[Arm-netbook] next step is a boot image

[Luke Kenneth Casson Leighton]

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

On Thu, Jan 19, 2023 at 9:06 AM Andreas Grapentin <andreas at grapentin.org> wrote:
>
>
>
> > On 18. Jan 2023, at 14:54, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
> >
> > On Tuesday, January 17, 2023, Andreas Grapentin <andreas at grapentin.org <mailto:andreas at grapentin.org>>
> > wrote:
> >>
> >> U-Boot SPL 2013.07-07841-g569c37da7d-dirty (Jan 17 2023 - 19:37:10)
> >> Board: EOMA68_A20
> >> DRAM: 1024 MiB
> >> CPU: 960000000Hz, AXI/AHB/APB: 3/2/2
> >> SUNXI SD/MMC: 0
> >
> > okaay the SPL loader will now be trying to look on sd/mmc 0
> > for a u-boot image.  clearly it is not finding it.
>
> From looking at the sunxi spl code, this is the enumeration of all detected mmc slots,
> not the configured one. It would be good to compare the output to a known good board.

ah - right. then you may have an earlier revision of the EOMA68-A20
which does indeed have sd/mmc 0 attached to the micro-sd socket.

in which case the advised build instructions - which are for the
*newer* EOMA68-A20 - will obviously not work.

> I started looking at the micro desktop board with my multimeter and did some checks, but it’s difficult without reference to a known good board. But what is maybe noteworthy is that of the three larger capacitors on the board just behind the power socket, both sides of all of them are connected to ground.

that's a serious short, yes, if the resistance between them is zero
(or close to it).  check the 5v rail.

> I assume that part of the board is responsible for the power control?

7-22v down to 5v, yes.


> I’ve noticed that the boot loops above are pretty random —
> it might be possible I’m not supplying enough power to the microsd slot,
> I’ll try to use a stronger power supply.

that would be unwise as it will cause further burnouts due to the short.

> Otherwise, I’m pretty certain I’m using the correct microsd slot, because configuring any other slot in boards.cfg results in timeout errors in the MMC code, which leads to the reported error -1

you are better off powering from USB-OTG entirely bypassing
the MD or removing the RT8288 entirely from the PCB.

the problem with not using the MD is you have to insert wires
directly into the EOMA68-A20 tx/rx and GND holes.  done that
before, it was a pain-in-the-ass but it worked.  you do NOT need
power because they are open-drain.

l.