[Arm-netbook] RK3399

[Luke Kenneth Casson Leighton]

On Fri, Feb 9, 2018 at 11:38 AM, Pičugins Arsenijs <crimier at yandex.ru> wrote:
> I've been looking at battery power solutions. EEE PCs use 2S LiIon batteries, meaning that usual PMIC like AXP209 don't fit.

 there are dual-cell solutions out there, google bunnie huang laptop
power board.

> Thankfully, we don't need to do as much as AXP209 does (and the computer card has an AXP209 in it anyway).

 yes but it's placed into "5V DC input only mode" i.e. VBUS is shorted
to DCIN (read the datassheet on this).  cards must be treated as
OTG-POWER-CAPABLE.  this is IMPORTANT.  you need to respect the fact
that EOMA68's 5V power is DUAL DIRECTION JUST LIKE OTG POWER.

 so you cannot just shove 5V in to the EOMA68 card you ABSOLUTELY MUST
have a one-way current-limiter at the ABSOLUTE MINIMUM (SY6280 does
this job very well).  this will terminate all and any possibility of
doing OTG powering from incoming OTG Chargers but it is safer than
fucking up and killing the card *and* the Housing *and* the battery
*and* the DC mains power supply *and* the OTG Charger due to a current
fight between conflicting incoming power supplies.

 bottom line: please do NOT design this circuit without public
consultation and without my FINAL approval.  remember, i am
responsible for ensuring that the standard is safe for people to use.
if you do not agree to this then you may NOT claim it is interoperable
with EOMA68, you may not make ANY mention of EOMA68 anywhere at all.
not even to say "it is quotes like quotes EOMA68...."

 apologies but i really need to be strict about this as it is down to
user safety.  get it wrong and you could end up killing someone due to
a lithium battery fire.

l.