Fast prototyping

DIY STUFF
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I’m going to brainstorm some user interaction using this combination of touch sensor ring and light emitting ring. I won’t get full benefit from it because I’m a little colour blind (enough that I used to think grass was red when I was a small child) but with suitable adjustments I should be able to convey quite a lot of information.

The Neopixels could give persistence to touch, and colour changes could be used to represent time (so a touch starts out at the blue end and then fades towards the red end of the spectrum over say five seconds.) Or the “size” (applied pressure?) of the touch could be represented by colour.

There are many possibilities, subject to the limitation of only 24 Neopixels in the ring. I imagine finer rings with smaller and more numerous Neopixels will become available in due course.

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Other effects include animation. This can be used for instance to indicate direction of movement. Or if you’re keying in some music the adjacent LEDs can light up showing the major and minor thirds, dominant and so on when you type a harmonic sequence. With 24 LEDs you get up to two octaves. You can do exactly the same with a Trill Bar but I think the ring format makes more sense for displaying music, which is a very cyclic phenomenon. So you could use a control like this for sequencing. It’s reasonably compact, and would easily fit into a panel 10cm wide.

Speaking of sequencing, I’m vaguely aware of Euclidean rhythms but I’m not sure whether this kind of display format would be useful in that context. 24 is divisible by 2, 3, 4, 6, 8, and 12, for what it’s worth. I’ll investigate.

Other thoughts: a simple menu system could be implemented using blocks of pixels around the ring. The colours could match inscriptions around the dial, not unlike a circular slide rule. I have a number of these in my collection and, in my opinion, at their best they’re the pinnacle of beauty and function.

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This may interest you @Bitnik : https://www.instructables.com/Electric-Puzzle-Game/

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Thanks. I don’t want to use printing techniques, I find 2D printers annoying enough and gave up using them nearly ten years ago. 3D sounds even more fiddly from what I’ve seen on this forum. There are some good ideas about connections, though.

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I’m really loving this thread. I keep returning to it and finding really ingenious ideas. Thanks everybody.

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So it’s become apparent to me that I’m really good at procrastinating. At this point I have drawers full of components and a head full of ideas but nothing really started. I get to the breadboard stage, at best, and lose interest. Well, that’s me.

I’ll talk here about something I’m doing which is tangentially related to the topic of this board, in that it’s about sound. The other day I bought a Raspberry Pi 4B 8GB and put it into my margarine tub in place of the Pi 3, and then installed Ubuntu Server (because Debian doesn’t yet have a stable 64-bit release for the Arm processors) on the old 120GB SSD left over after I upgraded my laptop storage to 480GB (hint: SSD is very cheap right now, and it’s much more fit for purpose than those micro-SD cards commonly used with Raspberry Pi and Beaglebone systems.) Contrary to my expectation, the system just worked as soon as I plugged in the SATA-to-USB-C cable, and turned the Pi 4 on. I didn’t even need to provide auxiliary power to the SSD, the Pi 4 seems to handle it on its own without any glitches.

I got to work making a server as backup to my VPS, because I have discovered I enjoy running server systems. With port forwarding for ssh and https, it’s a very pleasant experience. I like having a distinct domain name, and I recently discovered you can hire one for peanuts as long as you don’t insist on a .com suffix. My VPS provider, OVH, will register or renew a .ovh domain for about £2 a year. They provide direct support for dynamic DNS so it’s an ideal solution.

The only thing I can’t do is run a mail server. The upshot is that I may own the hardware but I don’t own the internet connection and the internet provider is not keen to gain a reputation for hosting spammers. Instead I use an account from a company called Zoho to run my domain email. They’re amazingly responsive to my queries so that places them streets ahead of the behemoth Gmail. I started with their excellent free account but have decided to upgrade to IMAP support and 10GB mail storage for the princely sum of £1 per month. It gives me the freedom to explore alternatives to SMTP in case I really do want to have an internet email solution on my own systems.

It’s very good as a server, and I’ve noticed that there are a lot of sound-related projects for the Pi. A problem was that I had the Pi 4 in a well ventilated margarine tub sitting at the bottom of the stairs connected to the router by an ethernet patch cable. I don’t have a wired network any more (who does?) so without threading cat 6 cable around the house that is the limit of available ethernet range. Either the margarine tub sits next to the router or I find a new solution to routing.

Thinking about using the Pi 4 as a sound source, I explored the possibility of using wireless HDMI so I could send the sound from the margarine tub to my speakers via a HDMI-to-RCA sound extractor. Even if such a solution proved physically viable, it’s currently more expensive than I’d like. Wireless HDMI systems of suitable range and quality starts at around £80 and then I’d need to convert the HDMI to analogue at the receiving end. I also have concerns about the physical vulnerability of the gear itself. It would be safest in my bedroom where I could also tinker with it more easily. I could also more easily power it down when we don’t need it.

By way of synergy, I recently rearranged my bedroom so that at long last I get to use my nice big video monitor again, and mounted the speakers behind the bed for great stereo. The sound goes from my laptop via USB to a Scarlett 2i2 connected to my Presonus Eris 3.5 monitor speakers, while a DisplayPort-to-HDMI cable feeds the video to the LG monitor. I can watch FX-heavy TV like The Expanse and Picard and get a pretty immersive experience via the laptop running Prime Video (we also have NetFlix and DisneyPlus accounts and the BBC is free to use.) This is a big step up from watching on my phone, particularly regarding the sound.

So last night after some analysis I tweaked the router’s port forwarding to use the WiFi routing to the Pi 4, took the margarine tub upstairs and connected the audio output of the Pi 4 to the stereo line-in jack of my speakers, and turned it on. The port forwarding still works over Wifi and the server traffic is so low in both quantity and urgency that I don’t really need the ethernet cable. I tested the sound by playing a mp3 on the Raspberry Pi 4, and the results are very good. If I need better sound quality I stll have the option of a HDMI-to-RCA sound extractor (basically a DAC between one of the two digital HDMI outputs of the Pi 4 and the analogue RCA L-R inputs of the speakers.)

So now I have the makings of a Hi Fi sound player in a margarine tub my bedroom. I’m looking at Linux applications like Mopidy and Snapserver. I can also run SuperCollider Server and the like on the Pi4 and get brain-exploding Hi-Fi synth effects. Software is amazing, you can do so much just by tapping and swiping on your mobile phone.

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The latency from the Raspberry Pi 4 is fierce, and without any adequate DAC on the stereo audio out it’s just not worth running SuperCollider Server. Fortunately I have kit that brings serious audio to the game, principally Bela. This 100% open source hardware based on the Beaglebone board has a sub-millisecond latency while running Linux, which I don’t expect any Raspberry Pi hardware to match without serious reengineering.

So I’m experimenting with ways to run the server component of SuperCollider on the Bela and drive it from the client running on the Pi. SuperCollider is quite flexible here: the client and the server can converse in a variant of Open Sound Control (OSC) over almost any substrate (though RFC 1149 may be a little too slow). One possibility would be to set up a low latency tunnel via the GPIO pins. I need to benchmark the connection with plain old ethernet first, though.

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Norns shield is a DAC sitting on top of a pi3 with lua and supercollider under the hood. No latency issues with that setup.

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The Norns Shield sounds like a lot of fun, though pricey at $280 for a ready-built shield from Monome.

My latency issues could probably be improved by tweaking the Linux kernel. I think I was just shocked at Pi4’s sluggishness after getting used to the nimbleness of the user-space kernel preemption configuration on the Bela. Running some Supercollider scripts through the Bela into my powered speakers gave some very satisfying vibes tonight. Running the scripts on the far more powerful Pi4 should allow the Bela system to devote more of its resources to making the sounds.

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I got this DAC HAT for my pi zero. Works a treat, and doesnt break the bank.

Important thing is to get a dac that uses I2s.

Here is the output from my ongoing soundfont based sampler project. Any latency i experience isnt caused by the DAC.

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Incidentally while studying Android audio I happened upon this article about an Android megadrone project inspired by Sam’s work. Here coder Don Turner describes how he debugged the initially noisy implementation of a 100-oscillator multidrone written with the Oboe audio toolkit.

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I dropped music for a long time, mainly because of trauma from abruptly losing a much-treasured piece of hardware (Akai Miniak) simply because our autistic daughter went into meltdown. She did nothing more than cut the DC power supply cable with a pair of scissors. The Miniak is no longer delivering audio output, although the computerised interface is working well. The result of her momentary aberration was quite devastating to my morale, because a substantial financial and emotional investment has been cancelled. I value her much more than any music, and she really could not have known the effect her vandalism would have. But still, it hurts.

I hoped I would get over it. I think now, nearly a year later, it’s time to put that to the test.

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So I finally bit the bullet and ordered another second-hand Akai Miniak on eBay. This one is going to be guarded carefully. I’ve stopped leaving my kit out where it can be trashed, and I’ve learned some “safety first” rules. Such as not leaving gear connected to the mains, which there’s no real excuse for given that all UK mains sockets have a built-in power switch on the live terminal.

I have misgivings about this purchase as there is an element of “sunk costs” fallacy, but during the brief period I owned a functioning Miniak I must admit I had a lot of fun. I had just started to get to grips with a very good third-party software patch editor for the Miniak and I’d love to continue the experience.

The price is £300 which is comparable to far less capable analogue kit (albeit new) I’ve bought. I hope it will get me over the hump.

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Wow, I love the way this guy just brainstorms an entire hardware design off the top of his head. I wonder what he did next. He’s on fire!

Seriously, though, I really need to a get a few of those elusive items, “round tuits”

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This reply is likely 6months late, but I recently had similar issues with a fates / Norns like clone on the Pi Zero and it was because the cpu governor. You have to set the governor to “performance” or the cpu speed will lag the performance demands for real-time audio.
Edit /etc/rc.local and add echo "performance" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor and reboot

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So you have more info / a link about the pi zero norns project? I think the Norns and monome is very cool and I would like a cheaper alternative! :slight_smile:

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The seller hinted that the kit wasn’t necessarily in a usable state, withdrew the item from sale and refunded. I love eBay’s no-nonsense policies.

Other options for acquiring a used Miniak are risky and expensive. Maybe I’ll have to actually fix the audio circuitry of my Miniak. I really loved the intimate involvement in sound construction it gave me.

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@Bitnik , if I’m reading your subtext correctly, I think you want to repair rather than replace. My autistic daughter has broken stuff over the years and our rule is you broke it you help fix it. Sometimes she’s been at the bench, other times she was making cakes to sell and pay for parts. Regardless of an explanation of autism it’s reasonable to take responsibility for her actions and make repairs.
So whether you fix it or replace it I hope your daughter gets involved.
Best to all x

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She’s a lovely person and wouldn’t hesitate to fund a new synth if I asked, which I may well do. I’d rather not try to engage her enthusiasm with electronics, as I’m too timid already without the added pressure of trying to work out whatever it is I’m doing and how she could help.

I managed to do some purposeful noodling on my two semi-modulars, Crave and Neutron, this week. I now have a decent knowledge of the Crave, but the Neutron will need more study. Meanwhile it’s handy to use the Crave to set up a sequence to feed into the Neutron while I play around. I mucked around trying to use the Crave’s “External audio” input to blend results from all three 3340s and both LFOs together. The results were still very unpredictable but I think it can produce musical sounds and I just need to get a better knowledge of the Neutron.

For resources I’ve used the excellent YouTube channels “Music with Eric” and “David Clements”, among others.

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Good to hear. Though it’s less about the money and more about involvement in the consequences. Both my kids help with the old man chores like reading resistor codes, ic and diode labels and picking tiny parts off the floor.
Keep us posted

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