-nmra watchdog seems to lose a byte of idle from the beginning somehow
- (don't know if this happens with host-supplied data)
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-
-watchdog should disable CDU
-
-
-residual stuff from CDU is present and changes pt0 when you
- * turn on
- * say `+' to master to turn on CDU
- * switch to programming mode
- pt0 on pic2 is the one nearest the switch box, moving to hacker's right
- (we think - I haven't checked this yet)
+race between cdu off (due to watchdog or short) and points
layout polarity diagram colourful segment encoding: