[Arm-netbook] EOMA68 laptop battery management.

[Jakub Kákona]

Hello,

I take look on the bq24193's datasheet and I think it is almost perfect IC
for intended application.
STC3115 seems to by quite cheap but not the best solution.

We currently have quite outdated, but still better battery gas gauging
design based on BQ34Z100.

Documentation is here
http://www.mlab.cz/Modules/PowerSupply/LION1CELL01A/DOC/LION1CELL01A.pdf

I think the main work should be the redesign of our LION1CELL01A module
with bq24193 charger integrated in it. We should do it in KiCAD probably in
form of new MLAB module (for testing). The exact PCB for Libre laptop
should be derived from it then.

Is current blocks/circuit schematic of Libre laptop somewhere? I do not
understand how the higher voltages (+5V) or +12 (for LCD) are efficiently
generated from battery? Has this design higher efficiency than two balanced
cells connected in series?

---
ok, well actually there is a sub-task that i could do with your help
on: i need a 15 watt *single-cell* battery charger / monitor board
5.0V and can be controlled via I2C as to which direction the power
goes... *and* can take DC input at the same time. i've found the
bq24193, it's the best i could yet find that will do the job. the
only thing is, its I2C interface is hard-wired to 1.8v and i need 3.0
to 3.3v, so there will be some level-shifting needed there. it also
will need a battery monitor (coulomb counter) - the STC3115 QFN is
what i had in mind, but if you have something better please do say so.
PCB size needs to be no bigger than 32 x 85mm, 1.5mm thickness, 2
layer *ONLY*, components *ONLY* on one side, no through-hole
components or connectors are allowed, and there is a severe [hard]
height limit of 5.5mm so the only DC connector i could find which can
handle 5A and is within that limit is the PJ-018H-SMT from CUI Inc.
also, i really loved the solar panel idea and it turns out that the
PJ-018H-SMT has a 3-pin arrangement, so in theory a diode and a solar
panel in series between pins 2 and 3 would provide solar power when
the DC-jack is disconnected. pin 3 (to which the solar panel would be
wired) would be disconnected when the DC jack is in. pin 2 is GND.
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[Luke Kenneth Casson Leighton]

Post by Jakub Kákona
Hello,
I take look on the bq24193's datasheet and I think it is almost perfect IC
for intended application.

good to hear. there are some variants btw - bq24192, 24191, 24196 -
it would be good if you could double-check which one is best. the
USB-OTG functionality @ 3A is *critical* because EOMA68's 5V power
rail is *REVERSIBLE*. basically you can either *PROVIDE* 5V power or
the CPU cards can be *PROVIDED WITH* power.

so i am using the USB-OTG rail of the bq2419x series to provide up to
15W of power to the *entire* laptop.

Post by Jakub Kákona
STC3115 seems to by quite cheap but not the best solution.
We currently have quite outdated, but still better battery gas gauging
design based on BQ34Z100.

if you've got something better, _great_.

Post by Jakub Kákona
Documentation is here
http://www.mlab.cz/Modules/PowerSupply/LION1CELL01A/DOC/LION1CELL01A.pdf

looks great. it's almost the right size as well.

Post by Jakub Kákona
I think the main work should be the redesign of our LION1CELL01A module with
bq24193 charger integrated in it. We should do it in KiCAD probably in form
of new MLAB module (for testing). The exact PCB for Libre laptop should be
derived from it then.

.... it's almost perfect as-is. if you can keep the bits which
should not go into the laptop on a snap-off area along the bottom of
the PCB then it's pretty much done already.

Post by Jakub Kákona
Is current blocks/circuit schematic of Libre laptop somewhere?

honestly... you're the first person ever to ask. i'll generate some
schematic PDFs and point you at them shortly. i will also document
the pinouts of the various connectors, as that will be part of the
specification for the Power PCB.

Post by Jakub Kákona
I do not
understand how the higher voltages (+5V) or +12 (for LCD) are efficiently
generated from battery?

the LCD is only 4 watts (despite being 15.6in), backlight is around
3W, and when run at only 30hz the LCD uses under 1W. a single simple
step-up converter to around 17-20v @ 150mA constant current is
therefore perfectly ok, from a 5V supply.

this is *not* a monstrous "let's burn the user's eyes out with a 20W
backlight and dazzle them with 5W worth of 3480x2000 pixels @120fps
needing 5GHZ worth of bandwidth".

so i've used a Silergy SY7201 (or equivalent), it's a SOT23-6, it's
got a power dissipation rating of 0.4W - it does the job.


+5V comes from the USB-OTG function of the bq24193. that can provide
up to 3A, which is perfect, and is exactly what's needed. so there is
no need for a 5V regulator.

the "normal" power output is battery-level (4.2v) and does *not* need
to be stepped up. it goes straight (solely and exclusively) to PCB2 -
the "Embedded Controller" board. this is actually a 3.3v part, so
there is a 3.3v regulator.

basically the EC board - which manages power, keyboard, touchscreen,
and provides RTC functionality etc - is the *only* thing which needs
continuous power, so that's run off of the bq24193's "main output".

the EC board is where the I2C interface goes [NOT to the EOMA68 CPU
Card!]. so it is the EC's job to perform "on / off" function. the
*EC* controls the CPU Card's power state. the *EC* tells the bq24193
to switch the USB-OTG power to 5V @ 3A. the *EC* listens to the
battery status (from the bq34z100).


basically, this is *not* a "standard laptop", it's an "embedded"
design. so there is no 5V rail, and there is no 12V rail: embedded
power ICs for single-cell applications can therefore be considered.

Post by Jakub Kákona
Has this design higher efficiency than two balanced
cells connected in series?

given that the maximum power required is only 15W, which is within the
budget of the bq2419x series, i am more concerned about simplicity of
design (and completing this product) than i am about running
efficiency. a 2-cell design is far more complex to design - apart
from anything, 2 cells would need to be sourced of exactly the right
size, and it took me months to find even the current battery.

later however, once this first laptop is out the door, i will begin a
2nd design which will need something like a 30 to 35 watt budget (more
USB ports, built-in SSD, etc.) and at that point a 2-cell or 3-cell
design is going to be needed. however, the implications for that
design decision are MASSIVE. the casework - which has already taken
well over a year to complete - would need a total overhaul.

l.

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[Luke Kenneth Casson Leighton]

argh - the bq2419x series only provides up to 1.5A @ 5V in USB-OTG
mode, not 3A. which rules it out. it's otherwise perfect, damnit.
i'll have another search - bq2416x series isn't good enough as it only
does 2.5A.

i'm currently updating
http://rhombus-tech.net/community_ideas/laptop_15in/ to add connector
specifications. PDF schematics and layout image links:
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB3_rev2_1.pdf
Loading Image...
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB2_2.pdf

l.

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[GaCuest]

mode, not 3A. which rules it out. it's otherwise perfect, damnit.
i'll have another search - bq2416x series isn't good enough as it only
does 2.5A.
i'm currently updating
http://rhombus-tech.net/community_ideas/laptop_15in/ to add connector
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB3_rev2_1.pdf

Forbidden

You don't have permission to access 
/~lkcl/eoma/laptop_15in/laptop_15in_PCB3_rev2_1.pdf on this server.

http://hands.com/~lkcl/eoma/laptop_15in/pcb3_layout.png
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB2_2.pdf
l.
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[Luke Kenneth Casson Leighton]

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Post by GaCuest

mode, not 3A. which rules it out. it's otherwise perfect, damnit.
i'll have another search - bq2416x series isn't good enough as it only
does 2.5A.
i'm currently updating
http://rhombus-tech.net/community_ideas/laptop_15in/ to add connector
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB3_rev2_1.pdf

Forbidden
You don't have permission to access
/~lkcl/eoma/laptop_15in/laptop_15in_PCB3_rev2_1.pdf on this server.

sorted, thx.

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[Luke Kenneth Casson Leighton]

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On Wed, Mar 2, 2016 at 1:43 PM, Luke Kenneth Casson Leighton

Post by Luke Kenneth Casson Leighton
mode, not 3A. which rules it out. it's otherwise perfect, damnit.

ok, i thought about this, and i reckon that it'd be ok to do this:

* use the USB-OTG "boost mode" to provide USB-OTG power to the EOMA68
CPU Card [only]
* put the SYS-V output through to the main PCB1, where it will do
boost conversion to 5.0V for USB ICs. SYS-V output could go directly
into the step-up converter for the LCD backlight, and also directly
into the 3.3v regulator.

so... the spec doesn't change, just the implementation of PCB1.

l.

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[Jakub Kákona]

Hi,
It looks like power schema I expect that is already been done. But a
current design is still not fully clear to me.
I will probably print the schematics PDFs on large A3 sheets tomorrow and
try to find out how the Libre internals are interconnected currently..

Thanks

Post by Luke Kenneth Casson Leighton
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On Wed, Mar 2, 2016 at 1:43 PM, Luke Kenneth Casson Leighton

Post by Luke Kenneth Casson Leighton
mode, not 3A. which rules it out. it's otherwise perfect, damnit.

* use the USB-OTG "boost mode" to provide USB-OTG power to the EOMA68
CPU Card [only]
* put the SYS-V output through to the main PCB1, where it will do
boost conversion to 5.0V for USB ICs. SYS-V output could go directly
into the step-up converter for the LCD backlight, and also directly
into the 3.3v regulator.
so... the spec doesn't change, just the implementation of PCB1.
l.
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[Luke Kenneth Casson Leighton]

Post by Jakub Kákona
Hi,
It looks like power schema I expect that is already been done.

it hasn't. you're missing some history (dating back several months).
the LTC4155 was chosen because the datasheet *CLAIMED* that it was
compliant with USB-OTG power provision. however, what they neglected
to state was that USB-OTG power is *DISABLED* when a 5V DC input is
plugged in.

basically, replace LTC4155 with bq24193, and STC3115 with BQ34Z100.

the only complication is that there will need to be a bi-directional
Open Drain level shifter to convert the GPIOs for the bq24193. e.g. a
TXS0104E.

why is a level shifter needed? because the bq24193 operates its GPIO
at 1.8V, and the STM32F072 operates its GPIO at 3.3v. so the I2C and
GPIO signals from the bq24193 need to go through a level-shifter. it
needs to be bi-directional because SDA (I2C data) is bi-directional.

for the BQ34Z100, apparently it can take REGIN as a reference voltage.
so, for this, the Reference Voltage from the EC board (VREF_3V3)
should be hooked directly to this pin. that takes care of the GPIO
voltage levels for the BQ34Z100.

Post by Jakub Kákona
But a
current design is still not fully clear to me.

as this is a complex inter-dependent 4-PCB design with 18 months of
design work in 3 of the PCBs and 4 years design work in the EOMA68
standard, that is not surprising.

however, fortunately, the only part that you need to be absolutely
clear on is the Power PCB.

if you'd like me to fully explain the full design i'm happy to do
so.... just bear in mind that it may take some time.

Post by Jakub Kákona
I will probably print the schematics PDFs on large A3 sheets tomorrow and
try to find out how the Libre internals are interconnected currently..

by then phil should have had a chance to update the wiki and bring it
out of broken-ness. in the meantime i'm attaching the pcbs.mdwn page
which contains the specifications of the connectors. you only need to
be concerned about PCB2-to-PCB3 and PCB1-to-PCB3. PCB1-to-PCB2 is for
how the EOMA68 CPU Card and the Embedded Controller talk to each
other.

l.

[Luke Kenneth Casson Leighton]

---
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On Wed, Mar 2, 2016 at 4:48 PM, Luke Kenneth Casson Leighton

Post by Jakub Kákona
But a
current design is still not fully clear to me.

ok i've created a diagram, it's basically identical to the current
PCB3 schematic, except LTC4155 is replaced by a combination of bq24193
plus txs0104 plus 1.8v regulator, and STC3115 is replace by BQ34Z100.

Loading Image...

key differences from what you *might* be expecting this Charger PCB to have:

1) there is NO 5V rail.
2) there is NO 12V rail
3 ) there is NO 3.3v rail
4) the (appx) 4.2V "SYS" voltage from the Charger IC goes straight out *as-is*
5) Digital GPIO requires a REF voltage to be safe and meaningful.
this *has* to be EXTERNALLY SUPPLIED.
6) many devices are now USB-OTG compliant (2-way power),
so that is a power output (***AND POWER INPUT***)

from what you wrote, you *may* have considered that something like
this would be useful:

1) 5V DC output
2) 12V DC output
3) 3.3v output
4) DC charging input

such a board is not useful for this project, because such a design is
for a standard laptop. this isn't a standard laptop, it's a
USB-OTG-powered "embedded" device.

l.

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[Jakub Kákona]

Thanks for the diagram!
But I have one more question. Is it really necessarily to operate bq24193's
I²C bus at 1.8V?
According to datasheet http://www.ti.com/lit/ds/symlink/bq24193.pdf
The 1.8V was used only as example of operating voltage..
The Absolute Maximum Ratings for all SDA, SCL and INT pins is 7V and both
are "i2c standard open collectors" and could be pulled-up to any rail
within the operating voltage range..
Therefore I think the Voltage translator is not necessary...

Kaklik

Post by Luke Kenneth Casson Leighton
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On Wed, Mar 2, 2016 at 4:48 PM, Luke Kenneth Casson Leighton

Post by Jakub Kákona
But a
current design is still not fully clear to me.

ok i've created a diagram, it's basically identical to the current
PCB3 schematic, except LTC4155 is replaced by a combination of bq24193
plus txs0104 plus 1.8v regulator, and STC3115 is replace by BQ34Z100.
http://hands.com/~lkcl/eoma/laptop_15in/pcb3_diagram.png
1) there is NO 5V rail.
2) there is NO 12V rail
3 ) there is NO 3.3v rail
4) the (appx) 4.2V "SYS" voltage from the Charger IC goes straight out *as-is*
5) Digital GPIO requires a REF voltage to be safe and meaningful.
this *has* to be EXTERNALLY SUPPLIED.
6) many devices are now USB-OTG compliant (2-way power),
so that is a power output (***AND POWER INPUT***)
from what you wrote, you *may* have considered that something like
1) 5V DC output
2) 12V DC output
3) 3.3v output
4) DC charging input
such a board is not useful for this project, because such a design is
for a standard laptop. this isn't a standard laptop, it's a
USB-OTG-powered "embedded" device.
l.
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[Luke Kenneth Casson Leighton]

Post by Jakub Kákona
Thanks for the diagram!

no problem.

Post by Jakub Kákona
But I have one more question. Is it really necessarily to operate bq24193's
I²C bus at 1.8V?

i don't know! :)

Post by Jakub Kákona
According to datasheet http://www.ti.com/lit/ds/symlink/bq24193.pdf
The 1.8V was used only as example of operating voltage..
The Absolute Maximum Ratings for all SDA, SCL and INT pins is 7V and both
are "i2c standard open collectors" and could be pulled-up to any rail within
the operating voltage range..
Therefore I think the Voltage translator is not necessary...

if you reckon an STM32F072 could handle it, then fine. that saves
at least 2 ICs, which is great. if you'd like to actually test it,
STM32F072-NUCLEO boards are only $EUR 10 from rs-online, mouser, arrow
and digikey.

ok, so key question: what sort of timescale do you think you'd be
able to do this in? reason i ask is, i need to work out the timeline.

practical matters: i used eurocircuits to get the PCBs done, they
were about 7-10 days (unless you pay extra), and around $EUR 70 for
QTY2. i have some components (connectors, switches, capacitors) i can
send you.

more practical matters: from mid-april i'm going to be moving to a
new country *every month* until the end of the year, to track getting
this into a first production run.

l.

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[Jakub Kákona]

What is primary function of STM32F072 MCU? Is in necessary for LCD
configuration?
Is it STM32F072's firmware already written?
I am pretty sure in fact - I²C should be operated on only one voltage level
~3V3. But I do not know how the data from battery management I²C bus goes
to the EOMA68 card.

What EDA software are you using? The circuit sheets has very unusual
graphic style. It would be good if we work in common design tool.

Timescale:
I expect two iteration in PCB design. One of local PCB manufacturers offer
prototyping service as 36 EUR per 1dm² of two sided PCB.
http://www.pragoboard.cz/en/pool_servis
Two pcs of planned PCBs probably fits well in to this area. Standard
manufacturing time is 7 days.
Therefore for purpose of time planning I expect the fully functional PCB
design at the end of March or on first week in April.

Shipping:
I do not know the price of shipping costs to you. But I have address in
Prague (Czech Republic) ZIP code: 18100

I expect the price of shipping will be equivalent to value of connectors or
other passive components, therefore sending it separately won't have much
sense.

Post by Luke Kenneth Casson Leighton

Post by Jakub Kákona
Thanks for the diagram!

no problem.

Post by Jakub Kákona
But I have one more question. Is it really necessarily to operate

bq24193's

Post by Jakub Kákona
I²C bus at 1.8V?

i don't know! :)

Post by Jakub Kákona
According to datasheet http://www.ti.com/lit/ds/symlink/bq24193.pdf
The 1.8V was used only as example of operating voltage..
The Absolute Maximum Ratings for all SDA, SCL and INT pins is 7V and both
are "i2c standard open collectors" and could be pulled-up to any rail

within

Post by Jakub Kákona
the operating voltage range..
Therefore I think the Voltage translator is not necessary...

if you reckon an STM32F072 could handle it, then fine. that saves
at least 2 ICs, which is great. if you'd like to actually test it,
STM32F072-NUCLEO boards are only $EUR 10 from rs-online, mouser, arrow
and digikey.
ok, so key question: what sort of timescale do you think you'd be
able to do this in? reason i ask is, i need to work out the timeline.
practical matters: i used eurocircuits to get the PCBs done, they
were about 7-10 days (unless you pay extra), and around $EUR 70 for
QTY2. i have some components (connectors, switches, capacitors) i can
send you.
more practical matters: from mid-april i'm going to be moving to a
new country *every month* until the end of the year, to track getting
this into a first production run.
l.
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Post by Jakub Kákona
What is primary function of STM32F072 MCU?

functions PLURAL.

* real-time clock
* power manager (on/off, emergency reset)
* battery manager
* keyboard
* trackpad and mouse buttons (all handled by a 3.5in LCD with a built-in CTP)

Post by Jakub Kákona
Is in necessary for LCD configuration?

the mouse trackpad is not a trackpad, it is a 480x272 3.5in LCD with
a Capacative Touchpanel. this LCD must be configured and programmed
to display buttons and scrollbars.

you may be confusing this EC-controlled 3.5in 480x272 LCD with the
main laptop's 15.6in 1366x768 LCD. the one that's controlled by the
EC is the touchpanel one (mouse trackpad). the one that's controlled
by the main PCB is the main laptop LCD.

the two are **NOT** linked in any way, shape or form.

Post by Jakub Kákona
Is it STM32F072's firmware already written?

partially. it's available as GPLv3+ source code.

Post by Jakub Kákona
I am pretty sure in fact - I²C should be operated on only one voltage level
~3V3.

it's not - the voltage level is chosen by the IC designer, or...
well, look at the datasheet of the variable-voltage I2C EEPROM ICs for
an example. they run anywhere between 1.2 and 5.0v and the I2C high /
low levels are usually 0.7x and 0.3x the VREF voltage.

Post by Jakub Kákona
But I do not know how the data from battery management I²C bus goes
to the EOMA68 card.

via the USB interface of the STM32F072. the STM32F072 can emulate up
to 7 different end-points, so currently i have:

* USB CDCACM - this comes up as /dev/ttyUSB0 on GNU/Linux and
connecting to it you can read status info.... such as battery data
* USB HID Keyboard - the keyboard

i still have to do the mouse end-point.

Post by Jakub Kákona
What EDA software are you using? The circuit sheets has very unusual graphic
style. It would be good if we work in common design tool.

if you use KiCAD i will reluctantly install it. KiCAD is "simple"
enough to do this job. the developers have chosen a path that will
keep it from ever being used for any kind of professional-grade
product development.

Post by Jakub Kákona
I expect two iteration in PCB design. One of local PCB manufacturers offer
prototyping service as 36 EUR per 1dm² of two sided PCB.
http://www.pragoboard.cz/en/pool_servis

cool. local is great.

Post by Jakub Kákona
Two pcs of planned PCBs probably fits well in to this area. Standard
manufacturing time is 7 days.
Therefore for purpose of time planning I expect the fully functional PCB
design at the end of March or on first week in April.

fantastic

Post by Jakub Kákona
I do not know the price of shipping costs to you. But I have address in
Prague (Czech Republic) ZIP code: 18100
I expect the price of shipping will be equivalent to value of connectors or
other passive components, therefore sending it separately won't have much
sense.

ok.... the only thing is, one of the switches (a right-angle tactile
switch) is hard to get hold of in Europe. remember that this is
targetted at mass-volume, *not* at the "let's sell 1,000 and be
happy... therefore we'll get everything on digikey @ a 2 to 10x markup
and be happy" market, so some of the parts i've chosen have to be
chosen because they're available in huge volumes in china.

if however you can find a right-angle tactile switch that's available
world-wide... great. if not, i'll give you the P/N of the one i
found.

l.

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[Luke Kenneth Casson Leighton]

hi jakub,

http://rhombus-tech.net/community_ideas/laptop_15in/pcbs/

here's pictures of the current layout, you can see i made a couple of
mistakes - most glaringly-obvious one is the battery connector had to
go over some components, second is that i have the power-output
connector to PCB1 in the wrong place.

i've added some notes for you at the above page, ok?

l.

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[Luke Kenneth Casson Leighton]

On Wed, Mar 2, 2016 at 1:43 PM, Luke Kenneth Casson Leighton

Post by Luke Kenneth Casson Leighton
i'm currently updating
http://rhombus-tech.net/community_ideas/laptop_15in/ to add connector
specifications.

... which i've moved to
http://rhombus-tech.net/community_ideas/laptop_15in/pcbs/

but there is currently a synchronisation error in ikiwiki, please do
NOT edit the wiki for the moment.

Post by Luke Kenneth Casson Leighton
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB3_rev2_1.pdf
http://hands.com/~lkcl/eoma/laptop_15in/pcb3_layout.png
http://hands.com/~lkcl/eoma/laptop_15in/laptop_15in_PCB2_2.pdf
l.

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