Some okay CMYK results from DrawingBot, finally …

decorative 8-sided symmetrical square tile sketched out in cyan, magenta, yellow and grey felt tip pen on a plotter
drawn using a Roland DXY-1300 plotter on Strathmore Multimedia using DeSerres medium tip pens, ~60 minutes plotting time, 180 × 180 mm

After a tonne of faffing about, I finally got something out of my plotter using Drawing Bot. I’d heard about it during the Bold Machines’ Intro to Pen Plotters course I’m taking, and the results that other people were getting looked encouraging. But for me, they weren’t great.

Maybe I was choosing too large images, but my main problem was ending up with plots with far too many lines: these would take days to plot. The controls on Drawing Bot also seemed limited: density and resolution seemed to be the only controls that do much. Drawing Bot itself wasn’t very reliable: it would sometimes go into “use all the cores!” mode when it was supposed to be idling. It would also sometimes zoom in on part of the image and fail to unzoom without quitting. Is a 32 GB i7 8-core (oldish, but still game) too little for this software? Forget any of the Voronoi plots if you want to see results today.

The source image was a geometric tile that I’d frisketed out years ago, forgotten about, and then found when I unstuck it from under a stack of papers. It’s somewhat artisanally coloured by me in watercolour, and the mistakes and huge water drop are all part of its charm:

geometric tile picked out in brown, red, pink, green  and various shades of faded blue, separated by rough white frisket lines
source image for plotter output

If WordPress will allow an SVG, here’s what Drawing Bot made of it:

scribbly linedrawing of the tile image in CMYK process colours
Drawing Bot SVG output: yes, it’s that faint

I do like the way that Drawing Bot seems to have ignored some colours, like the rose pink around the outside. The green border really is mostly cyan with a touch of black.

I haven’t magically found perfect CMYK pens in HP/Roland pen format. I couldn’t even find the Schwan-Stabilo Point 88 pens that Lauren Gardner at Bold Machines recommends. But the local DeSerres did deliver a selection of their own-brand 1.0mm Mateo Markers that are physically close to the Point 88s in size, but use a wider 1 mm fibre tip. They are also cheap; did I mention that?

The colours I chose were:

  • for cyan: Mint Green; RGB colour: #52C3A5; SKU: DFM-53
  • for magenta: Neon Pink; RGB colour: #FF26AB; SKU: DFM-F23
  • for yellow: Neon Yellow; RGB colour: #F3DE00; SKU: DFM-F01
  • for black: Green Grey 5; RGB colour: #849294; SKU: DFM-80

The RGB colours are from DeSerres’ website, and show that I’m not wildly off. Target process colours are the top row versus nominal pen colours on the bottom:

target vs pen CMYK colours
yes, there are fluo colours in there

I knew to avoid pure black, as it would overpower everything in the plot.

To make the pens work with the DXY-1300, I modified juliendorra/3D-printable-plotter-adapters-for-pens-and-refills: Use your favorite pens with vintage HP plotters: parametric code to create custom adapters to work the the DeSerres pens. Here are my changed files, just in case my PR isn’t accepted:

Overall, it plotted quite well. I plotted directly from Inkscape, one layer/pen at a time, from light (yellow) to dark (grey). Using the pen 1 slot had its disadvantages: the DXY has little pen boots to stop the pens drying, but these unfortunately get filled with old ink. The scribbly dark markings in the NNE and SSW orange kites in the plot are from the yellow pen picking up old black ink from the pen boot. Next time I’ll clean the plotter better.

Tetris for Applesoft BASIC

a tetris game tableau, paused, with a completed line of bricks about to be removed
a very paused game

Paleotronic’s Tetris for Applesoft BASIC is a surprisingly decent version for something that’s written in an interpreted language. It’s not what anyone would call zippy, but it’s not so slow that you want to give up.

Paleotronic want you to type it in, but life’s too short for that. You can play it in your browser on the Internet Archive: Tetris for Applesoft BASIC by Mark Stock

Or download an auto-booting Apple II disk image:


  • , — move left
  • . — move right
  • A — rotate left
  • R — rotate right
  • Z — drop
  • P — pause
  • Q — quit

Life’s also too short for correcting OCR errors in BASIC code. Tesseract is hilariously bad at recognizing source code, so I had to go through this several times. AppleCommander’s BASIC Tools was very handy for catching the last of the errors with its variable dump: caught the cases of the TO keyword converted to the variable T0 … and frankly, I am no fan of SmartQuotes when applied to source code, either.

Here’s the source, straight from the interpreter with all its weird spacing:

10  GOSUB 1000
100 W = W +1: IF W >LV  THEN W = 0: GOSUB 350
110 K =  PEEK(KB): IF K > = H  THEN  POKE KC,H:K = K -H: GOSUB 300
190  GOTO 100
225 PY = PY *A2: HLIN X1,X2 AT PY: HLIN X1,X2 AT PY +A1: RETURN 
300  ON E(K) GOTO 30000,330,340,350,360,30100
310  RETURN 
330 X = X -1: GOTO 400
340 X = X +1: GOTO 400
350 DN = 1:Y = Y +1: GOSUB 400:DN = 0: RETURN 
360 S = S +1: IF S/4 =  INT(S/4)  THEN S = S -4
400  GOSUB 500
410  GOSUB 800: IF F = 0  THEN X = XX:Y = YY:S = SS: GOSUB 420: IF DN  THEN  GOSUB 900
420  COLOR= CF: FOR PP = 1 TO 4:PX = X +X(S,PP):PY = Y +Y(S,PP): GOSUB 200: NEXT PP:XX = X:YY = Y:SS = S:D = 0: RETURN 
510  COLOR= CB: FOR PP = 1 TO 4:PX = XX +X(SS,PP):PY = YY +Y(SS,PP): GOSUB 200: NEXT PP:DD = 0: RETURN 
800 F = 1: FOR PP = 1 TO 4:PY = Y +Y(SS,PP): ON ( FN PC(X +X(S,PP)) >0) GOTO 805: NEXT PP: RETURN 
805 F = 0: RETURN 
850 F = 1: RETURN 
900 P = 10: GOSUB 30300
905 RN = 0:Y = YM
910 X = XL
920 PY = Y: IF  FN PC(X) = CB  THEN 950
930 X = X +1: IF X < = XR  THEN 920
940 R(RN) = Y:RN = RN +1
950 Y = Y -1: IF Y > = 0  THEN 910
960  IF RN  THEN  GOSUB 30400
970 Y = 0
980 X =  INT((XR -XL)/2) +XL
985 S =  INT( RND(1) *NS):CF = C(S):S = S *4
995  GOTO 31000
1000  DIM E(127),X(27,4),Y(27,4),R(40)
1010  TEXT : HOME : GR 
1011  PRINT "WELCOME..."
1014 LM = 10
1015 XM = 10:YM = 15
1016 XL =  INT((40 -XM)/2)
1017 XR = XL +XM -1
1021 A1 = 1
1022 A2 = 2
1030  DEF  FN PC(X) =  SCRN( X,PY *A2)
1040 CB = 0
1050 XX = 20:YY = 0:SS = 0
1100 KB =  -16384
1110 KC =  -16368
1120 H = 128
1130  REM QUIT
1131 E( ASC("Q")) = 1
1132 E( ASC("Q") -64) = 1
1141 E(8) = 2
1142 E( ASC(",")) = 2
1151 E(21) = 3
1152 E( ASC(".")) = 3
1161 E(32) = 4
1162 E( ASC("Z")) = 4
1171 E( ASC("R")) = 5
1172 E(13) = 5
1173 E( ASC("A")) = 5
1180 E( ASC("P")) = 6
1181 E( ASC("P") -64) = 6
1185  GOSUB 2000
1186  GOSUB 1300
1191  PRINT 
1193  GOTO 31020
1300  COLOR= 4: FOR I = 0 TO 19:X1 = 0:X2 = 39:PY = I: GOSUB 225: NEXT 
1320  COLOR= CB: FOR I = 0 TO YM:X1 = XL:X2 = XR:PY = I: GOSUB 225: NEXT 
1350  RETURN 
1400  DATA 1
1401  DATA 0,0,1,0,0,1,1,1
1402  DATA 0,0,1,0,0,1,1,1
1403  DATA 0,0,1,0,0,1,1,1
1404  DATA 0,0,1,0,0,1,1,1
1410  DATA 2
1411  DATA 0,1,1,1,2,1,3,1
1412  DATA 1,0,1,1,1,2,1,3
1413  DATA 0,1,1,1,2,1,3,1
1414  DATA 1,0,1,1,1,2,1,3
1420  DATA 12
1421  DATA 1,1,0,1,1,0,2,1
1422  DATA 1,1,0,1,1,0,1,2
1423  DATA 1,1,0,1,2,1,1,2
1424  DATA 1,1,1,0,2,1,1,2
1430  DATA 13
1431  DATA 1,1,0,1,2,1,0,2
1432  DATA 1,1,1,0,1,2,2,2
1433  DATA 1,1,0,1,2,1,2,0
1434  DATA 1,1,1,0,1,2,0,0
1440  DATA 9
1441  DATA 1,1,0,1,2,1,2,2
1442  DATA 1,1,1,0,1,2,2,0
1443  DATA 1,1,0,1,2,1,0,0
1444  DATA 1,1,1,0,1,2,0,2
1450  DATA 3
1451  DATA 1,1,1,0,0,0,2,1
1452  DATA 1,1,1,0,0,1,0,2
1453  DATA 1,1,1,0,0,0,2,1
1454  DATA 1,1,1,0,0,1,0,2
1460  DATA 6
1461  DATA 1,1,0,1,1,0,2,0
1462  DATA 1,1,0,1,0,0,1,2
1463  DATA 1,1,0,1,1,0,2,0
1464  DATA 1,1,0,1,0,0,1,2
1990  DATA  -1
2000 X = 0:Y = 0
2010 NS = 0
2020  READ C: IF C < > -1  THEN C(NS) = C: FOR J = 0 TO 3: FOR I = 1 TO 4: READ X(NS *4 +J,I): READ Y(NS *4 +J,I): NEXT I: NEXT J:NS = NS +1: GOTO 2020
2030  RETURN 
21210 P = 1: RETURN 
30000  TEXT : HOME : END 
30100  HOME 
30120 P = 1
30130 K =  PEEK(KB): IF K > = H  THEN  POKE KC,H:K = K -H: GOSUB 30200
30140  IF P  THEN 30130
30150  HOME 
30160  PRINT "SCORE ";SC; TAB( 21);"LEVEL ";LM -LV +1
30170  RETURN 
30200  ON E(K) GOTO 30000,30210,30210,30210,30210,30220
30210  RETURN 
30220 P = 0
30230  RETURN 
30300 SC = SC +P
30310  VTAB 21: HTAB 7
30320  PRINT SC;
30330  RETURN 
30400 RN = RN -1
30410  FOR C = 0 TO 32
30415  COLOR= C
30420  FOR I = 0 TO RN:X1 = XL:X2 = XR:PY = R(I): GOSUB 225: NEXT I
30430  FOR I = 0 TO 2: NEXT I
30440  NEXT C
30450  FOR I = 0 TO RN
30460 Y = R(I) +I
30470 YP = Y -1: FOR X = XL TO XR:PY = YP: COLOR=  FN PC(X):PX = X:PY = Y: GOSUB 200: NEXT X:Y = Y -1: IF Y >0  THEN 30470
30480 P = 100: GOSUB 30300
30490  NEXT I
30495  RETURN 
31000  VTAB 22: PRINT 
31010  PRINT "              GAME OVER"
31020 P = 1
31030 K =  PEEK(KB): IF K > = H  THEN  POKE KC,H:K = K -H: GOSUB 31200
31040  IF P  THEN 31030
31050 D = 1
31060 SC = 0:LV = LM
31070  GOSUB 30150
31080  GOSUB 1300
31090  GOTO 905
31200  ON E(K) GOTO 30000
31210 P = 0: RETURN 

If only AppleSoft had a RENUM command, the code might not look so messy

digging the BlueSCSI

I like old (as in 68K old) Apple Macintoshes, but I don’t like their hard drives. Apple used SCSI drives, which were super-cool at the time (multiple drives on one bus! extra devices like SCSI scanners, too!) but now seem an absolute pain. There may be a lot to complain about with USB storage, but compared to SCSI, it just works.

While the 40 MB Quantum SCSI drive in my Mac Classic II still works, it gets really full really fast and that old spinning rust won’t spin forever. One of the newer ways to replace a SCSI drive is the BlueSCSI, an open-everything design based on a cheap Blue Pill micro-controller board, a Micro-SD card slot and some passive components. The whole kit is very affordable, and a local maker sells them, so it was worth a try.

I’ve had nothing but miserable failure with Blue Pill boards, and very quickly moved on to STM32F4 board that actually work. It didn’t fill me with much hope that the board I got with my kit looked like this, end on:

end-on view of a blue micro controller PCB which has - mystifyingly - two micro-USB connectors, one on either face of the PCB
There are two USB connectors on this board.
There are two of ____.

Despite that oddness, it all soldered up fine (the surface-mount card slot was a little fiddly) and it fits inside the Classic II’s cavernously empty shell wherever I choose to stick it down.

I thought I knew what I was doing in making filesystem images (hence my recent nonsense anent HFS utilities), but clearly I was wrong. The 2 GB images I made in Basilisk II weren’t recognized at all. For now, I’m booting from one of the RaSCSI canned boot images plus a couple of the blank formatted drive images to put my own custom system on.

I’m trying to get as much as possible set up on the Micro-SD card while I can still access it, as the Classic II’s case is not something you can pop open on a whim. It needs a special long-thin Torx T15 driver to even get the case partially open, then you have to ease/fight the case the rest of the way. Aside from the faint ponk of dodgy analogue board caps (I’ll fix ’em one day, I promise!), you have to remember to tiptoe around the life-ending voltages lurking at the back of the CRT when you’re working there. Retrotechnology: it smells bad and it can kill you!

A feature I really appreciate with the BlueSCSI is that it dumps a status log on the card every time it boots. It took me a while to get the hang of naming images correctly, but I’d have been absolutely lost without logs with this level of detail:

BlueSCSI <-> SD -
 VERSION: 1.0-20210410
 SdFat version: 2.0.6
 SdFat Max FileName Length: 32
 Initialized SD Card - lets go!
 Not an image: LOG.txt
 Imagefile: HD10_512 753.hda / 41943040bytes / 40960KiB / 40MiB
 Imagefile: HD20_512 BS.hda / 41943040bytes / 40960KiB / 40MiB
 Imagefile: HD40 MacHD-1000MB.hda / 1048576000bytes / 1024000KiB / 1000MiB
 Imagefile: HD30_512 MacHD-500MB.hda / 524288000bytes / 512000KiB / 500MiB
  1: 512:----:
  2: 512:----:
  3: 512:----:
  4: 512:----:
 Finished initialization of SCSI Devices - Entering main loop.

So I’ve got four SCSI drives pretending to live on this card, and even if one of them’s not quite named correctly (HD40 MacHD-1000MB.hda should be called HD40_512 MacHD-1000MB.hda), it’s been found okay.

Powering a Cambridge Z88 with a MT3068 module

keyboard of a small computer with a USB cabled gadget on top of it
my Z88 → USB power cable, with slightly stoory Z88 underneath

I got a Cambridge Computer Z88 again, after perhaps 30 years of not having one. They are very nice little portable computers, remarkable for packing a multi-tasking OS into an 8-bit machine that runs for weeks on 4× AA batteries.

But the Z88 is a Clive Sinclair joint, so there’s going to be at least one deeply weird and/or ill-advised detail about it. For me, it’s the power adapter. The original had a 6 V centre-positive barrel connector, but in true Sinclair fashion, that wasn’t quite ideal.

The DC power comes through a diode, which drops it down to ~5.2 V. The batteries supply up to 6 V and there’s no protection circuit, so the DC adapter won’t do anything until the internal batteries discharge down to that level. This is far from ideal.

The clever way of dealing with this was Rakewell’s Z88 PSU. This was a variable voltage PSU set to deliver 7 V, so that even when dropped through the power diode, it wouldn’t deplete the batteries.

Unfortunately, Rakewell stopped selling these a while ago. But I remembered I had a some MT3608 (datasheet) boards bought at a hamfest some years back. MT3608s are boost DC-DC converters, so they’ll convert from a lower DC voltage to a higher one, typically at least +2  V higher than the input. With a hacked-up USB cable, a small length of DC cable with a connector and a 3d printed case, I built one that works quite well, at least in the short time I’ve tested it.

  • I used the MT3608 step up DC boost box design from Thingiverse
  • Newer MT3608 boards sometimes feature a micro-USB connector, which is much more convenient than hacking up a USB cable
  • It’s really important to know how to adjust a MT3608 DC-DC Booster before connecting the final voltage, as it’s very easy to burn the board out
  • You can’t use a computer USB port to power an MT3608, as the cable’s not smart enough to negotiate a decent amount of current. A good phone charger should be enough.
  • I set the voltage output to be 7.05 V, with no load

niche 68K Mac emulation needs

black and white screenshot of Macintosh System 7 desktop showing Disk First Aid icon
It amazes me how you manage to live in anything that small“: actual size Mac Classic II screenshot

So I’m refurbishing the Mac Classic II I got in 2016 now that I’ve found that BlueSCSI is a fairly cheap way of providing large replacement storage. The 40 MB (yes, 40 MB) drive from 1992 can finally be replaced.

Hit a snag, though: DiskCopy won’t copy a disk with errors, which this drive seemed to have. DiskCopy also won’t repair the boot disk, so you have to find a bootable floppy or some other way to work around this limitation. The only readily available bootable disk image I could find was the System 7.1 Disk Tools floppy — which reported no errors on my drive! Later versions of Disk First Aid would fix it, but weren’t provided on a bootable image.

Here’s the 7.1 Disk Tools floppy with all of the apps replaced by Disk First Aid 7.2. Both of these were found on the Internet Archive’s mirror and combined:

Disk duly repaired, DiskCopy was happy, backup complete. Eventually: the Classic II is not a fast machine at all.

I love the old Mac icons, how they packed so much into so few pixels:

enlarged icon: stylized ambulance with flashing light and driver, side is a floppy disk, there are motion lines at back and the whole icon is slanted to indicate speed/rush
Disk First Aid icon

It’s a stylized ambulance with flashing light and driver, the side is a floppy disk, it’s got motion lines and the whole icon is slanted to indicate speed/rush. Nice!

Vaguely related: most old Mac software is stored as Stuffit! archives. These don’t really work too well on other systems, as they use a compression scheme all their own and are specialized to handle the forked filesystem that old Macs use. Most emulators won’t know what to do with them unless you jump through hoops in the transfer stage.

Fortunately, the ancient Linux package hfsutils knows the ways of these hoops, if only you tell it when to jump. The script below takes a Stuffit! file as its sole argument, and creates a slightly larger HFS image containing the archive, with all the attributes set for Stuffit! Expander or what-have-you to unpack it.

# sitdsk - make an HFS image containing a properly typed sit file
# requires hfsutils
# scruss, 2021-07

    [ $# -ne 1 ]
    echo Usage: $0 file.sit
    exit 1

# hformat won't touch anything smaller than 800 KB,
#  so min image size will be 800 * 1.25 = 1000 KB
size=$(du -k "$1" | awk '{print ($1 >= 800)?$1:800}')
dd status=none of="$dsk" if=/dev/zero bs=1K count=$((size * 125 / 100))
hformat -l "$base" "$dsk"
# note that hformat does an implicit 'hmount'
hcopy "$1" ':'
# and hcopy silently changes underscores to spaces
hattrib -t 'SIT!' -c 'SITx' ":$(echo ${1} | tr '_' ' ')"
hls -l

What this does:

  1. creates a blank image file roughly 25% larger than the archive (or 1000 KB, whichever is the larger) using dd;
  2. ‘formats’ the image file with an HFS filesystem using hformat;
  3. copies the archive to the image using hcopy;
  4. attempts to set the file type and creator using hattrib;
  5. lists the archive contents using hls;
  6. disconnects/unmounts the image from the hfsutils system using humount.

Notice I said it “attempts” to set the file type. hfsutils does some file renaming on the fly, and all I know about is that it changes underscores to spaces. So if there are other changes made by hfsutils, this step may fail. The package also gets really confused by images smaller than 800 KB, so small archives are rounded up in size to keep hformat happy.

Pied Beauty, ya pie

I’m of an age that I had to learn to recite Gerard Manley Hopkins’ Pied Beauty at school, on several different occasions. I did not excel at learning poems by heart; at least, not the ones I was told to learn. I have a difficult relationship with the poem, you could say.

So when my mother-in-law asked for me to recite it for her daily poetry readings (and knowing full well what she would get), I said yes. Here’s something like what she got:

Pied Beauty, read by Stewart Russell — much against his better judgment

It’s a great poem, but one that should never be inflicted on a teenage boy. Yer man GMH was quite the one for making up words: brinded isn’t a thing, and I dunno what happened with the accents on ‘áll trádes’, but they’ve gone well into the twee zone. And as for ‘trout that swim’: is there any other kind, Gerry? Mibbee there’s ones that fly where you’re from, but they’re all strictly aquatic here.

Raspberry Pi Pico with TTP223 Touch Sensor

This is almost too trivial to write up, as the TTP223 does exactly what you’d expect it to do with no other components.

breadboard with Raspberry Pi Pico and small blue capacitive touch sensor
TTP223 sensor board connected to GP22 / physical pin 29

Breakout boards for the TTP223 capacitive touch sensor come in a whole variety of sizes. The ones I got from Simcoe DIY are much smaller, have a different connection order, and don’t have an indicator LED. What they all give you, though, is a single touch/proximity switch for about $1.50

Trivial code to light the Raspberry Pi Pico’s LED when a touch event is detected looks like this:

import machine
touch = machine.Pin(22, machine.Pin.IN)
led = machine.Pin(25, machine.Pin.OUT)

while True:

For the default configuration, the sensor’s output goes high while a touch is detected, then goes low. This might not be the ideal configuration for you, so these sensor boards have a couple of solder links you can modify:

  1. Active Low — sometimes you want a switch to indicate a touch with a low / 0 V signal. On the boards I have, the A link controls that: put a blob of solder across it to reverse the switch’s sense.
  2. Toggle — if you want the output to stay latched at one level until you touch it again, a blob of solder across the T link will do that. Unlike a mechanical switch, this won’t stay latched after a power cycle, though.

And that’s all it does. Sometimes it’s nice to have a sensor that does exactly one thing perfectly well.

Directing, 2003-08-14 Toronto

A woman in business attire stands in the middle of a downtown street. It is late afternoon on 14th August 2003, the first day of the blackout. She is facing west along a street with streetcar lines: her shadow from a beam of sunlight from between two buildings is prominent behind her. Her dark jacket is folded over her left arm, and her right arm is extended in a Stop gesture. No traffic is visible, but there are many pedestrians visible behind her
Directing, 2003-08-14 Toronto

Not a great scan, but it’s a photo I thought I’d lost forever.

Taken in Toronto on the afternoon of the 2003 blackout, I was struck by the way she directed traffic in the middle of the intersection.

(as previously shared on mltshp and subsequently to twitter.)

CardKB mini keyboard with MicroPython

small computer screen with text
** Type stuff, Esc to end **

then further down: "hello I am smol keeb"
it really is the size of a credit card
(running with a SeeedStudio Wio Terminal)

I got one of these CardKB Mini Keyboards to see if I could use it for small interactives with MicroPython devices. It’s very small, and objectively not great as a mass data entry tool. “Better than a Pocket C.H.I.P. keyboard” is how I’d describe the feel. It’s also pretty reliable.

It’s got an I²C Grove connector, and its brains are an ATMega chip just like an Arduino. It’s strictly an ASCII keyboard: that is, it sends the 8-bit ASCII code of the key combination you pressed. It doesn’t send scan codes like a PC keyboard. The driver source is in the CardKB m5-docs, so if you really felt ambitious you could write a scan code-like firmware for yourself.

The device appears at I²C peripheral address 95, and returns a single byte when polled. That byte’s either 0 if no key was pressed, or the character code of what was pressed. The Esc key returns chr(27), and Enter returns CR. If you poll the keyboard too fast it seems to lose the plot a little, so a tiny delay seems to help

Here’s a small demo for MicroPython that acts as the world’s worst typewriter:

# M5Stack CardKB tiny keyboard - scruss, 2021-06
# MicroPython - Raspberry Pi Pico

from machine import Pin, I2C
from time import sleep_ms

i2c = I2C(1, scl=Pin(7), sda=Pin(6))
cardkb = i2c.scan()[0]  # should return 95
if cardkb != 95:
    print("!!! Check I2C config: " + str(i2c))
    print("!!! CardKB not found. I2C device", cardkb,
          "found instead.")

ESC = chr(27)
NUL = '\x00'
CR = "\r"
LF = "\n"
c = ''

print("** Type stuff, Esc to end **")

while (c != ESC):
    # returns NUL char if no character read
    c = i2c.readfrom(cardkb, 1).decode()
    if c == CR:
        # convert CR return key to LF
        c = LF
    if c != NUL or c != ESC:
        print(c, end='')

And here’s the CircuitPython version. It has annoying tiny differences. It won’t let me use the I²C Grove connector on the Wio Terminal for some reason, but it does work much the same:

# M5Stack CardKB tiny keyboard - scruss, 2021-06
# CircuitPython - SeeedStudio Wio Terminal
# NB: can't use Grove connector under CPY because CPY

import time
import board
import busio

i2c = busio.I2C(board.SCL, board.SDA)

while not i2c.try_lock():

cardkb = i2c.scan()[0]  # should return 95
if cardkb != 95:
    print("!!! Check I2C config: " + str(i2c))
    print("!!! CardKB not found. I2C device", cardkb,
          "found instead.")

ESC = chr(27)
NUL = '\x00'
CR = "\r"
LF = "\n"
c = ''
b = bytearray(1)

# can't really clear screen, so this will do
for i in range(12):
print("** Type stuff, Esc to end **")
for i in range(8):

while (c != ESC):
    # returns NUL char if no character read
    i2c.readfrom_into(cardkb, b)
    c = b.decode()
    if c == CR:
        # convert CR return key to LF
        c = LF
    if c != NUL or c != ESC:
        print(c, end='')

# be nice, clean up

An hour of Pink Noise

cover made by netpbm, of course
an hour of soothing 2-channel noise

Direct download: 01-pink_noise.mp3

There are a million variations on the simple “use sox to play masking pink noise“, such as:

play -n synth pinknoise gain -3

This will play synthesized pink noise until you hit Ctrl-C.

But it you want two independent noise channels rather than mono, that’s a little more complex. It’s probably easier to download/play the MP3 file above than show you the command line.

Note that MP3s really aren’t designed to encode such random data, and it’s likely that your player will cause the audio to clip in a couple of places. I’m not quite sure why it does this, but it does it repeatably.

If you want to create this for yourself (and create a bonus lossless FLAC, which was far too large to upload here), here’s what I did to make this:



# make the track
sox --combine merge "|sox --norm=-3 -c 1 -b 16 -r 44100 -n -p synth $duration pinknoise" "|sox --norm=-3 -c 1 -b 16 -r 44100 -n -p synth $duration pinknoise" -c 2 -b 16 -r 44100 $outfile fade $fade fade 0 $duration $fade gain -n -3

# make the cover
# 1 - text - 500 x 500 px
pnmcat -white -tb <(pbmmake -white 500 114) <(pbmtextps -font HelveticaBold -fontsize 64 -resolution 180 "PINK" | pnmcrop) <(pbmmake -white 32 32) <(pbmtextps -font HelveticaBold -fontsize 64 -resolution 180 "NOISE" | pnmcrop) <(pbmmake -white 500 114) > cover-text.pbm
# 2 - make the noise bg
pgmnoise 500 500 > cover-noise.pgm
# 3 - make the magenta text
ppmchange black magenta cover-text.pbm > cover-text-magenta.ppm
# 4 - overlay with transparency
pnmcomp -alpha=<(pnminvert cover-text.pbm | pbmtopgm 35 35 ) cover-text-magenta.ppm cover-noise.pgm | cjpeg -qual 50 -opt -baseline -dct float > cover.jpg
# delete the temporary image files, leaving cover.jpg
rm -f cover-text.pbm cover-noise.pgm cover-text-magenta.ppm

# make the mp3
lame -V 2 --noreplaygain -m s --tt 'Pink Noise' --ta 'Pink Noise' --tl 'Pink Noise' --ty $(date +%Y) --tc "scruss, 2021-05" --tn 1/1 --tg Ambient --ti cover.jpg "$outfile" 01-pink_noise.mp3

# make the flac (and delete wav file)
flac --best --output-name=01-pink_noise.flac --delete-input-file --picture=cover.jpg --tag="TITLE=Pink Noise" --tag="ARTIST=Pink Noise" --tag="ALBUM=Pink Noise" --tag="DATE=$(date +%Y)" --tag="COMMENT=scruss, 2021-05" --tag="GENRE=Ambient" --tag="TRACKNUMBER=1" --tag="TRACKTOTAL=1" "$outfile"

You’ll likely need these packages installed:

sudo apt install sox libsox-fmt-all ghostscript gsfonts-x11 netpbm lame flac libjpeg-progs

The cheapest Micro SD card interface in the world

a micro-sd adapter with 7 0.1"-pitch header pins  soldered onto its contacts
micro-SD adapter + pins + solder = working SD interface

It’s only a serial SPI interface, but you can’t beat the price. It should only be used with 3.3 V micro-controllers like the Raspberry Pi Pico, since micro-SD cards don’t like 5 V directly at all.

You might want to pre-tin the pins and apply some extra flux on both surfaces, because these pads are thin and you don’t want to melt them. I used my standard SnAgCu lead-free solder without trouble, though.

label sticker image for 7 pins, from left to right DO, GND, CLK, 3V3, GND, DI, CS
got a label maker? This label’s the same length as an SD card is wide, as shown above.
Made entirely with netpbm

You only need to use one of the Ground connections for the card to work.