U403: change from 74LVC2G125 to 74LVC2G126 The two parts have the same footprint and pinout, but '126 3-state buffers have active-high OE inputs instead of active-low. The change is purely for software benefit: having GPIO 11/12 set to 1 correspond to that current contribution being enabled will be much more intuitive for developers and tinkerers.

#pin name	pin number
nOE1		1
A:0		2
A:1		3
A:2		4
A:3		5
A:4		6
A:5		7
A:6		8
A:7		9
GND		10
Y:7		11
Y:6		12
Y:5		13
Y:4		14
Y:3		15
Y:2		16
Y:1		17
Y:0		18
nOE2		19
Vcc		20