rsdio's Recent Posts

I was away from this thread for a long time, but it is great to see the two of you helping each other out on these platforms. I will soon be working on a Cortex M4 implementation running a lot slower than 1 GHz, so I may need to focus on optimization. Thanks for sharing all of your notes as you worked!

(moved to Hardware)

@rastkopravi
MW is ModWheel? ... same as MIDI CC #1?

@andrewbird

As for bypassing running a laptop, that's the point: Performance would certainly be stand-alone, i.e., without a laptop. Just the Soundplane and your synth of choice, with only the The Soundplane-to-CV in between. It would have on-board non-volatile memory for your custom settings, and that could be easily loaded from a USB Memory Stick. SDHC card support would require dedicated hardware, increasing the cost and panel real estate, so it's doubtful that particular format would be supported.

As for bypassing running a modular synth, I'm not exactly sure that I follow. I assume you mean that you'd like to use a standard Analog synth, even if you don't already have a modular. There should be no issue with that, technologically, although there does need to be some sort of case, even if it's a small modular rack or just a metal box. We'll keep the options open as much as possible, within reason.

Are there any settings that you might need to change on the fly during a performance? Anything that a few customizable presets wouldn't cover? Keep the ideas coming!

Very interesting.

And, to state what's probably obvious to most people here, your 2-in 4-out low-latency system could be used to build a DIY 4x2 pressure sensitive surface. I'm sure the AM335x has sufficient power to calculate 2,000 multi-point FFT conversions per second.

Yes, constant latency is more easily ignored than jitter.

I was concerned about FS because the Soundplane is FS. So, it seems like the MTT would be forced to add latency.

Really cool project!

Sorry for the detailed questions, but do the USB Multi-Transaction Translator hubs add any latency when performing their feature? Seems like it would be unavoidable, although High Speed frame latency is only 1/8th Full Speed latency. Hopefully the total latency is only 1 ms + 0.125 ms = 1.125 ms.

Meanwhile, I assume that your STM32F7 Discovery Kit firmware must implement High Speed USB, otherwise the Multi-TT hub would not really provide any advantage when connected there.

You may not actually need as high as 125 kHz sampling rate.

With only 16 carriers and a target 500 Hz update rate instead of 1 kHz, you could possibly sample as low as 31.25 kHz or 32 kHz. Then you'd only need 32 frequency bins from a 64-point FFT, and that might be easier to perform with limited DSP capabilities. Your bandwidth might be one quarter that of the 8x64 Soundplane, so perhaps you don't need the reduction we attained by converting to the frequency domain. Instead of the Soundplane's 768 kB/s USB bandwidth, you might be able to get by with 384 kB/s of time domain information. You can cut that down to 192 kB/s via FFT. Of course, this assumes 12-bit samples. The Soundplane uses ADC chips that operate at 1 MHz. If you use 24-bit audio ADC chips, you'll need 8 of them (or an 8-channel CODEC), but the 24-bit data will double your bandwidth needs unless you dither down the bit depth before sending over USB.

In any case, you'll still need isochronous USB packets, whether time domain or frequency domain, in order to guarantee that the USB Host will allocate enough bandwidth to guarantee delivery of the data stream without dropouts.

Sorry for all the numbers - I hope I didn't do any of the math incorrectly.

p.s. A CODEC may simplify things, since you could have sine wave outputs and ADC inputs on a single chip with a single sample rate. However, I don't really know of any 16-out, 8-in CODEC parts. Designing around a lower sample rate may offer more converter chip options for your project. You might get better results around 60 kHz than 30 kHz, though, with the understanding that this would double your bandwidth requirements.

Sounds like fun! Keep us posted.

The paper never mentions whether the haptic vibrations reduce the sensitivity of the Soundplane by the nature of them being placed between the surface and the sensor. I'd be curious to know how much of the haptic vibration is picked up by the Soundplane's sensors, given that the haptic frequency is bandpass-filtered to 40 Hz - 400 Hz, and the Soundplane has the ability to read vibrations up to 500 Hz.

The closing remarks do admit that more research is needed, so I'd be curious to read a followup paper.

Wow! I had not seen Juglans before.

The piece has such a wide palette of sounds as well as dynamic range. I watched the video before reading the followup comments, and I couldn't tell that you were selecting sounds. I can see how that might not be your preferred way to play. Let us know if you find a different solution - or if you have any more videos to share.

Keep us posted, thetechnobear, and maybe even create a new thread (separate from HD MIDI) when your Axoloti supports 14-bit CC. If it works well, I hope the offical Soundplane client will support 14-bit CC out of the box.

I've used the environment in Logic Studio Pro to both generate and respond to 14-bit CC as a test, but I've not actually checked whether any of my synths support it. Does Zebra?

Considering that this is one of those chicken-and-egg situations, maybe if you add support for 14-bit CC to Axoloti, more people would become aware of it and think about adding support elsewhere.

The Livid Instruments Ohm64 and family support 14-bit CC generation, but it's difficult to find a control surface that's accurate enough.

HD MIDI sounds like a bold departure, but I think we've yet to tap the limits of 1983 MIDI.

@thetechnobear
Of the many things you have to tackle, you could get a start by looking for USB Host isochronous examples, such as would allow you to connect a USB Audio interface and stream audio. If you can get that going on your STM32F4, then you could probably easily host the Soundplane with a few modifications. Actually, the Soundplane requires much less complex support than an audio interface, although it's using about 3 times the bandwidth of 24-bit stereo audio. That's (a)
Of course, processing touches is the next step after that, and you have the client source as a guide for that (b).

How is HD MIDI different? We have 14-bit Pitch Bend (X), and at least the potential for 14-bit CC for expression (Y) and pressure (Z). I didn't realize that the Soundplane client didn't produce 14-bit CC already, so I'm wondering whether anyone has added that feature. It should be relatively easy to add.

Testing could be done with something like the Encore Expressionist MIDI-to-CV, which has 16-bit D/A ranging from -3V to +10V. What hardware synths out there support 14-bit CC modulation?

Hi Scott, can we get an update on your progress? I'm probably not the only one who is interested to read about what you were able to get working, and whether you've upgraded to the STM32F4 and floating point.

Very nice! I'm happy to see the wide range of playing styles and musical styles on the Soundplane.

One limitation of putting CV outputs on the Soundplane is the power supply. USB provides +5 V, but modular racks typically provide ±15 V and sometimes as much as ±18 V. There would be a serious drain on the USB power if it were boosted high enough to interface with modular, not to mention the noise created by a switching power supply needed for boosting voltage like that. Some of the better CV interfaces provide pitch CV from -3 V to +10 V to span many octaves, so we'd like to match that range with the Soundplane for maximum flexibility. Restricting pitch to 0V and +5 V would be rather limiting.

So, yeah, there are space and engineering issues like the power supply and processing that would make it very challenging to squeeze everything in the Soundplane case. It's much easier to start with a modular power supply and bring it down to 5 V than to go the other way.

Thanks for the idea, though. It's fun to consider approaching things from a different angle.

Thank you for the details of your patches, ngwese. This seems similar to what I needed to do with the Matrix-12 to open up the envelope. Oberheim allows multiple CV sources to be mixed in the VCA input.

If you care to describe how you use slew and/or lag, that might be helpful.

There's certainly no downside to questions!

The computer-based configuration side of this modular system could be open source, just like for the Soundplane.

I'm curious: How many open source products actually have compelling features available from a third party? Can you list them? I'd like to get a sense of the community's skill set.

There will be expansion for more touches. If you're willing to spend extra, then at least ten full touches will be possible (40 CV outputs), probably in sets of two touches each. I doubt that it makes sense to go beyond that.

Some form of configuration for the outputs will be possible (range, precision), but the minimal interface may require some or all voltage configuration to be done on a computer and then stored in the module for regular use. Presets will be available so that you're not stuck with just one setup when you don't have a computer around.

I'm fairly certain that Gate or Trigger or Velocity Gate will be possible in firmware for those who need different things. That way, you won't need to derive a gate or use a comparator unless you really want extra outputs without buying another expander.

Hi samola,

This module will be a USB Host so that it can communicate with the Soundplane (a USB Device). The USB-MIDI features you're discussing are USB Device features. Believe it or not, 95% of the chips out there can only do one at a time, so it's either Host or Device, but not both. Another factor is that you need one kind of connector to be a Host, and another to be a Device. The only universal USB connector is OTG (On The Go), which is the tiny connector found on cell phones. It (OTG) seems like a horrible interface to put on a module, so that pretty much rules out USB-MIDI features. I think there are plenty of options in that area anyway, so please continue to have fun with your CVPal! I see the Soundplane as something parallel to that, rather than a replacement.

Early mockups based on actual board layouts look like 6HP might fit, but that might be tight. I'm fairly certain that 8HP will work. This is for a minimum of 2 touchs, which is 8 CV outputs, grouped as Gate with X, Y, and Z. Thanks for chiming in, ngwese and others.

Thanks, shedacq. That page looks like it might be specific to Windows 10. Looking around at some of the chapters, there are references to Windows 8. I'll take a further look when I have some time.

MIDI will certainly be supported, although it may not be part of the base configuration. It's just so easy to support MIDI in terms of both interface hardware and programming. I love MIDI, and the first public demonstrations of the Soundplane used MIDI, but there's no way we'd drop the ball and miss out on the opportunity to have a tightly-coupled CV output that's higher resolution than MIDI. Therefore, the primary focus will be on the CV outputs.

Thanks for the additional input, Chris. Perhaps I was thinking too minimal - where zone maps and presets are created on a computer before a performance, downloaded into the module, and then the module could only call up presets without the ability to edit them.

I like knobs for controlling analog signals, but encoders seem better for editing discrete values such as zone boundaries. Considering the totally freeform options for zone mapping on the Soundplane, I can't actually envision a knob-based editing interface that would work. Some of the example zones have 23 regions, with multiple parameters each for extents, scaling, etc. I can't see knobs for those fitting into a module. But if someone were to draw a mock-up, I'd certainly take a look with an open mind.

Let's assume for the moment that presets and zones are neither edited nor displayed on the module's front panel. What other aspects of the operations would need to be visualized? We've discussed LED indication for each Gate, and some way to know which preset is active, but what else is really needed for performance? I think a few brave souls have put together a system with Soundplane and MIDI/CV converters who might be able to give feedback on what sort of real-time control is needed for performance. I'm hoping to get this discussion going again, now that I'm actually creating schematics and PCB layouts.

Here are a few things that won't be in the product:

1) Bluetooth

2) abuses of USB connectors that violate the specifications

3) unkeyed modular power connectors

4) tiny USB OTG connectors that belong on a cell phone

The Bluetooth industry is dominated by products that barely work because everyone wants to make the cheapest module. They're a serious headache to develop a professional quality product with, and they often don't have all the features listed in the data sheets. Personally, I think that it would be a bad idea to put radio signals in a module, unless you actually want to synthesize radio signals.

USB offers many tempting options for remote configuration and firmware upgrades, but there is a better solution that makes USB moot...

Hello all! Great comments so far. I've been remiss in not checking this forum more often.

I logged in to ask how much modular real estate people are willing to devote to a Soundplane-to-CV converter. The A-198 is 8-HP, the qMI is 24-HP, and those MOTM are 14-HP. The absolute minimum base model would be USB-A plus 8 CV jacks, so 8-HP would be a tight fit. A monster with an OLED per voice could easily grow beyond 24-HP and take a whole rack. What do people want?

I worry that throwing too many features into this will end up turning people away, who either don't have the space or who may actually be at odds with the aesthetic. Another consideration is that every feature takes time to develop, even if it only adds a few dollars to the bill of materials.

The Soundplane draws an average of 300 mA when active. It draws 80 mA when first connected, before the power light comes on, but it's not terribly useful in that temporary mode (which is required by the USB standards).

We'll definitely design the Soundplane Host so that it doesn't overload the typical power supply, although it might take some investigative work to find out what level of power supply most people have, versus what they'll need for the Soundplane.

Stay tuned!