Posts Tagged RPi

Makergear M2: Octopi Camera Mount

Octopirint / Octopi works wonderfully well as a controller / G-Code feeder for my Makergear M2. After putting up with an ungainly mass of tape for far too long, I printed Toddman’s Pi Camera Mount:

Pi Camera - M2 Mount - Slic3r
Pi Camera – M2 Mount – Slic3r

Which snapped together exactly like it should:

Makergear M2 - Pi Camera Mount
Makergear M2 – Pi Camera Mount

A strip of double-sided foam tape attaches it to the Pi’s case, which is Velcro-ed to the M2’s frame. The cable may be too long, but avoids sharp bends on the way out of the case.

The whole lashup works fine:

Pi Camera - M2 Mount - Octopi timelapse
Pi Camera – M2 Mount – Octopi timelapse

That’s a second set intended for the CNC 3018-Pro, but it didn’t fit quite as well. The B brackets are slightly too long (or their pivots are slightly too close to their base) to allow the C plates to turn 90° to the mount:

Pi Camera - M2 Mount - Config 2 diagram
Pi Camera – M2 Mount – Config 2 diagram

Nothing one can’t fix with nibbling & filing, but I long for parametric designs …

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Raspberry Pi “Moster” Heatsink Retaping

A pair of colorful laser-cut stacked acrylic Raspberry Pi cases with “Moster” (*) heatsinks arrived, with the intent of dressing up the HP 7475A plotters for their next Show-n-Tell:

Moster RPi Heatsink - assembled case
Moster RPi Heatsink – assembled case

Unfortunately, the thermal tape on one of the CPU heatsinks was sufficiently wrinkled to prevent good contact with the CPU:

RPi taped heatsinks - as received
RPi taped heatsinks – as received

The seller sent a replacement copper slug with tape on one side. Presumably, they glue it to the heatsink with thermal silicone:

Moster RPi Heatsink - silicone adhesive
Moster RPi Heatsink – silicone adhesive

Of which, I have none on hand.

So I did what I should have done originally, which was to drop a few bucks on a lifetime supply of thermally conductive heatsink tape, apply it to the bare side of the slug and stick the slug to the heatsink with their tape:

Moster RPi Heatsink - replacement adhesive tape
Moster RPi Heatsink – replacement adhesive tape

The blue stuff is the separation film, with the tape being white. It doesn’t match the black tape on the other side, but seems gooey enough to work.

Done!

Despite the heatsink hype, ball grid array chips dissipate most of their heat through their pads (and perhaps a central thermal pad) into the PCB, so sticking a heatsink atop the package is largely decorative, along the lines of hotrod ornamentation.

The epoxy packages used in previous Raspberry Pi iterations had better thermal conductivity to their top surface:

RPi 3 B - epoxy CPU
RPi 3 B – epoxy CPU

Than the more recent metal-top packages, which surely have inert-gas fill under the lid:

RPi 3 B - metal CPU
RPi 3 B – metal CPU

Pix cropped after being pilfered from the Official Raspberry Pi site.

Yes, the heatsink does conduct some heat into the air, even if not nearly as much as you might want.

(*) I’m pretty sure “Moster” was a typo in the original eBay listing which took on a life of its own to become something of an unofficial trademark. All of the search results ship from Duluth, Georgia (USA), regardless of the nominal seller; feel free to draw your own conclusions.

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Ripping Vinyl Records on a Raspberry Pi

Having already set up a Raspberry Pi streaming radio player for the living room, it seemed reasonable to also use it for recording audio from the long-disused turntable. A pair of RCA cables from the amplifier’s TAPE 2 REC outputs to the Behringer UCA202 USB audio interface got the audio where it needed to be:

RPi streamer - Behringer UCA202 USB audio box
RPi streamer – Behringer UCA202 USB audio box

Fiddle with the amp to select the phonograph, poke the TAPE 2 button to send audio to/from the UCA202, fire up an SSH session, kill the streaming audio program, and figure out what audio hardware is out there:

$ arecord -l
**** List of CAPTURE Hardware Devices ****
card 1: CODEC [USB Audio CODEC], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Not much else to choose from on a Raspberry Pi, so see what the UCA202 can do:

$ arecord --dump-hw-params 
Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono
HW Params of device "default":
--------------------
ACCESS:  MMAP_INTERLEAVED RW_INTERLEAVED
FORMAT:  S8 S16_LE
SUBFORMAT:  STD
SAMPLE_BITS: [8 16]
FRAME_BITS: [8 32]
CHANNELS: [1 2]
RATE: [8000 48000]
PERIOD_TIME: [1000 65536000]
PERIOD_SIZE: [16 524288]
PERIOD_BYTES: [64 524288]
PERIODS: [2 1024]
BUFFER_TIME: (666 131072000]
BUFFER_SIZE: [32 1048576]
BUFFER_BYTES: [64 1048576]
TICK_TIME: ALL
--------------------
arecord: set_params:1233: Sample format non available
Available formats:
- S8
- S16_LE

Given those limited choices, 16 bit little-endian at 48 kHz seems like a no-brainer.

Find out all the ALSA device names:

$ arecord -L
null
    Discard all samples (playback) or generate zero samples (capture)
sysdefault:CARD=CODEC
    USB Audio CODEC, USB Audio
    Default Audio Device
front:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    Front speakers
surround21:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    4.0 Surround output to Front and Rear speakers
surround41:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
iec958:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    IEC958 (S/PDIF) Digital Audio Output
dmix:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    Direct sample mixing device
dsnoop:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    Direct sample snooping device
hw:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    Direct hardware device without any conversions
plughw:CARD=CODEC,DEV=0
    USB Audio CODEC, USB Audio
    Hardware device with all software conversions

They all point to the same hardware, so AFAICT the default device will work fine.

Try recording something directly to the RPi’s /tmp directory, using the --format=dat shortcut for “stereo 16 bit 48 kHz” and --mmap to (maybe) avoid useless I/O:

$ arecord --format=dat --mmap --vumeter=stereo --duration=$(( 30 * 60 ))  /tmp/Side\ 1.wav
Recording WAVE '/tmp/Side 1.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
                                  +02%|01%+                                   overrun!!! (at least 1.840 ms long)
                                  +02%|02%+                                   overrun!!! (at least 247.720 ms long)
                                +# 07%|06%##+                                 overrun!!! (at least 449.849 ms long)
                                 + 03%|02%+                                   overrun!!! (at least 116.850 ms long)

Huh. Looks like “writing to disk” sometimes takes far too long, which seems to be the default for MicroSD cards.

The same thing happened over NFS to the file server in the basement:

$ arecord --format=dat --mmap --vumeter=stereo --duration=$(( 30 * 60 ))  /mnt/part/Transfers/Side\ 1.wav

Recording WAVE '/mnt/part/Transfers/Side 1.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo

                               +   09%|07%  +                                 overrun!!! (at least 660.372 ms long)

                                +# 08%|06%# +                                 overrun!!! (at least 687.906 ms long)

So maybe it’s an I/O thing on the RPi’s multiplexed / overloaded USB + Ethernet hardware?

Trying a USB memory jammed into the RPi, under the assumption it might be better at recording than the MicroSD Card:

$ arecord --format=dat --mmap --vumeter=stereo --duration=$(( 30 * 60 ))  /mnt/part/Side\ 1.wav
Recording WAVE '/mnt/part/Side 1.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
                                  +01%|01%+                                   overrun!!! (at least 236.983 ms long)

Well, if it’s overrunning the default buffer, obviously it needs Moah Buffah:

$ arecord --format=dat --mmap --vumeter=stereo --buffer-time=1000000 --duration=$(( 30 * 60 ))  /mnt/part/Side\ 1.wav
Recording WAVE '/mnt/part/Side 1.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
                               +## 10%|06%# +                                 overrun!!! (at least 359.288 ms long)

When brute force doesn’t work, you’re just not using enough of it:

$ arecord --format=dat --mmap --vumeter=stereo --buffer-time=2000000 --duration=$(( 30 * 60 ))  /mnt/part/Side\ 1.wav
Recording WAVE '/mnt/part/Side 1.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
                                  +00%|00%+                                   

Sampling four bytes at 48 kHz fills 192 kB/s, so a 2 s buffer blots up 384 kB, which seems survivable even on a Raspberry Pi.

The audio arrives at 11.5 MB/min, so an LP side with 20 min of audio will require about 250 MB of disk space. The USB memory was an ancient 2 GB card, so all four sides filled it halfway:

$ ll /mnt/part
total 1.1G
drwxr-xr-x  2 ed   root 4.0K Dec 31  1969  ./
drwxr-xr-x 17 root root 4.0K Jun  7 19:15  ../
-rwxr-xr-x  1 ed   root 281M Sep  1 14:38 'Side 1.wav'*
-rwxr-xr-x  1 ed   root 242M Sep  1 15:01 'Side 2.wav'*
-rwxr-xr-x  1 ed   root 265M Sep  1 15:27 'Side 3.wav'*
-rwxr-xr-x  1 ed   root 330M Sep  1 15:58 'Side 4.wav'*

Side 4 is a bit longer than the rest, because I was folding laundry and the recording stopped at the 30 minute timeout after 10 minutes of silence.

Now, to load ’em into Audacity, chop ’em into tracks, and save the lot as MP3 files …

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Raspberry Pi vs. MicroSD: Another One Bites the Dust

The Raspberry Pi running the MPCNC recently seized up with baffling symptoms, which generally indicates the poor little MicroSD card serving as a “hard disk” has failed:

Defunct Sandisk Ultra 32 GB MicroSD
Defunct Sandisk Ultra 32 GB MicroSD

I managed to open a terminal emulator, whereupon all of the non-built-in shell commands couldn’t be found.

Proceed as before: binary-copy the entire MicroSD card to another one, pop it in the RPi, and it’s all good again.

For the record, the new card is an unused Samsung Evo Plus. I do not understand the difference between the “Evo Plus” and “Evo+” branding, other than to suspect one of being a very good fake.

In round numbers, MicroSD cards seem to last a year under what seems like not-too-demanding service; I’m not running the MPCNC all day, every day.

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Logitech “QuickCam Pro 5000” Ball Camera Disassembly

Another alignment camera contestant from the Big Box o’ Junk Cameras:

Logitech Pro 5000 Ball Camera - overview
Logitech Pro 5000 Ball Camera – overview

It’s a Logitech QuickCam Pro 5000 with a native 640×480 resolution. For no obvious reason, it seems to work better on a Raspberry Pi than the Logitech QuickCam for Notebooks Deluxe I ripped apart a few weeks ago, where “better” is defined as “shows a stable image”. I have no explanation for anything.

Remove the weird bendy foot-like object by pulling straight out, then remove the single screw from the deep hole visible just behind the dent in the top picture:

Logitech Pro 5000 Ball Camera - disassembled
Logitech Pro 5000 Ball Camera – disassembled

The stylin’ curved plate on the top holds the microphone and a button, neither of which will be of use in its future life. Unplug and discard, leaving the USB cable as the only remaining connection:

Logitech Pro 5000 Ball Camera - USB connector
Logitech Pro 5000 Ball Camera – USB connector

Inexplicably, the cable shield is soldered to the PCB, so the connector doesn’t do much good. Hack the molded ball off of the cable with a diagonal cutter & razor knife, taking more care than I did to not gouge the cable insulation.

A glue dot locks the focusing threads:

Logitech Pro 5000 Ball Camera - focus glue
Logitech Pro 5000 Ball Camera – focus glue

Gentle suasion with a needle nose pliers pops the dot, leaving the lens free to focus on objects much closer than infinity:

Logitech QuickCam Pro 5000 - short focus
Logitech QuickCam Pro 5000 – short focus

Now, to conjure a simpleminded mount …

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Xiaomi-Dafang Hacks: FTP Server for Camera Files

Since the PiHole runs all the time, it now hosts an FTP server to stash snapshots from the cameras onto a 64 GB USB stick. I installed ProFTPD, which Just Worked with a few configuration tweaks:

UseIPv6             off
ServerName          "PiHole"
DefaultRoot         /mnt/cameras
RequireValidShell   off

The cameras use the BusyBox ftpput command to stash their images (with the hostname prepended), which requires a few changes to motion.conf in the cameras:

ftp_snapshot=true
ftp_host="192.168.1.2"
ftp_port=21
ftp_username=$(/bin/hostname)
ftp_password="make up your own"
ftp_stills_dir=$(/bin/hostname)

The last line uses a separate directory for each camera, although they quickly ran into the FAT32 limit of 64 K files per directory; reformatting the USB stick with an ext3 filesystem solved that problem.

Fortunately, nothing much ever happens around here

New Utility Pole Arrives
New Utility Pole Arrives

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Algorithmic Art

This evening I’ll be showing off my Algorithmic Art at the HV Open Mad Science Fair.

There’ll be glowing glassware:

Vacuum Tube LEDs - halogen lamp - purple phase
Vacuum Tube LEDs – halogen lamp – purple phase

Ancient electronics with modern hardware:

21HB5A - Guilloche platter
21HB5A – Guilloche platter

Blinking LEDs atop Brutalist analog electronics:

Astable RGB LED - green phase
Astable RGB LED – green phase

A classic HP 7475A plotter hammering math onto paper from a Raspberry Pi running Chiplotle:

HP 7475A Plotter - LED paper illumination
HP 7475A Plotter – LED paper illumination

Some take-home art:

Superformula Plots - A-size paper
Superformula Plots – A-size paper

And, as always, a good time will be had by all!

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