early stage debugging on a real product

[Andy Shevchenko]

On Wed, Nov 25, 2020 at 7:11 PM Siarhei Siamashka
<siarhei.siamashka at gmail.com> wrote:
> On Wed, Nov 25, 2020 at 5:36 PM Andy Shevchenko
> <andy.shevchenko at gmail.com> wrote:

...

> Does this tablet / phone have an MMC slot?

In fact it does.

> For example, on all
> Allwinner tablets it is technically possible to use MMC pins for UART
> via a different non-standard pin mux setup and a breakout board:
>
>   https://linux-sunxi.org/MicroSD_Breakout
>   https://linux-sunxi.org/File:MSI_Primo81_and_MicroSD_breakout.jpg
>
> Also are you sure that there are really no UART pads on the PCB to
> solder some wires if you disassemble your tablet / phone?

There are UARTs which are soldered with real devices connected. MMC
can be switched to GPIO, so it would be rather bitbanging with some
non-standard speed.
Does U-Boot have a bitbang UART driver?

-- 
With Best Regards,
Andy Shevchenko