-detector on detector seems to spuriously set B1 or B2 or at least
- panic DR when we honour it
+avoid retransmitting too often (S9.2 C l114-)
+
+as a result of running, then touching track near panel to induce detection
-crash readout: master i2c should go into known state
layout polarity diagram colourful segment encoding:
make moveable feature selection in subseg2display bitwise rather than