[Arm-netbook] Block Diagram EOMA-68 Handheld Games Console

Luke Kenneth Casson Leighton lkcl at lkcl.net
Fri Sep 5 12:48:54 BST 2014

there are two EINT lines on EOMA68.  i suggest that one of them be
connected to the AXP209, and the other to the STM32F072, although
because there are only 2 this leaves some slight issue with the
touchpanel to resolve (in linux kernel source, which will need

the problem is this: things like the touchpanel it is fairly essential
(because you want to wake up the entire device based on an EINT) to
have external interrupt.

one alternative to modifying the linux kernel source is to have a NAND
(NOR?) IC multiplexing multiple IRQ lines from various peripheral ICs
onto the one EINT line.

another alternative is to wire the AXP209 to the STM32F (on one of its
GPIOs, then put that into EINT mode), then have the STM32F software
generate a simple GPIO pull-up out to one of the EOMA68 EINTs.

so instead of doing the multiplexing using a NAND (NOR) gate IC, you
do it in software (firmware) instead.

then you can do whatever you want, without modifying any linux kernel source.

so, you need to identify which devices have IRQ outputs.  i count these:

* Accelerometer
* Touch panel
* AXP209
* STM32F072xx
* MicroSD
* Headphone detect

all of these _should_ be connected to (generate) EINTs... but there
are only 2 EINTs available...

* analog joysticks are exactly that, they always generate data so
there is no concept of "IRQ"
* power button is connected to the AXP209 so the AXP209 does the "IRQ"
* Buttons are converted to USB HID (keyboard) events via the STM32F072
in software...

anything else?


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