ESP-32 WROOM discrepancy in quickref page

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albtrentadue
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ESP-32 WROOM discrepancy in quickref page

Post by albtrentadue » Tue Mar 16, 2021 10:57 pm

Hello
I see a discrepancy between the quickref page in the micropython website and the ESP32-WROOM datasheet.

In the ESP-32 quickref page: https://docs.micropython.org/en/latest/ ... ckref.html
I can read in the "Pins and GPIO" section:
Pins 6, 7, 8, 11, 16, and 17 are used for connecting the embedded flash, and are not recommended for other uses
In the datasheet from the Espressif site https://www.espressif.com/sites/default ... eet_en.pdf
I can read in the section 2.2 Pin Description - page 4:
Pins SCK/CLK, SDO/SD0, SDI/SD1, SHD/SD2, SWP/SD3 and SCS/CMD, namely, GPIO6 to GPIO11 are
connected to the integrated SPI flash integrated on the module and are not recommended for other uses
Same is reported in the pin table before this text.

So it seems that pin 16 and 17 are not among those reserved by the embedded flash.
Which is correct?

Thanks for help
- Alberto

davef
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Location: Christchurch, NZ

Re: ESP-32 WROOM discrepancy in quickref page

Post by davef » Tue Mar 16, 2021 11:54 pm

These are the notes I picked up somewhere:
Don’t use these ESP32 GPIO

6 to 11 SPI flash, not brought-out
16 & 17 PSRAM, think this is for the WROVER part
Maybe, there is some confusion between WROVER and WROOM.

albtrentadue
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Re: ESP-32 WROOM discrepancy in quickref page

Post by albtrentadue » Fri Mar 19, 2021 10:58 pm

Thank you, davef.

Apart from the fact that I clearly trust Espressif's datasheet more than whatever webpage, my goal is to point out to ESP32 quickref authors that such note can/should be improved:
Pins 1 and 3 are REPL UART TX and RX respectively
Pins 6, 7, 8, 11, 16, and 17 are used for connecting the embedded flash, and are not recommended for other uses
Pins 34-39 are input only, and also do not have internal pull-up resistors
One may then be prevented from using GPIO16 and GPIO17 for no reason.

davef
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Re: ESP-32 WROOM discrepancy in quickref page

Post by davef » Tue Mar 23, 2021 7:53 pm

I think for any change to happen one has to raise an issue on the relevant GitHub Micropython ESP32 page. Maybe here https://github.com/micropython/micropython-esp32

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pythoncoder
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Re: ESP-32 WROOM discrepancy in quickref page

Post by pythoncoder » Thu Mar 25, 2021 8:14 am

This is quite confusing. I researched this when the ESP32 WROOM and WROVER were new and concluded that 6-10 inclusive are for internal flash. GPIO 16-17 and 22 are for SPIRAM (where fitted - WROVER). As I recall I got this information from Espressif documentation.

If this is correct, GPIO 9 and 10 are also illegal. GPIO11 is not brought out. On SPIRAM boards 22 is also barred.

A definitive answer would be good.
Peter Hinch
Index to my micropython libraries.

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mattyt
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Re: ESP-32 WROOM discrepancy in quickref page

Post by mattyt » Thu Mar 25, 2021 12:58 pm

Thanks for raising this @albtrentadue. If we can get a definitive answer I'm happy to make the change to the docs; I'm guilty of writing the confusing original!

I've created issue #7068 ESP32 Quickref pin guidance should be improved.

But please continue to discuss and share your findings (here or in the ticket) as it's still not exactly clear what the guidance should be.

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mcauser
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Re: ESP-32 WROOM discrepancy in quickref page

Post by mcauser » Thu Mar 25, 2021 10:25 pm

Should that https://github.com/micropython/micropython-esp32 repo be marked as archived to avoid confusion, now that it has been merged into mainline?

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