Hi Tim,

if you use the ESP32 without the PSRAM, for example the ESP32-WROOM, then you have CLOCKIN (GPIO_0) and CLOCLOUT/CLOCKOUT180 available. When you use the ESP32 with PSRAM, as on the WROVER modules, the CLOCLOUT/CLOCKOUT180 are occupied by the PSRAM and not available.

The CLOCKIN (GPIO_0) is a bit on the ESP32 is also a strap pin, means its status is read while booting. It need to be isolated while booting from external oscillators, for example with an analog switch.

We faced several problems with the ESP32-WROVER, with PYH like the LAN8720, what do not stop the clock out while in reset. Other PYH like the IP101 worked without a problem. And when the ESP32 is the Ethernet clock source, there was no problem at all.

If you dont need the additional PSRAM, i suggest the ESP32-WROOM and the ESP32 as clock source. If you need the ESP32 to be the clock sink on GPIO_0, you must ensure that the clock is disabled while the ESP32 is in reset, and a few mS after that.

BR,
Michael


Am 2022-11-01 19:19, schrieb Alan C. Assis:
Hi Tim,

Probably you saw that you will need to use some external clock.

You can try to use the ESP32 generated clock CLOCKOUT (ideally you can
add a 0R option option to use CLOCKOUT180 instead) and connect it to
GTXCK.

Case it doesn't work you will need an external 50MHz oscillator.

BR,

Alan

On 10/29/22, TimH <t...@jti.uk.com.invalid> wrote:
I meant esp32 not esr32. The naming is too similar lol

On 29 Oct 2022, at 15:51, Tim Hardisty <t...@jti.uk.com.invalid> wrote:

Thanks Alan! SAMA5D2 has RMII so definitely a possibility. EFR32 is a much better value device compared to SiLabs Bluetooth 5 module currently used, and has WiFi as a bonus - so I will investigate it's IDE and see how easy it is to implement a GATT-based solution, or to load HCI firmware so I can be reasonably confident I'm not digging a big hole for myself if I
make this change.


On 29/10/2022, 13:23, "Alan C. Assis" <acas...@gmail.com> wrote:

   More info here:


https://e2e.ti.com/support/processors-group/processors/f/processors-forum/366759/am335x-rmii-direct-connection-between-two-devices

   Same TI guy who said it was impossible latter talk internally and
   discovered that there was a customer already using it.

BTW, you will need to have RMII supported by both MCUs (yes, ESP32 has
RMII).

   BR,

   Alan

   On 10/29/22, Alan C. Assis <acas...@gmail.com> wrote:
Hi Tim,

I just searched if it was possible to connect two Ethernet MAC
directly without using PHY and it is possible, so it will not involve
cost for you:

https://stackoverflow.com/questions/39503466/can-two-ethernet-mac-chips-be-connected-directly-without-going-thru-phy

BR,

Alan

On 10/29/22, Tim Hardisty <t...@jti.uk.com.invalid> wrote:
Thanks for your clarifications Alan - I have messaged Espressif (your
reply
ended up in SPAM otherwise I might not have needed to) so I guess I'll
get
a
similar answer.

There is HCI (RCP) firmware for the SiLabs module so I can try that -
it's
the £7 per module saving of Espressif vs. SiLabs, plus getting WiFi for
free
that appeals. SAMA5D2 has Ethernet - unused on my board so it is not an
idea
that is completely out of the question:  writing USRSOCK for the
Espressif
module is probably beyond me at this time!

On 29/10/2022, 00:20, "Alan C. Assis" <acas...@gmail.com> wrote:

   Hi Tim,

   On 10/28/22, Tim Hardisty <t...@jti.uk.com.invalid> wrote:
Bit of a tangential question this, but I know there are folk on
here
who
are much more conversant with the way NuttX can be used with WiFi
and
Bluetooth modules than I am.


I think these are important questions and other people could face
   similar issues in the future.

I may have an opportunity forced on me to have to respin my custom
board
which currently has a SiLabs Bluetooth SoC as well as the main
SAMA5D2
processor. I used that module as I already have experience of it -
but
that
predates my NuttX journey.

I see there are some very good value combined WiFi + Bluetooth
modules
now
(Espressif for example...and I know there's a well-known proponent
of
those
devices here lol) and, having seen a few other questions here, I am
thinking
that I can go the HCI route and make use of the Bluetooth Stack in
NuttX:
and add WiFi capability to my board at the same time. Winner!


   First let me explain the differences:

   Espressif modules are not used as external modules on NuttX,
   everything is integrated inside the chip.

During the WildernessLab's presentation on NuttX Workshop their team
   shown an ESP32 solution sharing WiFi as an external module.
But they didn't use the default USRSOCK route, they implemented a
new
   solution at home.

I'm hoping I can program up a suitable module with generic radio
co-processor software (HCI I think, and whatever is needed for
WiFi)
and
access it via UART from my main processor and have it all under the
NuttX
system in a much more easily managed manner than a separate app on
the
SiLabs SoC that just happens to communicate on some way with my
main
app on
the SAMA5D2.

Have I got this right? Is an Espressif module a good choice (email
me
direct
if you want to !!)?


For Bluetooth (BLE) if there is a HCI firmware to SiLabs chip, then
it
could be possible to you use it, but you'll need to do some tests
and
   debugging to get things working.

   For WiFi things are more complex because you need to implement a
   USRSOCK yourself to the chip.

I never tested others possibilities: i.e. share Internet using SLIP between ESP32 and SAMA5D2, should be an easier route if it works,
but
   of course you wil be limited to UART speed.

   Ethernet could be a better option (since ESP32 has Ethernet
hardware),
   but it seems like an ugly and expensive workaround.

   BR,

   Alan









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