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.
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?
So Dr. Blake “PROTODOME” Troise (previously) made a chiptune album that’s entirely synthesized by an Atmel/Microchip ATmega328P microcontroller in realtime. And every chip needs a PCB, right? So Blake released the album as a physical device you can solder up for yourself.
Of course, having the PCB lying flat doesn’t allow you to see Marianne Thompson’s great pixel cover art, or read the liner notes on the back — and risks having the circuit short out on random tinny things on your desk. (Maybe that’s just my desk, though.)
This stand allows you to display the board at a convenient 75° angle, but also allows the PCB to be flipped forward so you can read the liner notes comfortably. Yeah, I may have been a crate-digger at one time.
For something to do with my head, I’m taking the RAC Advanced Ham Radio course. The exam uses a non-programmable scientific calculator. I thought that all my calculators were programmable, but we found this one lurking in the basement and it’s just perfect:
This is one of the few calculators I’ve seen that both displays and takes inputs in SI units. How to put it into SI engineering display mode is explained in this delightful (archived) site Casio fx-115MS.
Entering numbers with SI prefixes is simple: type the number, then Shift and hit the prefix. So to enter 300000, you’d type 300 Shift 4 to get 300 k.
You do have to be a little careful reading the display in this mode, though. The display above reads 221 × 10-3 (from the m at right), or 0.221.
I don’t see any calculator in Casio’s current range that offers this handy feature. Guess I’m lucky I found it before the exam!
Audio can be a bit dismal on a Raspberry Pi. Once you get a configuration that works, sometimes you’re not sure how you got there and you’ll do anything to keep that arcane setup going. It’s better than it was.
Speech synthesis or TTS adds an extra layer for potential failure. One of the popular Linux TTS systems, eSpeak, hasn’t seen much development in almost a decade and seems to only work through workarounds and hand-waving.
Thankfully, there’s a fork of eSpeak that is maintained: espeak-ng. Better yet, it’s packaged with Raspberry Pi OS and can be installed quite easily:
In my simple tests, it output everything I expected of it.
eSpeak had a Python module that kinda worked, but espeak-ng’s is much more ambitious, and (mostly) does what it sets out to do. You can install it like this:
sudo pip3 install py-espeak-ng
py-espeak-ng has some documentation, but it’s still got some trial and error in getting it to work. The biggest issue that held me up was that the module needs to be initialized with a voice that espeak-ng already knows about. If you don’t specify a voice, or specify one that the system doesn’t know about, you won’t get any errors — but you won’t get any output, either.
Here’s a small Python example that you’ll probably want to try with no-one else within earshot. It repeats the same English phrase (a favourite of elocution teachers) in every English regional language that espeak-ng knows about. In addition, since I’m a dictionary nerd, it outputs phonetics too.
# -*- coding: utf-8 -*-
# an espeakng elocution lesson from scruss, 2020-07
# I suffered this at school, now you get to as well!
# You will need to:
# sudo apt install espeak-ng espeak-ng-data libespeak-ng-dev
# sudo pip3 install py-espeak-ng
from espeakng import ESpeakNG
from time import sleep
# you have to initialize with a voice that exists
# `espeak-ng --voices=en` will list English ones
esng = ESpeakNG(voice='en-gb')
esng.pitch = 32
esng.speed = 150
phrase = "Father's car is a Jaguar and pa drives rather fast. "\
"Castles, farms and draughty barns, all go charging past."
for voice in esng.voices:
print('Using voice:', voice['language'],
'for', voice['voice_name'], '-')
esng.voice = voice['language']
ipa = esng.g2p(phrase, ipa=2)
print(voice['language'], 'phonetics:', ipa)
Be thankful you can’t hear the output. The IPA output, however, is a thing of beauty:
Father's car is a Jaguar and pa drives rather fast. Castles, farms and draughty barns, all go charging past.
Using voice: en-029 for English_(Caribbean) -
en-029 phonetics: fˈɑːdaz kˈɑ͡əɹ ɪz a d͡ʒˈaɡwɑ͡ə and pˈɑː dɹˈa͡ɪvz ɹˈɑːda fˈa͡astkˈa͡asɛlzfˈɑ͡əmz and dɹˈa͡afti bˈɑ͡ənzˈɔːl ɡˌo͡ʊ t͡ʃˈɑ͡əd͡ʒɪn pˈa͡ast
Using voice: en-gb for English_(Great_Britain) -
en-gb phonetics: fˈɑːðəz kˈɑːɹ ɪz ɐ d͡ʒˈaɡwɑː and pˈɑː dɹˈa͡ɪvz ɹˈɑːðə fˈastkˈasə͡lzfˈɑːmz and dɹˈafti bˈɑːnzˈɔːl ɡˌə͡ʊ t͡ʃˈɑːd͡ʒɪŋ pˈast
Using voice: en-gb-scotland for English_(Scotland) -
en-gb-scotland phonetics: fˈa:ðɜz kˈaːr ɪz ɐ d͡ʒˈaɡwaːr and pˈa: drˈa͡ɪvz rˈa:ðɜ fˈa:stkˈa:sə͡lzfˈaːrmz and drˈa:fte bˈaːrnzˈɔːl ɡˌoː t͡ʃˈaːrd͡ʒɪŋ pˈa:st
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 tried to do — and come close, but not actually managed to exactly replicate — 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 atall.
So here’s the code. It should compile on any Fortran compiler:
! GENERATE FIGURE FROM BROOKS-MATELSKI PAPER C.1978
! THAT EVENTUALLY BECAME KNOWN AS THE MANDELBROT SET
! - SCRUSS, 2020-06
! 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=70, MAXIT=36)
CI=MAP(REAL(J), 1.0, REAL(ROWS), -0.89, 0.89)
CR=MAP(REAL(I), 1.0, REAL(COLS), -2.0, 0.45)
DO 100, K=1,MAXIT
Z = Z**2 + C
IF (ABS(Z) .GT. 2) THEN
GO TO 101
REAL FUNCTION MAP(X, XMIN, XMAX, YMIN, YMAX)
REAL X, XMIN, XMAX, YMIN, YMAX
MAP = YMIN + (YMAX - YMIN) * ((X - XMIN) / (XMAX - XMIN))
The results are close:
but not quite right. 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:
# brkmat - Brooks-Matelski proto ASCII Mandelbrot set - scruss, 2020-06
# -*- coding: utf-8 -*-
def valmap(value, istart, istop, ostart, ostop):
return ostart + (ostop - ostart) * ((value - istart) / (istop - istart))
rows = 31
cols = 70
maxit = 36
for y in range(rows):
ci = valmap(float(y + 1), 1.0, float(rows), -0.89, 0.89)
for x in range(cols):
cr = valmap(float(x + 1), 1.0, float(cols), -2.0, 0.45)
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 = ' '