[time-nuts] GPS message jitter (preliminary results)
holrum at hotmail.com
Thu Jul 21 14:02:10 EDT 2016
I bit bang serial all the time... it is much easier if to do if you are only banging serial output. Reading serial streams at higher bit rates while doing other useful stuff can be challenging... particularly if you don't have a timer handy.
I once coded up a PIC to output a time code / status overlay on a video screen (bit banged video/hsync/vsync streams) while sending simultaneously sending serial data out another pin. One's gotta love the PICs rigid clocks-per-instruction architecture when coding up things like that. On another product (video capture -> JPEG -> serial stream) I replaced over 30 TTL IC's with a single PIC generating various timing and control pulses, all lovingly and precisely bit banged.
Looking closer at the Jupiter-T message timing, it's obvious that they have it timed and aligned down to the bit level (or better).
I agree this approach has limited appeal these days, but my point is that old-style bit-banging serial IO does have certain time nut advantages
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