, reset the counter and turn off all the LEDs
• repeat from “If pin 1 is shorted to ground …” until too bored to continue.

Here’s the code:

# SIM-SimStapler / RealStapler - scruss, 2020-04
# circuitpython on CPX - stapler between D1 (A7) and GND

from adafruit_circuitplayground import cp
import board
from digitalio import DigitalInOut, Direction, Pull
import time

# set up stapler on pin D1 (port A7): goes LOW when pressed
stapler = DigitalInOut(board.D1)
stapler.direction = Direction.INPUT
stapler.pull = Pull.UP

# set up pixels - not too bright
cp.pixels.brightness = 0.1
# turn all pixels off
for i in range(10):
    cp.pixels[i] = (0, 0, 0)

count = 0
while True:
    # stapler pressed, so increase count
    if not stapler.value:
        count = count + 1
        # only count first press, not if held
        while not stapler.value:
            pass
        time.sleep(0.1)

    # light up pixels clockwise for each press
    for i in range(count):
        cp.pixels[9 - i] = (0, 255, 0)

    # get a bonus Penelope Keith every ten presses
    if count == 10:
        cp.play_file("splendid.wav")
        # turn all pixels off after bonus
        for i in range(count):
            cp.pixels[i] = (0, 0, 0)
        # and reset counter for next time
        count = 0

Here’s the code and sample ready to be copied to your CIRCUITPYTHON drive:

(The sample is a slightly tweaked version of Freeverse’s original Bonus.wav. I ran it through an equalizer to make it sound less awful through the CPX’s tinny little speaker. I was also today years old when I found out that the sample wasn’t Penelope Keith from To the Manor Born, but Jen Krasinski, a staffer at Freeverse.)

The connection (singular) is simple:

Have an appropriate amount of fun!

I suppose I could also have done this on the BrainPad, but I haven’t set it up with MicroPython yet, and I don’t have time to drag coding blocks around. Also, this is not any project to associate with the word “brain” …

If the video doesn’t work: local link.

Model: Moose Head for Materio3D by Morena Protti (modified)
Clear PLA with manual colouring using ShinHan Touch markers

So it seems my lifelong nickname is/was a Piedmontese word for noise, crash/clatter/bang or scream/shout/squawk:

An early 19th century dictionary written by an Italian count had my number all along.