PCB1 - Main Board

This is the PCB that takes the EOMA68 CPU Card. It takes USB-OTG-style 5V @ 3A power (which is reversible), contains the LVDS converter IC for the screen, as well as USB connections to the EC board (PCB2), a USB2 Hub and a USB Audio IC (CM108AH).

PCB2 - Embedded Controller Board

This PCB contains an STM32F072, which is permanently powered by PCB1. The STM32F072 monitors power, controls the on/off state of the EOMA68 CPU Card, emulates a keyboard and trackpad as USB devices and much more.

PCB3 - Power Board

This PCB manages the battery, and provides power to both PCB1 and PCB2. It also has a power switch (which is connected directly to the STM32F072 on PCB2 as a "soft switch"). There is also a Battery Charge Monitor (coulomb counter).


  • PCB3 really does face upside-down, the pictures are taken with the laptop face-down.
  • the battery you can see it overlaps the PCB - it's plastic sheath but still, there must be no components on the long side, at least 6mm.
  • the PCB doesn't actually slot into the long edge of the casework, but i did leave off any components on the lower long side, as well.
  • the off-PCB connectors need to be Right-Angle! the clearance is 6mm, so a vertical SIP Header won't do.
  • battery connector should probably be side-to-side (aligned with the long length) just as in the pictures, so that the cables don't have to be bent
  • the power button is from ALPS, P/N SKRTLAE10 - it's a right-angle push switch (like the one on LION1CELL01A but only R/A). i can't find EU suppliers but it's extremely common in China.
  • the DC jack is CUI INC PJ-018H-SMT - this is easy to get hold of.

Picture of current PCB:

battery pcb rev1 and battery.png battery pcb rev1 and battery side.png

Specification for PCB2-to-PCB3 connector

PCB2-to-PCB3 connector specification
Pin Number Function Description
2 SCL I2C Clock (PCB2 STM32F072 Master)
3 SDA I2C Data
4 BATC_PSEL To Battery IC, indicates power selection
5 BATC_CD From Battery IC, indicates Charge Status
6 BATC_ALARM From Battery IC, indicates Interrupt
7 PWRON Connected to PCB3 external switch (for reset, power)
8 CHRG_IQRN From Battery Coulomb IC, indicates Interrupt
9 VREF_3V3 Provided by PCB2 as Digital I/O Ref for PCB3
10 SYS-V Provided by PCB3 to power PCB2 (nominal 4.2v)

Specification for PCB1-to-PCB3 connector

Pin Number Function Description
2 EOMA68-5V0 5V power lane for EOMA68 card
3 SYS_V System Voltage (5V from buck-boost converter)
4 SYS_V "

Specification for PCB1-to-PCB2 connector

Pin Number Function Description
2 USB_DM USB- to STM32F072
3 USB_DP USB+ to STM32F072
5 EXT_BOOT0 BOOT selection (firmware mode) to STM32F072 (PCB2)
6 EXT_NRST Hard RESET of STM32F072 (PCB2)
7 PWRON_EOMA68 From STM32F072 (PCB2) to EOMA68 (PCB1) "Power On"
8 VREFTTL From PCB1, used for level shifting of EXT_BOOT0

Revision of PCB schematics

PCB3 - Power Board

  • connect thermistor for BQ24193 USB OTG Charger between BAT_NTC and GND (not TS which is wired to the fuel guage) [done]
  • change DVCC to SYS-V (otherwise LEDs won't work) [done]
  • connect EOMA68 power - suggested schematic: https://nextcloud.devpi.de/s/3Ekp2ipbNepU7OW