Bela Gem, two new boards

willismorse

giuliomoro We are going for 8x DC-coupled audio inputs on the multi in the end (from the TLV320ADC3140). They are differential or single-ended but the input range is about 1.5V ±1V, so you'll likely need an external voltage shifter/scaler to handle standard CV levels.

This just keeps getting better. Thanks for the update.

giuliomoro

An update on this and parallel processing: https://www.crowdsupply.com/bela/bela-gem-stereo-and-multi/updates/i-o-and-parallel-processing

click bait image:

AndyCap

Are you guys moving to Xenomai 4?

giuliomoro

yes

giuliomoro

A new workflow we are going to support is to run Arduino-like code and send messages between that and a Bela C++- or Pd-based project. Here's a basic example to get started: https://github.com/BelaPlatform/BelaArduino-example. In ino.cpp you can write Arduino-like code (a lot of code can just be copy/pasted in from your .ino sketches); you can run a Pd patch at the same time and use pdSendMessage() and pdReceiveMessage() to communicate between the two. This allows to easily intermix procedural and dataflow languages, using each where it's best suited. This example also shows a prototype of the control panel that will eventually be integrated in the IDE: this is a p5 GUI that allows to monitor inputs and outputs and even override them (e.g.: to simulate connected potentiometers on the input, or to generate test signals on the outputs). There is no requirement to use all three components (Arduino, Pd and control panel) at once, e.g.: you can use Arduino with C++ code or the control panel without Arduino.

Limitations and quirks:

Support for Arduino libraries is limited, but will be expanded. In principle, most existing Arduino libraries based on Wire or or Adafruit_I2CDevice should work. Let us know specific things that don't work and we can look into adding them.
timing of anything running in loop() is less accurate than it would be on Arduino, for two reasons:
- it runs on a core shared with other processes (especially on the first generation Belas).
- I/O is actually managed by the Bela core, so that writes will be flushed to the pin when the next render() callback runs and any value you read refers to what was read when the last render() callback ran. In most cases this is not a big deal, but in a couple of cases you'll need special approaches:
- write-then-read (e.g.: set a pin high, then read an input that relies on that pin actually being high) operations require to add a delay after the write to make sure the output value is actually written to the pin before we attempt to read back
- writing to the same output multiple times may result in some outputs being dropped unless you add an appropriate delay after each write. In the common case of bitbanging a clock on one pin while shifting data on another, consider using shiftOut() instead.
as on some Bela boards analogWrite() actually means analogWrite(), we add a pwmWrite() that bitbangs a PWM on a Bela digital channel (and is somewhat closer to the analogWrite() behaviour of the Arduino Uno, though with a lower bitclock)
API and whatnot is subject to change

Try it out: This also runs on older Belas and requires Bela's dev branch with the addition of these two libraries:

x_x

giuliomoro Pepper users: we see you. As soon as we'll have a chance to work on it, we'll provide an adapter board that allows you to upgrade your existing Pepper to use a PocketBeagle 2 instead of the BBB, providing a cost effective upgrade path.

Does that mean the old Bela cape will be compatible with the new PocketBeagle 2 through the adapter board?

x_x

Are there any plans for DIY Eurorack solutions similar to Pepper for the 'Bela Gem Multi' ?

max

x_x there is going to be an adapter board to attach the PB2 to a Pepper/Bela. We are not sure if it will just an open source project with the files, a kit or a finished product. Either way it will be an easy upgrade.

x_x

max My apologies for the delayed response. I'm not receiving notifications for some reason.
Being able to upgrade my existing Pepper is fantastic news! Count me in!
Thank You

znmeb

I'm finally getting back to ChucK. I'm currently in the process of getting it running on a Raspberry Pi Zero 2 W with PiOS Lite and USB audio dongles. Is there a cross-build tool chain for the Bela Gem / PocketBeagle 2 that will run on, say, a 64 GB 8 core x86_64 Linux box or a 4 GB Raspberry Pi 4? GCC on the Pi Zero is painful beyond words because of the limited RAM (512MB) and the PocketBeagle 2 is similarly constrained.

giuliomoro

I've been using an arm64 build of gcc and clang on an arm64 mac host, either natively or via docker, and it worked OK. Not sure what the x86_64 options are, but even if you can't find one, then running the compiler from the board itself inside a docker image (or otherwise use qemu) should be doable, albeit a bit slower.

znmeb

giuliomoro Thanks! Qemu is probably my best option on the x86_64 - 64 GB of RAM and 8 cores / 16 threads. But the Pi 5 can probably do the job; it runs Distrobox / podman containers fine. So does the Pi 4 but it's slower and has less RAM.

I've got PocketBeagle 2s to test on, but no easy way to get audio out until the Gem hardware gets here.

symasmith

Impressive upgrade!

jayrope

Is there currently no way to order Gem from the EU Store. If so, will that change or even when will that change?
Thanks a lot,

giuliomoro

Until the crowdsupply campaign is fulfilled (we are planning to ship the boards to them in December), we cannot sell Gem anywhere else. Once those are fulfilled, it will become available through our usual channels - as well as mouser.com .

jayrope

Thank you @giuliomoro - will wait for a EU store appearance then.

slk

I am looking into integrating the Bela Gem with an EEG recording platform, and ideally I would like to supply the Bela Gem with a 3.2V supply for this purpose. It seems that the Pocketbeagle 2 does support this lover supply voltage through the battery connector on the board, but will the Bela work with a supply from the battery connector on the Pocketbeagle?
Would you be able to share more details about the components on the Bela Gem, ideally a schematic.

I addition, to implemening the Bela Gem with the EEG recording platform, I am also hoping to upgrade a shield that I made for the previous Bela version (see link below), so more details on the schematic would also be very helpful in this regard.
https://ece.au.dk/forskning/forskningscentre/center-for-ear-eeg/projects/large-scale-ear-eeg-hyperscanning/hyperscanner/triggerbox-1

giuliomoro

The schematic of the GemStereo is very similar to that of the BelaMini rev C.

Powering from 3.2V may be possible but it will possibly cause some noise issues, as the internal regulators will not be working properly and you'll have to make sure the incoming voltage is well regulated - and that may not even be good enough. Can you not provide something like 3.7V?

That shield seems to be using the 16 digital I/Os. Those are directly connected to the PB2, so you wouldn't care much about what's on the Gem, but only about what pins to use. The below should give you all you need:

Pinout of digital pins is the same for Stereo and Multi. Note that D5, D6 and D8 don't have the "D" (for lack of space).

slk

Thank you @giuliomoro, great to hear that it might be possible to use a lower supply voltage.

From the Belamini rev. C it seems that the only regulator on the Bela board is the MIC5317 LDO regulating to 1.8V.
Is that also the case for the Bela Gem?
The opamps for the analog inputs and the ADC support a supply down to 3V, so I guess it should be possible if we can provide a regulated supply above 3V.
Do you use the same op-amp, ADC, and DAC in the BelaMini and Gem?

Great to hear that the digital pins is available in a similar manner on the Gem.

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