[Arm-netbook] EOMA68 laptop battery management.

Luke Kenneth Casson Leighton lkcl at lkcl.net
Thu Mar 3 13:15:52 GMT 2016

crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

On Thu, Mar 3, 2016 at 10:06 AM, Jakub Kákona <kaklik at mlab.cz> wrote:

> 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)

> 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.

> Is it STM32F072's firmware already written?

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

> 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.

> 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.

> 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.

> 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

 cool.  local is great.

> 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.

 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


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