ESP32

ChibiOS public support forum for topics related to the Espressif ESP32 family of micro-controllers.
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Giovanni
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Re: ESP32

Postby Giovanni » Wed Nov 14, 2018 2:46 pm

There is not much moderation to do as I wrote, surprisingly enough in 10 years this forum never needed serious moderation.

Up to you to organize this effort. moderators are just names put up there.

Giovanni

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Re: ESP32

Postby Marco » Wed Nov 14, 2018 7:26 pm

Giovanni wrote:I just created the forum (icon missing), moving this topic there.

Anybody volunteering as moderator? not much to do anyway, usually I cut problems "at the root".

Giovanni


I can do it if needed, i don’t mind. :)

Marco

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 12:19 am

This doc provides more in depth info on the cpu,memory,peripherals,interupt matrix,clocks, up, and all the on-board peripheral controllers... I think it's getting close to what u wanted...?

https://espressif.com/sites/default/fil ... ual_en.pdf

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 12:28 am

Ok, I think I found the right reference ...

https://0x04.net/~mwk/doc/xtensa.pdf
"Xtensa® Instruction Set Architecture (ISA) Reference Manual For All Xtensa Processor Cores"

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Re: ESP32

Postby Giovanni » Thu Nov 15, 2018 7:25 am

Some relevant points I got from that document:

1) There is no dual stack like Cortex-M but it has a dedicated bit PS.UM that can be used for SW stack switching.
2) There is a stack overflow/underflow protection that is very useful.
3) EPC and PS should be part of port_extctx.
4) Very few registers (a12 – a15) are callee-saved so part of port_intctx, this means that switching from thread to thread is going to be very fast.
5) The xtensa has a lot of option, we need to target a specific implementation or set of options.

Giovanni

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 1:20 pm

Regarding the 'options, we are targeting what is known as the 'esp32' 'SOC', so it's certainly a very specific single silicon, that is a dual core Tensilica Xtensa LX6 running at 240mhz, and the Wikipedia page says it's 520 KiB SRAM and the identifier of the chip is ESP32-D0WDQ6 and typically has 4MiB of external flash attached.

References:
https://en.m.wikipedia.org/wiki/ESP32

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 1:36 pm

Here is the definitive list from espressif of what core options are included in the esp32, and what are not.... and other goodies...
https://github.com/espressif/esp-idf/bl ... core-isa.h

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 1:39 pm

Configuration overlay can be found here...
https://github.com/jcmvbkbc/crosstool-N ... _esp32.tar

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 1:46 pm

I also just discovered that the Zephyr OS , another embedded rtos, also runs on the esp32, so just worth mentioning.. .

Reference:
https://docs.zephyrproject.org/latest/i ... ephyr.html
https://docs.zephyrproject.org/latest/b ... esp32.html

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Re: ESP32

Postby davidbuzz » Thu Nov 15, 2018 2:01 pm

ABI and overlay and calling conventions discussed and linked here: https://www.esp32.com/viewtopic.php?t=4227


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