[Letux-kernel] LX16 status

[H. Nikolaus Schaller]

Hi all,
it was a little quiet around the next version of the LX16 hardware...

Well, there was essentially no progress except that another project did suggest to use the
ESP32-WROOM modules.

There is a kernel driver
https://github.com/espressif/esp-hosted/tree/master/esp_hosted_ng/host
and I managed to integrate it into a mainline kernel:
https://git.goldelico.com/?p=letux-kernel.git;a=shortlog;h=refs/heads/letux/esp-hosted-ng
with a strange Makefile...
But it compiles and can be manually modprobed because DTS fixes are missing.

Well, there is no hardware yet but in 2-3 weeks I will have one for testing.
A still open question is how to flash the firmware... On all the modules I am aware of
it is installed in /lib/firmware and the sdio driver takes care of flashing.
Not so for ESP32...

But the decision is almost done to replace the Ath10k based module (although it is dual band)
with the ESP32.

The other open question was how to handle power supply for the v0.3.

Now my plan is to have two USB-C sockets.
One is for power in only and no data.
The other is connected to USB2 D+ and D- and should become dual role i.e. can be either power/data in
or power/data out (if other is supplied with power in).

Power is switched by a TPS211x chip so that nobody can destroy something by shorting two different
USB power sources.
For the port with D+ and D- I plan to add a power switch (TPS2552) reversed, e.g. if power comes in
from the other port it can be fed as power out to the data capable port.
This needs some thought so that the TPS211x doesn't think it should switch back :)

And, we need some small circuitry to switch the CC1/2 resistors which indicate the USB-C port
type so that a client in host mode knows that it can draw power.
So we will get an "OTG" capable USB-C port (well, it is no longer called OTG in this case but
Dual Role, I think).

Of course there are nice fully integrated USB-C controllers like the FUSB302B but they need a
dedicated I2C interface... No problem on devices like with OMAP where the TWL PMIC is already
connected through I2C but not for our LX16.

So let's see how fast I can implement this in new hardware so that we can continue on software.

BR,
Nikolaus