SimonK FlyShot (digital speed command, closed-loop) - Default to safe minimum speed on boot, etc.

Code (plus a precompiled bs_nfet.hex for ACE discrete drive and Spider boards, etc.)

Now defaults to ~35,000erpm (~5000rpm with 14 pole motors, or about 36 fps root speed on a standard Hy-Con) at boot time.

Also, the safety governor (safety here being from the ESC's perspective, meaning avoiding exceeding the frequency limit of the inverter control loop) has been set back to the stock TIMING_MAX = 0x0080 (312,500erpm) in this so this is now universal to high speed applications out of the box whereas me leaving it at 0x00e0 in the last one may have "gotcha'd" someone.

/u/matthewbregg had a good suggestion in this thread about defaulting to a low speed. I had been considering this type of feature, but this thread got me thinking about safety and failsafe control a bit more in general. Thus this, and the new velocity watchdog code on the S-Core's end.

It really makes sense just in general that a closed-loop drive doesn't try to spin to the moon if you haven't informed it of what speed it should go... Makes sense, right?

Some setups (very large wheels and high-velocity multistages in particular) could even conceivably be mechanically intolerant of overspeed. With ordinary BLDC configurations, that wouldn't happen, because the battery and motor kv would have been selected to avoid that, but with closed-loop configurations that are trying to have stiff speed regulation with a lot of available torque at some operating speed, it may very well be that there is enough bus voltage that reaching hazardous speeds and blowing shit up is possible if uncontrolled. My previous idea was that one would just set TIMING_MAX to an appropriate safety governor setting which removes the need for a default low speed in that regard, but in general, flashing ESCs to configure them is a pain in the ass and it is better to make a drive firmware be universal and live-configurable over the wire.

Bregg also implemented a version requiring identical FlyShot commands to be sent twice to apply a speed update, and this is a most excellent addition for applications that do not have speed feedback and cannot selftest their flywheel speeds, like most Ultracage setups and FDLs and whatnot. These variants are also compatible with my gear by nature, but the above code doesn't have that feature because I want a higher speed update rate and smoother speed adjustment when live-adjusting speed and it is not necessary to be that overzealous with speed feedback present. In any case, just like Dshot commands, one-time FlyShot commands should always be sent about 10 times anyway as a matter of course.