MarkT

That's about 5ppm out, not bad for standard quartz crystals (which are usually rated +/- 20, 30 or 50ppm). What accuracy do you need?

CMOS latchup is common in this sort of situation (phantom powering).

Generate all the harmonics under 22kHz and sum them? Easy, not efficient...

Internally compilers will use hashtables for lots of things like names, constants and identifiers, so any arbitrary ordering could be down to the hash function on the day. Also optimization passes might order things by expected usage too...

For speed and for their saturating arithmetic...

Which begs the question what key release velocity is a note-on zero-velocity packet equivalent to?

If I remember rightly triangle isn't bandlimited, but has much lower spurious tone levels as its not a discontinuous waveform (rather its derivative is discontinuous).

A note off message is equivalent to a note-on with zero velocity - you should always treat them identically (in an ideal world). What I'm not clear about is if the velocity value in a note-off message has any meaning...

Next to the ADC where you want the interference to be minimized.

SDcard pull heavy currents when writing and erasing, unless you have separate regulation for ADC and SDcard this will cause noise spikes on the ADC readings - adding lots of bulk capacitance can help (millifarads, not microfarads) by attenuating...

Can you adding debugging output then?

Can you snoop the traffic?

BTW 0.24ms latency is 8cm in air, which seems to be overkill really.

You are wiring TX <-> RX in both directions?

Single LiFePO4 cell is 3.3V or so, although somewhat higher fully charged...

Is the flight controller 3.3V ? It needs to be to talk to the T4, otherwise it'll roast it.

Doesn't the datasheet show the signal paths?

Nearby mobile phone? Are you using an SD card on the Teensy?

The pciture shows the ground wire is not running alongside the other wires, so there's a whole heap of loop inductance that you don't want there. Every signal line should run alongside a ground return wire, ideally a return ground wire per...

Normally they top out at 1.35V each.

Try 4 NiMH rechargable AA batteries (about 5.3V), which should have better high current handling. 3 x alkaline AA is only 4.5V and thus much closer to undervoltage cutoff, and the max current is less than with good NiMH cells. 1000uF is not...

Well with only one active node the packet's don't get ACK'd and the single node will eventully fall into passive error mode if it sends packets regularly?

Post your code? A couple of snippets aren't enough... BTW a line input will low pass filter a guitar output as guitars want 1M input impedance typically.

How hot is it getting with these continual erases?

Another Teensy 4.1 based synth/control

The cap will be reducing the level of noise - you don't need to slow down the edge (in fact the standard solution is normally a 74HC14 which has proper amounts of hysteresis, much less noise sensitive then). The noteworthy fact is that a CMOS...

WD40 is not safe for many plastics, I would not risk it on electronics. Air-dusters or electrical contact cleaner are perhaps safer choices?

Just that 100nF is commonly stocked for decoupling caps by many, 10nF would be plenty too.

100k : (100k || 100nF). divider would be me choice, half the LiPo voltage to about 2V, 30uA drain.

Perhaps the better question is what are you trying to actually do?

Just do digitalWrite(pin, HIGH); pinMode(pin, OUTPUT); It unlikely to matter that a weak pullup got enabled a microsecond or so before the pinMode() call?

Well that's an oscillator by definition, the system integrates the control input, which is the integral of the error (if only an I term), so 180 phase shift added to the negative feedback turning it to positive feedback... P term does the bulk...

Its oscillating, so the I term is likely too large, and possibly the gain term too (P). Are you using the D term?

I'll repeat those pink bags don't shield from ESD, they just don't generate much static when handled (compared to raw polythene etc). The silver/grey bags are Faraday cages, but non-shorting (the ultra-thin aluminium layer is sandwiched), so...

I'd suggest using 1000+ ohm ferrite, and say 10 ohm resistor, then the mic can have less supply droop and good filtering?

Indeed the headphone socket is only for headphones/earbuds, not for outgoing signals.

Something like this: The source sees about 120 ohms, but centre-biased, so that at 3.3V supply it only has to drive about +/-12mA, not 25mA This terminates the line well enough that reflections are not a problem. Its an old trick that saves...

That's a good point! I guess a raw TCP/IP connection is the closest match...