[Letux-kernel] [OpenOCD-devel] [PATCH]: d86217d board: add Skytone Alpha 400

[Daniel Glöckner]

Hi,

maybe CCing the OpenOCD list wasn't a good idea. We are not really
talking about JTAG. I have dropped that list.

On Sat, Oct 24, 2020 at 04:26:43PM +0200, H. Nikolaus Schaller wrote:
> Unfortunately a lot of documentation about these devices has been lost.
> AFAIR there was Kwaak (some early public Wiki) and the wayback machine has archived
> some parts, but for example I could no longer find the photos about
> disassembly.

Here are the scans I made 11 years ago:
https://c.gmx.net/@325285928782273387/m-VYZa6xShCenrH1mgbBpA
It's so big because of the lossless compression. The images can be extracted
with the pdfimages tool from Poppler. They use non-square pixels. I think I
used an old CCD scanner that could do 600dpi only in one direction because
of its better depth of focus.

> Another problem is that I am no longer experienced in the details how to
> boot from SD card... AFAIR there was some special key combination and if
> one get it wrong the system will overwrite flash where only JTAG could
> recover the bricked device.

But thanks to Lubomir OpenOCD now knows how to access the flash.

According to the U-Boot source code the key combinations are:

Shift-L + Fn + Ctrl-L + Shift-R:
	mmcinit
	fatload mmc 0 0x80600000 minipc.img
	nand erase 0 0xa00000
	nand write 0x80600000 0 0xa00000
	boot

Shift-L + Fn + Ctrl-L:
	mmcinit
	fatload mmc 0 0x80600000 uimage
	nand erase 0x100000 0x180000
	nand write 0x80600000 0x100000 0x180000
	bootm

Shift-L + Fn + Shift-R:
	mmcinit
	fatload mmc 0 0x80600000 minifs.img
	nand erase 0x500000 0x500000
	nand write 0x80600000 0x500000 0x500000
	boot

Shift-L + Fn + Esc:
	set bootfile minipc.img
	tftp
	nand read 0x82000000 0x400000 0x100000
	nand erase 0 0xa00000
	nand write 0x80600000 0 0xa00000
	nand erase 0x400000 0x100000
	nand write 0x82000000 0x400000 0x100000
	bootm

Shift-L + Fn:
	mmcinit
	fatload mmc 0 0x80600000 uimage
	bootm

Fn + Ctrl-L + B:
	set bootfile u-boot
	tftp
	nand erase 0 0x100000
	nand write 0x80600000 0 0x100000
	bootm

Fn + Ctrl-L + K:
	set bootfile uImage-2
	tftp
	nand erase 0x100000 0x300000
	nand write 0x80600000 0x100000 0x300000
	bootm

Fn + Ctrl-L + M:
	set bootfile minifs.img
	tftp
	nand erase 0x500000 0x500000
	nand write 0x80600000 0x500000 0x500000
	bootm

else normal boot:
	nboot 0x80600000 0 0x100000
	bootm

There are lots of other key combinations that achieve the same because the
code in most cases just checks if a row of the key matrix is low while six
columns are driven low.

> Hardware-wise these devices (Skytone, Elonex, Letux and many more) seem
> to be the same.

There are tiny differences, f.ex. the wifi module.

Best regards,

  Daniel