"David W. Schultz" <[email protected]> writes: > Both NFPA 1122 and 1127 require that launch systems include a removable > safety interlock in series with the launch switch. TRA uses NFPA 1127 as > their safety code and NAR requires following the NFPA codes at all NAR > launches. So this is a problem.
I wasn't aware that a removable interlock was an explicit requirement. I just looked and couldn't find the current NFPA text anywhere online. I'd like to read the actual text... any idea where I can find it? > The fix is to replace the silly guarded toggle switch with a key > switch for safe/arm. Right, pretty easy change. I'll look at the details tomorrow. > Put a lanyard on the key so the LCO can hang it around his neck when not > in use. (Stash a spare key inside the case.) Sigh... all part of the reason I personally detest key switches. My observation is that key switches get turned, but the key rarely gets pulled out in practice. But .. [sigh] .. rules are rules. > Those switch connections make me nervous. They connect unprotected GPIO > pins to parts that are being handled by the user. Sure the switch body > will provide some protection from ESD but how much? A series resistor > would help a lot. Large enough to limit currents in the ESD diodes on > the GPIO pins but small enough to work with the internal pullups. Sure. In several years of use, we've seen no issues with zapping the SOC's in-built ESD protection on the protos, but resistors are cheap and I can easily add them to the board revision I'm preparing to send out to fab. Thanks for the suggestion. > Oh, I thought that the FCC prohibited encryption for amateur radio: > 47 CFR 97.309(b) Has that changed? 97.309(b) does not apply because we're not encrypting the content, thus we are in no way "obscuring the meaning of any communication". What we're doing is appending a crypto checksum to each packet to authenticate the link. That's been a common mechanism on amateur radio control links for a long time. The closest thing I can find to an official pronouncement about this is in the ARRL comments in response to RM-11699, which they opposed. In those comments, they indicate that conversations with the FCC led to agreement that encryption for authentication on things like repeater control links was already allowed, and thus not a reason to accept the request that lead to that RM. I'll note in passing that there's also 97.215(b), though I don't think the FCC had model rockets in mind when discussing telecommand of model craft. Sure feels like an analogous use, though. Bdale
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