The Potato

… is a thing to help soldering DIN connectors. I had some made at JLCPCB, and will have them for sale at World of Commodore tomorrow.

a rectangular green circuit board with markings for various DIN connectors, and holes for the connector pins to fin through. One of the sets of holes is filled by a 7-pin 270° DIN connector, ready for soldering.

There are various pinouts for retrocomputers on the board. There is also the slogan THE POTATO, with a smiling cartoon potato next to it
Sven Petersen’s “The Potato” – front. DIN7 connector not included
a rectangular green circuit board with markings for various DIN connectors, and holes for the connector pins to fin through. One of the sets of holes is filled by a 7-pin 270° DIN connector, ready for soldering.

There are various pinouts for retrocomputers on the board. There is also the slogan DE KANTÜFFEL, with a smiling cartoon potato next to it
Sven Petersen’s “The Potato” – back

You can get the source from svenpetersen1965/DIN-connector_soldering-aid-The-Potato. I had the file Rev. 0/Gerber /gerber_The_Potato_noFrame_v0a.zip made, and it seems to fit connector pins well.

Each Potato is made up of two PCBs, spaced apart by a nylon washer and held together by M3 nylon screws.

can we…?

This is a mini celebratory post to say that I’ve fixed the database encoding problems on this blog. It looks like I will have to go through the posts manually to correct the errors still, but at least I can enter, store and display UTF-8 characters as expected.

“? µ ° × — – ½ ¾ £ é?êè”, he said with some relief.

Postmortem: For reasons I cannot explain or remember, the database on this blog flipped to an archaic character set: latin1, aka ISO/IEC 8859-1. A partial fix was effected by downloading the entire site’s database backup, and changing all the following references in the SQL:

  • CHARSET=latin1 → CHARSET=utf8mb4
  • COLLATE=latin1_german2_ci → COLLATE=utf8mb4_general_ci
  • COLLATE utf8mb4_general_ci → COLLATE utf8mb4_general_ci
  • latin1_general_ci → utf8mb4_general_ci
  • COLLATE latin1_german2_ci → COLLATE utf8mb4_general_ci
  • CHARACTER SET latin1 → CHARACTER SET utf8mb4

For additional annoyance, the entire SQL dump was too big to load back into phpmyadmin, so I had to split it by table. Thank goodness for awk!

#!/usr/bin/awk -f

BEGIN {
    outfile = "nothing.sql";
}

/^# Table: / {
    # very special comment in WP backup that introduces a new table
    # last field is table_name,
    # which we use to create table_name.sql
    t = $NF
    gsub(/`/, "", t);
    outfile = t ".sql";
}

{
    print > outfile;
}

The data still appears to be confused. For example, in the post Compose yourself, Raspberry Pi!, what should appear as “That little key marked “Compose”” appears as “That little key marked “Compose””. This isn’t a straight conversion of one character set to another. It appears to have been double-encoded, and wrongly too.

Still, at least I can now write again and have whatever new things I make turn up the way I like. Editing 20 years of blog posts awaits … zzz

SYN6288 TTS board from AliExpress

After remarkable success with the SYN-6988 TTS module, then somewhat less success with the SYN-6658 and other modules, I didn’t hold out much hope for the YuTone SYN-6288, which – while boasting a load of background tunes that could play over speech – can only convert Chinese text to speech

small blue circuit board with 6 MHz crystal oscillator, main chip, input headers at bottom and headphone jack/speaker output at top
as bought from quason official store: SYN6288 speech synthesis module

The wiring is similar to the SYN-6988: a serial UART connection at 9600 baud, plus a Busy (BY) line to signal when the chip is busy. The serial protocol is slightly more complicated, as the SYN-6288 requires a checksum byte at the end.

As I’m not interested in the text-to-speech output itself, here’s a MicroPython script to play all of the sounds:

# very crude MicroPython demo of SYN6288 TTS chip
# scruss, 2023-07
import machine
import time

### setup device
ser = machine.UART(
    0, baudrate=9600, bits=8, parity=None, stop=1
)  # tx=Pin(0), rx=Pin(1)

busyPin = machine.Pin(2, machine.Pin.IN, machine.Pin.PULL_UP)


def sendspeak(u2, data, busy):
    # modified from https://github.com/TPYBoard/TPYBoard_lib/
    # u2 = UART(uart, baud)
    eec = 0
    buf = [0xFD, 0x00, 0, 0x01, 0x01]
    # buf = [0xFD, 0x00, 0, 0x01, 0x79]  # plays with bg music 15
    buf[2] = len(data) + 3
    buf += list(bytearray(data, "utf-8"))
    for i in range(len(buf)):
        eec ^= int(buf[i])
    buf.append(eec)
    u2.write(bytearray(buf))
    while busy.value() != True:
        # wait for busy line to go high
        time.sleep_ms(5)
    while busy.value() == True:
        # wait for it to finish
        time.sleep_ms(5)


for s in "abcdefghijklmnopqrstuvwxy":
    playstr = "[v10][x1]sound" + s
    print(playstr)
    sendspeak(ser, playstr, busyPin)
    time.sleep(2)

for s in "abcdefgh":
    playstr = "[v10][x1]msg" + s
    print(playstr)
    sendspeak(ser, playstr, busyPin)
    time.sleep(2)

for s in "abcdefghijklmno":
    playstr = "[v10][x1]ring" + s
    print(playstr)
    sendspeak(ser, playstr, busyPin)
    time.sleep(2)

Each sound starts and stops with a very loud click, and the sound quality is not great. I couldn’t get a good recording of the sounds (some of which of which are over a minute long) as the only way I could get reliable audio output was through tiny headphones. Any recording came out hopelessly distorted:

I’m not too disappointed that this didn’t work well. I now know that the SYN-6988 is the good one to get. It also looks like I may never get to try the XFS5152CE speech synthesizer board: AliExpress has cancelled my shipment for no reason. It’s supposed to have some English TTS function, even if quite limited.

Here’s the auto-translated SYN-6288 manual, if you do end up finding a use for the thing

SYN-6988 Speech with MicroPython

Full repo, with module and instructions, here: scruss/micropython-SYN6988: MicroPython library for the VoiceTX SYN6988 text to speech module

(and for those that CircuitPython is the sort of thing they like, there’s this: scruss/circuitpython-SYN6988: CircuitPython library for the YuTone VoiceTX SYN6988 text to speech module.)

I have a bunch of other boards on order to see if the other chips (SYN6288, SYN6658, XF5152) work in the same way. I really wonder which I’ll end up receiving!

Update (2023-07-09): Got the SYN6658. It does not support English TTS and thus is not recommended. It does have some cool sounds, though.

Embedded Text Command Sound Table

The github repo references Embedded text commands, but all of the sound references was too difficult to paste into a table there. So here are all of the ones that the SYN-6988 knows about:

  • Name is the string you use to play the sound, eg: [x1]sound101
  • Alias is an alternative name by which you can call some of the sounds. This is for better compatibility with the SYN6288 apparently. So [x1]sound101 is exactly the same as specifying [x1]sounda
  • Type is the sound description from the manual. Many of these are blank
  • Link is a playable link for a recording of the sound.
NameAliasTypeLink
sound101sounda
sound102soundb
sound103soundc
sound104soundd
sound105sounde
sound106soundf
sound107soundg
sound108soundh
sound109soundi
sound110soundj
sound111soundk
sound112soundl
sound113soundm
sound114soundn
sound115soundo
sound116soundp
sound117soundq
sound118soundr
sound119soundt
sound120soundu
sound121soundv
sound122soundw
sound123soundx
sound124soundy
sound201phone ringtone
sound202phone ringtone
sound203phone ringtone
sound204phone rings
sound205phone ringtone
sound206doorbell
sound207doorbell
sound208doorbell
sound209doorbell
sound301alarm
sound302alarm
sound303alarm
sound304alarm
sound305alarm
sound306alarm
sound307alarm
sound308alarm
sound309alarm
sound310alarm
sound311alarm
sound312alarm
sound313alarm
sound314alarm
sound315alert/emergency
sound316alert/emergency
sound317alert/emergency
sound318alert/emergency
sound401credit card successful
sound402credit card successful
sound403credit card successful
sound404credit card successful
sound405credit card successful
sound406credit card successful
sound407credit card successful
sound408successfully swiped the card
SYN-6988 Sound Reference

MicroPython on the Seeed Studio Wio Terminal: it works!

A while back, Seeed Studio sent me one of their Wio Terminal devices to review. It was pretty neat, but being limited to using Arduino to access all of it features was a little limiting. I still liked it, though, and wrote about it here: SeeedStudio Wio Terminal

Small screen device showing geometric pattern
Wio Terminal, doing a thing

There wasn’t any proper MicroPython support for the device as it used a MicroChip/Atmel SAMD51 ARM® Cortex®-M4 micro-controller. But since I wrote the review, one developer (robert-hh) has worked almost entirely solo to make SAMD51 and SAMD21 support useful in mainline MicroPython.

Hey! Development is still somewhere between “not quite ready for prime time” and “beware of the leopard”. MicroPython on the SAMD51 works remarkably well for supported boards, but don’t expect this to be beginner-friendly yet.

I thought I’d revisit the Wio Terminal and see what I could do using a nightly build (downloaded from Downloads – Wio Terminal D51R – MicroPython). Turns out, most of the board works really well!

What doesn’t work yet

  • Networking/Bluetooth – this is never going to be easy, especially with Seeed Studio using a separate RTL8720 SoC. It may not be entirely impossible, as previously thought, but so far, wifi support seems quite far away
  • QSPI flash for program storagethis is not impossible, just not implemented yet this works now too, but it’s quite slow since it relies on a software SPI driver. More details: samd51: MicroPython on the Seeed Wio Terminal · Discussion #9838 · micropython
  • RTCthis is a compile-time option, but isn’t available on the stock images. Not all SAMD51 boards have a separate RTC oscillator, and deriving the RTC from the system oscillator would be quite wobbly. RTC works now! It may even be possible to provide backup battery power and have it keep time when powered off. VBAT / PB03 / SPI_SCK is broken out to the 40-pin connector.

What does work

  • Display – ILI9341 320×240 px, RGB565 via SPI
  • Accelerometer – LIS3DHTR via I²C
  • Microphone – analogue
  • Speaker – more like a buzzer, but this little PWM speaker element does allow you to play sounds
  • Light Sensor – via analogue photo diode
  • IR emitter – PWM, not tied to any hardware protocol
  • Internal LED – a rather faint blue thing, but useful for low-key signalling
  • Micro SD Card – vi SPI. Works well with MicroPython’s built-in virtual file systems
  • Switches and buttons – three buttons on the top, and a five-way mini-joystick
  • I²C via Grove Connector – a second, separate I²C channel.

I’ll go through each of these here, complete with a small working example.

Wio Terminal main board
Inside the remarkably hard-to-open Wio Terminal

LED

Let’s start with the simplest feature: the tiny blue LED hidden inside the case. You can barely see this, but it glows out around the USB C connector on the bottom of the case.

  • MicroPython interfaces: machine.Pin, machine.PWM
  • Control pin: Pin(“LED_BLUE”) or Pin(15), or Pin(“PA15”): any one of these would work.

Example: Wio-Terminal-LED.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-LED.py - blink the internal blue LED
# scruss, 2022-10
# -*- coding: utf-8 -*-

from machine import Pin
from time import sleep_ms

led = Pin("LED_BLUE", Pin.OUT)  # or Pin(15) or Pin("PA15")

try:
    while True:
        led.value(not led.value())
        sleep_ms(1200)
except:
    led.value(0)  # turn it off if user quits
    exit()

IR LED

I don’t have any useful applications of the IR LED for device control, so check out Awesome MicroPython’s IR section for a library that would work for you.

  • MicroPython interfaces: machine.PWM
  • Control pin: Pin(“PB31”)

Example: Wio-Terminal-IR_LED.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-IR_LED.py - blink the internal IR LED
# scruss, 2022-10
# -*- coding: utf-8 -*-

# Hey! This is a completely futile exercise, unless you're able
# to see into the IR spectrum. But we're here to show you the pin
# specification to use. For actual useful libraries to do stuff with
# IR, take a look on https://awesome-micropython.com/#ir

# So this is a boring blink, 'cos we're keeping it short here.
# You might be able to see the LED (faintly) with your phone camera

from machine import Pin, PWM
from time import sleep_ms

ir = PWM(Pin("PB31"))  # "IR_CTL" not currently defined

try:
    while True:
        ir.duty_u16(32767)  # 50% duty
        ir.freq(38000)  # fast flicker
        sleep_ms(1200)
        ir.duty_u16(0)  # off
        sleep_ms(1200)
except:
    ir.duty_u16(0)  # turn it off if user quits
    exit()

Buttons

There are three buttons on top, plus a 5-way joystick on the front. Their logic is inverted, so they read 0 when pressed, 1 when not. It’s probably best to use machine.Signal with these to make operation more, well, logical.

  • MicroPython interface: machine.Signal (or machine.Pin)
  • Control pins: Pin(“BUTTON_3”) or Pin(92) or Pin(PC28) – top left; Pin(“BUTTON_2”) or Pin(91) or Pin(PC27) – top middle; Pin(“BUTTON_1”) or Pin(90) or Pin(PC26) – top right; Pin(“SWITCH_B”) or Pin(108) or Pin(PD12) – joystick left; Pin(“SWITCH_Y”) or Pin(105) or Pin(PD09) – joystick right; Pin(“SWITCH_U”) or Pin(116) or Pin(PD20) – joystick up; Pin(“SWITCH_X”) or Pin(104) or Pin(PD08) – joystick down; Pin(“SWITCH_Z”) or Pin(106) or Pin(PD10) – joystick button

Example: Wio-Terminal-Buttons.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-Buttons.py - test the buttons
# scruss, 2022-10
# -*- coding: utf-8 -*-

# using Signal because button sense is inverted: 1 = off, 0 = on
from machine import Pin, Signal
from time import sleep_ms

pin_names = [
    "BUTTON_3",  # Pin(92)  or Pin(PC28) - top left
    "BUTTON_2",  # Pin(91)  or Pin(PC27) - top middle
    "BUTTON_1",  # Pin(90)  or Pin(PC26) - top right
    "SWITCH_B",  # Pin(108) or Pin(PD12) - joystick left
    "SWITCH_Y",  # Pin(105) or Pin(PD09) - joystick right
    "SWITCH_U",  # Pin(116) or Pin(PD20) - joystick up
    "SWITCH_X",  # Pin(104) or Pin(PD08) - joystick down
    "SWITCH_Z",  # Pin(106) or Pin(PD10) - joystick button
]

pins = [None] * len(pin_names)
for i, name in enumerate(pin_names):
    pins[i] = Signal(Pin(name, Pin.IN), invert=True)

while True:
    for i in range(len(pin_names)):
        print(pins[i].value(), end="")
    print()
    sleep_ms(100)

Buzzer

A very quiet little PWM speaker.

  • MicroPython interfaces: machine.PWM
  • Control pin: Pin(“BUZZER”) or Pin(107) or Pin(“PD11”)

Example: Wio-Terminal-Buzzer.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-Buzzer.py - play a scale on the buzzer with PWM
# scruss, 2022-10
# -*- coding: utf-8 -*-

from time import sleep_ms
from machine import Pin, PWM

pwm = PWM(Pin("BUZZER", Pin.OUT))  # or Pin(107) or Pin("PD11")
cmaj = [262, 294, 330, 349, 392, 440, 494, 523]  # C Major Scale frequencies

for note in cmaj:
    print(note, "Hz")
    pwm.duty_u16(32767)  # 50% duty
    pwm.freq(note)
    sleep_ms(225)
    pwm.duty_u16(0)  # 0% duty - silent
    sleep_ms(25)

Light Sensor

This is a simple photo diode. It doesn’t seem to return any kind of calibrated value. Reads through the back of the case.

  • MicroPython interfaces: machine.ADC
  • Control pin: machine.ADC(“PD01”)

Example code: Wio-Terminal-LightSensor.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-LightSensor.py - print values from the light sensor
# scruss, 2022-10
# -*- coding: utf-8 -*-

from time import sleep_ms
from machine import ADC

# PD15-22C/TR8 photodiode
light_sensor = ADC("PD01")

while True:
    print([light_sensor.read_u16()])
    sleep_ms(50)

Microphone

Again, a simple analogue sensor:

  • MicroPython interfaces: machine.ADC
  • Control pin: machine.ADC(“MIC”)

Example: Wio-Terminal-Microphone.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-Microphone.py - print values from the microphone
# scruss, 2022-10
# -*- coding: utf-8 -*-

from time import sleep_ms
from machine import ADC

mic = ADC("MIC")

while True:
    print([mic.read_u16()])
    sleep_ms(5)

Grove I²C Port

The Wio Terminal has two Grove ports: the one on the left (under the speaker port) is an I²C port. As I don’t know what you’ll be plugging in there, this example does a simple bus scan. You could make a, appalling typewriter if you really wanted.

  • MicroPython interfaces: machine.I2C (channel 3), machine. Pin
  • Control pins: scl=Pin(“SCL1”), sda=Pin(“SDA1”)

Example: Wio-Terminal-Grove-I2C.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-Grove-I2C.py - show how to connect on Grove I2C
# scruss, 2022-10
# -*- coding: utf-8 -*-

from machine import Pin, I2C

# NB: This doesn't do much of anything except list what's
# connected to the left (I²C) Grove connector on the Wio Terminal

i2c = I2C(3, scl=Pin("SCL1"), sda=Pin("SDA1"))
devices = i2c.scan()

if len(devices) == 0:
    print("No I²C devices connected to Grove port.")
else:
    print("Found these I²C devices on the Grove port:")
    for n, id in enumerate(devices):
        print(" device", n, ": ID", id, "(hex:", hex(id) + ")")

LIS3DH Accelerometer

This is also an I²C device, but connected to a different port (both logically and physically) than the Grove one.

  • MicroPython interfaces: machine.I2C (channel 4), machine. Pin
  • Control pins: scl=Pin(“SCL0”), sda=Pin(“SDA0”)
  • Library: from MicroPython-LIS3DH, copy lis3dh.py to the Wio Terminal’s small file system. Better yet, compile it to mpy using mpy-cross to save even more space before you copy it across

Example: Wio-Terminal-Accelerometer.py (based on tinypico-micropython/lis3dh library/example.py)

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-Accelerometer.py - test out accelerometer
# scruss, 2022-10
# -*- coding: utf-8 -*-
# based on
#  https://github.com/tinypico/tinypico-micropython/tree/master/lis3dh%20library

import lis3dh, time, math
from machine import Pin, I2C

i2c = I2C(4, scl=Pin("SCL0"), sda=Pin("SDA0"))
imu = lis3dh.LIS3DH_I2C(i2c)

last_convert_time = 0
convert_interval = 100  # ms
pitch = 0
roll = 0

# Convert acceleration to Pitch and Roll
def convert_accell_rotation(vec):
    x_Buff = vec[0]  # x
    y_Buff = vec[1]  # y
    z_Buff = vec[2]  # z

    global last_convert_time, convert_interval, roll, pitch

    # We only want to re-process the values every 100 ms
    if last_convert_time < time.ticks_ms():
        last_convert_time = time.ticks_ms() + convert_interval

        roll = math.atan2(y_Buff, z_Buff) * 57.3
        pitch = (
            math.atan2((-x_Buff), math.sqrt(y_Buff * y_Buff + z_Buff * z_Buff)) * 57.3
        )

    # Return the current values in roll and pitch
    return (roll, pitch)


# If we have found the LIS3DH
if imu.device_check():
    # Set range of accelerometer (can be RANGE_2_G, RANGE_4_G, RANGE_8_G or RANGE_16_G).
    imu.range = lis3dh.RANGE_2_G

    # Loop forever printing values
    while True:
        # Read accelerometer values (in m / s ^ 2).  Returns a 3-tuple of x, y,
        # z axis values.  Divide them by 9.806 to convert to Gs.
        x, y, z = [value / lis3dh.STANDARD_GRAVITY for value in imu.acceleration]
        print("x = %0.3f G, y = %0.3f G, z = %0.3f G" % (x, y, z))

        # Convert acceleration to Pitch and Roll and print values
        p, r = convert_accell_rotation(imu.acceleration)
        print("pitch = %0.2f, roll = %0.2f" % (p, r))

        # Small delay to keep things responsive but give time for interrupt processing.
        time.sleep(0.1)

SD Card

  • MicroPython interfaces: machine.SPI (channel 6), machine.Pin, machine.Signal
  • Control Pins: Pin(“SD_SCK”), Pin(“SD_MOSI”), Pin(“SD_MISO”) for SD access. Pin(“SD_DET”) is low if an SD card is inserted, otherwise high
  • Library: copy sdcard.py from micropython-lib to the Wio Terminal’s file system.

Rather than provide a small canned example (there’s one here, if you must: Wio-Terminal-SDCard.py) here’s my boot.py startup file, showing how I safely mount an SD card if there’s one inserted, but keep booting even if it’s missing:

# boot.py - MicroPython / Seeed Wio Terminal / SAMD51

import sys

sys.path.append("/lib")

import machine
import gc
import os
import sdcard

machine.freq(160000000)  # fast but slightly jittery clock
gc.enable()

# mount SD card if there's one inserted
try:
    sd_detected = machine.Signal(
        machine.Pin("SD_DET", machine.Pin.IN),
        invert=True,
    )
    sd_spi = machine.SPI(
        6,
        sck=machine.Pin("SD_SCK"),
        mosi=machine.Pin("SD_MOSI"),
        miso=machine.Pin("SD_MISO"),
        baudrate=40000000,
    )
    sd = sdcard.SDCard(sd_spi, machine.Pin("SD_CS"))
    if sd_detected.value() == True:
        os.mount(sd, "/SD")
        print("SD card mounted on /SD")
    else:
        raise Exception("SD card not inserted, can't mount /SD")
except:
    print("SD card not found")


ILI9341 Display

I’m going to use the library rdagger/micropython-ili9341: MicroPython ILI9341Display & XPT2046 Touch Screen Driver because it’s reliable, and since it’s written entirely in MicroPython, it’s easy to install. It’s not particularly fast, though.

The Wio Terminal may have an XPT2046 resistive touch controller installed, but I haven’t been able to test it. There are LCD_XL, LCD_YU, LCD_XR and LCD_YD lines on the schematic that might indicate it’s there, though.

  • MicroPython interfaces: machine.SPI (channel 7), machine.Pin.
  • Control Pins: Pin(“LCD_SCK”), Pin(“LCD_MOSI”), Pin(“LCD_MISO”). Pin(“LED_LCD”) is the backlight control
  • Library: copy ili9341.py from rdagger /micropython-ili9341 to the Wio Terminal’s file system.

This demo draws rainbow-coloured diamond shapes that change continuously.

Example: Wio-Terminal-Screen.py

# MicroPython / Seeed Wio Terminal / SAMD51
# Wio-Terminal-Screen.py - output something on the ILI9341 screen
# scruss, 2022-10
# -*- coding: utf-8 -*-


from time import sleep
from ili9341 import Display, color565
from machine import Pin, SPI


def wheel565(pos):
    # Input a value 0 to 255 to get a colour value.
    # The colours are a transition r - g - b - back to r.
    # modified to return RGB565 value for ili9341 - scruss
    (r, g, b) = (0, 0, 0)
    if (pos < 0) or (pos > 255):
        (r, g, b) = (0, 0, 0)
    if pos < 85:
        (r, g, b) = (int(pos * 3), int(255 - (pos * 3)), 0)
    elif pos < 170:
        pos -= 85
        (r, g, b) = (int(255 - pos * 3), 0, int(pos * 3))
    else:
        pos -= 170
        (r, g, b) = (0, int(pos * 3), int(255 - pos * 3))
    return (r & 0xF8) << 8 | (g & 0xFC) << 3 | b >> 3


# screen can be a little slow to turn on, so use built-in
# LED to signal all is well
led = Pin("LED_BLUE", Pin.OUT)

backlight = Pin("LED_LCD", Pin.OUT)  # backlight is not a PWM pin
spi = SPI(
    7, sck=Pin("LCD_SCK"), mosi=Pin("LCD_MOSI"), miso=Pin("LCD_MISO"), baudrate=4000000
)
display = Display(spi, dc=Pin("LCD_D/C"), cs=Pin("LCD_CS"), rst=Pin("LCD_RESET"))
display.display_on()
display.clear()
led.on()  # shotgun debugging, embedded style
backlight.on()

# use default portrait settings: x = 0..239, y = 0..319
dx = 3
dy = 4
x = 3
y = 4
i = 0

try:
    while True:
        # display.draw_pixel(x, y, wheel565(i))
        display.fill_hrect(x, y, 3, 4, wheel565(i))
        i = (i + 1) % 256
        x = x + dx
        y = y + dy
        if x <= 4:
            dx = -dx
        if x >= 234:
            dx = -dx
        if y <= 5:
            dy = -dy
        if y >= 313:
            dy = -dy
except:
    backlight.off()
    led.off()
    display.display_off()

MicroPython MIDI mayhem (kinda)

It pleased me to learn about umidiparser – MIDI file parser for Micropython. Could I use my previous adventures in beepy nonsense to turn a simple MIDI file into a terrible squeaky rendition of same? You betcha!

MIDI seems to be absurdly complex. In all the files I looked at, there didn’t seem to be much of a standard in encoding whether the note duration was in the NOTE_ON event or the NOTE_OFF event. Eventually, I managed to fudge a tiny single channel file that had acceptable note durations in the NOTE_OFF events. Here is the file:

I used the same setup as before:

Raspberry Pi Pico with small piezo speaker connected to pins 23 and 26
piezo between pins 26 and 23

With this code:

# extremely crude MicroPython MIDI demo
# MicroPython / Raspberry Pi Pico - scruss, 2022-08
# see https://github.com/bixb922/umidiparser

import umidiparser
from time import sleep_us
from machine import Pin, PWM

# pin 26 - GP20; just the right distance from GND at pin 23
#  to use one of those PC beepers with the 4-pin headers
pwm = PWM(Pin(20))
led = Pin('LED', Pin.OUT)


def play_tone(freq, usec):
    # play RTTL/midi notes, also flash onboard LED
    # original idea thanks to
    #   https://github.com/dhylands/upy-rtttl
    print('freq = {:6.1f} usec = {:6.1f}'.format(freq, usec))
    if freq > 0:
        pwm.freq(int(freq))       # Set frequency
        pwm.duty_u16(32767)       # 50% duty cycle
    led.on()
    sleep_us(int(0.9 * usec))     # Play for a number of usec
    pwm.duty_u16(0)               # Stop playing for gap between notes
    led.off()
    sleep_us(int(0.1 * usec))     # Pause for a number of usec


# map MIDI notes (0-127) to frequencies. Note 69 is 440 Hz ('A4')
freqs = [440 * 2**((float(x) - 69) / 12) for x in range(128)]

for event in umidiparser.MidiFile("lg2.mid", reuse_event_object=True):
    if event.status == umidiparser.NOTE_OFF and event.channel == 0:
        play_tone(freqs[event.note], event.delta_us)

This isn’t be any means a general MIDI parser, but is rather specialized to play monophonic tunes on channel 0. The result is gloriously awful:

apologies to LG

INA219 Current Sensor and MicroPython

More Micropython programmers — and especially beginners — should know about Awesome MicroPython. It’s a community-curated list of remarkably decent MicroPython libraries, frameworks, software and resources. If you need to interface to a sensor, look there first.

For example, take the INA219 High Side DC Current Sensor. It’s an I²C sensor able to measure up to 26 V, ±3.2 A. It does this by measuring the voltage across a 0.1 ohm precision shunt resistor with its built-in 12-bit ADC. I got a customer return from the store that was cosmetically damaged but still usable, so I thought I’d try it with the simplest module I could find in Awesome MicroPython and see how well it worked.

I guess I needed a test circuit too. Using all of what was immediately handy — a resistor I found on the bench and measured at 150.2 ohm — I came up with this barely useful circuit:

simple circle with 3.3 V DC supply ad two resistors of 150.2 ohms and 0.1 ohms in series
Should indicate a current of 3.3 / (150.2 + 0.1) = 21.96 mA

The INA219 would be happier with a much higher current to measure, but I didn’t have anything handy that could do that.

Looking in Awesome MicroPython’s Current section, I found robert-hh/INA219: INA219 Micropython driver. It doesn’t have much (okay, any) documentation, but it’s a very small module and the code is easy enough to follow. I put the ina219.py module file into the /lib folder of a WeAct Studio RP2040 board, and wrote the following code:

# INA219 demo - uses https://github.com/robert-hh/INA219

from machine import Pin, I2C
import ina219

i = I2C(0, scl=Pin(5), sda=Pin(4))
print("I2C Bus Scan: ", i.scan(), "\n")

sensor = ina219.INA219(i)
sensor.set_calibration_16V_400mA()

# my test circuit is 3V3 supply through 150.2 ohm resistor
r_1 = 150.2
r_s = 0.1  # shunt resistor on INA219 board

# current is returned in milliamps
print("Current       / mA: %8.3f" % (sensor.current))
# shunt_voltage is returned in volts
print("Shunt voltage / mV: %8.3f" % (sensor.shunt_voltage * 1000))
# estimate supply voltage from known resistance * sensed current
print("3V3 (sensed)  / mV: %8.3f" % ((r_1 + r_s) * sensor.current))

with everything wired up like this (Blue = SDA, Yellow = SCL):

breadboard with RP2040 pico board and INA219 sensor board benath it, and the 150 ohm wired as a circuit on the side
all of the wires

Running it produced this:

I2C Bus Scan:  [64] 

Current       / mA:   22.100
Shunt voltage / mV:    2.210
3V3 (sensed)  / mV: 3321.630

So it’s showing just over 22 mA: pretty close to what I calculated!

It works! It works!

on a messy desk, a small USB midi keyboard is connected to a Korg NTS-1 mini synthesizer via a small micro-controller board that acts as a USB host for the Akai keyboard, converting USB MIDI to traditional MIDI for the Korg
Akai LPK25 keyboard has USB MIDI out, but the Korg NTS-1 only has regular MIDI in. The little board in the middle acts as a USB host for the Akai and MIDI source for the Korg

This is great: gdsports/midiuartusbh: MIDI DIN to MIDI USB Host Converter allows your USB MIDI instruments to act as traditional MIDI controllers. It uses a Adafruit Trinket M0 to act as the USB host and MIDI output.

I modified gdsports’ design very slightly:

  1. Instead of using a 74AHCT125 Logic level converter and driver, I used a FET-based SparkFun Logic Level Converter
  2. Instead of a 5-pin DIN socket, I used a 3.5 mm stereo socket.

And it works!

breadboard showing Trinket M0 microcontroller board, logic level shifter, audio socket breakout and two resistors
Breadboard layout for MIDI-standard 3.5 mm output (Korg). The resistors are both 220 ohm, and the boards need 5 V power

Mystery lockdown phone message

“Just a test call. Time to stay home. Stay safe and stay home.”

This message from an unknown caller has sat on our landline answering machine since 2020 or 2021. No idea who or what sent it. All I know is it came in just before noon on a Tuesday morning. The entirely synthesized voice makes me think it’s a junk call, but there’s no scam attached. Just this message, slightly eerie, quite inexplicable.

The Quite Rubbish Clock, mk.2

this is bad and I should feel bad

In early 2013, I must’ve been left unsupervised for too long since I made The Quite Rubbish Clock:

It still isn’t human readable …

Written in (Owen Wilson voice) kind of an obsolete vernacular and running on hardware that’s now best described as “quaint”, it was still absurdly popular at the time. Raspberry Pis were still pretty new, and people were looking for different things to do with them.

I happened across the JASchilz/uQR: QR Code Generator for MicroPython the other day, and remembered I had some tiny OLED screens that were about the same resolution as the old Nokia I’d used in 2013. I wondered: could I …?

small microcontroller board with USB C cable attached and an OLED screen on top. The OLED is displaying a QR code which reads '172731'
OLED Shield on a LOLIN S2 Mini: very smol indeed

The board is a LOLIN S2 Mini with a OLED 0.66 Inch Shield on top, all running MicroPython. One limitation I found in the MicroPython QR library was that it was very picky about input formats, so it only displays the time as HHMMSS with no separators.

Source, of course:

# -*- coding: utf-8 -*-
# yes, the Quite Rubbish Clock rides again ...
# scruss, 2022-06-30
# MicroPython on Lolin S2 Mini with 64 x 48 OLED display
# uses uQR from https://github.com/JASchilz/uQR
# - which has problems detecting times with colons

from machine import Pin, I2C, RTC
import s2mini  # on Lolin ESP32-S2 Mini
import ssd1306
from uQR import QRCode

WIDTH = 64  # screen size
HEIGHT = 48
SIZE = 8  # text size
r = RTC()

# set up and clear screen
i2c = I2C(0, scl=Pin(s2mini.I2C_SCL), sda=Pin(s2mini.I2C_SDA))
oled = ssd1306.SSD1306_I2C(WIDTH, HEIGHT, i2c)
oled.fill(0)


def snazz():
    marquee = [
        "   **",
        "   **",
        "   **",
        "   **",
        "   **",
        "********",
        " ******",
        "  ****",
        "   **",
        " quite",
        "rubbish",
        " clock",
        "  mk.2",
        "<scruss>",
        " >2022<"
    ]
    for s in marquee:
        oled.scroll(0, -SIZE)  # scroll up one text line
        oled.fill_rect(0, HEIGHT-SIZE, WIDTH,
                       SIZE, 0)  # blank last line
        oled.text("%-8s" % s, 0, HEIGHT-SIZE)  # write text
        oled.show()
        time.sleep(0.25)
    time.sleep(5)
    oled.fill(1)
    oled.show()


snazz()  # tedious crowd-pleasing intro

qr = QRCode()
while True:
    qr.add_data("%02d%02d%02d" % r.datetime()[4:7])
    qr.border = 1  # default border too big to fit small screen
    m = qr.get_matrix()
    oled.fill(1)
    for y in range(len(m)):
        for x in range(len(m[0])):
            # plot a double-sized QR code, centred, inverted
            oled.fill_rect(9 + 2*x, 1 + 2*y, 2, 2, not m[y][x])
    oled.show()
    time.sleep(0.05)
    qr.clear()

If your output is glitchy, you might need to put the following in boot.py:

import machine
machine.freq(240000000)

This increases the ESP32-S2’s frequency from 160 to 240 MHz.

Adding RGB LEDs to an illuminated arcade button

Somewhat painterly view of the button doing its thing. The weird clunking sound is my camera’s continuous focus. For a clearer but more flickery view, see here

Following on from a customer query at Elmwood Electronics, I can confirm that one can install install addressable RGB LEDs/NeoPixels inside one of these large buttons. It’s not the easiest build, so whether one should attempt this is another matter entirely.

You’ll need:

  • Large Arcade Button with LED – 60 mm White (tall version) – this is larger and more domed than the flat-top one that Adafruit sells
  • RGB LEDs – I used a generic 8 LED ring, but anything not too tall and under 45 mm in diameter should fit. Either a 7 X WS2812 5050 RGB LED Ring or Adafruit’s NeoPixel Ring – 12 x WS2812 5050 RGB LED with Integrated Drivers could also work
  • Thin (and I mean thin: I used 28 AWG) Silicone Cover Stranded-Core Wire in several colours. You’ll want to cut this quite long at first, as you have to ease it through some tiny holes in the button assembly. If you solder connectors on the end, you won’t be able to disassemble or install the button without cutting them off. Do I speak from experience here? You betcha!
  • The usual soldering/hot gluing/bending/prying/grabbing/cutting tools you already know and love. In addition, you might consider a non-marring spudger and a pair of small(ish) arterial forceps (aka hemostats, aka Kelly forceps, aka fishing hook removal pliers)

I’m not going to cover soldering the wires to the LED PCB in any depth here. You’ll need three wires: 5 V power, Ground and Data. Even though the LEDs I used need 5 V power, they are quite happy with 3.3 V logic on the data line. They need more than 3.3 V power to light, though.

a large arcade machine style button on the left: it has a clear domed top and a threaded base. On the right is the combined microswitch and LED holder that fits into the button base
The button in two pieces, as you might expect to receive it
the top of the button disassembled into its main parts: bezel ring at top left, threaded lock ring at bottom, and main button mechanism. The mechanism is upside down, so the return spring and button actuators can be seen inside the threaded shaft
Main parts of the button top, once you’ve removed the lock ring
Close up of inside the shaft: return spring and its retainer tabs, and button actuators can be seen
First step is to ease the spring out without bending it too much or breaking the retainer tabs
Close up of inside the shaft: the tips of a pair of forceps have eased the top of the spring past its retainers
I used small forceps to ease the spring out. Once you get it started, it unscrews easily from behind the retainers
Close up of inside the shaft: the button actuators have been pushed down the shaft, allowing the top of the button to be pulled out
Now the spring is out the way, you can squeeze in the actuator tabs and push them down the shaft to liberate the button top
button top components arranged: black threaded button base on left, return spring in the middle, and domed clear top with white underside and white actuators sticking down
The button top disassembled
clear button top attached to its white underside. A blunt metal tool (spudger) is pointed at the push-fit join between the two parts
Carefully lever off the clear top with a blunt tool like a spudger. Now would have been a great time to clean dust and other wee bits off your workspace, as they’ll surely end up inside the button, looking nasty
clear button top separated from its white base. A translucent white diffuser is inside the clear top. The white base has a hollow centre and a circular cavity
The button top opened up. The cavity is about 45 mm in diameter and only a few millimetres deep
The microswitch with the LED holder attached on top. The blade of a blunt metal spudger is inserted under a plastic tab that holds the LED holder onto the switch
Removing the LED holder from the microswitch is done by levering open (gently) the plastic tab that clamps the holder onto the switch.
the LED holder at left, and the bare microswitch. The LED holder has an LED in a white plastic retainer, and below it two spade contacts. The switch has three spade connectors: Com(mon) on the base, and "NO 3" (Normally Open) and "NC 2" on the right side. Normal operation connects COM and NO
LED holder and microswitch separated. For normal button operation, the contacts NO and COM become connected when the button is pressed. The spade contacts on the LED holder look like they should come out, and they will (soon)
LED holder disassembled into two parts. The black LED holder base is on the left, with the two conenctor clips slightly blurry at top. On the right is the LED in its white support, pulled out of the holder base
Pull the LED out from the holder, and you’ll see the metal clips that held it in place. These clips have to come out: I found the pushing them in slightly while pulling down on the spade connector eased them out eventually
White button top underside with an 8 RGB LED ring hot glued into it. Three thin insulated wires (from top: yellow (data), red (5 V) and black (GND)) are previously soldered behind the LED board, and are secured against strain with a large deposit of hot glue
LED ring hot glued into place. Make sure that the wires are properly secured, as you don’t want to take this apart again
threaded button base with clear top fitted, seen from underneath. The white button actuators have been pushed back into place, and the three coloured wires are feeding through the hole in the shaft. The return spring is outside the wires, and is being fitted around the retainers inside the shaft
Fit the clear button top back inside the base, feeding the wires through the shaft. Fitting the return spring back in is a bit more chaotic than getting it out. I ended up jamming it in with forceps, and it seemed to sort out okay despite that
underside of the button shaft, with microswitch attached to LED holder. The wires coming from the LED ring inside the button top have been fed through the small cavities where the original LED holder clips/contacts have been removed. The red/black power wires are on the side towards us, while the yellow data wire is behind the microswitch
The really fiddly bit: feeding the wires through the tiny gaps where the LED holder clips/contacts used to be. Even using thin (28 AWG) silicone covered wire, all three wires couldn’t fit down one side. Make sure the wires are pulled gently through, and aren’t snagged anywhere
Fully reassembled button, with microswitch installed into its bayonet connector in the threaded shaft, and the button actuator lined up with the microswitch lever on the left. The yellow data wire is in front of the microswitch at bottom
Finished! Make sure that the switch actuates properly by lining up the LED holder in the bayonets inside the shaft. Of course, you’ll have wanted to install the button in your project before doing this assembly, as you’ll have to feed those pesky wires back through again if you haven’t …

More Magic Designer Nonsense

This is what I simulated earlier – except drawn on a real Magic Designer. Something’s off with what I modelled …
All of these are drawn with the Magic Designer angle set to 57, which puts the crank discs exactly in phase. The blue circle in the middle is an exactly image of a crank disc, if perhaps a very dull plot.

Slightly imperfect Hoot-Nanny/Magic Designer simulation

round figure with three interlaced 6-fold curves picked out in red, green and blue
I even emulated the locating notches at the edge of the paper …

Simulated (and not quite right yet) output from a “HOOT-NANNY” or Magic Designer, a proto-Spirograph toy that drew six-sided curves on round paper sheets. It was made by Howard B. Jones and Co. of Chicago, IL and first sold in 1929. The company’s better known for producing Jones Plugs and Sockets, sometimes known as Cinch-Jones connectors. The “HOOT-NANNY” name was dropped when production moved to the Northern Signal Company of Saukville, WI.

My eBay-acquired Magic Designer is quite beaten up, and doesn’t always produce accurate results. Here’s how one should look, from the instruction pamphlet:

diagram of the Magic Designer toy: central turntable holding paper is rotated by crank at bottom right. On the left are two crank discs (upper and lower) each with a crank pin that can fit into holes along two arms. These arms are joined at a pivot, and in the centre of this pivot is a pencil.

The upper crank disc can be moved in an arc relative to the lower disc. This is controlled by a locking shift lever on the right
I can’t shake the feeling this was originally something like an artillery ranging tool or suchlike

As far as I’ve been able to work out, the parameters of the machine are:

  • central turntable is 6″ in diameter, with 192 gear teeth around the edge;
  • each crank disc is 1″ diameter (32 teeth), with the crank pin at 3/8″ radius;
  • the shift lever has a 10-70 degree scale, which corresponds to moving the upper crank disc between 30-90 degrees of arc from the lower (fixed) crank disc;
  • the pencil arms have 18 holes labelled A to R, at 1/4″ spacing from 5.75 to 1.5″. The perpendicular distance from the pivot holes to the pencil is 5/16″. This small offset makes very little difference to the overall arm length.

If we model the toy with a fixed turntable:

  • the crank pins describe epitrochoids around the edge of the paper;
  • the pencil point traces the intersection of two circles of radius the lengths of the pencil arms, each centred on a crank pin.

Here’s a very simple model in Python that emits a hard-coded (but editable) pattern in HP-GL: Slightly imperfect Python simulation of the “HOOT-NANNY” (or Magic Designer) drawing toy (static local copy: hootnanny.zip). It doesn’t do anything with the fixed circle studs (yet)

Autumn in Canada: PicoMite version

more leaves

So I ported autumn in canada from OpenProcessing to PicoMite BASIC on the Raspberry Pi Pico:

a small black screen images with text in the centre: autumn in canada scruss, 2021-11 just watch ...
no leaves
a small black screen images with text in the centre: autumn in canada scruss, 2021-11 just watch ... with one red and one orange maple leaf sitting on top of it
a couple of leaves
a small black screen images with text in the centre: autumn in canada scruss, 2021-11 just watch ... with four red/yellow/orange maple leaves sitting on top of it
more leaves
a small black screen images with text in the centre: autumn in canada scruss, 2021-11 just watch ... with sixteen simulated fallen maple leaves mostly covering it
plenty of leaves
a small black screen image completely covered with many simulated fallen maple leaves
far too many leaves

The biggest thing that tripped me up was that PicoMite BASIC starts arrays at 0. OPTION BASE 1 fixes that oversight. It would have been nice to have OpenProcessing’s HSV colour space, and an editor that could handle lines longer than 80 characters that didn’t threaten to bomb out if you hit the End key, but it’ll serve.

Source below:

' autumn in canada
' scruss, 2021-11
' a take on my https://openprocessing.org/sketch/995420 for picomite

OPTION base 1
RANDOMIZE TIMER
' *** initialize polar coords of leaf polygon and colour array
DIM leaf_rad(24), leaf_ang(24), px%(24), py%(24)
FOR i=1 TO 24
    READ leaf_rad(i)
NEXT i
FOR i=1 TO 24
    READ x
    leaf_ang(i)=RAD(x)
NEXT i

DIM integer c%(8)
FOR i=1 TO 8
    READ r%, g%, b%
    c%(i)=RGB(r%,g%,b%)
NEXT i

' *** set up some limits
min_scale%=INT(MIN(MM.HRES, MM.VRES)/8)
max_scale%=INT(MIN(MM.HRES, MM.VRES)/6)
min_angle=-30
max_angle=30
min_x%=min_scale%
min_y%=min_x%
max_x%=MM.HRES - min_x%
max_y%=MM.VRES - min_y%

CLS
TEXT MM.HRES/2, INT(MM.VRES/3), "autumn in canada", "CM"
TEXT MM.HRES/2, INT(MM.VRES/2), "scruss, 2021-11", "CM"
TEXT MM.HRES/2, INT(2*MM.VRES/3), "just watch ...", "CM"

kt%=0
DO
    cx% = min_x% + INT(RND * (max_x% - min_x%))
    cy% = min_y% + INT(RND * (max_y% - min_y%))
    angle = min_angle + RND * (max_angle - min_angle)
    sc% = min_scale% + INT(RND * (max_scale% - min_scale%))
    col% = 1 + INT(RND * 7)
    leaf cx%, cy%, sc%, angle, c%(7), c%(col%)
    kt% = kt% + 1
LOOP UNTIL kt% >= 1024

END

SUB leaf x%, y%, scale%, angle, outline%, fill%
    FOR i=1 TO 24
        px%(i) = INT(x% + scale% * leaf_rad(i) * COS(RAD(angle)+leaf_ang(i)))
        py%(i) = INT(y% - scale% * leaf_rad(i) * SIN(RAD(angle)+leaf_ang(i)))
    NEXT i
    POLYGON 24, px%(), py%(), outline%, fill%
END SUB

' radii
DATA 0.536, 0.744, 0.608, 0.850, 0.719
DATA 0.836, 0.565, 0.589, 0.211, 0.660, 0.515
DATA 0.801, 0.515, 0.660, 0.211, 0.589, 0.565
DATA 0.836, 0.719, 0.850, 0.608, 0.744, 0.536, 1.000
' angles
DATA 270.000, 307.249, 312.110, 353.267, 356.540
DATA 16.530, 18.774, 33.215, 3.497, 60.659, 72.514
DATA 90.000, 107.486, 119.341, 176.503, 146.785, 161.226
DATA 163.470, 183.460, 186.733, 227.890, 232.751, 270.000, 270.000
' leaf colours
DATA 255,0,0, 255,36,0, 255,72,0, 255,109,0
DATA 255,145,0, 255,182,0, 255,218,0, 255,255,0

You could probably use AUTOSAVE and paste the text into the PicoMite REPL. I used an ILI9341 SPI TFT LCD Touch Panel with my Raspberry Pi Pico along with some rather messy breadboard wiring.

Fun fact: the maple leaf polygon points are derived from the official definition of the flag of Canada.

Modding an Adafruit PIR for 3.3 volts

green circuit board covered in surface mount components. A grey wire has been soldered to the output pin of the SOT-89 package 7133-1 voltage regulator
slightly dodgy soldering of a grey jumper wire to the Vout pin of the PIR’s voltage regulator

Consider the Adafruit PIR (motion) sensor (aka PIR Motion Sensor, if you’re in Canada). Simple, reliable device, but only runs from a 5 V supply. Yes, there are smaller PIRs that run off 3.3 V, but if this is what you have, you need to do some soldering. Annoyingly, the sensor on the board is a 3.3 V part, but the carrier was designed in Olden Tymes when King 5 V ruled.

You can try powering it from 3.3 V, but it’ll go all off on its own randomly as its own power supply won’t be supplying enough voltage. There are a couple of sites on how to modify these PIRs that either describe old kit you can’t get any more, or do it completely wrongly. Just one post on the Adafruit support forum gets it right.

One way of doing this is to provide 3.3 V directly to the output pin of the voltage regulator, and ignore the 5 V power line entirely. The regulator’s a SOT89-3 part that looks a bit like this:

71xx-1 SOT-89 package outline, with three pins at the bottom and one large ground tab (connected to centre pin, but not visible) at the top
wee leggy thing

In the photo above, it’s flipped over. Whichever way it’s oriented, we want to put power directly into the Vout pin. There may be easier points to solder this to than a tiny surface mount pin (almost definitely one of the capacitors) but this has held for me.

How to use it in MicroPython? Like the TTP223 capacitive touch sensors I looked at before, a PIR gives a simple off/on output, so you can use something like this:

from machine import Pin
from time import sleep_ms

pir = Pin(21, Pin.IN)

while True:
    print("[", pir.value(), "]")
    sleep_ms(1000)

value() will return 1 if there’s movement, 0 if not. There are trigger time and sensitivity potentiometers to fiddle with on the board if you need to tweak the output.

line graph showing output signal going from 0 to 1, back down to 0 and ending at one over a period of about 20 seconds
Thonny plotter output showing a couple of movement detections. High output (on my device) stays up for about 4 seconds, so you can be pretty leisurely about polling PIRs

Just remember: don’t connect the 5 V power line if you make this mod. I’m not responsible for any smoke emitted if you do — but I can always sell you a replacement …