CV outs from Gem

rthorntn

Great update!

With the GPIO, can that be seen by the provided software stack, if I connect a 3.3V square wave to a GPIO, can I use that as a clock/gate/trigger in say Pure Data?

giuliomoro

Sure. 16 GPIOs are sampled at audio rate and you can use them in puredata as audio signals or just receive a message when an input changes and send a message when you want to change an output

rthorntn

So cool, thanks!

I assume the same goes for GPIO as output, there is a setting somewhere where I can set a GPIO to either input or output?

Like I could set a bunch of GPIO to output and use them as sequencer gates!

Can PB2 GPIO handle say velocity CV?

giuliomoro

rthorntn , there is a setting somewhere where I can set a GPIO to either input or output

Yes

rthorntn Can PB2 GPIO handle say velocity CV?

I am not sure what you mean by that.

rthorntn

giuliomoro rthorntn Can PB2 GPIO handle say velocity CV?

I am not sure what you mean by that.

Thanks, apologies, I should have provided more detail, I mean, can the GPIO on the PB2 (with PWM) output (with the addition of an external LPF) the 127 discrete values that MIDI velocity CV can generate?

Update: maybe the PB2 doesn't have PWM, or only has 4 PWM, not sure (Gem might be using any PWM pins that there are), the Teensy 4.1 has 35 PWM output pins so I just kinda assumed the PB2 had quite a few.

rthorntn

What would be the easiest way to do oscilloscope music on the Gem, can I play a wave file out of the DC coupled interfaces?

I was taking a look at https://github.com/jameshball/osci-render/releases/download/v1.33.2/osci-render-unix-1.33.2.jar today but this outputs to a sound card, I don't think the DC coupled interfaces on Gem will show up as audio outputs?

Or maybe the TLV320AIC3106:

shows up as an audio output
allows any internal hpf to be disabled or dialed back
doesn't have capacitors on the outputs or they can be bypassed

giuliomoro

Most pins that are not otherwise used on the PB2 can be used for PWM in one of these ways:

Using an actual PWM peripheral (a handful of pins, bitclock in the tens of MHz)
as a Bela GPIO (up to 16 pins, same bitclock as the audio rate)
as a PRU PWM pin (8 or more pins, with a bitclock of 6MHz or less)

Additionally you have DC-coupled audio outputs (2 on GemStereo (TLV320AIC3104) , 10 on the GemMulti (TLV320AIC3106 and ES9080Q)).

rthorntn I was taking a look at https://github.com/jameshball/osci-render

It's written in JUCE, and JUCE has a target doe the Bela API.

rthorntn don't think the DC coupled interfaces on Gem will show up as audio outputs?

It may show up as an ALSA device if we get the driver to work.