[Arm-netbook] Laptop PCB schematics

[Luke Kenneth Casson Leighton]

ok soooo on laptop_15in_PCB1_rev2_2.pdf quadrant 2D page 1 you have
the STM32F072 board connector (to PCB2) and quadrant D1 you have the
power connector (to PCB3).  that connector's fairly straightforward,
except the names should be VCC-5V0 not SYS-V.   or, more to the point:
SYS-V on laptop_15in_PCB1_rev2_2 *is* VCC-5V0.

now let's look at laptop_15in_PCB2_3.pdf.  J6 is where things aren't
properly synchronised as i hadn't completed the redesign.  here - pin
10 - *really is* SYS-V from PCB2's J4 - because it's the "incoming
battery voltage" which powers the STM32F072 board's 3.3v regulator,
that power *must* remain permanently on, as the STM32F072 needs to be
permanently powered (so that it can monitor battery status interrupts
etc.) it also supplies (as 3.3v) the VREFTTL for PCB3 for any digital
GPIO...

*sigh* which is why i had the level converter on-board PCB3 because
all the STM32F072's GPIO is @ 3.3v, whilst the TI ICs are @ 1.8v.

it must also stay in control of all the power for the main laptop -
that's why 5V_EN is connected to PCB3's J4, and you can see from
PCB2's J6 i haven't yet updated the names of the pins.

yes the battery-sense thing is weird: you musn't connect the battery
directly to GND, you have to do that via a rather heavy-duty very
accurate 0.01R resistor, use differential-pairs to wire up the
current-sensing, make it very very pretty and completely symmetrical,
so that there's no chance of EM interference even the slightest little
bit with that hyper-sensitive voltage reading (microvolts) going into
the battery-sense IC.

all not yet completed etc. etc.

l.